TransDigm (TDG) 10-K 13 Nov 17 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2017	Nov. 06, 2017	Mar. 31, 2017
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	TDG
Entity Registrant Name	TRANSDIGM GROUP INC
Entity Central Index Key	1,260,221
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		51,959,702
Entity Public Float			$ 10,561,787,638

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
CURRENT ASSETS:
Cash and cash equivalents	$ 650,561	$ 1,586,994
Trade accounts receivable—Net	636,127	576,339
Inventories—Net	730,681	724,011
Assets held-for-sale	77,500	0
Prepaid expenses and other	38,683	43,353
Total current assets	2,133,552	2,930,697
PROPERTY, PLANT AND EQUIPMENT—Net	324,924	310,580
GOODWILL	5,745,338	5,679,452
OTHER INTANGIBLE ASSETS—Net	1,717,862	1,764,343
OTHER	53,985	41,205
TOTAL ASSETS	9,975,661	10,726,277
CURRENT LIABILITIES:
Current portion of long-term debt	69,454	52,645
Short-term borrowings—trade receivable securitization facility	299,587	199,771
Accounts payable	148,761	156,075
Accrued liabilities	335,888	344,112
Liabilities held-for-sale	17,304	0
Total current liabilities	870,994	752,603
LONG-TERM DEBT	11,393,620	9,943,191
DEFERRED INCOME TAXES	500,949	492,255
OTHER NON-CURRENT LIABILITIES	161,302	189,718
Total liabilities	12,926,865	11,377,767
STOCKHOLDERS’ DEFICIT:
Common stock—$.01 par value; authorized 224,400,000 shares; issued 56,093,659 and 55,767,767 shares at September 30, 2017 and 2016, respectively	561	558
Additional paid-in capital	1,095,319	1,028,972
Accumulated deficit	(3,187,220)	(1,146,963)
Accumulated other comprehensive loss	(85,143)	(149,787)
Treasury stock, at cost; 4,159,207 and 2,433,035 shares at September 30, 2017 and 2016, respectively	(774,721)	(384,270)
Total stockholders’ deficit	(2,951,204)	(651,490)
TOTAL LIABILITIES AND STOCKHOLDERS’ DEFICIT	$ 9,975,661	$ 10,726,277

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Sep. 30, 2016
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	224,400,000	224,400,000
Common stock, shares issued	56,093,659	55,767,767
Treasury stock, shares	4,159,207	2,433,035

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
NET SALES	$ 3,504,286	$ 3,171,411	$ 2,707,115
COST OF SALES	1,519,659	1,443,348	1,257,270
GROSS PROFIT	1,984,627	1,728,063	1,449,845
SELLING AND ADMINISTRATIVE EXPENSES	415,575	382,858	321,624
AMORTIZATION OF INTANGIBLE ASSETS	89,226	77,445	54,219
INCOME FROM OPERATIONS	1,479,826	1,267,760	1,074,002
INTEREST EXPENSE—Net	602,589	483,850	418,785
REFINANCING COSTS	39,807	15,794	18,393
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	837,430	768,116	636,824
INCOME TAX PROVISION	208,889	181,702	189,612
INCOME FROM CONTINUING OPERATIONS	628,541	586,414	447,212
LOSS FROM DISCONTINUED OPERATIONS, NET OF TAX	(31,654)	0	0
NET INCOME	596,887	586,414	447,212
NET INCOME APPLICABLE TO COMMON STOCK	$ 437,630	$ 583,414	$ 443,847
Net earnings per share:
Net earnings per share from continuing operations—basic and diluted	$ 8.45	$ 10.39	$ 7.84
Net loss per share from discontinued operations—basic and diluted	(0.57)	0	0
Basic and diluted (in dollars per share)	7.88	10.39	7.84
Cash dividends paid per common share (in dollars per share)	$ 46	$ 0	$ 0
Weighted-average shares outstanding:
Basic and diluted	55,530	56,157	56,606

Condensed Consolidated Statemen

Condensed Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Net income	$ 596,887	$ 586,414	$ 447,212
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	22,241	(31,846)	(29,448)
Interest rate swap and cap agreements	34,471	(9,648)	(35,604)
Pension liability adjustments	7,932	(12,284)	(5,786)
Other comprehensive income (loss), net of tax	64,644	(53,778)	(70,838)
TOTAL COMPREHENSIVE INCOME	$ 661,531	$ 532,636	$ 376,374

Consolidated Statement of Chang

Consolidated Statement of Changes in Stockholders' Deficit - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Treasury Stock
BALANCE at Sep. 30, 2014	$ (1,556,099)	$ 538	$ 794,767	$ (2,150,293)	$ (25,171)	$ (175,940)
BALANCE (in shares) at Sep. 30, 2014		53,832,246				1,415,100
Unvested dividend equivalent payments	(14,151)			(14,151)
Compensation expense recognized for employee stock options and restricted stock	31,500		31,500
Excess tax benefits related to share-based payment arrangements	61,965		61,965
Exercise of employee stock options and restricted stock activity, net	61,687	$ 13	61,674
Exercise of employee stock options and restricted stock activity, net (in shares)		1,248,175
Common stock issued	418		418
Common stock issued (in shares)		19,673
Net income	447,212			447,212
Interest rate swaps and caps, net of tax	(35,604)				(35,604)
Foreign currency translation adjustments	(29,448)				(29,448)
Pension liability adjustments, net of tax	(5,786)				(5,786)
BALANCE at Sep. 30, 2015	(1,038,306)	$ 551	950,324	(1,717,232)	(96,009)	$ (175,940)
BALANCE (in shares) at Sep. 30, 2015		55,100,094				1,415,100
Unvested dividend equivalent payments	(16,145)			(16,145)
Compensation expense recognized for employee stock options and restricted stock	48,306		48,306
Exercise of employee stock options and restricted stock activity, net	29,544	$ 7	30,112			$ 575
Exercise of employee stock options and restricted stock activity, net (in shares)		666,709				2,548
Treasury stock purchased	(207,755)					$ (207,755)
Treasury stock purchased (in shares)						(1,015,387)
Common stock issued	230		230
Common stock issued (in shares)		964
Net income	586,414			586,414
Interest rate swaps and caps, net of tax	(9,648)				(9,648)
Foreign currency translation adjustments	(31,846)				(31,846)
Pension liability adjustments, net of tax	(12,284)				(12,284)
BALANCE at Sep. 30, 2016	$ (651,490)	$ 558	1,028,972	(1,146,963)	(149,787)	$ (384,270)
BALANCE (in shares) at Sep. 30, 2016	55,767,767	55,767,767				2,433,035
Dividends paid	$ (2,422,295)			(2,422,295)
Unvested dividend equivalent payments	(214,849)			(214,849)
Compensation expense recognized for employee stock options and restricted stock	44,931		44,931
Exercise of employee stock options and restricted stock activity, net	20,550	$ 3	21,177			$ 630
Exercise of employee stock options and restricted stock activity, net (in shares)		324,908				2,548
Treasury stock purchased	$ (389,800)					$ (389,821)
Treasury stock purchased (in shares)	(1,723,624)					(1,723,624)
Common stock issued	$ 239		239
Common stock issued (in shares)		984
Net income	596,887			596,887
Interest rate swaps and caps, net of tax	34,471				34,471
Foreign currency translation adjustments	22,241				22,241
Pension liability adjustments, net of tax	7,932				7,932
BALANCE at Sep. 30, 2017	$ (2,951,204)	$ 561	$ 1,095,319	$ (3,187,220)	$ (85,143)	$ (774,721)
BALANCE (in shares) at Sep. 30, 2017	56,093,659	56,093,659				4,159,207

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
OPERATING ACTIVITIES:
Net income	$ 596,887	$ 586,414	$ 447,212
Net loss from discontinued operations	31,654	0	0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	50,937	43,455	35,939
Amortization of intangible assets and product certification costs	90,088	78,215	57,724
Amortization of debt issuance costs, original issue discount and premium	21,106	16,211	15,797
Refinancing costs	39,807	15,794	18,393
Non-cash equity compensation	45,524	48,306	31,500
Excess tax benefits related to share-based payment arrangements	0	0	(61,965)
Deferred income taxes	(918)	5,808	660
Changes in assets/liabilities, net of effects from acquisitions of businesses:
Trade accounts receivable	(54,669)	(80,114)	(25,418)
Inventories	5,127	(2,073)	(25,974)
Income taxes receivable/payable	18,219	(12,299)	65,418
Other assets	(10,564)	(4,919)	(12,392)
Accounts payable	(10,354)	(6,657)	13,480
Accrued interest	(958)	17,933	(3,934)
Accrued and other liabilities	(33,153)	(22,776)	(35,502)
Net cash provided by operating activities	788,733	683,298	520,938
INVESTING ACTIVITIES:
Capital expenditures, net of disposals	(71,013)	(43,982)	(54,871)
Payments made in connection with acquisitions	(136,295)	(1,399,064)	(1,624,278)
Acquisition of Schroth, net of cash acquired	(79,695)	0	0
Net cash used in investing activities	(287,003)	(1,443,046)	(1,679,149)
FINANCING ACTIVITIES:
Excess tax benefits related to share-based payment arrangements	0	0	61,965
Proceeds from exercise of stock options	21,177	30,112	61,674
Dividends paid	(2,581,552)	(3,000)	(3,365)
Treasury stock purchased	(389,821)	(207,755)	0
Proceeds from term loans, net	2,937,773	1,711,515	1,515,954
Repayment on term loans	(1,284,698)	(834,409)	(1,025,318)
Proceeds from senior subordinated notes, net	300,386	939,584	445,303
Cash tender and redemption of senior subordinated notes due 2021, including premium	528,847	0	0
Proceeds from trade receivable securitization facility, net	99,471	0	0
Financing fees and other	(17,571)	(3,580)	(1,266)
Net cash (used in) provided by financing activities	(1,443,682)	1,632,467	1,054,947
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	5,519	242	(2,251)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(936,433)	872,961	(105,515)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	1,586,994	714,033	819,548
CASH AND CASH EQUIVALENTS, END OF PERIOD	650,561	1,586,994	714,033
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid during the period for interest	587,718	448,608	398,939
Cash paid during the period for income taxes	$ 185,295	$ 183,291	$ 127,363

DESCRIPTION OF THE BUSINESS

DESCRIPTION OF THE BUSINESS	12 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
DESCRIPTION OF THE BUSINESS	DESCRIPTION OF THE BUSINESS Description of the Business —TransDigm Group Incorporated (“TD Group”), through its wholly-owned subsidiary, TransDigm Inc., is a leading global designer, producer and supplier of highly engineered aircraft components for use on nearly all commercial and military aircraft in service today. TransDigm Inc., along with TransDigm Inc.’s direct and indirect wholly-owned operating subsidiaries (collectively, with TD Group, the “Company” or “TransDigm”), offers a broad range of proprietary aerospace components. TD Group has no significant assets or operations other than its 100% ownership of TransDigm Inc. TD Group’s common stock is listed on the New York Stock Exchange, or the NYSE, under the trading symbol “TDG.” Major product offerings, substantially all of which are ultimately provided to end-users in the aerospace industry, include mechanical/electro-mechanical actuators and controls, ignition systems and engine technology, specialized pumps and valves, power conditioning devices, specialized AC/DC electric motors and generators, NiCad batteries and chargers, engineered latching and locking devices, rods and locking devices, engineered connectors and elastomers, databus and power controls, cockpit security components and systems, specialized cockpit displays, aircraft audio systems, specialized lavatory components, seat belts and safety restraints, engineered interior surfaces and related components, lighting and control technology, military personnel parachutes, high performance hoists, winches and lifting devices, and cargo loading, handling and delivery systems.

ACQUISITIONS

ACQUISITIONS	12 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
ACQUISITIONS	ACQUISITIONS During the last three fiscal years, the Company completed the acquisitions of Schroth, Y&F/Tactair, DDC, Breeze-Eastern, PneuDraulics, Pexco Aerospace, Adams Rite Aerospace GmbH and Telair Cargo Group. Additionally, during the third quarter of fiscal 2017, the Company acquired three separate aerospace product lines (collectively, the “Third Quarter 2017 Acquisitions”). The Company accounted for the acquisitions using the acquisition method and included the results of operations of the acquisitions in its consolidated financial statements from the effective date of each acquisition. As of September 30, 2017 , the one-year measurement period is open for Schroth and the Third Quarter 2017 Acquisitions and therefore the assets acquired and liabilities assumed related to these acquisitions are subject to adjustment until the end of the respective one-year measurement period. The Company is in the process of obtaining a third-party valuation of certain tangible and intangible assets of the Third Quarter 2017 Acquisitions; therefore, the values attributed to those acquired assets and liabilities in the consolidated financial statements are subject to adjustment. Pro forma net sales and results of operations for the acquisitions, had they occurred at the beginning of the applicable fiscal year ended September 30, 2017 or 2016 , are not material and, accordingly, are not provided. The acquisitions strengthen and expand the Company’s position to design, produce and supply highly engineered proprietary aerospace components in niche markets with significant aftermarket content and provide opportunities to create value through the application of our three core value-driven operating strategies (obtaining profitable new business, improving our cost structure, and providing highly engineered value-added products to customers). The purchase price paid for each acquisition reflects the current earnings before interest, taxes, depreciation and amortization (EBITDA) and cash flows, as well as the future EBITDA and cash flows expected to be generated by the business, which are driven in most cases by the recurring aftermarket consumption over the life of a particular aircraft, estimated to be approximately 25 to 30 years . Third Quarter 2017 Acquisitions – During the third quarter of fiscal 2017, the Company acquired the Third Quarter 2017 Acquisitions for a total purchase price of approximately $106.3 million in cash, which includes working capital settlements totaling $1.0 million paid in the third and fourth quarter of 2017. All three product lines consist primarily of proprietary, sole source products with significant aftermarket content. The products include highly engineered aerospace controls, quick disconnect couplings, and communication electronics. Each product line acquired was consolidated into an existing TransDigm reporting unit within TransDigm's Power & Control segment. The Company expects that approximately $62 million of goodwill recognized for the acquisitions will be deductible for tax purposes over 15 years and approximately $9 million of goodwill recognized for the acquisitions will not be deductible for tax purposes. Schroth – On February 22, 2017, the Company acquired all of the outstanding stock of Schroth Safety Products GmbH and certain aviation and defense assets and liabilities from subsidiaries of Takata Corporation (collectively, "Schroth"), for a total purchase price of approximately $89.7 million , of which $79.7 million was paid in cash (including a working capital settlement of $0.8 million paid in the third quarter of 2017) and the remaining approximately $10.0 million of which is accrued primarily related to an indemnity holdback to be settled within the one-year measurement period. In connection with the settlement of a Department of Justice investigation into the competitive effects of the acquisition, during the fourth quarter of 2017, the Company committed to dispose of the Schroth business. Therefore, Schroth was classified as held-for-sale as of September 30, 2017. The results of operations of Schroth are reflected as discontinued operations in the accompanying consolidated financial statements. Schroth designs and manufactures proprietary, highly engineered, advanced safety systems for aviation, racing and military ground vehicles around the world. Prior to being classified as discontinued operations, Schroth was included in TransDigm's Airframe segment. The loss from discontinued operations in the consolidated statements of income includes a $32.0 million impairment charge to write down Schroth’s assets to estimated fair value. The impairment charge recorded in the fourth quarter of 2017 was based on an internal assessment around the recovery of the Schroth assets. Schroth’s assets have been recorded at fair value in the consolidated balance sheet as of September 30, 2017. Further disclosure related to Schroth’s discontinued operations is included in Note 22. Y&F/Tactair – On September 23, 2016, the Company acquired all of the outstanding stock of Young & Franklin, Inc., the parent company of Tactair Fluid Controls, Inc., for approximately $258.8 million in cash, which includes a working capital settlement of $2.7 million paid in the first quarter of 2017. Y&F/Tactair manufactures proprietary, highly engineered valves and actuators. Y&F/Tactair is included in TransDigm’s Power & Control segment. The purchase price includes approximately $74.5 million of tax benefits being realized by the Company over a 15 -year period that began in the first quarter of fiscal 2017. The Company expects that approximately $124 million of goodwill recognized for the acquisition will be deductible for tax purposes over 15 years and approximately $8 million of goodwill recognized for the acquisition will not be deductible for tax purposes. Data Device Corporation – On June 23, 2016, the Company acquired all of the outstanding stock of ILC Holdings, Inc., the parent company of Data Device Corporation, for a total purchase price of approximately $997.7 million in cash, which includes a working capital settlement of $1.4 million received in the first quarter of fiscal 2017. TransDigm financed the acquisition of DDC with cash proceeds from the issuance of senior subordinated notes due in June 2026 and term loans. DDC is a supplier of databus and power controls and related products that are used primarily in military avionics, commercial aerospace and space applications. DDC is included in TransDigm’s Power & Control segment. The total purchase price of DDC was allocated to the underlying assets acquired and liabilities assumed based upon management’s estimated fair values at the date of acquisition. To the extent the purchase price exceeded the estimated fair value of the net identifiable tangible and intangible assets acquired, such excess was allocated to goodwill. The following table summarizes the final purchase price allocation of the estimated fair values of the assets acquired and liabilities assumed at the transaction date (in thousands). Assets acquired: Current assets, excluding cash acquired $ 107,728 Property, plant, and equipment 20,818 Intangible assets 229,300 Goodwill 750,935 Other 2,036 Total assets acquired 1,110,817 Liabilities assumed: Current liabilities 26,520 Other noncurrent liabilities 86,642 Total liabilities assumed 113,162 Net assets acquired $ 997,655 Approximately $740 million of goodwill recognized for the acquisition is not deductible for tax purposes and approximately $11 million of goodwill recognized for the acquisition is deductible for tax purposes over 15 years. Breeze-Eastern – On January 4, 2016, the Company completed the tender offer for all of the outstanding stock of Breeze-Eastern for $19.61 per share in cash. The purchase price was approximately $205.9 million , of which $146.4 million (net of cash acquired of $ 30.8 million ) was paid at closing and $34.9 million was paid to dissenting shareholders during the first fiscal quarter of 2017. Of the $34.9 million payment, $28.7 million related to the original merger consideration and $6.2 million represented the settlement reached with the dissenting shareholders resolving the dispute over the dissenting shareholders’ statutory appraisal action. Of the $6.2 million settlement, $4.9 million was recorded as selling and administrative expense and $1.3 million was recorded as interest expense for statutory interest arising under Delaware General Corporate Law. Once the Company paid the $34.9 million settlement to the dissenting shareholders on October 20, 2016, the dissenting stockholders fully released their claims against the Company. Breeze-Eastern manufactures high performance lifting and pulling devices for military and civilian aircraft, including rescue hoists, winches and cargo hooks, and weapons-lifting systems. Breeze-Eastern is included in TransDigm’s Power & Control segment. All of the approximately $115 million of goodwill recognized for the acquisition is not deductible for tax purposes. PneuDraulics – On August 19, 2015, the Company acquired all of the outstanding stock of PneuDraulics, Inc. for approximately $321.5 million in cash, which is net of a working capital settlement received in fiscal 2016 of $2.0 million . PneuDraulics manufactures proprietary, highly engineered aerospace pneumatic and hydraulic components and subsystems for commercial transport, regional, business jet and military applications. PneuDraulics is included in TransDigm’s Power & Control segment. The purchase price includes approximately $108.1 million of tax benefits being realized by the Company over a 15 -year period that began in the fourth quarter of fiscal 2015. All of the approximately $223 million of goodwill recognized for the acquisition is deductible for tax purposes. Pexco Aerospace – On May 14, 2015, the Company acquired the assets of the aerospace business of Pexco LLC (“Pexco Aerospace”) for a total purchase price of approximately $496.4 million in cash. Pexco Aerospace manufactures extruded plastic interior parts for use in the commercial aerospace industry. Pexco Aerospace is included in TransDigm’s Airframe segment. The purchase price includes approximately $166.4 million of tax benefits being realized by TransDigm over a 15 -year period that began in the third quarter of fiscal 2015. All of the approximately $406 million of goodwill recognized for the acquisition is deductible for tax purposes. Adams Rite Aerospace GmbH – On March 31, 2015, the Company acquired the aerospace business of Franke Aquarotter GmbH (now known as Adams Rite Aerospace GmbH) for approximately $75.3 million in cash. Adams Rite Aerospace GmbH manufactures proprietary faucets and related products for use on commercial transports and regional jets. Adams Rite Aerospace GmbH is included in TransDigm’s Airframe segment. All of the approximately $64 million of goodwill recognized for the acquisition is not deductible for tax purposes. Telair Cargo Group – On March 26, 2015, the Company acquired all of the outstanding stock of Telair International GmbH (“Telair Europe”), all of the outstanding stock of Nordisk Aviation Products (“Nordisk”) and the assets of the AAR Cargo business (collectively, “Telair Cargo Group”). The total purchase price was approximately $730.9 million in cash. Telair Cargo Group manufactures aerospace on-board cargo loading and handling, restraint systems and unit load devices for a variety of commercial and military platforms with positions on a wide range of new and existing aircraft. The business consists of three reporting units: Telair Europe, Nordisk and Telair US. Telair Europe and Telair US are included in TransDigm’s Power & Control segment and Nordisk is included in TransDigm’s Airframe segment. Approximately $33 million of goodwill recognized for the acquisition is deductible for tax purposes and approximately $450 million of goodwill recognized for the acquisition is not deductible for tax purposes.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Consolidation —The accompanying consolidated financial statements were prepared in conformity with generally accepted accounting principles in the United States (“GAAP”) and include the accounts of TD Group and subsidiaries. All significant intercompany balances and transactions have been eliminated. Certain reclassifications have been made to the current period annual and interim final statements as during the fourth quarter of 2017, the Company committed to disposing of Schroth. As of September 30, 2017, Schroth was classified as held-for-sale and the results of operations for Schroth are reflected as discontinued operations in the accompanying consolidated financial statements. Refer to Note 22, “Discontinued Operations,” for further information. Revenue Recognition and Related Allowances —Revenue is recognized from the sale of products when title and risk of loss passes to the customer, which is generally at the time of shipment. Substantially all product sales are made pursuant to firm, fixed-price purchase orders received from customers. Provisions for estimated returns, uncollectible accounts and the cost of repairs under contract warranty provisions are provided for in the same period as the related revenues are recorded and are principally based on historical results modified, as appropriate, by the most current information available. Due to uncertainties in the estimation process, it is possible that actual results may vary from the estimates. Shipping and Handling Costs —Shipping and handling costs are included in cost of sales in the consolidated statements of income. Research and Development Costs —The Company expenses research and development costs as incurred and classifies such amounts in selling and administrative expenses. The expense recognized for research and development costs for the years ended September 30, 2017 , 2016 and 2015 was approximately $73.8 million , $58.6 million , and $48.3 million , respectively. Cash Equivalents —The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Allowance for Uncollectible Accounts —The Company reserves for amounts determined to be uncollectible based on specific identification of losses and estimated losses based on historical experience. The allowance also incorporates a provision for the estimated impact of disputes with customers. The determination of the amount of the allowance for doubtful accounts is subject to significant levels of judgment and estimation by management. If circumstances change or economic conditions deteriorate or improve, the allowance for doubtful accounts could increase or decrease. Inventories —Inventories are stated at the lower of cost or market. Cost of inventories is generally determined by the average cost and the first-in, first-out (FIFO) methods and includes material, labor and overhead related to the manufacturing process. Provision for potentially obsolete or slow-moving inventory is made based on management’s analysis of inventory levels and future sales forecasts. Property, Plant and Equipment —Property, plant and equipment are stated at cost and include improvements which significantly increase capacities or extend the useful lives of existing plant and equipment. Depreciation is computed using the straight-line method over the following estimated useful lives: land improvements from 10 to 20 years, buildings and improvements from 5 to 30 years, machinery and equipment from 2 to 10 years and furniture and fixtures from 3 to 10 years. Net gains or losses related to asset dispositions are recognized in earnings in the period in which dispositions occur. Routine maintenance, repairs and replacements are expensed as incurred. Property, plant and equipment is assessed for potential impairment whenever indicators of impairment are present by determining whether the carrying value of the property can be recovered through projected, undiscounted cash flows from future operations over the property’s remaining estimated useful life. Any impairment recognized is the amount by which the carrying amount exceeds the fair value of the asset. Fair value is measured based on quoted market prices in active markets, if available. If quoted market prices are not available, the estimate of fair value is based on various valuation techniques, including the discounted value of estimated future cash flows. Debt Issuance Costs, Premiums and Discounts —The cost of obtaining financing as well as premiums and discounts are amortized using the effective interest method over the terms of the respective obligations as a component of interest expense within the consolidated statements of income. Debt issuance costs are presented in the consolidated balance sheets as a direct reduction from the carrying amount of the related debt liabilities. Intangible Assets —Intangible assets consist of identifiable intangibles acquired or recognized in accounting for the acquisitions (trademarks, trade names, technology, order backlog and other intangible assets) and goodwill. Goodwill and intangible assets that have indefinite useful lives (i.e., trademarks and trade names) are subject to annual impairment testing. Management determines fair value using a discounted future cash flow analysis or other accepted valuation techniques. The Company performs an annual impairment test for goodwill and other intangible assets as of the first day of the fourth fiscal quarter of each year, or more frequently, if an event occurs or circumstances change that would more likely than not reduce fair value below current value. At the time of goodwill impairment testing, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount, and whether it is therefore necessary to perform the quantitative goodwill impairment test. The quantitative goodwill impairment test consists of two steps. The first step of the goodwill impairment test, used to identify potential impairment, compares the fair value of a reporting unit (as defined) with its carrying amount, including goodwill. If the fair value of the reporting unit exceeds its carrying amount, goodwill is not considered impaired, and the second step of the goodwill impairment test is unnecessary. The second step measures the amount of impairment, if any, by comparing the carrying value of the goodwill associated with a reporting unit to the implied fair value of the goodwill derived from the estimated overall fair value of the reporting unit and the individual fair values of the other assets and liabilities of the reporting unit. GAAP requires that the annual, and any interim, impairment assessment be performed at the reporting unit level. The reporting unit level is one level below an operating segment. Substantially all goodwill was determined and recognized for each reporting unit pursuant to the accounting for the merger or acquisition as of the date of each transaction. With respect to acquisitions integrated into an existing reporting unit, any acquired goodwill is combined with the goodwill of the reporting unit. The impairment test for indefinite lived intangible assets consists of a comparison between their fair values and carrying values. If the carrying amounts of intangible assets that have indefinite useful lives exceed their fair values, an impairment loss will be recognized in an amount equal to the sum of any such excesses. The Company assesses the recoverability of its amortizable intangible assets only when indicators of impairment are present by determining whether the amortization over their remaining lives can be recovered through projected, undiscounted cash flows from future operations. Amortization of amortizable intangible assets is computed using the straight-line method over the following estimated useful lives: technology from 20 to 22 years, order backlog over one year , and other intangible assets over 20 years. Stock-Based Compensation —The Company records stock-based compensation expense using the fair value method of accounting. Compensation expense is recorded over the vesting periods of the stock options, restricted stock and other stock-based incentives. No expense is recognized for any stock options, restricted stock and other stock-based incentives ultimately forfeited because the recipients fail to meet vesting requirements. Income Taxes —The Company accounts for income taxes using an asset and liability approach. Deferred taxes are recorded for the difference between the book and tax basis of various assets and liabilities. A valuation allowance is provided when it is more likely than not that some or all of a deferred tax asset will not be realized. Contingencies —During the ordinary course of business, the Company is from time to time threatened with, or may become a party to, legal actions and other proceedings. While the Company is currently involved in certain legal proceedings, it believes the results of these proceedings will not have a material adverse effect on its financial condition, results of operations, or cash flows. Estimates —The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Comprehensive Income (Loss) —The term “comprehensive income (loss)” represents the change in stockholders’ equity (deficit) from transactions and other events and circumstances resulting from non-stockholder sources. The Company’s accumulated other comprehensive income or loss, consisting principally of fair value adjustments to its interest rate swap and cap agreements (net of tax), cumulative foreign currency translation adjustments and pension liability adjustments (net of tax), is reported separately in the accompanying consolidated statements of comprehensive income. Foreign Currency Translation and Transactions —The assets and liabilities of subsidiaries located outside the United States are translated into U.S. dollars at the rates of exchange in effect at the balance sheet dates. Revenue and expense items are translated at the average monthly exchange rates prevailing during the period. Gains and losses resulting from foreign currency transactions are recognized currently in income, and those resulting from translation of financial statements are accumulated as a separate component of other comprehensive income (loss) for the period. Foreign currency gains or losses recognized currently in income from changes in exchange rates were immaterial to our results of operations. Earnings per Share —Earnings per share information is determined using the two-class method, which includes the weighted-average number of common shares outstanding during the period and other securities that participate in dividends (“participating securities”). Our vested stock options are considered “participating securities” because they include non-forfeitable rights to dividends. In applying the two-class method, earnings are allocated to both common stock shares and participating securities based on their respective weighted-average shares outstanding for the period. Diluted earnings per share information may include the additional effect of other securities, if dilutive, in which case the dilutive effect of such securities is calculated using the treasury stock method. Contingently issuable shares are not included in earnings per share until the period in which the contingency is satisfied; therefore, basic and diluted earnings per share are the same.

RECENT ACCOUNTING PRONOUNCEMENT

RECENT ACCOUNTING PRONOUNCEMENTS	12 Months Ended
	Sep. 30, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	RECENT ACCOUNTING PRONOUNCEMENTS In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, which creates a new topic in the Accounting Standards Codification (“ASC”) 606, “Revenue From Contracts With Customers .” In addition to superseding and replacing nearly all existing U.S. GAAP revenue recognition guidance, including industry-specific guidance, ASC 606 establishes a new control-based revenue recognition model; changes the basis for deciding when revenue is recognized over time or at a point in time; provides new and more detailed guidance on specific topics; and expands and improves disclosures about revenue. The new revenue standards may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The guidance is effective for the Company for annual reporting periods, including interim periods therein, beginning October 1, 2018, which is the Company’s planned date of adoption. The Company preliminarily expects to use the full retrospective method. The Company is continuing to evaluate the impact of the standard, and the planned adoption method is subject to change. For each reporting unit, we have evaluated a representative sample of contracts and other agreements with our customers and evaluated the provisions contained within these contracts and agreements in consideration of the five step model specified within ASC 606. We are in the process of documenting the impact of the standard on our current accounting policies and practices in order to identify material differences, if any, that would result from applying the new requirements to our revenue contracts. We continue to make progress on our assessment of ASC 606 and are also in the process of evaluating the impact, if any, on changes to our business processes, systems, and controls to support recognition and disclosure requirements under ASC 606. In September 2015, the FASB issued ASU 2015-16, "Simplifying the Accounting for Measurement-Period Adjustments," a new standard intended to simplify the accounting for measurement period adjustments in a business combination. Measurement period adjustments are changes to provisional amounts recorded when the accounting for a business combination is incomplete as of the end of a reporting period. The measurement period can extend for up to a year following the transaction date. During the measurement period, companies may make adjustments to provisional amounts when information necessary to complete the measurement is received. The new guidance requires companies to recognize these adjustments, including any related impacts to net income, in the reporting period in which the adjustments are determined. Companies are no longer required to retroactively apply measurement period adjustments to all periods presented. The guidance was effective for the Company on October 1, 2016. However, as early adoption was permissible, the Company adopted the pronouncement beginning October 1, 2015. The adoption of this standard did not have a significant impact on its consolidated financial statements and disclosures. In February 2016, the FASB issued ASU 2016-02, “Leases (ASC 842),” which will require that a lessee recognize assets and liabilities on the balance sheet for all leases with a lease term of more than twelve months, with the result being the recognition of a right of use asset and a lease liability. The guidance is effective for the Company for annual reporting periods, including interim periods therein, beginning October 1, 2019, with early adoption permitted. The Company is currently evaluating the impact of adopting this standard on its consolidated financial statements and disclosures. In March 2016, the FASB issued ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting.” The guidance requires the recognition of the income tax effects of awards in the income statement when the awards vest or are settled, thus eliminating additional paid in capital pools. The guidance also allows for the employer to repurchase more of an employee’s shares for tax withholding purposes without triggering liability accounting. In addition, the guidance allows for a policy election to account for forfeitures as they occur rather than on an estimated basis. ASU 2016-09 was effective for the Company for annual reporting periods, including interim periods therein, beginning October 1, 2017, with early adoption permitted. As early adoption is permissible, the Company adopted this standard in the fourth quarter of fiscal 2016. Changes were applied prospectively in accordance with the standard and prior periods were not adjusted. In addition, the Company continued to account for forfeitures on an estimated basis. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13)," which changes the impairment model for most financial assets. The new model uses a forward-looking expected loss method, which will generally result in earlier recognition of allowances for losses. ASU 2016-13 is effective for annual and interim periods beginning after December 15, 2019 and early adoption is permitted for annual and interim periods beginning after December 15, 2018. The Company is currently evaluating the impact of adopting this standard on its consolidated financial statements and disclosures. In August 2016, the FASB issued ASU 2016-15, "Statement of Cash Flows—Classification of Certain Cash Receipts and Cash Payments," which clarifies existing guidance related to accounting for cash receipts and cash payments and classification on the statement of cash flows. This guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, with early adoption permitted. The Company elected to early adopt this standard in the fourth quarter of fiscal 2017. The adoption of this standard did not have a significant impact on its consolidated statement of cash flows. In January 2017, the FASB issued ASU 2017-04, “Simplifying the Test for Goodwill Impairment,” to eliminate Step 2 from the goodwill impairment test in order to simplify the subsequent measurement of goodwill. The guidance is effective for fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The adoption of this standard is not expected to have a material impact on its consolidated financial statements and disclosures. In May 2017, the FASB issued ASU 2017-09, "Compensation—Stock Compensation (ASC 718): Scope of Modification Accounting," which provides clarity on which changes to the terms or conditions of share-based payment awards require an entity to apply the modification accounting provisions required in ASC 718. The standard is effective for all entities for annual periods beginning after December 15, 2017, with early adoption permitted, including adoption in any interim period for which financial statements have not yet been issued. The adoption of this standard is not expected to have a material impact on its consolidated financial statements and disclosures. In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (ASC 815): Targeted Improvements to Accounting for Hedging Activities,” which amends the FASB’s hedge accounting model to enable entities to better portray their risk management activities in financial statements. The guidance eliminates the requirement to separately measure and report hedge ineffectiveness and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The guidance also eases certain documentation and assessment requirements and modifies the accounting for components excluded from the assessment of hedge effectiveness. This guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. The Company is currently evaluating the impact of adopting this standard on its consolidated financial statements and disclosures.

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
EARNINGS PER SHARE (TWO-CLASS METHOD)	EARNINGS PER SHARE (TWO-CLASS METHOD) The following table sets forth the computation of basic and diluted earnings per share (in thousands, except per share data): Fiscal Years Ended September 30, 2017 2016 2015 Numerator for earnings per share: Net income from continuing operations $ 628,541 $ 586,414 $ 447,212 Less dividends paid on participating securities (159,257 ) (3,000 ) (3,365 ) $ 469,284 $ 583,414 $ 443,847 Net loss from discontinued operations (31,654 ) — — Net income applicable to common stock—basic and diluted $ 437,630 $ 583,414 $ 443,847 Denominator for basic and diluted earnings per share under the two-class method: Weighted average common shares outstanding 52,517 53,326 53,112 Vested options deemed participating securities 3,013 2,831 3,494 Total shares for basic and diluted earnings per share 55,530 56,157 56,606 Net earnings per share from continuing operations—basic and diluted $ 8.45 $ 10.39 $ 7.84 Net loss per share from discontinued operations—basic and diluted (0.57 ) — — Net earnings per share $ 7.88 $ 10.39 $ 7.84

SALES AND TRADE ACCOUNTS RECEIV

SALES AND TRADE ACCOUNTS RECEIVABLE	12 Months Ended
	Sep. 30, 2017
Receivables [Abstract]
SALES AND TRADE ACCOUNTS RECEIVABLE	SALES AND TRADE ACCOUNTS RECEIVABLE Sales —The Company’s sales and receivables are concentrated in the aerospace industry. TransDigm’s customers include: distributors of aerospace components; commercial airlines, large commercial transport and regional and business aircraft OEMs; various armed forces of the United States and friendly foreign governments; defense OEMs; system suppliers; and various other industrial customers. Two customers accounted for approximately 13% , 13% and 11% and 11% , 12% and 12% of the Company’s net sales for fiscal years ended 2017 , 2016 and 2015 , respectively. Sales to these customers were split approximately evenly between the Power & Control and Airframe segments. Sales to foreign customers, primarily in Western Europe, Canada and Asia, were $1,318.9 million , $1,169.5 million and $881.1 million during fiscal years ended 2017 , 2016 and 2015 . Trade Accounts Receivable —Trade accounts receivable consist of the following at September 30 (in thousands): 2017 2016 Trade accounts receivable—gross $ 639,946 $ 580,753 Allowance for uncollectible accounts (3,819 ) (4,414 ) Trade accounts receivable—net $ 636,127 $ 576,339 At September 30, 2017 , approximately 12% of the Company’s trade accounts receivable was due from one customer. In addition, approximately 42% of the Company’s trade accounts receivable was due from entities that principally operate outside of the United States. Credit is extended based on an evaluation of each customer’s financial condition and collateral is generally not required.

INVENTORIES

INVENTORIES	12 Months Ended
	Sep. 30, 2017
Inventory Disclosure [Abstract]
INVENTORIES	INVENTORIES Inventories consist of the following at September 30 (in thousands): 2017 2016 Raw materials and purchased component parts $ 496,899 $ 464,410 Work-in-progress 187,009 188,417 Finished Goods 131,548 153,253 Total 815,456 806,080 Reserves for excess and obsolete inventory (84,775 ) (82,069 ) Inventories—net $ 730,681 $ 724,011

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	12 Months Ended
	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment consist of the following at September 30 (in thousands): 2017 2016 Land and improvements $ 56,554 $ 57,510 Buildings and improvements 161,990 153,691 Machinery, equipment and other 376,659 338,527 Construction in progress 22,037 15,958 Total 617,240 565,686 Accumulated depreciation (292,316 ) (255,106 ) Property, plant and equipment—net $ 324,924 $ 310,580

INTANGIBLE ASSETS

INTANGIBLE ASSETS	12 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS	INTANGIBLE ASSETS Other intangible assets - net in the consolidated balance sheets consist of the following at September 30 (in thousands): 2017 2016 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Trademarks and trade names $ 729,931 $ — $ 729,931 $ 720,263 $ — $ 720,263 Technology 1,292,719 351,638 941,081 1,279,335 288,429 990,906 Order backlog 29,000 26,668 2,332 55,341 29,641 25,700 Other 63,599 19,081 44,518 43,331 15,857 27,474 Total $ 2,115,249 $ 397,387 $ 1,717,862 $ 2,098,270 $ 333,927 $ 1,764,343 Information regarding the amortization expense of amortizable intangible assets is detailed below (in thousands): Annual Amortization Expense: Years ended September 30, 2017 $ 89,226 2016 77,445 2015 54,219 Estimated Amortization Expense: Years ending September 30, 2018 $ 69,344 2019 67,011 2020 67,011 2021 67,011 2022 67,011 Intangible assets acquired during the year ended September 30, 2017 were as follows (in thousands): Gross Amount Amortization Period Intangible assets not subject to amortization: Goodwill $ 129,152 Trademarks and trade names 12,100 141,252 Intangible assets subject to amortization: Technology 33,800 20 years Order backlog 4,500 1 year 38,300 18 years Total $ 179,552 The changes in the carrying amount of goodwill by segment for the fiscal years ended September 30, 2016 and 2017 were as follows (in thousands): Power & Control Airframe Non- aviation Total Balance at September 30, 2015 $ 2,238,443 $ 2,392,408 $ 55,369 $ 4,686,220 Goodwill acquired during the year (Note 2) 1,008,510 — — 1,008,510 Purchase price allocation adjustments 505 (792 ) — (287 ) Currency translation adjustment 32 (15,023 ) — (14,991 ) Balance at September 30, 2016 3,247,490 2,376,593 55,369 5,679,452 Goodwill acquired during the year (Note 2) 70,369 58,783 — 129,152 Write-down of discontinued operations (Note 22) — (32,000 ) — (32,000 ) Reclass of goodwill acquired to assets held-for-sale (Note 22) — (26,783 ) — (26,783 ) Purchase price allocation adjustments (9,972 ) — — (9,972 ) Currency translation adjustment — 5,489 — 5,489 Balance at September 30, 2017 $ 3,307,887 $ 2,382,082 $ 55,369 $ 5,745,338

ACCRUED LIABILITIES

ACCRUED LIABILITIES	12 Months Ended
	Sep. 30, 2017
Payables and Accruals [Abstract]
ACCRUED LIABILITIES	ACCRUED LIABILITIES Accrued liabilities consist of the following at September 30 (in thousands): 2017 2016 Compensation and related benefits $ 68,945 $ 69,323 Interest 82,222 83,180 Breeze-Eastern dissenting shares (see Note 2) — 33,644 Interest rate swap agreements 20,740 29,191 Product warranties 22,971 24,334 Dividend equivalent payments—current (see Note 17) 56,506 19,503 Other 84,504 84,937 Total $ 335,888 $ 344,112

DEBT

DEBT	12 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
DEBT	DEBT The Company’s debt consists of the following at September 30 (in thousands): 2017 Gross Amount Debt Issuance Costs Original Issue Discount or Premium Net Amount Short-term borrowings—trade receivable securitization facility $ 300,000 $ (413 ) $ — $ 299,587 Term loans $ 6,973,009 $ (64,104 ) $ (18,948 ) $ 6,889,957 2020 Notes 550,000 (3,243 ) — 546,757 2022 Notes 1,150,000 (6,941 ) — 1,143,059 2024 Notes 1,200,000 (8,042 ) — 1,191,958 2025 Notes 750,000 (4,033 ) 4,182 750,149 2026 Notes 950,000 (8,806 ) — 941,194 11,573,009 (95,169 ) (14,766 ) 11,463,074 Less current portion 70,031 (577 ) — 69,454 Long-term debt $ 11,502,978 $ (94,592 ) $ (14,766 ) $ 11,393,620 2016 Gross Amount Debt Issuance Costs Original Issue Discount or Premium Net Amount Short-term borrowings—trade receivable securitization facility $ 200,000 $ (229 ) $ — $ 199,771 Term loans $ 5,288,708 $ (42,662 ) $ (11,439 ) $ 5,234,607 2020 Notes 550,000 (4,299 ) — 545,701 2021 Notes 500,000 (3,141 ) — 496,859 2022 Notes 1,150,000 (8,381 ) — 1,141,619 2024 Notes 1,200,000 (9,218 ) — 1,190,782 2025 Notes 450,000 (4,144 ) — 445,856 2026 Notes 950,000 (9,588 ) — 940,412 10,088,708 (81,433 ) (11,439 ) 9,995,836 Less current portion 53,074 (429 ) — 52,645 Long-term debt $ 10,035,634 $ (81,004 ) $ (11,439 ) $ 9,943,191 Trade Receivable Securitization Facility During fiscal 2014, the Company established a trade receivable securitization facility (the “Securitization Facility”). The Securitization Facility effectively increases the Company’s borrowing capacity depending on the amount of the domestic operations’ trade accounts receivable. The Securitization Facility includes the right for the Company to exercise annual one year extensions as long as there have been no termination events as defined by the agreement. The Company uses the proceeds from the Securitization Facility as an alternative to other forms of debt, effectively reducing borrowing costs. In August 2017, the Company amended the Securitization Facility to increase the borrowing capacity to $300 million and extend the maturity date to August 1, 2018 . As of September 30, 2017 , the Company has borrowed $300 million under the Securitization Facility. The Securitization Facility is collateralized by substantially all of the Company’s domestic operations’ trade accounts receivable. Repurchase of Senior Subordinated Notes due 2021 On October 13, 2016, the Company announced a cash tender offer for any and all of its outstanding 2021 Notes. On October 27, 2016, the Company redeemed a principal amount of approximately $158 million in 2021 Notes outstanding for total consideration of $1,060.50 (plus accrued and unpaid interest) for each $1,000 aggregate principal amount. The total consideration included an early tender premium of $30.00 per $1,000 principal amount of 2021 Notes payable only with respect to each note validly tendered and not revoked on or before October 26, 2016. On November 28, 2016, pursuant to the terms of the indenture governing the 2021 Notes, the Company redeemed the remaining principal of $342 million in 2021 Notes outstanding at a redemption price of 105.625% of the principal amount (plus accrued and unpaid interest). The Company recorded refinancing costs of $31.9 million during the fiscal year ended September 30, 2017 representing debt issuance costs expensed in conjunction with the redemption of the 2021 Notes. The costs consisted of the premium of $28.8 million paid to redeem the $500 million of 2021 Notes and the write-off of $3.1 million in unamortized debt issuance costs. Incremental Term Loan Assumption Agreement On October 14, 2016, the Company entered into an Incremental Term Loan Assumption Agreement (the “Assumption Agreement”) with Credit Suisse AG, as administrative agent and collateral agent, and as a lender, in connection with the 2016 term loans. The Assumption Agreement, among other things, provides for (i) additional tranche F term loans in an aggregate principal amount equal to $650 million , which were fully drawn on October 14, 2016, and (ii) additional delayed draw tranche F term loans in an aggregate principal amount not to exceed $500 million , which were fully drawn on October 27, 2016, the proceeds of which were used to repurchase the Company's 2021 Notes. The terms and conditions that apply to the additional tranche F term loans and the additional delayed draw tranche F term loans are substantially the same as the terms and conditions that apply to the tranche F term loans under the 2016 term loans immediately prior to the Assumption Agreement. The Company capitalized $11.3 million and expensed $0.2 million in refinancing costs associated with the Assumption Agreement during the fiscal year ended September 30, 2017 . Issuance of Senior Subordinated Notes On March 1, 2017, TransDigm Inc. issued $300 million in aggregate principal amount of its 2025 Notes at an issue price of 101.5% of the principal amount. The new notes offered were an additional issuance to our existing $450 million of 2025 Notes. The new notes offered, together with the existing 2025 Notes, are treated as a single class for all purposes under the indenture. The 2025 Notes bear interest at the rate of 6.5% per annum, which accrues from November 15, 2016 and is payable semiannually in arrears on May 15 and November 15 of each year, commencing on May 15, 2017. The 2025 Notes mature on May 15, 2025, unless earlier redeemed or repurchased, and are subject to the terms and conditions set forth in the indentures governing the 2025 Notes. In addition to the premium of $4.5 million recorded upon the issuance of the additional $300 million of 2025 Notes, the Company capitalized $0.4 million and expensed $3.7 million in refinancing costs representing fees associated with the issuance of the additional $300 million of 2025 Notes during the fiscal year ended September 30, 2017 . Amendment No. 2 to the Second Amended and Restated Credit Agreement On March 6, 2017, TD Group and certain subsidiaries of TransDigm entered into Amendment No. 2 to the Second Amended and Restated Credit Agreement, dated June 4, 2014, with Credit Suisse AG, as administrative agent and collateral agent (the "Agent"), and the other agents and lenders named therein. Amendment No. 2 permits, among other things, up to $1.5 billion of dividends and share repurchases over twelve months. If any portion of the $1.5 billion is not used for dividends or share repurchases over the twelve month period, such amount (not to exceed $500 million ) may be used to repurchase stock at any time thereafter. Amendment No. 2 also increased the general investment basket to the greater of $400 million and 8% of consolidated total assets. The Company capitalized $10.3 million and expensed $0.3 million in refinancing costs representing fees associated with Amendment No. 2 during the fiscal year ended September 30, 2017 . Amendment No. 3 to the Second Amended and Restated Credit Agreement On August 22, 2017, the Company entered into Amendment No. 3 to the Second Amended and Restated Credit Agreement. Pursuant to Amendment No. 3, TransDigm, among other things, incurred new Tranche G Term Loans in an aggregate principal amount equal to approximately $1.8 billion and repaid in full all of the Tranche C term loans outstanding under the Credit Agreement. The Tranche G Term Loans were fully drawn on August 22, 2017. The Tranche G Term Loans mature on August 22, 2024. The terms and conditions (other than maturity date) that apply to the Tranche G Term Loans, including pricing, are substantially the same as the terms and conditions that apply to the Tranche C term loans immediately prior to Amendment No. 3. Amendment No. 3 also permitted (a) payment of a special dividend, share repurchase, or combination thereof, in an aggregate amount up to approximately $1.3 billion within 60 days of the effective date of Amendment No. 3, and (b) certain additional restricted payments, including the ability of the Company to declare or pay dividends or repurchase stock, in an aggregate amount not to exceed $1.5 billion within twelve months of the effective date of Amendment No. 3 and is subject to 6.0x consolidated net leverage ratio for dividends and 4.0x consolidated secured net debt ratio for share repurchases. If any portion of the $1.5 billion is not used for dividends or share repurchases over such twelve month period, such amount (not to exceed $500 million ) may be used to repurchase stock at any time thereafter. The Company capitalized $7.1 million representing fees associated with Amendment No. 3 during the fiscal year ended September 30, 2017 . The Company capitalized $16.5 million and expensed $2.2 million in refinancing costs representing debt issuances costs associated with the Tranche G Term Loans during the fiscal year ended September 30, 2017 . Additionally, the Company wrote-off $1.5 million in unamortized debt issuance costs related to the Tranche C Term Loans. Term Loans As of September 30, 2017 and 2016 , TransDigm had $6,973.0 million and $5,288.7 million in fully drawn term loans and $600.0 million in revolving commitments. The term loans consist of five tranches as follows (in millions): Term Loan Facility Maturity Date Interest Rate Aggregate Principal as of September 30, 2017 2016 Tranche C February 28, 2020 LIBO rate (1) + 3.00% $ — $ 1,228.3 Tranche D June 4, 2021 LIBO rate (1) + 3.00% $ 798.1 $ 806.4 Tranche E May 14, 2022 LIBO rate (1) + 3.00% $ 1,503.4 $ 1,518.0 Tranche F June 9, 2023 LIBO rate (1) + 3.00% $ 2,857.0 $ 1,736.0 Tranche G August 22, 2024 LIBO rate (1) + 3.00% $ 1,814.5 $ — The interest rates per annum applicable to all of the existing tranches of term loans are, at TransDigm’s option, equal to either an alternate base rate or an adjusted LIBO rate for one, two, three or six-month (or to the extent agreed to by each relevant lender, nine or twelve-month) interest periods chosen by TransDigm, in each case plus an applicable margin percentage. The adjusted LIBO rate is subject to a floor of 0.75% . At September 30, 2017 and 2016 , the applicable interest rates were as follows: Term Loan Facility Interest Rate as of September 30, 2017 2016 Tranche C — % 3.75 % Tranche D 4.24 % 3.75 % Tranche E 4.24 % 3.75 % Tranche F 4.24 % 3.75 % Tranche G 4.26 % — % Debt Issuance Costs, Premiums and Discounts During the year ended September 30, 2017 , the Company recorded refinancing costs of $39.8 million representing debt issuance costs and premium expensed in conjunction with the new Tranche G Term Loans, the refinancing of the Tranche C Term Loans, and additional $300 million tack-on to the 6.375% Senior Subordinated Notes. During the year ended September 30, 2016 , the Company recorded refinancing costs of $15.8 million representing debt issuance costs expensed in conjunction with the refinancing of the Tranche C Term Loans. During the year ended September 30, 2015 the Company recorded refinancing costs of $18.4 million representing debt issuance costs expensed in conjunction with the refinancing of the Tranche B Term Loans and Revolving B Commitments. Interest Rate Swap and Cap Agreements See Note 20, “Derivatives and Hedging Instruments” for information about how our interest rate swap and cap agreements are used to manage interest rate risk associated with floating-rate borrowings under our credit facilities. Senior Subordinated Notes Senior Subordinated Notes Aggregate Principal Maturity Date Interest Rate 2020 Notes $550 million October 15, 2020 5.50% 2022 Notes $1,150 million July 15, 2022 6.00% 2024 Notes $1,200 million July 15, 2024 6.50% 2025 Notes $750 million May 15, 2025 6.50% 2026 Notes $950 million June 15, 2026 6.375% The Notes are subordinated to all of TransDigm’s existing and future senior debt, rank equally with all of its existing and future senior subordinated debt and rank senior to all of its future debt that is expressly subordinated to the Notes. The Notes are guaranteed on a senior subordinated unsecured basis by TD Group and its 100% -owned domestic subsidiaries named in the indentures. The guarantees of the Notes are subordinated to all of the guarantors’ existing and future senior debt, rank equally with all of their existing and future senior subordinated debt and rank senior to all of their future debt that is expressly subordinated to the guarantees of the Notes. See Note 25, “Supplemental Guarantor Information,” for further details. The Notes are structurally subordinated to all of the liabilities of TD Group’s non-guarantor subsidiaries. The Notes contain many of the restrictive covenants included in the Restated Credit Agreement. TransDigm is in compliance with all the covenants contained in the Notes. At September 30, 2017 , future maturities of long-term debt are as follows (in thousands): Years ended September 30, 2018 $ 70,031 2019 70,031 2020 70,031 2021 1,385,219 2022 2,641,834 Thereafter 7,335,863 $ 11,573,009

RETIREMENT PLANS

RETIREMENT PLANS	12 Months Ended
	Sep. 30, 2017
Postemployment Benefits [Abstract]
RETIREMENT PLANS	RETIREMENT PLANS Defined Contribution Plans — The Company sponsors certain defined contribution employee savings plans that cover substantially all of the Company’s non-union employees. Under certain plans, the Company contributes a percentage of employee compensation and matches a portion of employee contributions. The cost recognized for such contributions for the years ended September 30, 2017 , 2016 and 2015 was approximately $14.6 million , $12.7 million and $9.9 million , respectively. Defined Benefit Pension Plans — The Company maintains certain non-contributory defined benefit pension plans. The Company’s funding policy is to contribute actuarially determined amounts allowable under tax and statutory regulations for the qualified plans. The Company uses a September 30th measurement date for its defined benefit pension plans. The Company maintains certain qualified, non-contributory defined benefit pension plans, which together cover certain union employees. The plans provide benefits of stated amounts for each year of service. The plan assets as of September 30, 2017 and 2016 were approximately $69.9 million and $67.0 million , respectively. The Company’s projected benefit obligation for these defined benefit pension plans at September 30, 2017 and 2016 was $91.7 million and $100.6 million , respectively. The total liability recognized at September 30, 2017 and 2016 was $21.8 million and $33.6 million , respectively. The decrease in the total liability at September 30, 2017 compared to September 30, 2016 is primarily attributable to the change in pension assumptions, particularly a higher discount rate and expected rate of return on assets, for the AmSafe Bridport Limited pension plan. The net periodic pension cost recognized in the consolidated statements of income for the years ended September 30, 2017 , 2016 , and 2015 was $1.7 million , $1.0 million , and $0.6 million , respectively. The Company has a non-qualified, non-contributory defined benefit pension plan, which covers certain retired employees. The plan is unfunded and provides defined benefits based on the final average salary of the employees as defined in the plan. The projected benefit obligation for this defined benefit pension plan and the total liability recognized in the Consolidated Balance Sheet at September 30, 2017 and 2016 was approximately $8.8 million and $8.6 million , respectively. The net periodic pension cost recognized in the consolidated statements of income for each of the years ended September 30, 2017 , 2016 and 2015 was $0.4 million .

INCOME TAXES

INCOME TAXES	12 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company’s income tax provision on income from continuing operations consists of the following for the periods shown below (in thousands): Fiscal Years Ended September 30, 2017 2016 2015 Current Federal $ 179,884 $ 153,957 $ 163,182 State 8,596 9,234 7,823 Foreign 21,327 12,703 17,947 209,807 175,894 188,952 Deferred (918 ) 5,808 660 $ 208,889 $ 181,702 $ 189,612 The differences between the income tax provision on income from continuing operations at the federal statutory income tax rate and the tax provision shown in the accompanying consolidated statements of income for the periods shown below are as follows (in thousands): Fiscal Years Ended September 30, 2017 2016 2015 Tax at statutory rate of 35% $ 293,129 $ 268,841 $ 222,888 State and local income taxes, net of federal benefit 4,042 2,677 4,931 Stock compensation (50,314 ) (43,565 ) — Foreign rate differential (29,685 ) (30,079 ) (14,332 ) Domestic manufacturing deduction (17,832 ) (16,902 ) (17,834 ) Other—net 9,549 730 (6,041 ) Income tax provision $ 208,889 $ 181,702 $ 189,612 The components of the deferred taxes consist of the following at September 30 (in thousands): 2017 2016 Deferred tax liabilities: Intangible assets $ (647,140 ) $ (627,633 ) Property, plant and equipment (29,240 ) (31,438 ) Unremitted foreign earnings (10,784 ) (9,434 ) Employee benefits, compensation and other accrued obligations 107,195 86,229 Inventory 31,077 22,382 Net operating losses 33,462 29,266 Interest rate swaps and caps 15,961 36,478 Environmental 15,518 16,958 Product warranties 7,419 9,007 Other 8,797 3,216 Total (467,735 ) (464,969 ) Add: Valuation allowance (33,214 ) (27,286 ) Total net deferred tax liabilities $ (500,949 ) $ (492,255 ) At September 30, 2017 , the Company has United Kingdom net operating loss carryforwards of approximately $23.3 million , German net operating loss carryforwards of approximately $4.3 million and state net operating loss carryforwards of approximately $819.5 million that expire in various years from 2017 to 2034 . A valuation allowance has been established equal to the amount of the net operating losses that the Company believes will not be utilized. The Company had state tax credit carryforwards of $2.6 million that expire from 2023 to 2029 . The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction and various state and local jurisdictions, as well as foreign jurisdictions located in Belgium, Canada, China, France, Germany, Hong Kong, Hungary, Malaysia, Mexico, Norway, Singapore, Sri Lanka, Sweden and the United Kingdom. The Company is no longer subject to U.S. federal examinations for years before fiscal 2014. The Company is currently under examination in the U.S. for its fiscal 2014 federal taxes. The Company expects the examinations to be completed during fiscal 2018. In addition, the Company is subject to state income tax examinations for fiscal years 2009 and later. The cumulative amount of the Company’s foreign undistributed net earnings for which no deferred taxes have been provided is approximately $176.0 million at September 30, 2017 . The Company has no plans to repatriate such earnings in the foreseeable future. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): 2017 2016 Balance at beginning of period $ 8,706 $ 6,859 Additions based on tax positions related to the prior year 500 2,014 Additions based on tax positions related to the current year 1,643 913 Reductions based on tax positions related to the prior year (963 ) (801 ) Lapse in statute of limitations (1,231 ) (1,483 ) Acquisitions — 1,204 Balance at end of period $ 8,655 $ 8,706 Unrecognized tax benefits at September 30, 2017 and 2016 , the recognition of which would have an effect on the effective tax rate for each fiscal year, amounted to $8.7 million in each period. The Company classifies all income tax related interest and penalties as income tax expense, which were not significant for the years ended September 30, 2017 , 2016 and 2015 . As of September 30, 2017 and 2016 , the Company accrued $1.2 million and $1.1 million , respectively, for the potential payment of interest and penalties. The Company anticipates no significant changes to its total unrecognized tax benefits through fiscal 2017 .

ENVIRONMENTAL LIABILITIES

ENVIRONMENTAL LIABILITIES	12 Months Ended
	Sep. 30, 2017
Environmental Remediation Obligations [Abstract]
ENVIRONMENTAL LIABILITIES	ENVIRONMENTAL LIABILITIES Our operations and facilities are subject to a number of federal, state, local and foreign environmental laws and regulations that govern, among other things, discharges of pollutants into the air and water, the generation, handling, storage and disposal of hazardous materials and wastes, the remediation of contamination and the health and safety of our employees. Environmental laws and regulations may require that the Company investigate and remediate the effects of the release or disposal of materials at sites associated with past and present operations. Certain facilities and third-party sites utilized by the Company have been identified as potentially responsible parties under the federal superfund laws and comparable state laws. The Company is currently involved in the investigation and remediation of a number of sites under applicable laws. Estimates of the Company’s environmental liabilities are based on current facts, laws, regulations and technology. These estimates take into consideration the Company’s prior experience and professional judgment of the Company’s environmental advisors. Estimates of the Company’s environmental liabilities are further subject to uncertainties regarding the nature and extent of site contamination, the range of remediation alternatives available, evolving remediation standards, imprecise engineering evaluations and cost estimates, the extent of corrective actions that may be required and the number and financial condition of other potentially responsible parties, as well as the extent of their responsibility for the remediation. Accordingly, as investigation and remediation proceed, it is likely that adjustments in the Company’s accruals will be necessary to reflect new information. The amounts of any such adjustments could have a material adverse effect on the Company’s results of operations or cash flows in a given period. Based on currently available information, however, the Company does not believe that future environmental costs in excess of those accrued with respect to sites for which the Company has been identified as a potentially responsible party are likely to have a material adverse effect on the Company’s financial condition. Environmental liabilities are recorded when the liability is probable and the costs are reasonably estimable, which generally is not later than at completion of a feasibility study or when the Company has recommended a remedy or has committed to an appropriate plan of action. The Company also takes into consideration the estimated period of time in which payments will be required. The liabilities are reviewed periodically and, as investigation and remediation proceed, adjustments are made as necessary. Liabilities for losses from environmental remediation obligations do not consider the effects of inflation and anticipated expenditures are not discounted to their present value. The liabilities are not offset by possible recoveries from insurance carriers or other third parties, but do reflect anticipated allocations among potentially responsible parties at federal superfund sites or similar state-managed sites, third party indemnity obligations, and an assessment of the likelihood that such parties will fulfill their obligations at such sites. The Company’s consolidated balance sheets includes environmental remediation obligations at September 30, 2017 and 2016 of $39.9 million and $46.1 million , respectively.

CAPITAL STOCK

CAPITAL STOCK	12 Months Ended
	Sep. 30, 2017
Equity [Abstract]
CAPITAL STOCK	CAPITAL STOCK TD Group consists of 224,400,000 shares of $.01 par value common stock and 149,600,000 shares of $.01 par value preferred stock. The total number of shares of common stock issued at September 30, 2017 and 2016 was 56,093,659 and 55,767,767 , respectively. The total number of shares held in treasury at September 30, 2017 and 2016 were 4,159,207 and 2,433,035 , respectively. There were no shares of preferred stock outstanding at September 30, 2017 and 2016 . The terms of the preferred stock have not been established. The Board of Directors has previously authorized a common share repurchase program, which has been subject to amendments. On January 26, 2017, our Board of Directors increased the authorized amount of repurchases allowable under the stock program from $450 million to $472 million . The increase in the allowable repurchases under the stock repurchase program aligned the program with the restricted payments allowable under the Credit Agreement. On March 7, 2017, our Board of Directors authorized a new stock repurchase program replacing the $472 million program permitting repurchases of a portion of outstanding shares not to exceed $600 million in the aggregate, subject to any restrictions specified in the Credit Agreement and/or Indentures governing the existing Notes. During the fiscal year ended September 30, 2017, in the aggregate, the Company repurchased 1,723,624 shares at a cost of $389.8 million at the weighted average cost of $226.16 under its stock repurchase programs. As of September 30, 2017, the remaining amount of repurchases allowable under the $600 million program was $360.2 million subject to any restrictions specified in the Credit Agreement and/or Indentures governing the existing Notes. On November 8, 2017, o ur Board of Directors, authorized a new stock repurchase program replacing the $600 million program permitting repurchases of our outstanding shares not to exceed $650 million in the aggregate, subject to any restrictions specified in the Credit Agreement and/or Indentures governing the existing Notes.

SEGMENTS

SEGMENTS	12 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
SEGMENTS	SEGMENTS The Company’s businesses are organized and managed in three reporting segments: Power & Control, Airframe and Non-aviation. The Power & Control segment includes operations that primarily develop, produce and market systems and components that predominately provide power to or control power of the aircraft utilizing electronic, fluid, power and mechanical motion control technologies. Major product offerings include mechanical/electro-mechanical actuators and controls, ignition systems and engine technology, specialized pumps and valves, power conditioning devices, specialized AC/DC electric motors and generators, databus and power controls, high performance hoists, winches and lifting devices and cargo loading and handling systems. Primary customers of this segment are engine and power system and subsystem suppliers, airlines, third party maintenance suppliers, military buying agencies and repair depots. Products are sold in the original equipment and aftermarket market channels. The Airframe segment includes operations that primarily develop, produce and market systems and components that are used in non-power airframe applications utilizing airframe and cabin structure technologies. Major product offerings include engineered latching and locking devices, rods and locking devices, engineered connectors and elastomers, cockpit security components and systems, aircraft audio systems, specialized lavatory components, seat belts and safety restraints, engineered interior surfaces and related components, lighting and control technology, military personnel parachutes and cargo delivery systems. Primary customers of this segment are airframe manufacturers and cabin system suppliers and subsystem suppliers, airlines, third party maintenance suppliers, military buying agencies and repair depots. Products are sold in the original equipment and aftermarket market channels. The Non-aviation segment includes operations that primarily develop, produce and market products for non-aviation markets. Major product offerings include seat belts and safety restraints for ground transportation applications, mechanical/electro-mechanical actuators and controls for space applications, and refueling systems for heavy equipment used in mining, construction and other industries. Primary customers of this segment are off-road vehicle suppliers and subsystem suppliers, child restraint system suppliers, satellite and space system suppliers and manufacturers of heavy equipment used in mining, construction and other industries. The primary measurement used by management to review and assess the operating performance of each segment is EBITDA As Defined. The Company defines EBITDA As Defined as earnings before interest, taxes, depreciation and amortization plus certain non-operating items recorded as corporate expenses including refinancing costs, acquisition-related costs, transaction-related costs and non-cash compensation charges incurred in connection with the Company’s stock option plans. Acquisition-related costs represent accounting adjustments to inventory associated with acquisitions of businesses and product lines that were charged to cost of sales when the inventory was sold; costs incurred to integrate acquired businesses and product lines into the Company’s operations, facility relocation costs and other acquisition-related costs; transaction related costs comprising deal fees; legal, financial and tax diligence expenses and valuation costs that are required to be expensed as incurred and other acquisition accounting adjustments. EBITDA As Defined is not a measurement of financial performance under GAAP. Although the Company uses EBITDA As Defined to assess the performance of its business and for various other purposes, the use of this non-GAAP financial measure as an analytical tool has limitations, and it should not be considered in isolation or as a substitute for analysis of the Company’s results of operations as reported in accordance with GAAP. The Company’s segments are reported on the same basis used internally for evaluating performance and for allocating resources. The accounting policies for each segment are the same as those described in the summary of significant accounting policies in the Company’s consolidated financial statements. Intersegment sales and transfers are recorded at values based on market prices, which creates intercompany profit on intersegment sales or transfers that is eliminated in consolidation. Intersegment sales were insignificant for the periods presented below. Certain corporate-level expenses are allocated to the operating segments. The following table presents net sales by reportable segment (in thousands): Fiscal Years Ended September 30, 2017 2016 2015 Net sales to external customers Power & Control $ 1,948,166 $ 1,621,741 $ 1,330,135 Airframe 1,442,073 1,447,894 1,280,706 Non-aviation 114,047 101,776 96,274 $ 3,504,286 $ 3,171,411 $ 2,707,115 The following table reconciles EBITDA As Defined by segment to consolidated income from continuing operations before income taxes (in thousands): Fiscal Years Ended September 30, 2017 2016 2015 EBITDA As Defined Power & Control $ 981,041 $ 787,418 $ 653,050 Airframe 726,619 709,858 585,472 Non-aviation 41,460 28,228 22,406 Total segment EBITDA As Defined 1,749,120 1,525,504 1,260,928 Unallocated corporate expenses 38,557 30,308 27,274 Total Company EBITDA As Defined 1,710,563 1,495,196 1,233,654 Depreciation and amortization 141,025 121,670 93,663 Interest expense, net 602,589 483,850 418,785 Acquisition-related costs 31,191 57,699 36,205 Stock compensation expense 45,524 48,306 31,500 Refinancing costs 39,807 15,794 18,393 Other, net 12,997 (239 ) (1,716 ) Income from continuing operations before income taxes $ 837,430 $ 768,116 $ 636,824 The following table presents capital expenditures and depreciation and amortization by segment (in thousands): Fiscal Years Ended September 30, 2017 2016 2015 Capital expenditures Power & Control $ 32,424 $ 25,120 $ 24,664 Airframe 34,526 16,498 28,086 Non-aviation 3,981 2,169 1,889 Corporate 82 195 232 $ 71,013 $ 43,982 $ 54,871 Depreciation and amortization Power & Control $ 85,681 $ 65,488 $ 39,336 Airframe 51,440 52,198 50,355 Non-aviation 2,745 2,860 2,846 Corporate 1,159 1,124 1,126 $ 141,025 $ 121,670 $ 93,663 The following table presents total assets by segment (in thousands): September 30, 2017 September 30, 2016 Total assets Power & Control $ 5,218,006 $ 5,184,303 Airframe 3,923,172 3,922,532 Non-aviation 142,389 131,319 Corporate 614,594 1,488,123 Assets of discontinued operations 77,500 — $ 9,975,661 $ 10,726,277 The Company’s sales principally originate from the United States, and the Company’s long-lived assets are principally located in the United States.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION The Company’s stock compensation plans are designed to assist the Company in attracting, retaining, motivating and rewarding key employees, directors or consultants, and promoting the creation of long-term value for stockholders by closely aligning the interests of these individuals with those of the Company’s stockholders. The Company’s stock compensation plans provide for the granting of stock options, restricted stock and other stock-based incentives. Non-cash stock compensation expense recognized by the Company during the years ended September 30, 2017 , 2016 and 2015 was $45.5 million , $48.3 million and $31.5 million , respectively. The weighted-average grant date fair value of options granted during the fiscal years ended September 30, 2017 , 2016 and 2015 was $67.11 , $57.47 and $65.57 , respectively. Compensation expense is recognized based upon probability assessments of awards that are expected to vest in future periods. Such probability assessments are subject to revision and, therefore, unrecognized compensation expense is subject to future changes in estimate. As of September 30, 2017 , there was approximately $52.4 million of total unrecognized compensation expense related to non-vested awards expected to vest, which is expected to be recognized over a weighted-average period of 2.6 years . The fair value of the Company’s employee stock options was estimated at the date of grant using a Black-Scholes-Merton option-pricing model with the following weighted average assumptions for all options granted during the fiscal years ended: Fiscal Years Ended September 30, 2017 2016 2015 Risk-free interest rate 1.56% to 2.01% 1.33% to 1.73% 1.33% to 1.64% Expected life of options 5 years 5 years 5 years Expected dividend yield of stock — — — Expected volatility of stock 25% 25% 35% The risk-free interest rate is based upon the Treasury bond rates as of the grant date. The average expected life of stock-based awards is based on the Company’s actual historical exercise experience. Expected volatility of stock was calculated using a rate based upon the historical volatility of TransDigm’s common stock. Notwithstanding the special cash dividends declared and paid from time to time, the Company historically has not declared and paid regular cash dividends and does not anticipate declaring and paying regular cash dividends in future periods; thus, no dividend rate assumption is used. The total fair value of options vested during fiscal years ended September 30, 2017 , 2016 and 2015 was $42.9 million , $36.6 million and $14.9 million , respectively. 2014 Stock Option Plan In July 2014, the Board of Directors of TD Group adopted a new stock option plan, which was subsequently approved by stockholders on October 2, 2014. The 2014 stock option plan permits TD Group to award our key employees, directors or consultants stock options. The total number of shares of TD Group common stock reserved for issuance or delivery under the 2014 stock option plan is 5,000,000 , subject to adjustment in the event of any stock dividend or split, reorganization, recapitalization, merger, share exchange or any other similar corporate transaction or event. Performance Vested Stock Options —All of the options granted through September 30, 2017 under the 2014 stock option plan have been pursuant to an equity incentive program adopted by the Company in 2008. Under the 2008 equity incentive program, all of the options granted will vest based on the Company’s achievement of established operating performance goals. The following table summarizes the activity, pricing and other information for the Company’s performance vested stock-based award activity during the fiscal year ended September 30, 2017 : Number of Options Weighted-Average Exercise Price Per Option Weighted-Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at September 30, 2016 147,935 $ 228.73 Granted 738,974 266.18 Exercised (930 ) 231.16 Forfeited (23,280 ) 251.79 Expired (640 ) 232.64 Outstanding at September 30, 2017 862,059 $ 260.20 9.0 years $ (3,925,661 ) Expected to vest 397,725 $ 260.33 9.0 years $ (1,861,447 ) Exercisable at September 30, 2017 122,975 $ 246.01 8.8 years $ 1,186,026 At September 30, 2017 , there were 4,137,011 remaining shares available for award under TD Group’s 2014 stock option plan. 2006 Stock Incentive Plan In conjunction with the consummation of the Company’s initial public offering, a 2006 stock incentive plan was adopted by TD Group. In July 2008 and March 2011, the plan was amended to increase the number of shares available for issuance thereunder. TD Group reserved 8,119,668 shares of its common stock for issuance to key employees, directors or consultants under the plan. Awards under the plan may be in the form of options, restricted stock or other stock-based awards. Options granted under the plan will expire no later than the tenth anniversary of the applicable date of grant of the options, and will have an exercise price of not less than the fair market value of our common stock on the date of grant. Restricted stock granted under the plan vests over three years . Restricted Stock —The Company granted 17,700 restricted stock units with a weighted-average grant date fair value of $189.97 during the fiscal year ended September 30, 2015. During the fiscal year ended September 30, 2017 , 5,900 restricted stock units vested, and 5,900 restricted stock units were outstanding at September 30, 2017 . Performance Vested Stock Options —All of the options granted under the 2006 stock incentive plan have been pursuant to an equity incentive program adopted by the Company in 2008. Under the 2008 equity incentive program, all of the options granted will vest based on the Company’s achievement of established operating performance goals. The following table summarizes the activity, pricing and other information for the Company’s performance vested stock-based award activity during the fiscal year ended September 30, 2017 : Number of Options Weighted-Average Exercise Price Per Option Weighted-Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at September 30, 2016 5,239,871 $ 133.20 Granted — — Exercised (315,478 ) 66.67 Forfeited (138,179 ) 188.90 Expired (100 ) 226.34 Outstanding at September 30, 2017 4,786,114 $ 135.95 5.2 years $ 572,875,252 Expected to vest 1,052,250 $ 200.32 7.4 years $ 58,217,596 Exercisable at September 30, 2017 3,464,551 $ 110.36 4.3 years $ 503,350,041 The 2006 stock incentive plan expired on March 14, 2016 and no further shares were granted under the plan thereafter. 2003 Stock Option Plan Certain executives and key employees of the Company were granted stock options under TD Group’s 2003 stock option plan. Upon the closing of the acquisition of the Company by Warburg Pincus in 2003, certain employees rolled over certain then-existing options to purchase shares of common stock of TransDigm Holdings. These employees were granted rollover options to purchase an aggregate of 3,870,152 shares of common stock of TD Group (after giving effect to the 149.60 for 1.00 stock split effected on March 14, 2006) . All rollover options granted were fully vested on the date of grant. In addition to shares of common stock reserved for issuance upon the exercise of rollover options, an aggregate of 5,469,301 shares of TD Group’s common stock were reserved for issuance upon the exercise of new management options. In general, approximately 20% of all new management options vested based on employment service or a change in control. These time vested options had a graded vesting schedule of up to four years . Approximately 80% of all new management options vested (i) based upon the satisfaction of specified performance criteria, which is annual and cumulative EBITDA As Defined targets through 2008, or (ii) upon the occurrence of a change in control if the Investor Group (defined as Warburg Pincus and the other initial investors in TD Group) received a minimum specified rate of return. Unless terminated earlier, the options expire ten years from the date of grant. TD Group reserved a total of 9,339,453 shares of its common stock for issuance to the Company’s employees under the plan, which had all been issued as of September 30, 2013. Time Vested Stock Options —During the fiscal year ended September 30, 2016, 5,486 of the Company’s time vested stock-based options, with a weighted-average exercise price per option of $39.88 , were exercised. There were no remaining options outstanding as of September 30, 2016. Performance Vested Stock Options —The following table summarizes the activity, pricing and other information for the Company’s performance vested stock-based award activity during the fiscal year ended September 30, 2017 : Number of Options Weighted-Average Exercise Price Per Option Weighted-Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at September 30, 2016 86,329 $ 120.72 Granted — — Exercised (8,500 ) 34.88 Outstanding at September 30, 2017 77,829 $ 130.09 5.1 years $ 9,772,209 Exercisable at September 30, 2017 77,829 $ 130.09 5.1 years $ 9,772,209 The total intrinsic value of time, performance and rollover options exercised during the fiscal years ended September 30, 2017 , 2016 and 2015 was $61.1 million , $133.2 million and $206.9 million , respectively. In addition to shares issued pursuant to options exercised, during the fiscal year ended September 30, 2017 , 984 shares of common stock were issued with a weighted-average grant date fair value of $243.36 as payment to directors in lieu of cash. Dividend Equivalent Plans Pursuant to the Third Amended and Restated TransDigm Group Incorporated 2003 Stock Option Plan Dividend Equivalent Plan, the Second Amended and Restated TransDigm Group Incorporated 2006 Stock Incentive Plan Dividend Equivalent Plan and the 2014 Stock Option Plan Dividend Equivalent Plan, all of the options granted under the 2003 stock option plan, the 2006 stock incentive plan and the 2014 stock option plan are entitled to certain dividend equivalent payments in the event of the declaration of a dividend by the Company. Dividend equivalent payments on vested options were $19.5 million , $3.0 million and $3.4 million during the years ended September 30, 2017 , 2016 and 2015 , respectively. During the first quarter of 2017, in connection with the special dividend declared in October 2016, we paid $1,280.1 million for the special dividend and $76.4 million for the related dividend equivalent payments. During the fourth quarter of 2017, in connection with the special dividend declared in August 2017, we paid $1,142.2 million for the special dividend and $63.3 million for the related dividend equivalent payments. At September 30, 2017, there was $56.5 million recorded in accrued liabilities and $39.4 million accrued in other non-current liabilities on the consolidated balance sheets related to the future dividend equivalent payments.

LEASES

LEASES	12 Months Ended
	Sep. 30, 2017
Leases [Abstract]
LEASES	LEASES TransDigm leases certain manufacturing facilities, offices, equipment and vehicles. Such leases, some of which are noncancelable and, in many cases, include renewals, expire at various dates. Rental expense during the years ended September 30, 2017 , 2016 and 2015 was $19.0 million , $18.3 million and $14.0 million , respectively. Future minimum rental commitments at September 30, 2017 under operating leases having initial or remaining non-cancelable lease terms exceeding one year are $18.0 million in fiscal 2018 , $17.5 million in fiscal 2019 , $14.6 million in fiscal 2020 , $12.6 million in fiscal 2021 , $11.5 million in fiscal 2022 , and $33.6 million thereafter.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The following tables present our assets and liabilities that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy. The fair value hierarchy has three levels based on the reliability of the inputs used to determine fair value. Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and inputs (other than quoted prices) that are observable for the asset or liability, either directly or indirectly. Level 3 inputs are unobservable inputs for the asset or liability. A financial asset or liability’s classification within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement. The following summarizes the carrying amounts and fair values of financial instruments (in thousands): September 30, 2017 September 30, 2016 Level Carrying Amount Fair Value Carrying Amount Fair Value Assets: Cash and cash equivalents 1 $ 650,561 $ 650,561 $ 1,586,994 $ 1,586,994 Interest rate cap agreements (1) 2 12,904 12,904 4,232 4,232 Interest rate swap agreements (1) 2 2,905 2,905 — — — Liabilities: Interest rate swap agreements (2) 2 20,740 20,740 29,191 29,191 Interest rate swap agreements (3) 2 9,731 9,731 53,824 53,824 Short-term borrowings - trade receivable securitization facility (4) 1 299,587 299,587 199,771 199,771 Long-term debt, including current portion: Term loans (4) 2 6,889,957 6,965,628 5,234,607 5,284,037 2020 Notes (4) 1 546,757 558,250 545,701 566,500 2021 Notes (4) 1 — — 496,859 530,000 2022 Notes (4) 1 1,143,059 1,178,750 1,141,619 1,214,688 2024 Notes (4) 1 1,191,958 1,236,000 1,190,782 1,266,000 2025 Notes (4) 1 750,149 776,807 445,856 469,125 2026 Notes (4) 1 941,194 971,375 940,412 985,625 (1) Included in other non-current assets on the consolidated balance sheet. (2) Included in accrued liabilities on the consolidated balance sheet. (3) Included in other non-current liabilities on the consolidated balance sheet. (4) The carrying amount of the debt instrument is presented net of the debt issuance costs. The Company values its financial instruments using an industry standard market approach, in which prices and other relevant information is generated by market transactions involving identical or comparable assets or liabilities. No financial instruments were recognized using unobservable inputs. Interest rate swaps were measured at fair value using quoted market prices for the swap interest rate indexes over the term of the swap discounted to present value versus the fixed rate of the contract. The interest rate caps were measured at fair value using implied volatility rates of each individual caplet and the yield curve for the related periods. The estimated fair value of the Company’s term loans was based on information provided by the agent under the Company’s senior secured credit facility. The estimated fair values of the Company’s notes were based upon quoted market prices. There has not been any impact to the fair value of derivative liabilities due to the Company’s own credit risk. Similarly, there has not been any impact to the fair value of derivative assets based on the Company’s evaluation of counterparties’ credit risks. The fair value of cash and cash equivalents, trade accounts receivable-net and accounts payable approximated book value due to the short-term nature of these instruments at September 30, 2017 and 2016 .

DERIVATIVES AND HEDGING ACTIVIT

DERIVATIVES AND HEDGING ACTIVITIES	12 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVES AND HEDGING ACTIVITIES	DERIVATIVES AND HEDGING ACTIVITIES The Company is exposed to, among other things, the impact of changes in interest rates in the normal course of business. The Company’s risk management program is designed to manage the exposure and volatility arising from these risks, and utilizes derivative financial instruments to offset a portion of these risks. The Company uses derivative financial instruments only to the extent necessary to hedge identified business risks and does not enter into such transactions for trading purposes. The Company generally does not require collateral or other security with counterparties to these financial instruments and is therefore subject to credit risk in the event of nonperformance; however, the Company monitors credit risk and currently does not anticipate nonperformance by other parties. The Company has agreements with each of its swap and cap counterparties that contain a provision whereby if the Company defaults on the credit facility the Company could also be declared in default on its swaps and caps, resulting in an acceleration of payment under the swaps and caps. Interest rate swap and cap agreements are used to manage interest rate risk associated with floating-rate borrowings under our credit facility. The interest rate swap and cap agreements utilized by the Company effectively modify the Company’s exposure to interest rate risk by converting a portion of the Company’s floating-rate debt to a fixed rate basis through the expiration date of the interest rate swap and cap agreements, thereby reducing the impact of interest rate changes on future interest expense. These agreements involve the receipt of floating rate amounts in exchange for fixed rate interest payments over the term of the agreements without an exchange of the underlying principal amount. These derivative instruments qualify as effective cash flow hedges under GAAP. For these cash flow hedges, the effective portion of the gain or loss from the financial instruments was initially reported as a component of accumulated other comprehensive loss in stockholders’ deficit and subsequently reclassified into earnings in the same line as the hedged item in the same period or periods during which the hedged item affected earnings. The following table summarizes the Company’s interest rate swap agreements: Aggregate Notional Amount (in millions) Start Date End Date Related Debt Conversion of Related Variable Rate Debt to Fixed Rate of: $1,000 9/30/2014 6/30/2019 Tranche G Term Loans 5.4% (2.4% plus the 3% margin percentage) $400 9/30/2017 9/30/2022 Tranche G Term Loans 4.9% (1.9% plus the 3% margin percentage) $750 6/30/2020 6/30/2022 Tranche F Term Loans 5.5% (2.5% plus the 3% margin percentage) $500 12/30/2016 12/31/2021 Tranche F Term Loans 4.9% (1.9% plus the 3% margin percentage) $1,000 6/28/2019 6/30/2021 Tranche F Term Loans 4.8% (1.8% plus the 3% margin percentage) $750 3/31/2016 6/30/2020 Tranche D Term Loans 5.8% (2.8% plus the 3% margin percentage) The following table summarizes the Company’s interest rate cap agreements: Aggregate Notional Amount Start Date End Date Related Debt Offsets Variable Rate Debt Attributable to Fluctuations Above: $750 6/30/2020 6/30/2022 Tranche F Term Loans Three month LIBO rate of 2.5% $400 12/30/2016 12/31/2021 Tranche F Term Loans Three month LIBO rate of 2.5% $400 6/30/2016 6/30/2021 Tranche F Term Loans Three month LIBO rate of 2.0% $750 9/30/2015 6/30/2020 Tranche E Term Loans Three month LIBO rate of 2.5% All interest rate swap and cap agreements are recognized in our consolidated balance sheets at fair value. In accordance with GAAP, certain derivative asset and liability balances are offset where master netting agreements provide for the legal right of setoff. For classification purposes, we record the net fair value of each type of derivative position that is expected to settle in less than one year with each counterparty as a net current asset or liability and each type of long-term position as a net long-term asset or liability. The amounts shown in the table below represent the gross amounts of recognized assets and liabilities, the amounts offset in the consolidated balance sheet and the net amounts of assets and liabilities presented therein. September 30, 2017 September 30, 2016 Asset Liability Asset Liability Interest rate cap agreements $ 12,904 $ — $ 4,232 $ — Interest rate swap agreements 9,235 (36,801 ) — (83,015 ) Total 22,139 (36,801 ) 4,232 (83,015 ) Effect of counterparty netting (6,330 ) 6,330 — — Net derivatives as classified in the balance sheet (1) $ 15,809 $ (30,471 ) $ 4,232 $ (83,015 ) (1) Refer to Note 19, "Fair Value Measurements," for the consolidated balance sheet classification of our interest rate swap and cap agreements. In connection with the refinancing of the 2011 Term Loans, the Company no longer designated the interest rate swap agreements relating to the $353 million aggregate notional amount as cash flow hedges for accounting purposes. Accordingly, amounts previously recorded as a component of accumulated other comprehensive loss in stockholder’s deficit amortized into earnings totaled $3.2 million for the fiscal year ended September 30, 2015. There was no remaining amortization for these dedesignated swap agreements as of September 30, 2015. Based on the fair value amounts of the interest rate swap and cap agreements determined as of September 30, 2017 , the estimated net amount of existing gains and losses and caplet amortization expected to be reclassified into interest expense within the next twelve months is approximately $24.9 million . Effective September 30, 2016, the Company redesignated the interest rate cap agreements related to the $400 million and the $750 million aggregate notional amount with cap rates of 2.0% and 2.5% , respectively, based on the expected probable cash flows associated with the 2016 term loans and 2015 term loans in consideration of the Company’s ability to select one-month, two-month, three-month, or six-month LIBO rate set forth in the Credit Agreement. Accordingly, amounts previously recorded as a component of accumulated other comprehensive loss in stockholder’s deficit amortized into interest expense was $3.8 million for the fiscal year ended September 30, 2017. The accumulated other comprehensive loss to be reclassified into interest expense over the remaining term of the cap agreements is $10.8 million with a related tax benefit of $4.0 million as of September 30, 2017. The amount recorded as a component of accumulated other comprehensive loss in stockholders’ deficit related to these redesignated interest rate cap hedges as of September 30, 2016 was approximately $14.6 million with a related tax benefit of $5.5 million .

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE LOSS	12 Months Ended
	Sep. 30, 2017
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	ACCUMULATED OTHER COMPREHENSIVE LOSS The following table presents the components of “Accumulated other comprehensive loss” (“AOCI”) in the consolidated balance sheets, net of taxes, for the years ended September 30, 2017 , 2016 and 2015 (in thousands): Unrealized (loss) gain on derivatives designated and qualifying as cash flow hedges (2) Defined benefit pension plan activity (3) Currency translation adjustment Total Balance at September 30, 2015 $ (51,492 ) $ (12,013 ) $ (32,504 ) $ (96,009 ) Other comprehensive loss before reclassification (9,664 ) (12,284 ) (31,846 ) (53,794 ) Amounts reclassified from AOCI related to interest rate swap agreements (1) 16 — — 16 Net current-period other comprehensive loss $ (9,648 ) $ (12,284 ) $ (31,846 ) $ (53,778 ) Balance at September 30, 2016 $ (61,140 ) $ (24,297 ) $ (64,350 ) $ (149,787 ) Other comprehensive gain before reclassification 32,072 7,932 22,241 62,245 Amounts reclassified from AOCI related to interest rate swap agreements (1) 2,399 — — 2,399 Net current-period other comprehensive gain $ 34,471 $ 7,932 $ 22,241 $ 64,644 Balance at September 30, 2017 $ (26,669 ) $ (16,365 ) $ (42,109 ) $ (85,143 ) (1) This component of AOCI is included in interest expense (see Note 20, “Derivatives and Hedging Activities,” for additional details). (2) Unrealized (loss) gain represents interest rate swap and cap agreements, net of taxes of $(20,663) , $6,868 and $20,716 for the years ended September 30, 2017 , 2016 and 2015 , respectively. (3) Defined benefit pension plan activity represent pension liability adjustments, net of taxes of $(4,130) , $6,017 and $3,299 , respectively. A summary of reclassifications out of accumulated other comprehensive loss for or the years ended September 30, 2017 is provided below (in thousands): Description of reclassifications out of accumulated other comprehensive loss Amount reclassified Amortization from redesignated interest rate cap agreements (1) $ 3,829 Deferred tax benefit from redesignated interest rate cap agreements (1,430 ) Losses reclassified into earnings, net of tax $ 2,399 (1) This component of accumulated other comprehensive loss is included in interest expense (see Note 20, “Derivatives and Hedging Activity,” for additional information).

DISCONTINUED OPERATIONS

DISCONTINUED OPERATIONS	12 Months Ended
	Sep. 30, 2017
DISCONTINUED OPERATIONS [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	DISCONTINUED OPERATIONS In connection with the settlement of a Department of Justice investigation into the competitive effects of the acquisition, during the fourth quarter of 2017, the Company committed to dispose of the Schroth business. Therefore, Schroth was classified as held-for-sale as of September 30, 2017. The results of operations of Schroth are reflected as discontinued operations in the accompanying consolidated financial statements for all periods presented. The Company previously acquired Schroth in February 2017 (refer to Note 2, “Acquisitions”). Schroth designs and manufactures proprietary, highly engineered, advanced safety systems for aviation, racing and military ground vehicles around the world. The loss from discontinued operations in the consolidated statements of income includes a $32.0 million impairment charge to write down the Schroth assets to fair value. The impairment charge recorded in the fourth quarter of 2017 was based on an internal assessment of the recovery of Schroth’s assets. Schroth’s assets have been recorded at fair value in the consolidated balance sheets as of September 30, 2017. The following is the summarized operating results from the date of acquisition of February 22, 2017 to September 30, 2017 (in thousands): 2017 Net sales $ 24,590 Loss from discontinued operations before income taxes (5,709 ) Loss on classification as held-for-sale before income taxes (32,000 ) Income tax benefit 6,055 Loss from discontinued operations $ (31,654 ) At September 30, 2017, Schroth’s assets-held-for sale and liabilities held-for sale are $77.5 million and $17.3 million , respectively. The following is the summarized balance sheet of Schroth’s assets and liabilities held-for-sale as of September 30, 2017 (in thousands): Assets and Liabilities of Discontinued Operations Held-for-Sale Fiscal Year Ended September 30, 2017 Trade accounts receivable—Net $ 5,975 Inventories—Net 9,060 Prepaid expenses and other 809 Property, plant, and equipment—Net 4,367 Goodwill 26,783 Other intangible assets—Net 29,841 Other 665 Total assets of discontinued operations $ 77,500 Accounts payable $ 1,247 Accrued liabilities 12,801 Deferred income taxes 3,256 Total liabilities of discontinued operations $ 17,304

QUARTERLY FINANCIAL DATA (UNAUD

QUARTERLY FINANCIAL DATA (UNAUDTIED)	12 Months Ended
	Sep. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
QUARTERLY FINANCIAL DATA (UNAUDITED)	QUARTERLY FINANCIAL DATA (UNAUDITED) First Quarter Second Quarter Third Quarter Fourth Quarter (in thousands, except per share amounts) Year Ended September 30, 2017 (1) Net sales (2) $ 814,018 $ 868,728 $ 897,655 $ 923,885 Gross profit (2) 444,255 489,437 519,696 531,239 Income from continuing operations (2) 118,871 155,691 169,832 184,147 Loss from discontinued operations (2) — (186 ) (779 ) (30,689 ) Net income (2) 118,871 155,505 169,053 153,458 Net earnings per share from continuing operations—basic and diluted (3) $ 0.41 $ 2.78 $ 3.09 $ 2.21 Net loss per share from discontinued operations —basic and diluted (3) — — (0.01 ) (0.56 ) Net earnings per share—basic and diluted (3) $ 0.41 $ 2.78 $ 3.08 $ 1.65 First Quarter Second Quarter Third Quarter Fourth Quarter (in thousands, except per share amounts) Year Ended September 30, 2016 Net sales (2) $ 701,695 $ 796,801 $ 797,692 $ 875,223 Gross profit (2) 374,567 425,662 443,515 484,319 Net income (2) 129,441 141,683 160,622 154,668 Net earnings per share—basic and diluted (3) $ 2.23 $ 2.52 $ 2.88 $ 2.77 (1) Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Schroth as discontinued operations at September 30, 2017. See Note 22, “Discontinued Operations,” for additional information. (2) The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. See Note 2 “Acquisitions,” for additional details. (3) The sum of the earnings per share for the four quarters in a year does not necessarily equal the total year earnings per share.

SUPPLEMENTAL GUARANTOR INFORMAT

SUPPLEMENTAL GUARANTOR INFORMATION	12 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
SUPPLEMENTAL GUARANTOR INFORMATION	SUPPLEMENTAL GUARANTOR INFORMATION TransDigm’s 2020 Notes, 2022 Notes, 2024 Notes, 2025 Notes and 2026 Notes are jointly and severally guaranteed, on a senior subordinated basis, by TD Group and TransDigm Inc.’s 100% Domestic Restricted Subsidiaries, as defined in the Indentures. The following supplemental condensed consolidating financial information presents, in separate columns, the balance sheets of the Company as of September 30, 2017 and September 30, 2016 and its statements of income and cash flows for the fiscal years ended September 30, 2017 , 2016 and 2015 for (i) TransDigm Group on a parent only basis with its investment in subsidiaries recorded under the equity method, (ii) TransDigm Inc. including its directly owned operations and non-operating entities, (iii) the Subsidiary Guarantors on a combined basis, (iv) Non-Guarantor Subsidiaries and (v) the Company on a consolidated basis. Separate financial statements of TransDigm Inc. are not presented because TransDigm Inc.’s 2020 Notes, 2022 Notes, 2024 Notes, 2025 Notes and 2026 Notes are fully and unconditionally guaranteed on a senior subordinated basis by TD Group and all existing 100% owned domestic subsidiaries of TransDigm Inc. and because TD Group has no significant operations or assets separate from its investment in TransDigm Inc. TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING BALANCE SHEET AS OF SEPTEMBER 30, 2017 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated ASSETS CURRENT ASSETS: Cash and cash equivalents $ 2,416 $ 439,473 $ (203 ) $ 208,875 $ — $ 650,561 Trade accounts receivable—Net — — 25,069 652,807 (41,749 ) 636,127 Inventories—Net — 47,051 571,712 114,018 (2,100 ) 730,681 Assets held-for-sale — — 6,428 71,072 — 77,500 Prepaid expenses and other — 4,746 24,141 9,796 — 38,683 Total current assets 2,416 491,270 627,147 1,056,568 (43,849 ) 2,133,552 INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES (2,953,620 ) 10,263,999 7,599,210 966,675 (15,876,264 ) — PROPERTY, PLANT AND EQUIPMENT—Net — 16,032 261,434 47,458 — 324,924 GOODWILL — 85,905 4,996,034 663,399 — 5,745,338 OTHER INTANGIBLE ASSETS—Net — 27,620 1,438,006 252,236 — 1,717,862 OTHER — 20,316 27,567 6,102 — 53,985 TOTAL ASSETS $ (2,951,204 ) $ 10,905,142 $ 14,949,398 $ 2,992,438 $ (15,920,113 ) $ 9,975,661 LIABILITIES AND STOCKHOLDERS’ EQUITY (DEFICIT) CURRENT LIABILITIES: Current portion of long-term debt $ — $ 69,454 $ — $ — $ — $ 69,454 Short-term borrowings—trade receivable securitization facility — — — 299,587 — 299,587 Accounts payable — 14,712 137,948 37,667 (41,566 ) 148,761 Accrued liabilities — 180,916 103,902 51,070 — 335,888 Liabilities held-for-sale — — — 17,304 — 17,304 Total current liabilities — 265,082 241,850 405,628 (41,566 ) 870,994 LONG-TERM DEBT — 11,393,620 — — — 11,393,620 DEFERRED INCOME TAXES — 442,415 (99 ) 58,633 — 500,949 OTHER NON-CURRENT LIABILITIES — 61,347 73,245 26,710 — 161,302 Total liabilities — 12,162,464 314,996 490,971 (41,566 ) 12,926,865 STOCKHOLDERS’ (DEFICIT) EQUITY (2,951,204 ) (1,257,322 ) 14,634,402 2,501,467 (15,878,547 ) (2,951,204 ) TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY $ (2,951,204 ) $ 10,905,142 $ 14,949,398 $ 2,992,438 $ (15,920,113 ) $ 9,975,661 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING BALANCE SHEET AS OF SEPTEMBER 30, 2016 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated ASSETS CURRENT ASSETS: Cash and cash equivalents $ 13,560 $ 1,421,251 $ 8,808 $ 143,375 $ — $ 1,586,994 Trade accounts receivable—Net — — 26,210 561,124 (10,995 ) 576,339 Inventories—Net — 42,309 586,648 96,229 (1,175 ) 724,011 Prepaid expenses and other — 8,209 27,381 7,763 — 43,353 Total current assets 13,560 1,471,769 649,047 808,491 (12,170 ) 2,930,697 INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES (665,050 ) 9,671,019 6,182,809 861,647 (16,050,425 ) — PROPERTY, PLANT AND EQUIPMENT—Net — 15,991 250,544 44,045 — 310,580 GOODWILL — 68,593 4,952,950 657,909 — 5,679,452 OTHER INTANGIBLE ASSETS—Net — 24,801 1,483,285 256,257 — 1,764,343 OTHER — 10,319 24,063 6,823 — 41,205 TOTAL ASSETS $ (651,490 ) $ 11,262,492 $ 13,542,698 $ 2,635,172 $ (16,062,595 ) $ 10,726,277 LIABILITIES AND STOCKHOLDERS’ EQUITY (DEFICIT) CURRENT LIABILITIES: Current portion of long-term debt $ — $ 52,645 $ — $ — $ — $ 52,645 Short-term borrowings—trade receivable securitization facility — — — 199,771 — 199,771 Accounts payable — 15,347 120,455 31,560 (11,287 ) 156,075 Accrued liabilities — 159,909 123,646 60,557 — 344,112 Total current liabilities — 227,901 244,101 291,888 (11,287 ) 752,603 LONG-TERM DEBT — 9,943,191 — — — 9,943,191 DEFERRED INCOME TAXES — 434,013 (544 ) 58,786 — 492,255 OTHER NON-CURRENT LIABILITIES — 82,677 70,124 36,917 — 189,718 Total liabilities — 10,687,782 313,681 387,591 (11,287 ) 11,377,767 STOCKHOLDERS’ (DEFICIT) EQUITY (651,490 ) 574,710 13,229,017 2,247,581 (16,051,308 ) (651,490 ) TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY $ (651,490 ) $ 11,262,492 $ 13,542,698 $ 2,635,172 $ (16,062,595 ) $ 10,726,277 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF INCOME AND COMPREHENSIVE INCOME FOR THE YEAR ENDED SEPTEMBER 30, 2017 (Amounts in thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET SALES $ — $ 143,631 $ 2,911,950 $ 535,129 $ (86,424 ) $ 3,504,286 COST OF SALES — 79,403 1,191,770 333,985 (85,499 ) 1,519,659 GROSS PROFIT — 64,228 1,720,180 201,144 (925 ) 1,984,627 SELLING AND ADMINISTRATIVE EXPENSES 69 97,677 284,819 33,010 — 415,575 AMORTIZATION OF INTANGIBLE ASSETS — 1,003 80,053 8,170 — 89,226 (LOSS) INCOME FROM OPERATIONS (69 ) (34,452 ) 1,355,308 159,964 (925 ) 1,479,826 INTEREST EXPENSE (INCOME)—Net — 614,353 (1,248 ) (10,516 ) — 602,589 REFINANCING COSTS — 39,807 — — — 39,807 EQUITY IN INCOME OF SUBSIDIARIES (596,956 ) (1,318,945 ) — — 1,915,901 — INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES 596,887 630,333 1,356,556 170,480 (1,916,826 ) 837,430 INCOME TAX PROVISION — 33,377 156,251 19,261 — 208,889 INCOME FROM CONTINUING OPERATIONS 596,887 596,956 1,200,305 151,219 (1,916,826 ) 628,541 LOSS FROM DISCONTINUED OPERATIONS, NET OF TAX — — (9,496 ) (22,158 ) — (31,654 ) NET INCOME 596,887 596,956 1,190,809 129,061 (1,916,826 ) 596,887 OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX 64,644 31,603 16,310 58,856 (106,769 ) 64,644 TOTAL COMPREHENSIVE INCOME $ 661,531 $ 628,559 $ 1,207,119 $ 187,917 $ (2,023,595 ) $ 661,531 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF INCOME AND COMPREHENSIVE INCOME FOR THE YEAR ENDED SEPTEMBER 30, 2016 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET SALES $ — $ 132,407 $ 2,580,091 $ 486,198 $ (27,285 ) $ 3,171,411 COST OF SALES — 75,521 1,105,893 289,219 (27,285 ) 1,443,348 GROSS PROFIT — 56,886 1,474,198 196,979 — 1,728,063 SELLING AND ADMINISTRATIVE EXPENSES — 114,546 210,209 58,103 — 382,858 AMORTIZATION OF INTANGIBLE ASSETS — 684 65,299 11,462 — 77,445 (LOSS) INCOME FROM OPERATIONS — (58,344 ) 1,198,690 127,414 — 1,267,760 INTEREST EXPENSE (INCOME)—Net — 490,974 259 (7,383 ) — 483,850 REFINANCING COSTS — 15,794 — — — 15,794 EQUITY IN INCOME OF SUBSIDIARIES (586,414 ) (1,044,371 ) — — 1,630,785 — INCOME BEFORE INCOME TAXES 586,414 479,259 1,198,431 134,797 (1,630,785 ) 768,116 INCOME TAX (BENEFIT) PROVISION — (107,155 ) 285,887 2,970 — 181,702 NET INCOME $ 586,414 $ 586,414 $ 912,544 $ 131,827 $ (1,630,785 ) $ 586,414 OTHER COMPREHENSIVE (LOSS) INCOME, NET OF TAX (53,778 ) 6,381 (9,598 ) (39,461 ) 42,678 (53,778 ) TOTAL COMPREHENSIVE INCOME $ 532,636 $ 592,795 $ 902,946 $ 92,366 $ (1,588,107 ) $ 532,636 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF INCOME AND COMPREHENSIVE INCOME FOR THE YEAR ENDED SEPTEMBER 30, 2015 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET SALES $ — $ 131,378 $ 2,262,842 $ 324,675 $ (11,780 ) $ 2,707,115 COST OF SALES — 79,174 973,908 215,968 (11,780 ) 1,257,270 GROSS PROFIT — 52,204 1,288,934 108,707 — 1,449,845 SELLING AND ADMINISTRATIVE EXPENSES — 72,792 197,914 50,918 — 321,624 AMORTIZATION OF INTANGIBLE ASSETS — 1,392 45,337 7,490 — 54,219 (LOSS) INCOME FROM OPERATIONS — (21,980 ) 1,045,683 50,299 — 1,074,002 INTEREST EXPENSE (INCOME)—Net — 430,224 (487 ) (10,952 ) — 418,785 REFINANCING COSTS — 18,393 — — — 18,393 EQUITY IN INCOME OF SUBSIDIARIES (447,212 ) (773,510 ) — — 1,220,722 — INCOME BEFORE INCOME TAXES 447,212 302,913 1,046,170 61,251 (1,220,722 ) 636,824 INCOME TAX (BENEFIT) PROVISION — (144,299 ) 315,017 18,894 — 189,612 NET INCOME $ 447,212 $ 447,212 $ 731,153 $ 42,357 $ (1,220,722 ) $ 447,212 OTHER COMPREHENSIVE (LOSS) INCOME, NET OF TAX (70,838 ) (55,338 ) 770 (29,147 ) 83,715 (70,838 ) TOTAL COMPREHENSIVE INCOME (LOSS) $ 376,374 $ 391,874 $ 731,923 $ 13,210 $ (1,137,007 ) $ 376,374 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE YEAR ENDED SEPTEMBER 30, 2017 (Amounts in thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET CASH (USED IN) PROVIDED BY OPERATING ACTIVITIES $ (69 ) $ (587,800 ) $ 1,334,099 $ 42,028 $ 475 $ 788,733 INVESTING ACTIVITIES: Capital expenditures — (1,984 ) (63,305 ) (5,724 ) — (71,013 ) Acquisition of business, net of cash acquired — (136,295 ) — — — (136,295 ) Acquisition of Schroth, net of cash acquired — (79,695 ) — — — (79,695 ) Net cash used in investing activities — (217,974 ) (63,305 ) (5,724 ) — (287,003 ) FINANCING ACTIVITIES: Intercompany activities 2,939,121 (1,682,518 ) (1,279,805 ) 23,677 (475 ) — Proceeds from exercise of stock options 21,177 — — — — 21,177 Dividends paid (2,581,552 ) — — — — (2,581,552 ) Treasury stock purchased (389,821 ) — — — — (389,821 ) Proceeds from term loans, net — 2,937,773 — — — 2,937,773 Repayment on term loans — (1,284,698 ) — — — (1,284,698 ) Cash tender and redemption of senior subordinated notes due 2021, including premium — (528,847 ) — — — (528,847 ) Proceeds from senior subordinated notes, net — 300,386 — — — 300,386 Proceeds from trade receivable securitization facility, net — 99,471 — — — 99,471 Financing fees and other — (17,571 ) — — — (17,571 ) Net cash (used in) provided by financing activities (11,075 ) (176,004 ) (1,279,805 ) 23,677 (475 ) (1,443,682 ) EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS — — — 5,519 — 5,519 NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS (11,144 ) (981,778 ) (9,011 ) 65,500 — (936,433 ) CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD 13,560 1,421,251 8,808 143,375 — 1,586,994 CASH AND CASH EQUIVALENTS, END OF PERIOD $ 2,416 $ 439,473 $ (203 ) $ 208,875 $ — $ 650,561 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE YEAR ENDED SEPTEMBER 30, 2016 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET CASH (USED IN) PROVIDED BY OPERATING ACTIVITIES $ — $ (230,931 ) $ 944,152 $ (25,496 ) $ (4,427 ) $ 683,298 INVESTING ACTIVITIES: Capital expenditures — (1,716 ) (32,608 ) (9,658 ) — (43,982 ) Acquisition of business, net of cash acquired — (1,399,064 ) — — — (1,399,064 ) Net cash used in investing activities — (1,400,780 ) (32,608 ) (9,658 ) — (1,443,046 ) FINANCING ACTIVITIES: Intercompany activities 192,703 580,487 (910,647 ) 133,030 4,427 — Proceeds from exercise of stock options 30,112 — — — — 30,112 Dividends paid (3,000 ) — — — — (3,000 ) Treasury stock repurchased (207,755 ) — — — — (207,755 ) Proceeds from term loans, net — 1,711,515 — — — 1,711,515 Repayment on term loans — (834,409 ) — — — (834,409 ) Proceeds from senior subordinated notes, net — 939,584 — — — 939,584 Financing fees and other — (3,580 ) — — — (3,580 ) Net cash provided by (used in) financing activities 12,060 2,393,597 (910,647 ) 133,030 4,427 1,632,467 EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS — — — 242 — 242 NET INCREASE IN CASH AND CASH EQUIVALENTS 12,060 761,886 897 98,118 — 872,961 CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD 1,500 659,365 7,911 45,257 — 714,033 CASH AND CASH EQUIVALENTS, END OF PERIOD $ 13,560 $ 1,421,251 $ 8,808 $ 143,375 $ — $ 1,586,994 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE YEAR ENDED SEPTEMBER 30, 2015 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET CASH (USED IN) PROVIDED BY OPERATING ACTIVITIES $ — $ (298,797 ) $ 734,130 $ 82,451 $ 3,154 $ 520,938 INVESTING ACTIVITIES: Capital expenditures — (2,871 ) (44,564 ) (7,436 ) — (54,871 ) Acquisition of businesses, net of cash acquired (1,624,278 ) — — — (1,624,278 ) Net cash used in investing activities — (1,627,149 ) (44,564 ) (7,436 ) — (1,679,149 ) FINANCING ACTIVITIES: Intercompany activities (120,862 ) 867,990 (685,448 ) (58,526 ) (3,154 ) — Excess tax benefits related to share-based payment arrangements 61,965 — — — — 61,965 Proceeds from exercise of stock options 61,674 — — — — 61,674 Dividends paid (3,365 ) — — — — (3,365 ) Proceeds from term loans, net — 1,515,954 — — — 1,515,954 Repayment on term loans — (1,025,318 ) — — — (1,025,318 ) Proceeds from senior subordinated notes, net — 445,303 — — — 445,303 Financing fees and other — (1,266 ) — — — (1,266 ) Net cash (used in) provided by financing activities (588 ) 1,802,663 (685,448 ) (58,526 ) (3,154 ) 1,054,947 EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS — — — (2,251 ) — (2,251 ) NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS (588 ) (123,283 ) 4,118 14,238 — (105,515 ) CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD 2,088 782,648 3,793 31,019 — 819,548 CASH AND CASH EQUIVALENTS, END OF PERIOD $ 1,500 $ 659,365 $ 7,911 $ 45,257 $ — $ 714,033 *****

VALUATION AND QUALIFYING ACCOUN

VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Sep. 30, 2017
Valuation and Qualifying Accounts [Abstract]
VALUATION AND QUALIFYING ACCOUNTS	TRANSDIGM GROUP INCORPORATED VALUATION AND QUALIFYING ACCOUNTS FOR THE YEARS ENDED SEPTEMBER 30, 2017 , 2016 , AND 2015 (Amounts in Thousands) Column A Column B Column C Column D Column E Balance at Beginning of Period Additions Deductions from Reserve (1) Balance at End of Period Description Charged to Costs and Expenses Acquisitions Year Ended September 30, 2017 Allowance for doubtful accounts $ 4,414 $ 1,095 $ 363 $ (2,053 ) $ 3,819 Reserve for excess and obsolete inventory 80,039 17,361 4,254 (21,879 ) 79,775 Valuation allowance for deferred tax assets 27,286 5,928 — — 33,214 Year Ended September 30, 2016 Allowance for doubtful accounts $ 3,801 $ 1,043 $ 724 $ (1,154 ) $ 4,414 Reserve for excess and obsolete inventory 64,158 26,407 — (10,526 ) 80,039 Valuation allowance for deferred tax assets 17,645 9,641 — — 27,286 Year Ended September 30, 2015 Allowance for doubtful accounts $ 4,091 $ (376 ) $ 271 $ (185 ) $ 3,801 Reserve for excess and obsolete inventory 55,586 15,554 — (6,982 ) 64,158 Valuation allowance for deferred tax assets 24,267 (6,622 ) — — 17,645 (1) The amounts in this column represent charge-offs net of recoveries and the impact of foreign currency translation adjustments.

SUMMARY OF SIGNIFICANT ACCOUN33

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis Of Presentation And Consolidation	Basis of Presentation and Consolidation —The accompanying consolidated financial statements were prepared in conformity with generally accepted accounting principles in the United States (“GAAP”) and include the accounts of TD Group and subsidiaries. All significant intercompany balances and transactions have been eliminated. Certain reclassifications have been made to the current period annual and interim final statements as during the fourth quarter of 2017, the Company committed to disposing of Schroth. As of September 30, 2017, Schroth was classified as held-for-sale and the results of operations for Schroth are reflected as discontinued operations in the accompanying consolidated financial statements. Refer to Note 22, “Discontinued Operations,” for further information.
Revenue Recognition and Related Allowances	Revenue Recognition and Related Allowances —Revenue is recognized from the sale of products when title and risk of loss passes to the customer, which is generally at the time of shipment. Substantially all product sales are made pursuant to firm, fixed-price purchase orders received from customers. Provisions for estimated returns, uncollectible accounts and the cost of repairs under contract warranty provisions are provided for in the same period as the related revenues are recorded and are principally based on historical results modified, as appropriate, by the most current information available. Due to uncertainties in the estimation process, it is possible that actual results may vary from the estimates.
Shipping and Handling Costs	Shipping and Handling Costs —Shipping and handling costs are included in cost of sales in the consolidated statements of income.
Research and Development Costs	Research and Development Costs —The Company expenses research and development costs as incurred and classifies such amounts in selling and administrative expenses. The expense recognized for research and development costs for the years ended September 30, 2017 , 2016 and 2015 was approximately $73.8 million , $58.6 million , and $48.3 million , respectively.
Cash Equivalents	Cash Equivalents —The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents.
Allowance For Uncollectible Accounts	Allowance for Uncollectible Accounts —The Company reserves for amounts determined to be uncollectible based on specific identification of losses and estimated losses based on historical experience. The allowance also incorporates a provision for the estimated impact of disputes with customers. The determination of the amount of the allowance for doubtful accounts is subject to significant levels of judgment and estimation by management. If circumstances change or economic conditions deteriorate or improve, the allowance for doubtful accounts could increase or decrease.
Inventories	Inventories —Inventories are stated at the lower of cost or market. Cost of inventories is generally determined by the average cost and the first-in, first-out (FIFO) methods and includes material, labor and overhead related to the manufacturing process. Provision for potentially obsolete or slow-moving inventory is made based on management’s analysis of inventory levels and future sales forecasts.
Property, Plant and Equipment	Property, Plant and Equipment —Property, plant and equipment are stated at cost and include improvements which significantly increase capacities or extend the useful lives of existing plant and equipment. Depreciation is computed using the straight-line method over the following estimated useful lives: land improvements from 10 to 20 years, buildings and improvements from 5 to 30 years, machinery and equipment from 2 to 10 years and furniture and fixtures from 3 to 10 years. Net gains or losses related to asset dispositions are recognized in earnings in the period in which dispositions occur. Routine maintenance, repairs and replacements are expensed as incurred. Property, plant and equipment is assessed for potential impairment whenever indicators of impairment are present by determining whether the carrying value of the property can be recovered through projected, undiscounted cash flows from future operations over the property’s remaining estimated useful life. Any impairment recognized is the amount by which the carrying amount exceeds the fair value of the asset. Fair value is measured based on quoted market prices in active markets, if available. If quoted market prices are not available, the estimate of fair value is based on various valuation techniques, including the discounted value of estimated future cash flows.
Debt Issue Costs, Premiums and Discounts	Debt Issuance Costs, Premiums and Discounts —The cost of obtaining financing as well as premiums and discounts are amortized using the effective interest method over the terms of the respective obligations as a component of interest expense within the consolidated statements of income. Debt issuance costs are presented in the consolidated balance sheets as a direct reduction from the carrying amount of the related debt liabilities.
Intangible Assets	Intangible Assets —Intangible assets consist of identifiable intangibles acquired or recognized in accounting for the acquisitions (trademarks, trade names, technology, order backlog and other intangible assets) and goodwill. Goodwill and intangible assets that have indefinite useful lives (i.e., trademarks and trade names) are subject to annual impairment testing. Management determines fair value using a discounted future cash flow analysis or other accepted valuation techniques. The Company performs an annual impairment test for goodwill and other intangible assets as of the first day of the fourth fiscal quarter of each year, or more frequently, if an event occurs or circumstances change that would more likely than not reduce fair value below current value. At the time of goodwill impairment testing, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount, and whether it is therefore necessary to perform the quantitative goodwill impairment test. The quantitative goodwill impairment test consists of two steps. The first step of the goodwill impairment test, used to identify potential impairment, compares the fair value of a reporting unit (as defined) with its carrying amount, including goodwill. If the fair value of the reporting unit exceeds its carrying amount, goodwill is not considered impaired, and the second step of the goodwill impairment test is unnecessary. The second step measures the amount of impairment, if any, by comparing the carrying value of the goodwill associated with a reporting unit to the implied fair value of the goodwill derived from the estimated overall fair value of the reporting unit and the individual fair values of the other assets and liabilities of the reporting unit. GAAP requires that the annual, and any interim, impairment assessment be performed at the reporting unit level. The reporting unit level is one level below an operating segment. Substantially all goodwill was determined and recognized for each reporting unit pursuant to the accounting for the merger or acquisition as of the date of each transaction. With respect to acquisitions integrated into an existing reporting unit, any acquired goodwill is combined with the goodwill of the reporting unit. The impairment test for indefinite lived intangible assets consists of a comparison between their fair values and carrying values. If the carrying amounts of intangible assets that have indefinite useful lives exceed their fair values, an impairment loss will be recognized in an amount equal to the sum of any such excesses. The Company assesses the recoverability of its amortizable intangible assets only when indicators of impairment are present by determining whether the amortization over their remaining lives can be recovered through projected, undiscounted cash flows from future operations. Amortization of amortizable intangible assets is computed using the straight-line method over the following estimated useful lives: technology from 20 to 22 years, order backlog over one year , and other intangible assets over 20 years.
Stock-Based Compensation	Stock-Based Compensation —The Company records stock-based compensation expense using the fair value method of accounting. Compensation expense is recorded over the vesting periods of the stock options, restricted stock and other stock-based incentives. No expense is recognized for any stock options, restricted stock and other stock-based incentives ultimately forfeited because the recipients fail to meet vesting requirements.
Income Taxes	Income Taxes —The Company accounts for income taxes using an asset and liability approach. Deferred taxes are recorded for the difference between the book and tax basis of various assets and liabilities. A valuation allowance is provided when it is more likely than not that some or all of a deferred tax asset will not be realized.
Contingencies	Contingencies —During the ordinary course of business, the Company is from time to time threatened with, or may become a party to, legal actions and other proceedings. While the Company is currently involved in certain legal proceedings, it believes the results of these proceedings will not have a material adverse effect on its financial condition, results of operations, or cash flows.
Estimates	Estimates —The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Comprehensive Income (Loss)	Comprehensive Income (Loss) —The term “comprehensive income (loss)” represents the change in stockholders’ equity (deficit) from transactions and other events and circumstances resulting from non-stockholder sources. The Company’s accumulated other comprehensive income or loss, consisting principally of fair value adjustments to its interest rate swap and cap agreements (net of tax), cumulative foreign currency translation adjustments and pension liability adjustments (net of tax), is reported separately in the accompanying consolidated statements of comprehensive income.
Foreign Currency Transactions and Translations	Foreign Currency Translation and Transactions —The assets and liabilities of subsidiaries located outside the United States are translated into U.S. dollars at the rates of exchange in effect at the balance sheet dates. Revenue and expense items are translated at the average monthly exchange rates prevailing during the period. Gains and losses resulting from foreign currency transactions are recognized currently in income, and those resulting from translation of financial statements are accumulated as a separate component of other comprehensive income (loss) for the period. Foreign currency gains or losses recognized currently in income from changes in exchange rates were immaterial to our results of operations.
Earnings per Share	Earnings per Share —Earnings per share information is determined using the two-class method, which includes the weighted-average number of common shares outstanding during the period and other securities that participate in dividends (“participating securities”). Our vested stock options are considered “participating securities” because they include non-forfeitable rights to dividends. In applying the two-class method, earnings are allocated to both common stock shares and participating securities based on their respective weighted-average shares outstanding for the period. Diluted earnings per share information may include the additional effect of other securities, if dilutive, in which case the dilutive effect of such securities is calculated using the treasury stock method. Contingently issuable shares are not included in earnings per share until the period in which the contingency is satisfied; therefore, basic and diluted earnings per share are the same.
Recent Accounting Pronouncements	RECENT ACCOUNTING PRONOUNCEMENTS In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, which creates a new topic in the Accounting Standards Codification (“ASC”) 606, “Revenue From Contracts With Customers .” In addition to superseding and replacing nearly all existing U.S. GAAP revenue recognition guidance, including industry-specific guidance, ASC 606 establishes a new control-based revenue recognition model; changes the basis for deciding when revenue is recognized over time or at a point in time; provides new and more detailed guidance on specific topics; and expands and improves disclosures about revenue. The new revenue standards may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The guidance is effective for the Company for annual reporting periods, including interim periods therein, beginning October 1, 2018, which is the Company’s planned date of adoption. The Company preliminarily expects to use the full retrospective method. The Company is continuing to evaluate the impact of the standard, and the planned adoption method is subject to change. For each reporting unit, we have evaluated a representative sample of contracts and other agreements with our customers and evaluated the provisions contained within these contracts and agreements in consideration of the five step model specified within ASC 606. We are in the process of documenting the impact of the standard on our current accounting policies and practices in order to identify material differences, if any, that would result from applying the new requirements to our revenue contracts. We continue to make progress on our assessment of ASC 606 and are also in the process of evaluating the impact, if any, on changes to our business processes, systems, and controls to support recognition and disclosure requirements under ASC 606. In September 2015, the FASB issued ASU 2015-16, "Simplifying the Accounting for Measurement-Period Adjustments," a new standard intended to simplify the accounting for measurement period adjustments in a business combination. Measurement period adjustments are changes to provisional amounts recorded when the accounting for a business combination is incomplete as of the end of a reporting period. The measurement period can extend for up to a year following the transaction date. During the measurement period, companies may make adjustments to provisional amounts when information necessary to complete the measurement is received. The new guidance requires companies to recognize these adjustments, including any related impacts to net income, in the reporting period in which the adjustments are determined. Companies are no longer required to retroactively apply measurement period adjustments to all periods presented. The guidance was effective for the Company on October 1, 2016. However, as early adoption was permissible, the Company adopted the pronouncement beginning October 1, 2015. The adoption of this standard did not have a significant impact on its consolidated financial statements and disclosures. In February 2016, the FASB issued ASU 2016-02, “Leases (ASC 842),” which will require that a lessee recognize assets and liabilities on the balance sheet for all leases with a lease term of more than twelve months, with the result being the recognition of a right of use asset and a lease liability. The guidance is effective for the Company for annual reporting periods, including interim periods therein, beginning October 1, 2019, with early adoption permitted. The Company is currently evaluating the impact of adopting this standard on its consolidated financial statements and disclosures. In March 2016, the FASB issued ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting.” The guidance requires the recognition of the income tax effects of awards in the income statement when the awards vest or are settled, thus eliminating additional paid in capital pools. The guidance also allows for the employer to repurchase more of an employee’s shares for tax withholding purposes without triggering liability accounting. In addition, the guidance allows for a policy election to account for forfeitures as they occur rather than on an estimated basis. ASU 2016-09 was effective for the Company for annual reporting periods, including interim periods therein, beginning October 1, 2017, with early adoption permitted. As early adoption is permissible, the Company adopted this standard in the fourth quarter of fiscal 2016. Changes were applied prospectively in accordance with the standard and prior periods were not adjusted. In addition, the Company continued to account for forfeitures on an estimated basis. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13)," which changes the impairment model for most financial assets. The new model uses a forward-looking expected loss method, which will generally result in earlier recognition of allowances for losses. ASU 2016-13 is effective for annual and interim periods beginning after December 15, 2019 and early adoption is permitted for annual and interim periods beginning after December 15, 2018. The Company is currently evaluating the impact of adopting this standard on its consolidated financial statements and disclosures. In August 2016, the FASB issued ASU 2016-15, "Statement of Cash Flows—Classification of Certain Cash Receipts and Cash Payments," which clarifies existing guidance related to accounting for cash receipts and cash payments and classification on the statement of cash flows. This guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, with early adoption permitted. The Company elected to early adopt this standard in the fourth quarter of fiscal 2017. The adoption of this standard did not have a significant impact on its consolidated statement of cash flows. In January 2017, the FASB issued ASU 2017-04, “Simplifying the Test for Goodwill Impairment,” to eliminate Step 2 from the goodwill impairment test in order to simplify the subsequent measurement of goodwill. The guidance is effective for fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The adoption of this standard is not expected to have a material impact on its consolidated financial statements and disclosures. In May 2017, the FASB issued ASU 2017-09, "Compensation—Stock Compensation (ASC 718): Scope of Modification Accounting," which provides clarity on which changes to the terms or conditions of share-based payment awards require an entity to apply the modification accounting provisions required in ASC 718. The standard is effective for all entities for annual periods beginning after December 15, 2017, with early adoption permitted, including adoption in any interim period for which financial statements have not yet been issued. The adoption of this standard is not expected to have a material impact on its consolidated financial statements and disclosures. In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (ASC 815): Targeted Improvements to Accounting for Hedging Activities,” which amends the FASB’s hedge accounting model to enable entities to better portray their risk management activities in financial statements. The guidance eliminates the requirement to separately measure and report hedge ineffectiveness and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The guidance also eases certain documentation and assessment requirements and modifies the accounting for components excluded from the assessment of hedge effectiveness. This guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. The Company is currently evaluating the impact of adopting this standard on its consolidated financial statements and disclosures.

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	12 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes the final purchase price allocation of the estimated fair values of the assets acquired and liabilities assumed at the transaction date (in thousands). Assets acquired: Current assets, excluding cash acquired $ 107,728 Property, plant, and equipment 20,818 Intangible assets 229,300 Goodwill 750,935 Other 2,036 Total assets acquired 1,110,817 Liabilities assumed: Current liabilities 26,520 Other noncurrent liabilities 86,642 Total liabilities assumed 113,162 Net assets acquired $ 997,655

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Share	The following table sets forth the computation of basic and diluted earnings per share (in thousands, except per share data): Fiscal Years Ended September 30, 2017 2016 2015 Numerator for earnings per share: Net income from continuing operations $ 628,541 $ 586,414 $ 447,212 Less dividends paid on participating securities (159,257 ) (3,000 ) (3,365 ) $ 469,284 $ 583,414 $ 443,847 Net loss from discontinued operations (31,654 ) — — Net income applicable to common stock—basic and diluted $ 437,630 $ 583,414 $ 443,847 Denominator for basic and diluted earnings per share under the two-class method: Weighted average common shares outstanding 52,517 53,326 53,112 Vested options deemed participating securities 3,013 2,831 3,494 Total shares for basic and diluted earnings per share 55,530 56,157 56,606 Net earnings per share from continuing operations—basic and diluted $ 8.45 $ 10.39 $ 7.84 Net loss per share from discontinued operations—basic and diluted (0.57 ) — — Net earnings per share $ 7.88 $ 10.39 $ 7.84

SALES AND TRADE ACCOUNTS RECE36

SALES AND TRADE ACCOUNTS RECEIVABLE (Tables)	12 Months Ended
	Sep. 30, 2017
Receivables [Abstract]
Content Trade Accounts Receivable	Trade Accounts Receivable —Trade accounts receivable consist of the following at September 30 (in thousands): 2017 2016 Trade accounts receivable—gross $ 639,946 $ 580,753 Allowance for uncollectible accounts (3,819 ) (4,414 ) Trade accounts receivable—net $ 636,127 $ 576,339

INVENTORIES (Tables)

INVENTORIES (Tables)	12 Months Ended
	Sep. 30, 2017
Inventory Disclosure [Abstract]
Inventories	Inventories consist of the following at September 30 (in thousands): 2017 2016 Raw materials and purchased component parts $ 496,899 $ 464,410 Work-in-progress 187,009 188,417 Finished Goods 131,548 153,253 Total 815,456 806,080 Reserves for excess and obsolete inventory (84,775 ) (82,069 ) Inventories—net $ 730,681 $ 724,011

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	12 Months Ended
	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment consist of the following at September 30 (in thousands): 2017 2016 Land and improvements $ 56,554 $ 57,510 Buildings and improvements 161,990 153,691 Machinery, equipment and other 376,659 338,527 Construction in progress 22,037 15,958 Total 617,240 565,686 Accumulated depreciation (292,316 ) (255,106 ) Property, plant and equipment—net $ 324,924 $ 310,580

INTANGIBLE ASSETS (Tables)

INTANGIBLE ASSETS (Tables)	12 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	Other intangible assets - net in the consolidated balance sheets consist of the following at September 30 (in thousands): 2017 2016 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Trademarks and trade names $ 729,931 $ — $ 729,931 $ 720,263 $ — $ 720,263 Technology 1,292,719 351,638 941,081 1,279,335 288,429 990,906 Order backlog 29,000 26,668 2,332 55,341 29,641 25,700 Other 63,599 19,081 44,518 43,331 15,857 27,474 Total $ 2,115,249 $ 397,387 $ 1,717,862 $ 2,098,270 $ 333,927 $ 1,764,343
Schedule of Aggregate Amortization Expense	Information regarding the amortization expense of amortizable intangible assets is detailed below (in thousands): Annual Amortization Expense: Years ended September 30, 2017 $ 89,226 2016 77,445 2015 54,219
Schedule of Finite-Lived Intangible Assets, Future Amortization	Estimated Amortization Expense: Years ending September 30, 2018 $ 69,344 2019 67,011 2020 67,011 2021 67,011 2022 67,011
Schedule of Intangible Assets Acquired	Intangible assets acquired during the year ended September 30, 2017 were as follows (in thousands): Gross Amount Amortization Period Intangible assets not subject to amortization: Goodwill $ 129,152 Trademarks and trade names 12,100 141,252 Intangible assets subject to amortization: Technology 33,800 20 years Order backlog 4,500 1 year 38,300 18 years Total $ 179,552
Summary of Changes in Carrying Value of Goodwill	The changes in the carrying amount of goodwill by segment for the fiscal years ended September 30, 2016 and 2017 were as follows (in thousands): Power & Control Airframe Non- aviation Total Balance at September 30, 2015 $ 2,238,443 $ 2,392,408 $ 55,369 $ 4,686,220 Goodwill acquired during the year (Note 2) 1,008,510 — — 1,008,510 Purchase price allocation adjustments 505 (792 ) — (287 ) Currency translation adjustment 32 (15,023 ) — (14,991 ) Balance at September 30, 2016 3,247,490 2,376,593 55,369 5,679,452 Goodwill acquired during the year (Note 2) 70,369 58,783 — 129,152 Write-down of discontinued operations (Note 22) — (32,000 ) — (32,000 ) Reclass of goodwill acquired to assets held-for-sale (Note 22) — (26,783 ) — (26,783 ) Purchase price allocation adjustments (9,972 ) — — (9,972 ) Currency translation adjustment — 5,489 — 5,489 Balance at September 30, 2017 $ 3,307,887 $ 2,382,082 $ 55,369 $ 5,745,338

ACCRUED LIABILITIES (Tables)

ACCRUED LIABILITIES (Tables)	12 Months Ended
	Sep. 30, 2017
Payables and Accruals [Abstract]
Accrued Liabilities	Accrued liabilities consist of the following at September 30 (in thousands): 2017 2016 Compensation and related benefits $ 68,945 $ 69,323 Interest 82,222 83,180 Breeze-Eastern dissenting shares (see Note 2) — 33,644 Interest rate swap agreements 20,740 29,191 Product warranties 22,971 24,334 Dividend equivalent payments—current (see Note 17) 56,506 19,503 Other 84,504 84,937 Total $ 335,888 $ 344,112

DEBT (Tables)

DEBT (Tables)	12 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Schedule of Subordinated Borrowing [Table Text Block]	Senior Subordinated Notes Senior Subordinated Notes Aggregate Principal Maturity Date Interest Rate 2020 Notes $550 million October 15, 2020 5.50% 2022 Notes $1,150 million July 15, 2022 6.00% 2024 Notes $1,200 million July 15, 2024 6.50% 2025 Notes $750 million May 15, 2025 6.50% 2026 Notes $950 million June 15, 2026 6.375%
Schedule of Debt	The Company’s debt consists of the following at September 30 (in thousands): 2017 Gross Amount Debt Issuance Costs Original Issue Discount or Premium Net Amount Short-term borrowings—trade receivable securitization facility $ 300,000 $ (413 ) $ — $ 299,587 Term loans $ 6,973,009 $ (64,104 ) $ (18,948 ) $ 6,889,957 2020 Notes 550,000 (3,243 ) — 546,757 2022 Notes 1,150,000 (6,941 ) — 1,143,059 2024 Notes 1,200,000 (8,042 ) — 1,191,958 2025 Notes 750,000 (4,033 ) 4,182 750,149 2026 Notes 950,000 (8,806 ) — 941,194 11,573,009 (95,169 ) (14,766 ) 11,463,074 Less current portion 70,031 (577 ) — 69,454 Long-term debt $ 11,502,978 $ (94,592 ) $ (14,766 ) $ 11,393,620 2016 Gross Amount Debt Issuance Costs Original Issue Discount or Premium Net Amount Short-term borrowings—trade receivable securitization facility $ 200,000 $ (229 ) $ — $ 199,771 Term loans $ 5,288,708 $ (42,662 ) $ (11,439 ) $ 5,234,607 2020 Notes 550,000 (4,299 ) — 545,701 2021 Notes 500,000 (3,141 ) — 496,859 2022 Notes 1,150,000 (8,381 ) — 1,141,619 2024 Notes 1,200,000 (9,218 ) — 1,190,782 2025 Notes 450,000 (4,144 ) — 445,856 2026 Notes 950,000 (9,588 ) — 940,412 10,088,708 (81,433 ) (11,439 ) 9,995,836 Less current portion 53,074 (429 ) — 52,645 Long-term debt $ 10,035,634 $ (81,004 ) $ (11,439 ) $ 9,943,191
Schedule of Term Loans	At September 30, 2017 and 2016 , the applicable interest rates were as follows: Term Loan Facility Interest Rate as of September 30, 2017 2016 Tranche C — % 3.75 % Tranche D 4.24 % 3.75 % Tranche E 4.24 % 3.75 % Tranche F 4.24 % 3.75 % Tranche G 4.26 % — % As of September 30, 2017 and 2016 , TransDigm had $6,973.0 million and $5,288.7 million in fully drawn term loans and $600.0 million in revolving commitments. The term loans consist of five tranches as follows (in millions): Term Loan Facility Maturity Date Interest Rate Aggregate Principal as of September 30, 2017 2016 Tranche C February 28, 2020 LIBO rate (1) + 3.00% $ — $ 1,228.3 Tranche D June 4, 2021 LIBO rate (1) + 3.00% $ 798.1 $ 806.4 Tranche E May 14, 2022 LIBO rate (1) + 3.00% $ 1,503.4 $ 1,518.0 Tranche F June 9, 2023 LIBO rate (1) + 3.00% $ 2,857.0 $ 1,736.0 Tranche G August 22, 2024 LIBO rate (1) + 3.00% $ 1,814.5 $ —
Future Maturities of Long-Term Debt	At September 30, 2017 , future maturities of long-term debt are as follows (in thousands): Years ended September 30, 2018 $ 70,031 2019 70,031 2020 70,031 2021 1,385,219 2022 2,641,834 Thereafter 7,335,863 $ 11,573,009

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Tax Provision on Income Before Income Taxes	The Company’s income tax provision on income from continuing operations consists of the following for the periods shown below (in thousands): Fiscal Years Ended September 30, 2017 2016 2015 Current Federal $ 179,884 $ 153,957 $ 163,182 State 8,596 9,234 7,823 Foreign 21,327 12,703 17,947 209,807 175,894 188,952 Deferred (918 ) 5,808 660 $ 208,889 $ 181,702 $ 189,612
Schedule of Effective Income Tax Rate Reconciliation	The differences between the income tax provision on income from continuing operations at the federal statutory income tax rate and the tax provision shown in the accompanying consolidated statements of income for the periods shown below are as follows (in thousands): Fiscal Years Ended September 30, 2017 2016 2015 Tax at statutory rate of 35% $ 293,129 $ 268,841 $ 222,888 State and local income taxes, net of federal benefit 4,042 2,677 4,931 Stock compensation (50,314 ) (43,565 ) — Foreign rate differential (29,685 ) (30,079 ) (14,332 ) Domestic manufacturing deduction (17,832 ) (16,902 ) (17,834 ) Other—net 9,549 730 (6,041 ) Income tax provision $ 208,889 $ 181,702 $ 189,612
Components of Deferred Taxes	The components of the deferred taxes consist of the following at September 30 (in thousands): 2017 2016 Deferred tax liabilities: Intangible assets $ (647,140 ) $ (627,633 ) Property, plant and equipment (29,240 ) (31,438 ) Unremitted foreign earnings (10,784 ) (9,434 ) Employee benefits, compensation and other accrued obligations 107,195 86,229 Inventory 31,077 22,382 Net operating losses 33,462 29,266 Interest rate swaps and caps 15,961 36,478 Environmental 15,518 16,958 Product warranties 7,419 9,007 Other 8,797 3,216 Total (467,735 ) (464,969 ) Add: Valuation allowance (33,214 ) (27,286 ) Total net deferred tax liabilities $ (500,949 ) $ (492,255 )
Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): 2017 2016 Balance at beginning of period $ 8,706 $ 6,859 Additions based on tax positions related to the prior year 500 2,014 Additions based on tax positions related to the current year 1,643 913 Reductions based on tax positions related to the prior year (963 ) (801 ) Lapse in statute of limitations (1,231 ) (1,483 ) Acquisitions — 1,204 Balance at end of period $ 8,655 $ 8,706

SEGMENTS (Tables)

SEGMENTS (Tables)	12 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Net Sales by Reportable Segment	The following table presents net sales by reportable segment (in thousands): Fiscal Years Ended September 30, 2017 2016 2015 Net sales to external customers Power & Control $ 1,948,166 $ 1,621,741 $ 1,330,135 Airframe 1,442,073 1,447,894 1,280,706 Non-aviation 114,047 101,776 96,274 $ 3,504,286 $ 3,171,411 $ 2,707,115
EBITDA Defined by Segment to Consolidated Income Before Taxes Operations	The following table reconciles EBITDA As Defined by segment to consolidated income from continuing operations before income taxes (in thousands): Fiscal Years Ended September 30, 2017 2016 2015 EBITDA As Defined Power & Control $ 981,041 $ 787,418 $ 653,050 Airframe 726,619 709,858 585,472 Non-aviation 41,460 28,228 22,406 Total segment EBITDA As Defined 1,749,120 1,525,504 1,260,928 Unallocated corporate expenses 38,557 30,308 27,274 Total Company EBITDA As Defined 1,710,563 1,495,196 1,233,654 Depreciation and amortization 141,025 121,670 93,663 Interest expense, net 602,589 483,850 418,785 Acquisition-related costs 31,191 57,699 36,205 Stock compensation expense 45,524 48,306 31,500 Refinancing costs 39,807 15,794 18,393 Other, net 12,997 (239 ) (1,716 ) Income from continuing operations before income taxes $ 837,430 $ 768,116 $ 636,824
Capital Expenditures and Depreciation and Amortization by Segment	The following table presents capital expenditures and depreciation and amortization by segment (in thousands): Fiscal Years Ended September 30, 2017 2016 2015 Capital expenditures Power & Control $ 32,424 $ 25,120 $ 24,664 Airframe 34,526 16,498 28,086 Non-aviation 3,981 2,169 1,889 Corporate 82 195 232 $ 71,013 $ 43,982 $ 54,871 Depreciation and amortization Power & Control $ 85,681 $ 65,488 $ 39,336 Airframe 51,440 52,198 50,355 Non-aviation 2,745 2,860 2,846 Corporate 1,159 1,124 1,126 $ 141,025 $ 121,670 $ 93,663
Total Assets by Segment	The following table presents total assets by segment (in thousands): September 30, 2017 September 30, 2016 Total assets Power & Control $ 5,218,006 $ 5,184,303 Airframe 3,923,172 3,922,532 Non-aviation 142,389 131,319 Corporate 614,594 1,488,123 Assets of discontinued operations 77,500 — $ 9,975,661 $ 10,726,277

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted Average Assumptions for all Options Granted Estimated at Grant Date Using Black-Scholes-Merton Option-Pricing Model	The fair value of the Company’s employee stock options was estimated at the date of grant using a Black-Scholes-Merton option-pricing model with the following weighted average assumptions for all options granted during the fiscal years ended: Fiscal Years Ended September 30, 2017 2016 2015 Risk-free interest rate 1.56% to 2.01% 1.33% to 1.73% 1.33% to 1.64% Expected life of options 5 years 5 years 5 years Expected dividend yield of stock — — — Expected volatility of stock 25% 25% 35%
Summary of Activity, Pricing and Other Information for Performance Vested Stock-Based Award Activity	The following table summarizes the activity, pricing and other information for the Company’s performance vested stock-based award activity during the fiscal year ended September 30, 2017 : Number of Options Weighted-Average Exercise Price Per Option Weighted-Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at September 30, 2016 86,329 $ 120.72 Granted — — Exercised (8,500 ) 34.88 Outstanding at September 30, 2017 77,829 $ 130.09 5.1 years $ 9,772,209 Exercisable at September 30, 2017 77,829 $ 130.09 5.1 years $ 9,772,209 The following table summarizes the activity, pricing and other information for the Company’s performance vested stock-based award activity during the fiscal year ended September 30, 2017 : Number of Options Weighted-Average Exercise Price Per Option Weighted-Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at September 30, 2016 5,239,871 $ 133.20 Granted — — Exercised (315,478 ) 66.67 Forfeited (138,179 ) 188.90 Expired (100 ) 226.34 Outstanding at September 30, 2017 4,786,114 $ 135.95 5.2 years $ 572,875,252 Expected to vest 1,052,250 $ 200.32 7.4 years $ 58,217,596 Exercisable at September 30, 2017 3,464,551 $ 110.36 4.3 years $ 503,350,041 The following table summarizes the activity, pricing and other information for the Company’s performance vested stock-based award activity during the fiscal year ended September 30, 2017 : Number of Options Weighted-Average Exercise Price Per Option Weighted-Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at September 30, 2016 147,935 $ 228.73 Granted 738,974 266.18 Exercised (930 ) 231.16 Forfeited (23,280 ) 251.79 Expired (640 ) 232.64 Outstanding at September 30, 2017 862,059 $ 260.20 9.0 years $ (3,925,661 ) Expected to vest 397,725 $ 260.33 9.0 years $ (1,861,447 ) Exercisable at September 30, 2017 122,975 $ 246.01 8.8 years $ 1,186,026

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Carrying Amounts and Fair Values of Financial Instruments	The following summarizes the carrying amounts and fair values of financial instruments (in thousands): September 30, 2017 September 30, 2016 Level Carrying Amount Fair Value Carrying Amount Fair Value Assets: Cash and cash equivalents 1 $ 650,561 $ 650,561 $ 1,586,994 $ 1,586,994 Interest rate cap agreements (1) 2 12,904 12,904 4,232 4,232 Interest rate swap agreements (1) 2 2,905 2,905 — — — Liabilities: Interest rate swap agreements (2) 2 20,740 20,740 29,191 29,191 Interest rate swap agreements (3) 2 9,731 9,731 53,824 53,824 Short-term borrowings - trade receivable securitization facility (4) 1 299,587 299,587 199,771 199,771 Long-term debt, including current portion: Term loans (4) 2 6,889,957 6,965,628 5,234,607 5,284,037 2020 Notes (4) 1 546,757 558,250 545,701 566,500 2021 Notes (4) 1 — — 496,859 530,000 2022 Notes (4) 1 1,143,059 1,178,750 1,141,619 1,214,688 2024 Notes (4) 1 1,191,958 1,236,000 1,190,782 1,266,000 2025 Notes (4) 1 750,149 776,807 445,856 469,125 2026 Notes (4) 1 941,194 971,375 940,412 985,625 (1) Included in other non-current assets on the consolidated balance sheet. (2) Included in accrued liabilities on the consolidated balance sheet. (3) Included in other non-current liabilities on the consolidated balance sheet. (4) The carrying amount of the debt instrument is presented net of the debt issuance costs.

DERIVATIVES AND HEDGING ACTIV46

DERIVATIVES AND HEDGING ACTIVITIES (Tables)	12 Months Ended
	Sep. 30, 2017
Derivative [Line Items]
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]	The following table summarizes the Company’s interest rate swap agreements: Aggregate Notional Amount (in millions) Start Date End Date Related Debt Conversion of Related Variable Rate Debt to Fixed Rate of: $1,000 9/30/2014 6/30/2019 Tranche G Term Loans 5.4% (2.4% plus the 3% margin percentage) $400 9/30/2017 9/30/2022 Tranche G Term Loans 4.9% (1.9% plus the 3% margin percentage) $750 6/30/2020 6/30/2022 Tranche F Term Loans 5.5% (2.5% plus the 3% margin percentage) $500 12/30/2016 12/31/2021 Tranche F Term Loans 4.9% (1.9% plus the 3% margin percentage) $1,000 6/28/2019 6/30/2021 Tranche F Term Loans 4.8% (1.8% plus the 3% margin percentage) $750 3/31/2016 6/30/2020 Tranche D Term Loans 5.8% (2.8% plus the 3% margin percentage) The following table summarizes the Company’s interest rate cap agreements: Aggregate Notional Amount Start Date End Date Related Debt Offsets Variable Rate Debt Attributable to Fluctuations Above: $750 6/30/2020 6/30/2022 Tranche F Term Loans Three month LIBO rate of 2.5% $400 12/30/2016 12/31/2021 Tranche F Term Loans Three month LIBO rate of 2.5% $400 6/30/2016 6/30/2021 Tranche F Term Loans Three month LIBO rate of 2.0% $750 9/30/2015 6/30/2020 Tranche E Term Loans Three month LIBO rate of 2.5%
Schedule of Interest Rate Derivatives	The amounts shown in the table below represent the gross amounts of recognized assets and liabilities, the amounts offset in the consolidated balance sheet and the net amounts of assets and liabilities presented therein. September 30, 2017 September 30, 2016 Asset Liability Asset Liability Interest rate cap agreements $ 12,904 $ — $ 4,232 $ — Interest rate swap agreements 9,235 (36,801 ) — (83,015 ) Total 22,139 (36,801 ) 4,232 (83,015 ) Effect of counterparty netting (6,330 ) 6,330 — — Net derivatives as classified in the balance sheet (1) $ 15,809 $ (30,471 ) $ 4,232 $ (83,015 ) (1) Refer to Note 19, "Fair Value Measurements," for the consolidated balance sheet classification of our interest rate swap and cap agreements.

ACCUMULATED OTHER COMPREHENSI47

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	12 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	A summary of reclassifications out of accumulated other comprehensive loss for or the years ended September 30, 2017 is provided below (in thousands): Description of reclassifications out of accumulated other comprehensive loss Amount reclassified Amortization from redesignated interest rate cap agreements (1) $ 3,829 Deferred tax benefit from redesignated interest rate cap agreements (1,430 ) Losses reclassified into earnings, net of tax $ 2,399 (1) This component of accumulated other comprehensive loss is included in interest expense (see Note 20, “Derivatives and Hedging Activity,” for additional information).
Schedule of Accumulated Other Comprehensive Loss	The following table presents the components of “Accumulated other comprehensive loss” (“AOCI”) in the consolidated balance sheets, net of taxes, for the years ended September 30, 2017 , 2016 and 2015 (in thousands): Unrealized (loss) gain on derivatives designated and qualifying as cash flow hedges (2) Defined benefit pension plan activity (3) Currency translation adjustment Total Balance at September 30, 2015 $ (51,492 ) $ (12,013 ) $ (32,504 ) $ (96,009 ) Other comprehensive loss before reclassification (9,664 ) (12,284 ) (31,846 ) (53,794 ) Amounts reclassified from AOCI related to interest rate swap agreements (1) 16 — — 16 Net current-period other comprehensive loss $ (9,648 ) $ (12,284 ) $ (31,846 ) $ (53,778 ) Balance at September 30, 2016 $ (61,140 ) $ (24,297 ) $ (64,350 ) $ (149,787 ) Other comprehensive gain before reclassification 32,072 7,932 22,241 62,245 Amounts reclassified from AOCI related to interest rate swap agreements (1) 2,399 — — 2,399 Net current-period other comprehensive gain $ 34,471 $ 7,932 $ 22,241 $ 64,644 Balance at September 30, 2017 $ (26,669 ) $ (16,365 ) $ (42,109 ) $ (85,143 ) (1) This component of AOCI is included in interest expense (see Note 20, “Derivatives and Hedging Activities,” for additional details). (2) Unrealized (loss) gain represents interest rate swap and cap agreements, net of taxes of $(20,663) , $6,868 and $20,716 for the years ended September 30, 2017 , 2016 and 2015 , respectively. (3) Defined benefit pension plan activity represent pension liability adjustments, net of taxes of $(4,130) , $6,017 and $3,299 , respectively.

DISCONTINUED OPERATIONS (Tables

DISCONTINUED OPERATIONS (Tables)	12 Months Ended
	Sep. 30, 2017
DISCONTINUED OPERATIONS [Abstract]
Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	A summary of reclassifications out of accumulated other comprehensive loss for or the years ended September 30, 2017 is provided below (in thousands): Description of reclassifications out of accumulated other comprehensive loss Amount reclassified Amortization from redesignated interest rate cap agreements (1) $ 3,829 Deferred tax benefit from redesignated interest rate cap agreements (1,430 ) Losses reclassified into earnings, net of tax $ 2,399 (1) This component of accumulated other comprehensive loss is included in interest expense (see Note 20, “Derivatives and Hedging Activity,” for additional information).
Disposal Groups, Including Discontinued Operations [Table Text Block]	The following is the summarized operating results from the date of acquisition of February 22, 2017 to September 30, 2017 (in thousands): 2017 Net sales $ 24,590 Loss from discontinued operations before income taxes (5,709 ) Loss on classification as held-for-sale before income taxes (32,000 ) Income tax benefit 6,055 Loss from discontinued operations $ (31,654 ) At September 30, 2017, Schroth’s assets-held-for sale and liabilities held-for sale are $77.5 million and $17.3 million , respectively. The following is the summarized balance sheet of Schroth’s assets and liabilities held-for-sale as of September 30, 2017 (in thousands): Assets and Liabilities of Discontinued Operations Held-for-Sale Fiscal Year Ended September 30, 2017 Trade accounts receivable—Net $ 5,975 Inventories—Net 9,060 Prepaid expenses and other 809 Property, plant, and equipment—Net 4,367 Goodwill 26,783 Other intangible assets—Net 29,841 Other 665 Total assets of discontinued operations $ 77,500 Accounts payable $ 1,247 Accrued liabilities 12,801 Deferred income taxes 3,256 Total liabilities of discontinued operations $ 17,304

QUARTERLY FINANCIAL DATA (UNA49

QUARTERLY FINANCIAL DATA (UNAUDTIED) (Tables)	12 Months Ended
	Sep. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	First Quarter Second Quarter Third Quarter Fourth Quarter (in thousands, except per share amounts) Year Ended September 30, 2017 (1) Net sales (2) $ 814,018 $ 868,728 $ 897,655 $ 923,885 Gross profit (2) 444,255 489,437 519,696 531,239 Income from continuing operations (2) 118,871 155,691 169,832 184,147 Loss from discontinued operations (2) — (186 ) (779 ) (30,689 ) Net income (2) 118,871 155,505 169,053 153,458 Net earnings per share from continuing operations—basic and diluted (3) $ 0.41 $ 2.78 $ 3.09 $ 2.21 Net loss per share from discontinued operations —basic and diluted (3) — — (0.01 ) (0.56 ) Net earnings per share—basic and diluted (3) $ 0.41 $ 2.78 $ 3.08 $ 1.65 First Quarter Second Quarter Third Quarter Fourth Quarter (in thousands, except per share amounts) Year Ended September 30, 2016 Net sales (2) $ 701,695 $ 796,801 $ 797,692 $ 875,223 Gross profit (2) 374,567 425,662 443,515 484,319 Net income (2) 129,441 141,683 160,622 154,668 Net earnings per share—basic and diluted (3) $ 2.23 $ 2.52 $ 2.88 $ 2.77 (1) Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Schroth as discontinued operations at September 30, 2017. See Note 22, “Discontinued Operations,” for additional information. (2) The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. See Note 2 “Acquisitions,” for additional details. (3) The sum of the earnings per share for the four quarters in a year does not necessarily equal the total year earnings per share.

SUPPLEMENTAL GUARANTOR INFORM50

SUPPLEMENTAL GUARANTOR INFORMATION (Tables)	12 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Condensed Consolidating Balance Sheet	TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING BALANCE SHEET AS OF SEPTEMBER 30, 2017 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated ASSETS CURRENT ASSETS: Cash and cash equivalents $ 2,416 $ 439,473 $ (203 ) $ 208,875 $ — $ 650,561 Trade accounts receivable—Net — — 25,069 652,807 (41,749 ) 636,127 Inventories—Net — 47,051 571,712 114,018 (2,100 ) 730,681 Assets held-for-sale — — 6,428 71,072 — 77,500 Prepaid expenses and other — 4,746 24,141 9,796 — 38,683 Total current assets 2,416 491,270 627,147 1,056,568 (43,849 ) 2,133,552 INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES (2,953,620 ) 10,263,999 7,599,210 966,675 (15,876,264 ) — PROPERTY, PLANT AND EQUIPMENT—Net — 16,032 261,434 47,458 — 324,924 GOODWILL — 85,905 4,996,034 663,399 — 5,745,338 OTHER INTANGIBLE ASSETS—Net — 27,620 1,438,006 252,236 — 1,717,862 OTHER — 20,316 27,567 6,102 — 53,985 TOTAL ASSETS $ (2,951,204 ) $ 10,905,142 $ 14,949,398 $ 2,992,438 $ (15,920,113 ) $ 9,975,661 LIABILITIES AND STOCKHOLDERS’ EQUITY (DEFICIT) CURRENT LIABILITIES: Current portion of long-term debt $ — $ 69,454 $ — $ — $ — $ 69,454 Short-term borrowings—trade receivable securitization facility — — — 299,587 — 299,587 Accounts payable — 14,712 137,948 37,667 (41,566 ) 148,761 Accrued liabilities — 180,916 103,902 51,070 — 335,888 Liabilities held-for-sale — — — 17,304 — 17,304 Total current liabilities — 265,082 241,850 405,628 (41,566 ) 870,994 LONG-TERM DEBT — 11,393,620 — — — 11,393,620 DEFERRED INCOME TAXES — 442,415 (99 ) 58,633 — 500,949 OTHER NON-CURRENT LIABILITIES — 61,347 73,245 26,710 — 161,302 Total liabilities — 12,162,464 314,996 490,971 (41,566 ) 12,926,865 STOCKHOLDERS’ (DEFICIT) EQUITY (2,951,204 ) (1,257,322 ) 14,634,402 2,501,467 (15,878,547 ) (2,951,204 ) TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY $ (2,951,204 ) $ 10,905,142 $ 14,949,398 $ 2,992,438 $ (15,920,113 ) $ 9,975,661 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING BALANCE SHEET AS OF SEPTEMBER 30, 2016 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated ASSETS CURRENT ASSETS: Cash and cash equivalents $ 13,560 $ 1,421,251 $ 8,808 $ 143,375 $ — $ 1,586,994 Trade accounts receivable—Net — — 26,210 561,124 (10,995 ) 576,339 Inventories—Net — 42,309 586,648 96,229 (1,175 ) 724,011 Prepaid expenses and other — 8,209 27,381 7,763 — 43,353 Total current assets 13,560 1,471,769 649,047 808,491 (12,170 ) 2,930,697 INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES (665,050 ) 9,671,019 6,182,809 861,647 (16,050,425 ) — PROPERTY, PLANT AND EQUIPMENT—Net — 15,991 250,544 44,045 — 310,580 GOODWILL — 68,593 4,952,950 657,909 — 5,679,452 OTHER INTANGIBLE ASSETS—Net — 24,801 1,483,285 256,257 — 1,764,343 OTHER — 10,319 24,063 6,823 — 41,205 TOTAL ASSETS $ (651,490 ) $ 11,262,492 $ 13,542,698 $ 2,635,172 $ (16,062,595 ) $ 10,726,277 LIABILITIES AND STOCKHOLDERS’ EQUITY (DEFICIT) CURRENT LIABILITIES: Current portion of long-term debt $ — $ 52,645 $ — $ — $ — $ 52,645 Short-term borrowings—trade receivable securitization facility — — — 199,771 — 199,771 Accounts payable — 15,347 120,455 31,560 (11,287 ) 156,075 Accrued liabilities — 159,909 123,646 60,557 — 344,112 Total current liabilities — 227,901 244,101 291,888 (11,287 ) 752,603 LONG-TERM DEBT — 9,943,191 — — — 9,943,191 DEFERRED INCOME TAXES — 434,013 (544 ) 58,786 — 492,255 OTHER NON-CURRENT LIABILITIES — 82,677 70,124 36,917 — 189,718 Total liabilities — 10,687,782 313,681 387,591 (11,287 ) 11,377,767 STOCKHOLDERS’ (DEFICIT) EQUITY (651,490 ) 574,710 13,229,017 2,247,581 (16,051,308 ) (651,490 ) TOTAL LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY $ (651,490 ) $ 11,262,492 $ 13,542,698 $ 2,635,172 $ (16,062,595 ) $ 10,726,277
Supplemental Condensed Consolidating Statement of Income and Comprehensive Income	TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF INCOME AND COMPREHENSIVE INCOME FOR THE YEAR ENDED SEPTEMBER 30, 2017 (Amounts in thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET SALES $ — $ 143,631 $ 2,911,950 $ 535,129 $ (86,424 ) $ 3,504,286 COST OF SALES — 79,403 1,191,770 333,985 (85,499 ) 1,519,659 GROSS PROFIT — 64,228 1,720,180 201,144 (925 ) 1,984,627 SELLING AND ADMINISTRATIVE EXPENSES 69 97,677 284,819 33,010 — 415,575 AMORTIZATION OF INTANGIBLE ASSETS — 1,003 80,053 8,170 — 89,226 (LOSS) INCOME FROM OPERATIONS (69 ) (34,452 ) 1,355,308 159,964 (925 ) 1,479,826 INTEREST EXPENSE (INCOME)—Net — 614,353 (1,248 ) (10,516 ) — 602,589 REFINANCING COSTS — 39,807 — — — 39,807 EQUITY IN INCOME OF SUBSIDIARIES (596,956 ) (1,318,945 ) — — 1,915,901 — INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES 596,887 630,333 1,356,556 170,480 (1,916,826 ) 837,430 INCOME TAX PROVISION — 33,377 156,251 19,261 — 208,889 INCOME FROM CONTINUING OPERATIONS 596,887 596,956 1,200,305 151,219 (1,916,826 ) 628,541 LOSS FROM DISCONTINUED OPERATIONS, NET OF TAX — — (9,496 ) (22,158 ) — (31,654 ) NET INCOME 596,887 596,956 1,190,809 129,061 (1,916,826 ) 596,887 OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX 64,644 31,603 16,310 58,856 (106,769 ) 64,644 TOTAL COMPREHENSIVE INCOME $ 661,531 $ 628,559 $ 1,207,119 $ 187,917 $ (2,023,595 ) $ 661,531 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF INCOME AND COMPREHENSIVE INCOME FOR THE YEAR ENDED SEPTEMBER 30, 2016 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET SALES $ — $ 132,407 $ 2,580,091 $ 486,198 $ (27,285 ) $ 3,171,411 COST OF SALES — 75,521 1,105,893 289,219 (27,285 ) 1,443,348 GROSS PROFIT — 56,886 1,474,198 196,979 — 1,728,063 SELLING AND ADMINISTRATIVE EXPENSES — 114,546 210,209 58,103 — 382,858 AMORTIZATION OF INTANGIBLE ASSETS — 684 65,299 11,462 — 77,445 (LOSS) INCOME FROM OPERATIONS — (58,344 ) 1,198,690 127,414 — 1,267,760 INTEREST EXPENSE (INCOME)—Net — 490,974 259 (7,383 ) — 483,850 REFINANCING COSTS — 15,794 — — — 15,794 EQUITY IN INCOME OF SUBSIDIARIES (586,414 ) (1,044,371 ) — — 1,630,785 — INCOME BEFORE INCOME TAXES 586,414 479,259 1,198,431 134,797 (1,630,785 ) 768,116 INCOME TAX (BENEFIT) PROVISION — (107,155 ) 285,887 2,970 — 181,702 NET INCOME $ 586,414 $ 586,414 $ 912,544 $ 131,827 $ (1,630,785 ) $ 586,414 OTHER COMPREHENSIVE (LOSS) INCOME, NET OF TAX (53,778 ) 6,381 (9,598 ) (39,461 ) 42,678 (53,778 ) TOTAL COMPREHENSIVE INCOME $ 532,636 $ 592,795 $ 902,946 $ 92,366 $ (1,588,107 ) $ 532,636 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF INCOME AND COMPREHENSIVE INCOME FOR THE YEAR ENDED SEPTEMBER 30, 2015 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET SALES $ — $ 131,378 $ 2,262,842 $ 324,675 $ (11,780 ) $ 2,707,115 COST OF SALES — 79,174 973,908 215,968 (11,780 ) 1,257,270 GROSS PROFIT — 52,204 1,288,934 108,707 — 1,449,845 SELLING AND ADMINISTRATIVE EXPENSES — 72,792 197,914 50,918 — 321,624 AMORTIZATION OF INTANGIBLE ASSETS — 1,392 45,337 7,490 — 54,219 (LOSS) INCOME FROM OPERATIONS — (21,980 ) 1,045,683 50,299 — 1,074,002 INTEREST EXPENSE (INCOME)—Net — 430,224 (487 ) (10,952 ) — 418,785 REFINANCING COSTS — 18,393 — — — 18,393 EQUITY IN INCOME OF SUBSIDIARIES (447,212 ) (773,510 ) — — 1,220,722 — INCOME BEFORE INCOME TAXES 447,212 302,913 1,046,170 61,251 (1,220,722 ) 636,824 INCOME TAX (BENEFIT) PROVISION — (144,299 ) 315,017 18,894 — 189,612 NET INCOME $ 447,212 $ 447,212 $ 731,153 $ 42,357 $ (1,220,722 ) $ 447,212 OTHER COMPREHENSIVE (LOSS) INCOME, NET OF TAX (70,838 ) (55,338 ) 770 (29,147 ) 83,715 (70,838 ) TOTAL COMPREHENSIVE INCOME (LOSS) $ 376,374 $ 391,874 $ 731,923 $ 13,210 $ (1,137,007 ) $ 376,374
Supplemental Condensed Consolidating Statement of Cash Flows	TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE YEAR ENDED SEPTEMBER 30, 2017 (Amounts in thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET CASH (USED IN) PROVIDED BY OPERATING ACTIVITIES $ (69 ) $ (587,800 ) $ 1,334,099 $ 42,028 $ 475 $ 788,733 INVESTING ACTIVITIES: Capital expenditures — (1,984 ) (63,305 ) (5,724 ) — (71,013 ) Acquisition of business, net of cash acquired — (136,295 ) — — — (136,295 ) Acquisition of Schroth, net of cash acquired — (79,695 ) — — — (79,695 ) Net cash used in investing activities — (217,974 ) (63,305 ) (5,724 ) — (287,003 ) FINANCING ACTIVITIES: Intercompany activities 2,939,121 (1,682,518 ) (1,279,805 ) 23,677 (475 ) — Proceeds from exercise of stock options 21,177 — — — — 21,177 Dividends paid (2,581,552 ) — — — — (2,581,552 ) Treasury stock purchased (389,821 ) — — — — (389,821 ) Proceeds from term loans, net — 2,937,773 — — — 2,937,773 Repayment on term loans — (1,284,698 ) — — — (1,284,698 ) Cash tender and redemption of senior subordinated notes due 2021, including premium — (528,847 ) — — — (528,847 ) Proceeds from senior subordinated notes, net — 300,386 — — — 300,386 Proceeds from trade receivable securitization facility, net — 99,471 — — — 99,471 Financing fees and other — (17,571 ) — — — (17,571 ) Net cash (used in) provided by financing activities (11,075 ) (176,004 ) (1,279,805 ) 23,677 (475 ) (1,443,682 ) EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS — — — 5,519 — 5,519 NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS (11,144 ) (981,778 ) (9,011 ) 65,500 — (936,433 ) CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD 13,560 1,421,251 8,808 143,375 — 1,586,994 CASH AND CASH EQUIVALENTS, END OF PERIOD $ 2,416 $ 439,473 $ (203 ) $ 208,875 $ — $ 650,561 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE YEAR ENDED SEPTEMBER 30, 2016 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET CASH (USED IN) PROVIDED BY OPERATING ACTIVITIES $ — $ (230,931 ) $ 944,152 $ (25,496 ) $ (4,427 ) $ 683,298 INVESTING ACTIVITIES: Capital expenditures — (1,716 ) (32,608 ) (9,658 ) — (43,982 ) Acquisition of business, net of cash acquired — (1,399,064 ) — — — (1,399,064 ) Net cash used in investing activities — (1,400,780 ) (32,608 ) (9,658 ) — (1,443,046 ) FINANCING ACTIVITIES: Intercompany activities 192,703 580,487 (910,647 ) 133,030 4,427 — Proceeds from exercise of stock options 30,112 — — — — 30,112 Dividends paid (3,000 ) — — — — (3,000 ) Treasury stock repurchased (207,755 ) — — — — (207,755 ) Proceeds from term loans, net — 1,711,515 — — — 1,711,515 Repayment on term loans — (834,409 ) — — — (834,409 ) Proceeds from senior subordinated notes, net — 939,584 — — — 939,584 Financing fees and other — (3,580 ) — — — (3,580 ) Net cash provided by (used in) financing activities 12,060 2,393,597 (910,647 ) 133,030 4,427 1,632,467 EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS — — — 242 — 242 NET INCREASE IN CASH AND CASH EQUIVALENTS 12,060 761,886 897 98,118 — 872,961 CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD 1,500 659,365 7,911 45,257 — 714,033 CASH AND CASH EQUIVALENTS, END OF PERIOD $ 13,560 $ 1,421,251 $ 8,808 $ 143,375 $ — $ 1,586,994 TRANSDIGM GROUP INCORPORATED CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE YEAR ENDED SEPTEMBER 30, 2015 (Amounts in Thousands) TransDigm Group TransDigm Inc. Subsidiary Guarantors Non-Guarantor Subsidiaries Eliminations Total Consolidated NET CASH (USED IN) PROVIDED BY OPERATING ACTIVITIES $ — $ (298,797 ) $ 734,130 $ 82,451 $ 3,154 $ 520,938 INVESTING ACTIVITIES: Capital expenditures — (2,871 ) (44,564 ) (7,436 ) — (54,871 ) Acquisition of businesses, net of cash acquired (1,624,278 ) — — — (1,624,278 ) Net cash used in investing activities — (1,627,149 ) (44,564 ) (7,436 ) — (1,679,149 ) FINANCING ACTIVITIES: Intercompany activities (120,862 ) 867,990 (685,448 ) (58,526 ) (3,154 ) — Excess tax benefits related to share-based payment arrangements 61,965 — — — — 61,965 Proceeds from exercise of stock options 61,674 — — — — 61,674 Dividends paid (3,365 ) — — — — (3,365 ) Proceeds from term loans, net — 1,515,954 — — — 1,515,954 Repayment on term loans — (1,025,318 ) — — — (1,025,318 ) Proceeds from senior subordinated notes, net — 445,303 — — — 445,303 Financing fees and other — (1,266 ) — — — (1,266 ) Net cash (used in) provided by financing activities (588 ) 1,802,663 (685,448 ) (58,526 ) (3,154 ) 1,054,947 EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS — — — (2,251 ) — (2,251 ) NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS (588 ) (123,283 ) 4,118 14,238 — (105,515 ) CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD 2,088 782,648 3,793 31,019 — 819,548 CASH AND CASH EQUIVALENTS, END OF PERIOD $ 1,500 $ 659,365 $ 7,911 $ 45,257 $ — $ 714,033

DESCRIPTION OF THE BUSINESS - N

DESCRIPTION OF THE BUSINESS - Narratives (Detail)	Sep. 30, 2017
Accounting Policies [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent	100.00%

ACQUISITIONS - Narratives (Deta

ACQUISITIONS - Narratives (Detail) - USD ($) $ / shares in Units, $ in Thousands	Feb. 22, 2017	Sep. 23, 2016	Jun. 23, 2016	Jan. 04, 2016	Aug. 19, 2015	May 14, 2015	Mar. 31, 2015	Mar. 26, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired									$ 136,295	$ 1,399,064	$ 1,624,278
Loss on classification as held-for-sale before income taxes									32,000
Accrual for Environmental Loss Contingencies									$ 39,900	$ 46,100
Minimum
Business Acquisition [Line Items]
Estimated useful life of aircraft (in years)									25 years
Maximum
Business Acquisition [Line Items]
Estimated useful life of aircraft (in years)									30 years
Third Quarter 2017 Acquisitions [Member]
Business Acquisition [Line Items]
Tax benefit recognition period (in years)									15 years
Amount of goodwill expected to be tax deductible									$ 62,000
Business Acquisition, Preacquisition Contingency, Amount of Settlement									1,000
Business Acquisition, Goodwill, Expected Nondeductible Tax Amount									9,000
Payments to Acquire Businesses, Net of Cash Acquired									106,300
Schroth [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	$ 89,700
Payments to Acquire Businesses, Net of Cash Acquired	79,700
Business Combination, Consideration Transferred, Liabilities Incurred	$ 10,000
Loss on classification as held-for-sale before income taxes									32,000
Tactair
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 258,800
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent		$ 74,500
Tax benefit recognition period (in years)		15 years
Amount of goodwill expected to be tax deductible		$ 124,000
Business Acquisition, Preacquisition Contingency, Amount of Settlement									2,700
Business Acquisition, Goodwill, Expected Nondeductible Tax Amount		$ 8,000
Data Device Corporation
Business Acquisition [Line Items]
Business Combination, Consideration Transferred			$ 997,700
Tax benefit recognition period (in years)		15 years
Amount of goodwill expected to be tax deductible			11,000
Business Acquisition, Preacquisition Contingency, Amount of Settlement									1,400
Business Acquisition, Goodwill, Expected Nondeductible Tax Amount			740,000
Business acquisition, assumption of net indebtedness			$ 113,162
Breeze-Eastern
Business Acquisition [Line Items]
Business Combination, Consideration Transferred				$ 205,900
Business Combination, Consideration Transferred to Dissenting Shareholders				28,700
Business Acquisition, Goodwill, Expected Nondeductible Tax Amount				$ 115,000
Business Acquisition, Share Price				$ 19.61
Payments to Acquire Businesses, Net of Cash Acquired				$ 146,400
Cash Acquired from Acquisition				30,800
Business Combination, Consideration Transferred, Liabilities Incurred				34,900
Loss Contingency Accrual, Provision				6,200
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed				4,900
Interest Expense				$ 1,300
PneuDraulics, Inc.
Business Acquisition [Line Items]
Business Combination, Consideration Transferred					$ 321,500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent					$ 108,100
Tax benefit recognition period (in years)					15 years
Amount of goodwill expected to be tax deductible					$ 223,000
Business Acquisition, Preacquisition Contingency, Amount of Settlement									2,000
Pexco Aerospace, Inc.
Business Acquisition [Line Items]
Business Combination, Consideration Transferred						$ 496,400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent						$ 166,400
Tax benefit recognition period (in years)						15 years
Amount of goodwill expected to be tax deductible						$ 406,000
Adams Rite Aerospace GmbH
Business Acquisition [Line Items]
Business Combination, Consideration Transferred							$ 75,300
Business Acquisition, Goodwill, Expected Nondeductible Tax Amount							$ 64,000
Telair Cargo Group
Business Acquisition [Line Items]
Business Combination, Consideration Transferred								$ 730,900
Amount of goodwill expected to be tax deductible								33,000
Business Acquisition, Goodwill, Expected Nondeductible Tax Amount								$ 450,000
Working Capital [Member] | Schroth [Member]
Business Acquisition [Line Items]
Business Acquisition, Preacquisition Contingency, Amount of Settlement									$ 800

ACQUISITIONS - Schedule of Reco

ACQUISITIONS - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016	Jun. 23, 2016	Sep. 30, 2015
Business Acquisition [Line Items]
Goodwill	$ 5,745,338	$ 5,679,452		$ 4,686,220
Data Device Corporation
Business Acquisition [Line Items]
Current assets, excluding cash acquired			$ 107,728
Property, plant, and equipment			20,818
Intangible assets			229,300
Goodwill			750,935
Business Acquisition, Goodwill, Expected Nondeductible Tax Amount			740,000
Other			2,036
Total assets acquired			1,110,817
Current liabilities			26,520
Other noncurrent liabilities			86,642
Total liabilities assumed			113,162
Net assets acquired			$ 997,655

SUMMARY OF SIGNIFICANT ACCOUN54

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narratives (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Summary Of Significant Accounting Policies [Line Items]
Research and development expense	$ 73.8	$ 58.6	$ 48.3
Finite lived intangible asset useful life	18 years
Land Improvements | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	10 years
Land Improvements | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	20 years
Building and improvements | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	5 years
Building and improvements | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	30 years
Machinery and equipment | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	2 years
Machinery and equipment | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	10 years
Furniture and Fixtures | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	3 years
Furniture and Fixtures | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	10 years
Technology Intangible Assets | Minimum
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	20 years
Technology Intangible Assets | Maximum
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	22 years
Order backlog
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	1 year
Order backlog | Minimum
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	1 year
Other intangible assets | Minimum
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	20 years

RECENT ACCOUNTING PRONOUNCEME55

RECENT ACCOUNTING PRONOUNCEMENTS - Narratives (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt issue cost	$ 95,169	$ 81,433

EARNINGS PER SHARE - Computatio

EARNINGS PER SHARE - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Numerator for earnings per share:
Net income from continuing operations	$ 628,541	$ 586,414	$ 447,212
Less dividends paid on participating securities	(159,257)	(3,000)	(3,365)
Net Income Attributable to Continuing Operations Available To Common Stockholders Basic And Vested Options Deemed Participating Securities	469,284	583,414	443,847
Net loss from discontinued operations	(31,654)	0	0
Net income applicable to common stock-basic and diluted	$ 437,630	$ 583,414	$ 443,847
Denominator for basic and diluted earnings per share under the two-class method:
Weighted average common shares outstanding	52,517	53,326	53,112
Vested options deemed participating securities	3,013	2,831	3,494
Total shares for basic and diluted earnings per share (shares)	55,530	56,157	56,606
Net earnings per share from continuing operations—basic and diluted	$ 8.45	$ 10.39	$ 7.84
Net loss per share from discontinued operations—basic and diluted	(0.57)	0	0
Net earnings per share-basic and diluted (in dollars per share)	$ 7.88	$ 10.39	$ 7.84

SALES AND TRADE ACCOUNTS RECE57

SALES AND TRADE ACCOUNTS RECEIVABLE - Narratives (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Trade Accounts Receivable Securitization and Sale Program [Line Items]
Net Sales	$ 3,504,286	$ 3,171,411	$ 2,707,115
Accounts Receivable
Trade Accounts Receivable Securitization and Sale Program [Line Items]
Percentage of net sales from one customer	12.00%
Customer 1 | Sales Revenue, Net
Trade Accounts Receivable Securitization and Sale Program [Line Items]
Percentage of net sales from one customer	13.00%	13.00%	11.00%
Customer 2 | Sales Revenue, Net
Trade Accounts Receivable Securitization and Sale Program [Line Items]
Percentage of net sales from one customer	11.00%	12.00%	12.00%
Geographic Distribution, Foreign
Trade Accounts Receivable Securitization and Sale Program [Line Items]
Net Sales	$ 1,318,900	$ 1,169,500	$ 881,100
Geographic Distribution, Foreign | Accounts Receivable
Trade Accounts Receivable Securitization and Sale Program [Line Items]
Percentage of net sales from one customer	42.00%

SALES AND TRADE ACCOUNTS RECE58

SALES AND TRADE ACCOUNTS RECEIVABLE - Content Trade Accounts Receivable (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Receivables [Abstract]
Trade accounts receivable—gross	$ 639,946	$ 580,753
Allowance for uncollectible accounts	(3,819)	(4,414)
Trade accounts receivable—net	$ 636,127	$ 576,339

INVENTORIES - Schedule of Inven

INVENTORIES - Schedule of Inventories (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Inventory Disclosure [Abstract]
Raw materials and purchased component parts	$ 496,899	$ 464,410
Work-in-progress	187,009	188,417
Finished Goods	131,548	153,253
Total	815,456	806,080
Reserves for excess and obsolete inventory	(84,775)	(82,069)
Inventories—net	$ 730,681	$ 724,011

PROPERTY, PLANT AND EQUIPMENT -

PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment [Abstract]
Land and improvements	$ 56,554	$ 57,510
Buildings and improvements	161,990	153,691
Machinery, equipment and other	376,659	338,527
Construction in progress	22,037	15,958
Total	617,240	565,686
Accumulated depreciation	(292,316)	(255,106)
Property, plant and equipment-net	$ 324,924	$ 310,580

INTANGIBLE ASSETS - Schedule of

INTANGIBLE ASSETS - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 2,115,249	$ 2,098,270
Intangible Assets, Accumulated Amortization	397,387	333,927
OTHER INTANGIBLE ASSETS—Net	1,717,862	1,764,343
Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,292,719	1,279,335
Accumulated Amortization	351,638	288,429
Net	941,081	990,906
Order backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	29,000	55,341
Accumulated Amortization	26,668	29,641
Net	2,332	25,700
Other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	63,599	43,331
Accumulated Amortization	19,081	15,857
Net	44,518	27,474
Trademarks and trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets (Excluding Goodwill), Gross	729,931	720,263
Indefinite-Lived Intangible Assets, Accumulated Amortization	0	0
Intangible Assets (Excluding Goodwill), Net	$ 729,931	$ 720,263

INTANGIBLE ASSETS - Schedule 62

INTANGIBLE ASSETS - Schedule of Aggregate Amortization Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 89,226	$ 77,445	$ 54,219

INTANGIBLE ASSETS - Schedule 63

INTANGIBLE ASSETS - Schedule of Finite-Lived Assets, Future Amortization (Details) $ in Thousands	Sep. 30, 2017USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 69,344
Finite-Lived Intangible Assets, Amortization Expense, Year Two	67,011
Finite-Lived Intangible Assets, Amortization Expense, Year Three	67,011
Finite-Lived Intangible Assets, Amortization Expense, Year Four	67,011
Finite-Lived Intangible Assets, Amortization Expense, Year Five	$ 67,011

INTANGIBLE ASSETS - Schedule 64

INTANGIBLE ASSETS - Schedule of Intangible Assets Acquired (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 129,152	$ 1,008,510
Intangible assets not subject to amortization	141,252
Intangible assets subject to amortization	38,300
Total - Intangible assets both subject to and not subject to amortization	$ 179,552
Amortization Period (in years)	18 years
Goodwill
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 129,152
Trademarks and trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets not subject to amortization	12,100
Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	$ 33,800
Amortization Period (in years)	20 years
Order backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	$ 4,500
Amortization Period (in years)	1 year

INTANGIBLE ASSETS - Summary of

INTANGIBLE ASSETS - Summary of Changes in Carrying Value of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 5,679,452	$ 4,686,220
Goodwill acquired during the year	129,152	1,008,510
Loss on classification as held-for-sale before income taxes	(32,000)
Reclass of goodwill acquired to assets held-for-sale	(26,783)
Purchase price allocation adjustments	(9,972)	(287)
Other	5,489	(14,991)
Goodwill, Ending Balance	5,745,338	5,679,452
Power & Control
Goodwill [Line Items]
Goodwill, Beginning Balance	3,247,490	2,238,443
Goodwill acquired during the year	70,369	1,008,510
Loss on classification as held-for-sale before income taxes	0
Reclass of goodwill acquired to assets held-for-sale	0
Purchase price allocation adjustments	(9,972)	505
Other	0	32
Goodwill, Ending Balance	3,307,887	3,247,490
Airframe
Goodwill [Line Items]
Goodwill, Beginning Balance	2,376,593	2,392,408
Goodwill acquired during the year	58,783	0
Loss on classification as held-for-sale before income taxes	32,000
Reclass of goodwill acquired to assets held-for-sale	(26,783)
Purchase price allocation adjustments	0	(792)
Other	5,489	(15,023)
Goodwill, Ending Balance	2,382,082	2,376,593
Non-aviation
Goodwill [Line Items]
Goodwill, Beginning Balance	55,369	55,369
Goodwill acquired during the year	0	0
Loss on classification as held-for-sale before income taxes	0
Reclass of goodwill acquired to assets held-for-sale	0
Purchase price allocation adjustments	0	0
Other	0	0
Goodwill, Ending Balance	$ 55,369	$ 55,369

ACCRUED LIABILITIES - Schedule

ACCRUED LIABILITIES - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Payables and Accruals [Abstract]
Compensation and related benefits	$ 68,945	$ 69,323
Interest	82,222	83,180
Breeze-Eastern dissenting shares (see Note 2)	0	33,644
Interest rate swap agreements	20,740	29,191
Product warranties	22,971	24,334
Dividend Equivalent Payments On Certain Stock Options, Current	56,506	19,503
Other	84,504	84,937
Total	$ 335,888	$ 344,112

DEBT - Narratives (Detail)

DEBT - Narratives (Detail)	Mar. 01, 2017USD ($)	Nov. 28, 2016USD ($)	Sep. 30, 2017USD ($)$ / shares	Sep. 30, 2016USD ($)$ / shares	Sep. 30, 2015USD ($)$ / shares	Sep. 30, 2014	Aug. 22, 2017USD ($)	Mar. 06, 2017USD ($)	Oct. 27, 2016USD ($)	Oct. 14, 2016USD ($)	May 14, 2015USD ($)
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 600,000,000
Long-term Debt, Gross			11,573,009,000	$ 10,088,708,000
Debt instrument, face amount			11,573,009,000
Unamortized original issue discount			14,766,000	11,439,000
Refinancing costs			$ 39,807,000	$ 15,794,000	$ 18,393,000
Cash dividends paid per common share (in dollars per share) | $ / shares			$ 46	$ 0	$ 0
Payments of Dividends			$ 2,581,552,000	$ 3,000,000	$ 3,365,000
Percentage of ownership in subsidiary			100.00%
Asset-backed Securities
Debt Instrument [Line Items]
Debt Instrument, Term						1 year
Short-term Bank Loans and Notes Payable, Borrowing Capacity			$ 300,000,000
Short-term Bank Loans and Notes Payable, Gross			300,000,000	200,000,000
Unamortized original issue discount			0	0
Amended Securitization Facility due August 1, 2017 | Asset-backed Securities
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable, Gross			300,000,000
Third Amended And Restated Credit Agreement [Member] | Third Amended And Restated Credit Agreement [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Gross			7,100,000
Payment of special dividend or share repurchases within 60 days							$ 1,300,000,000
Restricted payments, dividend or stock repurchase, maximum							1,500,000,000
Restricted payments, stock repurchase, maximum							500,000,000
Term Loans
Debt Instrument [Line Items]
Long-term Debt, Gross			6,973,009,000	5,288,708,000
Unamortized original issue discount			18,948,000	11,439,000
Term Loans | Tranche G [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			1,814,500,000	$ 0
Debt Issuance Costs, Gross			$ 16,500,000
Basis spread on LIBOR			3.00%	0.00%
Debt instrument, face amount							$ 1,800,000,000
Refinancing costs			$ 2,200,000
Term Loans | Initial Additional Tranche F Term Loans [Member]
Debt Instrument [Line Items]
Debt instrument, face amount										$ 650,000,000
Term Loans | Delayed Draw Tranche F Term Loans [Member]
Debt Instrument [Line Items]
Debt instrument, face amount										$ 500,000,000
Term Loans | Tranche C
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 0	$ 1,228,300,000
Basis spread on LIBOR			0.00%	3.00%
Write-off of debt issuance costs			$ 1,500,000
Term Loans | Term Loans
Debt Instrument [Line Items]
Basis spread on LIBOR			0.75%
Term Loans | Tranche D
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 798,100,000	$ 806,400,000
Basis spread on LIBOR			3.00%	3.00%
Term Loans | Tranche E
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 1,503,400,000	$ 1,518,000,000
Basis spread on LIBOR			3.00%	3.00%
Term Loans | Tranche F
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 2,857,000,000	$ 1,736,000,000
Debt Issuance Costs, Gross			$ 11,300,000
Basis spread on LIBOR			3.00%	3.00%
Refinancing costs			$ 200,000
Senior Subordinated Notes | 5.50% Senior Subordinated Notes, Due 2020
Debt Instrument [Line Items]
Long-term Debt, Gross			550,000,000	$ 550,000,000
Unamortized original issue discount			$ 0	$ 0
Debt Instrument, Interest Rate, Stated Percentage			5.50%	5.50%
Senior Subordinated Notes | 7.50% Senior Subordinated Notes, Due 2021
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 500,000,000
Debt instrument, face amount			$ 500,000,000
Unamortized original issue discount				$ 0
Refinancing costs			31,900,000
Redemption premium of the 2018 Notes included in refinancing costs			28,800,000
Write-off of debt issuance costs			$ 3,100,000
Debt Instrument, Interest Rate, Stated Percentage			0.00%	7.50%
Debt Instrument, Repurchased Face Amount		$ 342,000,000							$ 158,000,000
Debt Instrument, Repurchase Amount									1,060.50
Debt Instrument, Redemption Price, Principal Amount Redeemed									1,000
Debt Instrument, Fee Amount									$ 30
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed		105.625%
Senior Subordinated Notes | 6.00% Senior Subordinated Notes, Due 2022
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 1,150,000,000	$ 1,150,000,000
Unamortized original issue discount			$ 0	$ 0
Debt Instrument, Interest Rate, Stated Percentage			6.00%	6.00%
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2024
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 1,200,000,000	$ 1,200,000,000
Unamortized original issue discount			$ 0	$ 0
Debt Instrument, Interest Rate, Stated Percentage			6.50%	6.50%
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2025
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 300,000,000		$ 750,000,000	$ 450,000,000							$ 450,000,000
Debt Instrument, Unamortized Premium	$ 4,500,000		4,182,000	$ 0
Debt Issuance Costs, Gross			400,000
Debt Instrument, Redemption Price, Percentage	101.50%
Refinancing costs			$ 3,700,000
Debt Instrument, Interest Rate, Stated Percentage	6.50%		6.50%	6.50%
Senior Subordinated Notes | 6.375% Senior Subordinated Notes, Due 2026
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 950,000,000	$ 950,000,000
Unamortized original issue discount			$ 0	$ 0
Debt Instrument, Interest Rate, Stated Percentage			6.375%	6.375%
Second Amended And Restated Credit Agreement [Member] | Second Amended And Restated Credit Agreement [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Gross			$ 10,300,000
Refinancing costs			$ 300,000
Restricted payments, dividend or stock repurchase, maximum								$ 1,500,000,000
Restricted payments, stock repurchase, maximum								500,000,000
Maximum General Investment Basket								$ 400,000,000
Maximum Investment as Percent of Consolidated Assets								0.08

DEBT - Schedule of Debt (Detail

DEBT - Schedule of Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Mar. 01, 2017	Sep. 30, 2016	May 14, 2015
Debt Instrument [Line Items]
Debt Issuance Costs, Net	$ (95,169)		$ (81,433)
Debt Instrument, Unamortized Discount	(14,766)		(11,439)
Short-term borrowings - trade receivable securitization facility	299,587		199,771
Long-term Debt, Gross	11,573,009		10,088,708
Total debt outstanding	11,463,074		9,995,836
Less current portion	69,454		52,645
Long-term Debt, Excluding Current Maturities, Gross	11,502,978		10,035,634
Deferred Finance Costs, Excluding Current Maturities	(94,592)		(81,004)
Debt Instrument, Unamortized Discount, Excluding Current Maturities	(14,766)		(11,439)
Long-term debt	11,393,620		9,943,191
Term Loans
Debt Instrument [Line Items]
Debt Issuance Costs, Net	(64,104)		(42,662)
Debt Instrument, Unamortized Discount	(18,948)		(11,439)
Long-term Debt, Gross	6,973,009		5,288,708
Total debt outstanding	6,889,957		5,234,607
Long-term Debt, Current Maturities
Debt Instrument [Line Items]
Debt Issuance Costs, Net	(577)		(429)
Debt Instrument, Unamortized Discount	0		0
Long-term Debt, Current Maturities, Gross	70,031		53,074
Less current portion	69,454		52,645
Asset-backed Securities
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable, Gross	300,000		200,000
Debt Issuance Costs, Net	(413)		(229)
Debt Instrument, Unamortized Discount	0		0
Short-term borrowings - trade receivable securitization facility	299,587		199,771
5.50% Senior Subordinated Notes, Due 2020 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net	(3,243)		(4,299)
Debt Instrument, Unamortized Discount	0		0
Long-term Debt, Gross	550,000		550,000
Total debt outstanding	546,757		545,701
7.50% Senior Subordinated Notes, Due 2021 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net			(3,141)
Debt Instrument, Unamortized Discount			0
Long-term Debt, Gross			500,000
Total debt outstanding	0		496,859
6.00% Senior Subordinated Notes, Due 2022 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net	(6,941)		(8,381)
Debt Instrument, Unamortized Discount	0		0
Long-term Debt, Gross	1,150,000		1,150,000
Total debt outstanding	1,143,059		1,141,619
6.50% Senior Subordinated Notes, Due 2024 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net	(8,042)		(9,218)
Debt Instrument, Unamortized Discount	0		0
Long-term Debt, Gross	1,200,000		1,200,000
Total debt outstanding	1,191,958		1,190,782
6.50% Senior Subordinated Notes, Due 2025 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net	(4,033)		(4,144)
Debt Instrument, Unamortized Premium	4,182	$ 4,500	0
Long-term Debt, Gross	750,000	$ 300,000	450,000	$ 450,000
Total debt outstanding	750,149		445,856
6.375% Senior Subordinated Notes, Due 2026 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net	(8,806)		(9,588)
Debt Instrument, Unamortized Discount	0		0
Long-term Debt, Gross	950,000		950,000
Total debt outstanding	$ 941,194		$ 940,412

DEBT - Schedule of Term Loans (

DEBT - Schedule of Term Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 01, 2017	May 14, 2015
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 11,573,009	$ 10,088,708
Term Loans
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 6,973,009	$ 5,288,708
Term Loans | Tranche C
Debt Instrument [Line Items]
Basis spread on LIBOR	0.00%	3.00%
Long-term Debt, Gross	$ 0	$ 1,228,300
Debt Instrument, Interest Rate, Effective Percentage	0.00%	3.75%
Term Loans | Tranche D
Debt Instrument [Line Items]
Basis spread on LIBOR	3.00%	3.00%
Long-term Debt, Gross	$ 798,100	$ 806,400
Debt Instrument, Interest Rate, Effective Percentage	4.24%	3.75%
Term Loans | Tranche E
Debt Instrument [Line Items]
Basis spread on LIBOR	3.00%	3.00%
Long-term Debt, Gross	$ 1,503,400	$ 1,518,000
Debt Instrument, Interest Rate, Effective Percentage	4.24%	3.75%
Term Loans | Tranche F
Debt Instrument [Line Items]
Basis spread on LIBOR	3.00%	3.00%
Long-term Debt, Gross	$ 2,857,000	$ 1,736,000
Debt Instrument, Interest Rate, Effective Percentage	4.24%	3.75%
Term Loans | Tranche G [Member]
Debt Instrument [Line Items]
Basis spread on LIBOR	3.00%	0.00%
Long-term Debt, Gross	$ 1,814,500	$ 0
Debt Instrument, Interest Rate, Effective Percentage	4.26%	0.00%
Senior Subordinated Notes | 5.50% Senior Subordinated Notes, Due 2020
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 550,000	$ 550,000
Debt Instrument, Interest Rate, Stated Percentage	5.50%	5.50%
Senior Subordinated Notes | 7.50% Senior Subordinated Notes, Due 2021
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 500,000
Debt Instrument, Interest Rate, Stated Percentage	0.00%	7.50%
Senior Subordinated Notes | 6.00% Senior Subordinated Notes, Due 2022
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 1,150,000	$ 1,150,000
Debt Instrument, Interest Rate, Stated Percentage	6.00%	6.00%
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2024
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 1,200,000	$ 1,200,000
Debt Instrument, Interest Rate, Stated Percentage	6.50%	6.50%
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2025
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 750,000	$ 450,000	$ 300,000	$ 450,000
Debt Instrument, Interest Rate, Stated Percentage	6.50%	6.50%	6.50%
Senior Subordinated Notes | 6.375% Senior Subordinated Notes, Due 2026
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 950,000	$ 950,000
Debt Instrument, Interest Rate, Stated Percentage	6.375%	6.375%

DEBT - Future Maturities of Lon

DEBT - Future Maturities of Long- Term Debt (Detail) $ in Thousands	Sep. 30, 2017USD ($)
Debt Disclosure [Abstract]
Year ended September 30, 2017	$ 70,031
Year ended September 30, 2018	70,031
Year ended September 30, 2019	70,031
Year ended September 30, 2020	1,385,219
Year ended September 30, 2021	2,641,834
Thereafter	7,335,863
Total	$ 11,573,009

DEBT -Schedule of Subordinated

DEBT -Schedule of Subordinated Borrowings (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Mar. 01, 2017	Sep. 30, 2016	May 14, 2015
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 11,573,009		$ 10,088,708
Senior Subordinated Notes | 5.50% Senior Subordinated Notes, Due 2020
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 550,000		$ 550,000
Debt Instrument, Interest Rate, Stated Percentage	5.50%		5.50%
Senior Subordinated Notes | 6.00% Senior Subordinated Notes, Due 2022
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 1,150,000		$ 1,150,000
Debt Instrument, Interest Rate, Stated Percentage	6.00%		6.00%
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2024
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 1,200,000		$ 1,200,000
Debt Instrument, Interest Rate, Stated Percentage	6.50%		6.50%
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2025
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 750,000	$ 300,000	$ 450,000	$ 450,000
Debt Instrument, Interest Rate, Stated Percentage	6.50%	6.50%	6.50%
Senior Subordinated Notes | 6.375% Senior Subordinated Notes, Due 2026
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 950,000		$ 950,000
Debt Instrument, Interest Rate, Stated Percentage	6.375%		6.375%

RETIREMENT PLANS - Narratives (

RETIREMENT PLANS - Narratives (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 14.6	$ 12.7	$ 9.9
Non-contributory defined benefit pension plans, qualified	The Company maintains certain qualified, non-contributory defined benefit pension plans, which together cover certain union employees.
Defined benefit plan, assets	$ 69.9	67
Defined benefit plan, accumulated benefit obligation	91.7	100.6
Defined benefit pension plan, liabilities	21.8	33.6
Net period pension, cost recognized	1.7	1	0.6
Total liabilities	8.8	8.6
Non-qualified
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, net periodic pension cost	$ 0.4	$ 0.4	$ 0.4

INCOME TAXES - Narratives (Deta

INCOME TAXES - Narratives (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Income Tax Contingency [Line Items]
State tax credit carryforward	$ 2.6
State tax credit carryforward expiration period	2023 to 2029
Foreign undistributed net earnings for which no deferred taxes have been provided	$ 176
Effect of unrecognized tax benefits on effective tax rate	8.7
Accrual for income tax penalties and interest	1.2	$ 1.1
State
Income Tax Contingency [Line Items]
Net operating loss carryforward	$ 819.5
Minimum
Income Tax Contingency [Line Items]
Net tax loss carryforwards, expiration years	2,017
Maximum
Income Tax Contingency [Line Items]
Net tax loss carryforwards, expiration years	2,034
UNITED KINGDOM | Federal and United Kingdom
Income Tax Contingency [Line Items]
Net operating loss carryforward	$ 23.3
GERMANY | Federal and United Kingdom
Income Tax Contingency [Line Items]
Net operating loss carryforward	$ 4.3

INCOME TAXES - Income Tax Provi

INCOME TAXES - Income Tax Provision on Income Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Current
Federal	$ 179,884	$ 153,957	$ 163,182
State	8,596	9,234	7,823
Foreign	21,327	12,703	17,947
Total Current	209,807	175,894	188,952
Deferred	(918)	5,808	660
Income tax provision	$ 208,889	$ 181,702	$ 189,612

INCOME TAXES - Income Tax Expen

INCOME TAXES - Income Tax Expense Reconciliation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Tax at statutory rate of 35%	$ 293,129	$ 268,841	$ 222,888
State and local income taxes, net of federal benefit	4,042	2,677	4,931
Income Tax Effects Allocated Directly to Equity, Employee Stock Options	(50,314)	(43,565)	0
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	(17,832)	(16,902)	(17,834)
Domestic manufacturing deduction	(29,685)	(30,079)	(14,332)
Other-net	(9,549)	(730)	6,041
Income tax provision	$ 208,889	$ 181,702	$ 189,612
Statutory tax rate	35.00%	35.00%	35.00%

INCOME TAXES - Components of De

INCOME TAXES - Components of Deferred Taxes (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Intangible assets	$ (647,140)	$ (627,633)
Property, plant and equipment	(29,240)	(31,438)
Unremitted foreign earnings	(10,784)	(9,434)
Employee benefits, compensation and other accrued obligations	107,195	86,229
Interest rate swaps	31,077	22,382
Net operating losses	33,462	29,266
Inventory	15,961	36,478
Environmental	15,518	16,958
Product warranties	7,419	9,007
Other	8,797	3,216
Total deferred tax liabilities	(467,735)	(464,969)
Add: Valuation allowance	(33,214)	(27,286)
Total net deferred tax liabilities	$ (500,949)	$ (492,255)

INCOME TAXES - Reconciliation o

INCOME TAXES - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 6,859
Additions based on tax positions related to the prior year	500	$ 2,014
Additions based on tax positions related to the current year	1,643	913
Reductions based on tax positions related to the prior year	(963)	(801)
Lapse in statute of limitations	(1,231)	(1,483)
Acquisitions	0	1,204
Balance at end of period	$ 8,706	$ 6,859

ENVIRONMENTAL LIABILITIES - Nar

ENVIRONMENTAL LIABILITIES - Narratives (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Environmental Remediation Obligations [Abstract]
Environmental remediation obligations	$ 39.9	$ 46.1

CAPITAL STOCK - Narratives (Det

CAPITAL STOCK - Narratives (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Nov. 08, 2017	Mar. 07, 2017	Jan. 21, 2016
Shareholders Equity [Line Items]
Common stock, shares authorized	224,400,000	224,400,000
Common stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	149,600,000	149,600,000
Preferred stock, par value	$ 0.01	$ 0.01
Common stock, shares issued	56,093,659	55,767,767
Treasury stock, shares	4,159,207	2,433,035
Preferred stock, shares outstanding	0	0
Shares repurchased under the program	1,723,624
Value of common stock repurchased	$ (389,800,000)	$ (207,755,000)
Treasury Stock Acquired, Average Cost Per Share	$ 226.16
March 7, 2017 Stock Repurchase Program [Member] [Member]
Shareholders Equity [Line Items]
Stock Repurchase Program, Authorized Amount				$ 600,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 360,200,000
January 21, 2016 Stock Repurchase Program
Shareholders Equity [Line Items]
Stock Repurchase Program, Authorized Amount					$ 450,000,000
Subsequent Event [Member] | November 8, 2017 Stock Repurchase Program [Member]
Shareholders Equity [Line Items]
Stock Repurchase Program, Authorized Amount			$ 650,000,000

SEGMENTS - Narratives (Detail)

SEGMENTS - Narratives (Detail)	12 Months Ended
	Sep. 30, 2017Segment
Segment Reporting [Abstract]
Number of reporting segments	3

SEGMENTS - Net Sales by Reporta

SEGMENTS - Net Sales by Reportable Segment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Net Sales	$ 3,504,286	$ 3,171,411	$ 2,707,115
Operating Segments | Power & Control
Segment Reporting Information [Line Items]
Net Sales	1,948,166	1,621,741	1,330,135
Operating Segments | Airframe
Segment Reporting Information [Line Items]
Net Sales	1,442,073	1,447,894	1,280,706
Operating Segments | Non-aviation
Segment Reporting Information [Line Items]
Net Sales	$ 114,047	$ 101,776	$ 96,274

SEGMENTS - EBITDA Defined by Se

SEGMENTS - EBITDA Defined by Segment to Consolidated Income Before Taxes Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	$ 1,710,563	$ 1,495,196	$ 1,233,654
Depreciation and amortization	141,025	121,670	93,663
Interest expense, net	602,589	483,850	418,785
Stock compensation expense	45,524	48,306	31,500
Refinancing costs	39,807	15,794	18,393
Income before income taxes	837,430	768,116	636,824
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	1,749,120	1,525,504	1,260,928
Operating Segments | Power & Control
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	981,041	787,418	653,050
Depreciation and amortization	85,681	65,488	39,336
Operating Segments | Airframe
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	726,619	709,858	585,472
Depreciation and amortization	51,440	52,198	50,355
Operating Segments | Non-aviation
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	41,460	28,228	22,406
Depreciation and amortization	2,745	2,860	2,846
Corporate, Non-Segment [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	38,557	30,308	27,274
Depreciation and amortization	1,159	1,124	1,126
Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Depreciation and amortization	141,025	121,670	93,663
Interest expense, net	602,589	483,850	418,785
Acquisition-related costs	31,191	57,699	36,205
Stock compensation expense	45,524	48,306	31,500
Refinancing costs		15,794	18,393
Other nonrecurring charges	$ 12,997	$ (239)	$ (1,716)

SEGMENTS - Capital Expenditures

SEGMENTS - Capital Expenditures and Depreciation and Amortization by Segment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Capital expenditures	$ 71,013	$ 43,982	$ 54,871
Depreciation and amortization	141,025	121,670	93,663
Operating Segments | Power & Control
Segment Reporting Information [Line Items]
Capital expenditures	32,424	25,120	24,664
Depreciation and amortization	85,681	65,488	39,336
Operating Segments | Airframe
Segment Reporting Information [Line Items]
Capital expenditures	34,526	16,498	28,086
Depreciation and amortization	51,440	52,198	50,355
Operating Segments | Non-aviation
Segment Reporting Information [Line Items]
Capital expenditures	3,981	2,169	1,889
Depreciation and amortization	2,745	2,860	2,846
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Capital expenditures	82	195	232
Depreciation and amortization	$ 1,159	$ 1,124	$ 1,126

SEGMENTS - Total Assets by Segm

SEGMENTS - Total Assets by Segment (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 9,975,661	$ 10,726,277
Operating Segments | Power & Control
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	5,218,006	5,184,303
Operating Segments | Airframe
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	3,923,172	3,922,532
Operating Segments | Non-aviation
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	142,389	131,319
Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	614,594	1,488,123
Discontinued Operations, Held-for-sale [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 77,500	$ 0

STOCK-BASED COMPENSATION - Narr

STOCK-BASED COMPENSATION - Narratives (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Mar. 31, 2011	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2003	Mar. 07, 2017	Jan. 26, 2017	Jan. 21, 2016	Oct. 02, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury Stock Acquired, Average Cost Per Share		$ 226.16
Non-cash equity compensation		$ 45,524,000	$ 48,306,000	$ 31,500,000
Stock option weighted-average grant date fair value		$ 67.11	$ 57.47	$ 65.57
Unrecognized compensation cost related to non-vested awards expected to vest		$ 52,400,000
Non-vested awards expected to vest weighted-average period		2 years 6 months 20 days
Fair value of options vested		$ 42,900,000	$ 36,600,000	$ 14,900,000
Special cash dividend paid per share (in dollars per share)		$ 46	$ 0	$ 0
Restricted stock granted during the period			17,700
Restricted stock weighted-average grant date fair value		$ 189.97
Restricted stock vested during the period		5,900
Restricted stock outstanding		5,900
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period		984
Weighted average grant date fair value, share issued		$ 243.36
Cash dividend and dividend equivalents paid		$ 214,849,000	$ 16,145,000	$ 14,151,000
Payments of Dividends		2,581,552,000	3,000,000	3,365,000
Dividend Equivalent Payments On Certain Stock Options, Current		56,506,000	19,503,000
Dividend Equivalent Payments on Certain Stock Options, Non-current		$ 39,400,000
2014 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock									5,000,000
2006 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock	8,119,668
Shares available for award		4,137,011
Restricted stock grant period in years	3 years
2003 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock										9,339,453
Shares available for award					3,870,152
Restricted stock grant period in years					4 years
Stock split, terms		TD Group (after giving effect to the 149.60 for 1.00 stock split effected on March 14, 2006)
Additional stock option granted					5,469,301
Stock option, expiry period					10 years
Total intrinsic value of options exercised		$ 61,100,000	133,200,000	206,900,000
2003 Stock Option Plan | Employee Service
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of vesting					20.00%
2003 Stock Option Plan | Other Than Employee Service
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of vesting					80.00%
Vested Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividends, Share-based Compensation, Cash		19,500,000	$ 3,000,000	$ 3,400,000
Time Vested Stock Options | 2003 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Exercised			5,486
Weighted-Average Exercise Price Per Option, Exercised			$ 39.88
Number of Options Exercisable at end of period			0
2017 declared dividend [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividends, Share-based Compensation, Cash		76,400,000
Payments of Dividends		1,280,100,000
August 2017 declared dividend [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividends, Share-based Compensation, Cash		63,300,000
Payments of Dividends		$ 1,142,200,000
January 21, 2016 Stock Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Repurchase Program, Authorized Amount								$ 450,000,000
January 26, 2017 Stock Repurchase Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Repurchase Program, Authorized Amount							$ 472,000,000
March 7, 2017 Stock Repurchase Program [Member] [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Repurchase Program, Authorized Amount						$ 600,000,000

STOCK-BASED COMPENSATION - Weig

STOCK-BASED COMPENSATION - Weighted Average Assumptions used to Estimate Fair Value of all Options at Grant Date using Black-Scholes-Merton Option-Pricing Model (Detail)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Risk-free interest rate, minimum	1.56%	1.33%	1.33%
Risk-free interest rate, maximum	2.01%	1.73%	1.64%
Expected life of options	5 years	5 years	5 years
Expected dividend yield of stock	0.00%	0.00%	0.00%
Expected volatility of stock	25.00%	25.00%	35.00%

STOCK-BASED COMPENSATION - Summ

STOCK-BASED COMPENSATION - Summary of Activity, Pricing and Other Information for Performance Vested Stock-Based Award Activity (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2003
2014 Stock Option Plan | Performance Vested Stock Options
Number of Options
Number of Options, Outstanding, beginning of period	147,935
Number of Options, Granted	738,974
Number of Options, Exercised	(930)
Number of Options, Forfeited	(23,280)
Number of Options, Expired	(640)
Number of Options, Outstanding, end of period	862,059
Number of Options, Expected to vest	397,725
Number of Options Exercisable at end of period	122,975
Weighted average exercise price per option
Weighted-Average Exercise Price Per Option, Outstanding, beginning of period	$ 228.73
Weighted-Average Exercise Price Per Option, Granted	266.18
Weighted-Average Exercise Price Per Option, Exercised	231.16
Weighted-Average Exercise Price Per Option, Forfeited	251.79
Weighted-Average Exercise Price Per Option, Expired	232.64
Weighted-Average Exercise Price Per Option, Outstanding, end of period	260.20
Weighted-Average Exercise Price Per Option, Expected to vest	260.33
Weighted-Average Exercise Price Per Option, Exercisable	$ 246.01
Weighted average remaining contractual term
Weighted-Average Remaining Contractual Term, Outstanding, years	9 years
Weighted-Average Remaining Contractual Term, Expected to vest, years	9 years
Weighted-Average Remaining Contractual Term, Exercisable, years	8 years 9 months
Aggregate intrinsic value
Aggregate Intrinsic Value, Outstanding	$ (3,925,661)
Aggregate Intrinsic Value, Expected to vest	(1,861,447)
Aggregate Intrinsic Value, Exercisable	$ 1,186,026
2006 Stock Incentive Plan
Number of Options
Number of Options, Granted	4,137,011
2006 Stock Incentive Plan | Performance Vested Stock Options
Number of Options
Number of Options, Outstanding, beginning of period	5,239,871
Number of Options, Granted	0
Number of Options, Exercised	(315,478)
Number of Options, Forfeited	(138,179)
Number of Options, Expired	(100)
Number of Options, Outstanding, end of period	4,786,114
Number of Options, Expected to vest	1,052,250
Number of Options Exercisable at end of period	3,464,551
Weighted average exercise price per option
Weighted-Average Exercise Price Per Option, Outstanding, beginning of period	$ 133.20
Weighted-Average Exercise Price Per Option, Granted	0
Weighted-Average Exercise Price Per Option, Exercised	66.67
Weighted-Average Exercise Price Per Option, Forfeited	188.90
Weighted-Average Exercise Price Per Option, Expired	226.34
Weighted-Average Exercise Price Per Option, Outstanding, end of period	135.95
Weighted-Average Exercise Price Per Option, Expected to vest	200.32
Weighted-Average Exercise Price Per Option, Exercisable	$ 110.36
Weighted average remaining contractual term
Weighted-Average Remaining Contractual Term, Outstanding, years	5 years 2 months
Weighted-Average Remaining Contractual Term, Expected to vest, years	7 years 5 months
Weighted-Average Remaining Contractual Term, Exercisable, years	4 years 4 months
Aggregate intrinsic value
Aggregate Intrinsic Value, Outstanding	$ (572,875,252)
Aggregate Intrinsic Value, Expected to vest	(58,217,596)
Aggregate Intrinsic Value, Exercisable	$ 503,350,041
2003 Stock Option Plan
Number of Options
Number of Options, Granted		3,870,152
2003 Stock Option Plan | Performance Vested Stock Options
Number of Options
Number of Options, Outstanding, beginning of period	86,329
Number of Options, Granted	0
Number of Options, Exercised	(8,500)
Number of Options, Outstanding, end of period	77,829
Number of Options Exercisable at end of period	77,829
Weighted average exercise price per option
Weighted-Average Exercise Price Per Option, Outstanding, beginning of period	$ 120.72
Weighted-Average Exercise Price Per Option, Granted	0
Weighted-Average Exercise Price Per Option, Exercised	34.88
Weighted-Average Exercise Price Per Option, Outstanding, end of period	130.09
Weighted-Average Exercise Price Per Option, Exercisable	$ 130.09
Weighted average remaining contractual term
Weighted-Average Remaining Contractual Term, Outstanding, years	5 years 1 month 15 days
Weighted-Average Remaining Contractual Term, Exercisable, years	5 years 1 month 15 days
Aggregate intrinsic value
Aggregate Intrinsic Value, Outstanding	$ (9,772,209)
Aggregate Intrinsic Value, Exercisable	$ 9,772,209

LEASES -Narratives (Detail)

LEASES -Narratives (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Leases [Abstract]
Annual rental expense	$ 19	$ 18.3	$ 14
Future minimum rental commitments due next twelve months	18
Future minimum rental commitments due in two years	17.5
Future minimum rental commitments due in three years	14.6
Future minimum rental commitments due in four years	12.6
Future minimum rental commitments due in five years	11.5
Future minimum rental commitments, due thereafter	$ 33.6

FAIR VALUE MEASUREMENTS Carryin

FAIR VALUE MEASUREMENTS Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($)	Sep. 30, 2017	Mar. 01, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, Assets, Carrying Amount	$ 650,561,000		$ 1,586,994,000	$ 714,033,000	$ 819,548,000
Short-term borrowings - trade receivable securitization facility, Carrying Amount	299,587,000		199,771,000
Long-term Debt	11,463,074,000		9,995,836,000
Other Noncurrent Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Cash Flow Hedge Asset at Carrying Value	12,904,000		4,232,000
Interest Rate Swap Asset Carrying Amount	2,905,000		0
Accrued Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements, Liabilities, Carrying Amount	20,740,000		29,191,000
Other Non-Current Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements, Liabilities, Carrying Amount	9,731,000		53,824,000
Term Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	6,889,957,000		5,234,607,000
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, Assets, Fair Value	650,561,000		1,586,994,000
Level 2 | Other Noncurrent Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	12,904,000		4,232,000
Interest Rate Swap Asset at Fair Value	2,905,000		0
Level 2 | Accrued Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Cash Flow Hedge Liability at Fair Value	20,740,000		29,191,000
Level 2 | Other Non-Current Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Cash Flow Hedge Liability at Fair Value	9,731,000		53,824,000
Level 2 | Term Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	6,965,628,000		5,284,037,000
5.50% Senior Subordinated Notes, Due 2020 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 546,757,000		$ 545,701,000
Debt Instrument, Interest Rate, Stated Percentage	5.50%		5.50%
5.50% Senior Subordinated Notes, Due 2020 | Level 1 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	$ 558,250,000		$ 566,500,000
7.50% Senior Subordinated Notes, Due 2021 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 0		$ 496,859,000
Debt Instrument, Interest Rate, Stated Percentage	0.00%		7.50%
7.50% Senior Subordinated Notes, Due 2021 | Level 1 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	$ 0		$ 530,000,000
6.00% Senior Subordinated Notes, Due 2022 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 1,143,059,000		$ 1,141,619,000
Debt Instrument, Interest Rate, Stated Percentage	6.00%		6.00%
6.00% Senior Subordinated Notes, Due 2022 | Level 1 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	$ 1,178,750,000		$ 1,214,688,000
6.50% Senior Subordinated Notes, Due 2024 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 1,191,958,000		$ 1,190,782,000
Debt Instrument, Interest Rate, Stated Percentage	6.50%		6.50%
6.50% Senior Subordinated Notes, Due 2024 | Level 1 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	$ 1,236,000,000		$ 1,266,000,000
6.50% Senior Subordinated Notes, Due 2025 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 750,149,000		$ 445,856,000
Debt Instrument, Interest Rate, Stated Percentage	6.50%	6.50%	6.50%
6.50% Senior Subordinated Notes, Due 2025 | Level 1 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	$ 776,807,000		$ 469,125,000
6.375% Senior Subordinated Notes, Due 2026 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 941,194,000		$ 940,412,000
Debt Instrument, Interest Rate, Stated Percentage	6.375%		6.375%
6.375% Senior Subordinated Notes, Due 2026 | Level 1 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	$ 971,375,000		$ 985,625,000
Asset-backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings - trade receivable securitization facility, Carrying Amount	299,587,000		199,771,000
Asset-backed Securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings - trade receivable securitization facility, Fair Value	$ 299,587,000		$ 199,771,000

DERIVATIVES AND HEDGING ACTIV90

DERIVATIVES AND HEDGING ACTIVITIES - Narratives (Detail) - USD ($)		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Jul. 01, 2017
Derivative [Line Items]
Deficit amortized into earnings				$ 3,200,000
2013 Credit Facility
Derivative [Line Items]
Interest rate swap, notional amount				$ 353,000,000
Interest Rate Swap and Cap
Derivative [Line Items]
Derivative loss to be recognized		$ 24,900,000
Interest Rate Cap
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Tax to be Transferred		4,000,000	$ 5,500,000
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Gross Amount to be Transferred		10,800,000	$ 14,600,000
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Interest Expense	[1]	$ 3,829,000
Tranche F | Interest Rate Cap
Derivative [Line Items]
Interest rate swap, notional amount					$ 400,000,000
Derivative, Cap Interest Rate		2.00%
Tranche E | Interest Rate Cap
Derivative [Line Items]
Interest rate swap, notional amount		$ 750,000,000
Derivative, Cap Interest Rate					2.50%
[1]	(1)This component of accumulated other comprehensive loss is included in interest expense (see Note 20, “Derivatives and Hedging Activity,” for additional information).

DERIVATIVES AND HEDGING ACTIV91

DERIVATIVES AND HEDGING ACTIVITIES - Schedule of Interest Rate Derivatives (Details) - USD ($)		Sep. 30, 2017	Jul. 01, 2017	Sep. 30, 2016
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 22,139,000		$ 4,232,000
Derivative Asset, Fair Value, Gross Liability		(36,801,000)		(83,015,000)
Derivative Asset, Collateral, Obligation to Return Cash, Offset		(6,330,000)		0
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		6,330,000		0
Derivative Asset	[1]	15,809,000		4,232,000
Derivative Liability	[1]	(30,471,000)		(83,015,000)
Interest Rate Cap
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		12,904,000		4,232,000
Derivative Asset, Fair Value, Gross Liability		$ 0		0
Interest rate swap agreements beginning June 28, 2019
Derivative [Line Items]
Derivative, Fixed Interest Rate		4.80%
Derivative, Variable Interest Rate		1.80%
Derivative, Basis Spread on Variable Rate		3.00%
Interest rate swap agreements beginning March 31, 2016
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.80%
Derivative, Variable Interest Rate		2.80%
Derivative, Basis Spread on Variable Rate		3.00%
Interest rate swap agreements beginning September 30, 2014
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.40%
Derivative, Variable Interest Rate		2.40%
Derivative, Basis Spread on Variable Rate		3.00%
Interest rate cap agreements beginning June 30, 2016
Derivative [Line Items]
Derivative, Cap Interest Rate		2.00%
Interest rate cap beginning September 30, 2015
Derivative [Line Items]
Derivative, Cap Interest Rate		2.50%
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 9,235,000		0
Derivative Asset, Fair Value, Gross Liability		$ (36,801,000)		$ (83,015,000)
Tranche F | Interest Rate Cap
Derivative [Line Items]
Interest rate swap, notional amount			$ 400,000,000
Derivative, Cap Interest Rate		2.00%
Tranche F | Interest Rate Cap [Member]
Derivative [Line Items]
Interest rate swap, notional amount		$ 750,000,000
Tranche F | Interest rate cap beginning December 30, 2016 [Member]
Derivative [Line Items]
Interest rate swap, notional amount		500,000,000
Tranche F | Interest rate swap beginning June 30, 2020 [Member]
Derivative [Line Items]
Interest rate swap, notional amount		750,000,000
Tranche F | Interest rate swap June 28, 2016 [Member]
Derivative [Line Items]
Interest rate swap, notional amount		1,000,000,000
Tranche G [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Interest rate swap, notional amount		1,000,000,000
Tranche G [Member] | Interest rate swap beginning September 30, 2017 [Member]
Derivative [Line Items]
Interest rate swap, notional amount		400,000,000
Tranche E | Interest Rate Cap
Derivative [Line Items]
Interest rate swap, notional amount		750,000,000
Derivative, Cap Interest Rate			2.50%
Tranche E | Interest rate cap agreements beginning June 30, 2016
Derivative [Line Items]
Interest rate swap, notional amount		400,000,000
Tranche E | Interest rate cap beginning September 30, 2015
Derivative [Line Items]
Interest rate swap, notional amount		750,000,000
Tranche D | Interest rate swap beginning March 31, 2016 [Member]
Derivative [Line Items]
Interest rate swap, notional amount		$ 750,000,000
[1]	Refer to Note 19, "Fair Value Measurements," for the consolidated balance sheet classification of our interest rate swap and cap agreements.

DERIVATIVES AND HEDGING ACTIV92

DERIVATIVES AND HEDGING ACTIVITIES - Schedule of Notional Amounts (Details) - USD ($)	Sep. 30, 2017	Jul. 01, 2017
Tranche F | Interest rate cap beginning December 30, 2016 [Member]
Derivative [Line Items]
Interest rate swap, notional amount	$ 400,000,000
Tranche F | Interest Rate Cap
Derivative [Line Items]
Interest rate swap, notional amount		$ 400,000,000
Tranche C | Interest Rate Swap [Member]
Derivative [Line Items]
Interest rate swap, notional amount	$ 1,000,000,000

ACCUMULATED OTHER COMPREHENSI93

ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016		Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax		$ 20,663	$ (6,868)		$ (20,716)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period		(149,787)	(96,009)
Other comprehensive loss before reclassification		62,245	(53,794)
Amounts reclassified from AOCI related to interest rate swap agreements	[1]	2,399	16
Interest rate swaps and caps, net of tax		34,471	(9,648)		(35,604)
Pension liability adjustments, net of tax		(7,932)	12,284		5,786
Foreign currency translation adjustments		22,241	(31,846)		(29,448)
Other comprehensive income (loss), net of tax		64,644	(53,778)		(70,838)
Balance at end of period		(85,143)	(149,787)		(96,009)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax		(4,130)	6,017		3,299
INCOME TAX PROVISION		208,889	181,702		189,612
Unrealized (loss) gain on derivatives designated and qualifying as cash flow hedges (2)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	[2]	(61,140)	(51,492)
Other comprehensive loss before reclassification		32,072	(9,664)	[2]
Amounts reclassified from AOCI related to interest rate swap agreements		2,399	16	[1],[2]
Interest rate swaps and caps, net of tax	[2]	34,471	(9,648)
Balance at end of period	[2]	(26,669)	(61,140)		(51,492)
Defined benefit pension plan activity (3)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	[3]	(24,297)	(12,013)
Other comprehensive loss before reclassification		7,932	(12,284)	[3]
Amounts reclassified from AOCI related to interest rate swap agreements		0	0	[1],[3]
Pension liability adjustments, net of tax	[3]	(7,932)	12,284
Balance at end of period	[3]	(16,365)	(24,297)		(12,013)
Currency translation adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period		(64,350)	(32,504)
Other comprehensive loss before reclassification		22,241	(31,846)
Amounts reclassified from AOCI related to interest rate swap agreements		0	0	[1]
Foreign currency translation adjustments		22,241	(31,846)
Balance at end of period		(42,109)	$ (64,350)		$ (32,504)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized (loss) gain on derivatives designated and qualifying as cash flow hedges (2)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest Expense	[4]	3,829
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
INCOME TAX PROVISION		(1,430)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		$ 2,399
[1]	This component of AOCI is included in interest expense (see Note 20, “Derivatives and Hedging Activities,” for additional details).
[2]	Unrealized (loss) gain represents interest rate swap and cap agreements, net of taxes of $(20,663), $6,868 and $20,716 for the years ended September 30, 2017, 2016 and 2015, respectively.
[3]	Defined benefit pension plan activity represent pension liability adjustments, net of taxes of $(4,130), $6,017 and $3,299, respectively.
[4]	(1)This component of accumulated other comprehensive loss is included in interest expense (see Note 20, “Derivatives and Hedging Activity,” for additional information).

DISCONTINUED OPERATIONS - Narra

DISCONTINUED OPERATIONS - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on classification as held-for-sale before income taxes	$ 32,000
Assets held-for-sale	77,500	$ 0
Liabilities held-for-sale	17,304	$ 0
Schroth [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on classification as held-for-sale before income taxes	$ 32,000

DISCONTINUED OPERATIONS - Sched

DISCONTINUED OPERATIONS - Schedule of Discontinued Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
NET SALES	$ 3,504,286	$ 3,171,411	$ 2,707,115
Loss on classification as held-for-sale before income taxes	(32,000)
Net loss from discontinued operations	(31,654)	0	0
Trade accounts receivable—Net	636,127	576,339
Inventories—Net	730,681	724,011
Prepaid expenses and other	38,683	43,353
PROPERTY, PLANT AND EQUIPMENT—Net	324,924	310,580
Goodwill	5,745,338	5,679,452	$ 4,686,220
OTHER INTANGIBLE ASSETS—Net	1,717,862	1,764,343
OTHER	53,985	41,205
Assets held-for-sale	77,500	0
Accounts payable	148,761	156,075
Accrued liabilities	335,888	344,112
DEFERRED INCOME TAXES	500,949	492,255
Liabilities held-for-sale	17,304	$ 0
Discontinued Operations, Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
NET SALES	24,590
Loss from discontinued operations before income taxes	(5,709)
Loss on classification as held-for-sale before income taxes	(32,000)
Income tax benefit	6,055
Net loss from discontinued operations	(31,654)
Trade accounts receivable—Net	5,975
Inventories—Net	9,060
Prepaid expenses and other	809
PROPERTY, PLANT AND EQUIPMENT—Net	4,367
Goodwill	26,783
OTHER INTANGIBLE ASSETS—Net	29,841
OTHER	665
Assets held-for-sale	77,500
Accounts payable	1,247
Accrued liabilities	12,801
DEFERRED INCOME TAXES	3,256
Liabilities held-for-sale	$ 17,304

QUARTERLY FINANCIAL DATA (UNA96

QUARTERLY FINANCIAL DATA (UNAUDTIED) - Schedule of Quarterly Financial Data (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended																12 Months Ended
		Sep. 30, 2017		Jul. 01, 2017		Apr. 01, 2017		Dec. 31, 2016		Sep. 30, 2016		Jul. 02, 2016		Apr. 02, 2016		Jan. 02, 2016		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Quarterly Financial Data [Line Items]
Net Sales																		$ 3,504,286	$ 3,171,411	$ 2,707,115
Gross Profit																		1,984,627	1,728,063	1,449,845
Net income from continuing operations																		628,541	586,414	447,212
Net loss from discontinued operations																		(31,654)	0	0
Net income																		$ 596,887	$ 586,414	$ 447,212
Net earnings per share from continuing operations—basic and diluted																		$ 8.45	$ 10.39	$ 7.84
Net loss per share from discontinued operations—basic and diluted																		(0.57)	0	0
Net earnings (loss) per share - basic and diluted (in dollars per share)																		$ 7.88	$ 10.39	$ 7.84
TransDigm Group
Quarterly Financial Data [Line Items]
Net Sales		$ 923,885	[1],[2]	$ 897,655	[1],[2]	$ 868,728	[1],[2]	$ 814,018	[1],[2]	$ 875,223	[2]	$ 797,692	[2]	$ 796,801	[2]	$ 701,695	[2]	$ 0	$ 0	$ 0
Gross Profit		531,239	[1],[2]	519,696	[1],[2]	489,437	[1],[2]	444,255	[1],[2]	484,319	[2]	443,515	[2]	425,662	[2]	374,567	[2]	0	0	0
Net income from continuing operations		184,147	[1],[2]	169,832	[1],[2]	155,691	[1],[2]	118,871	[1],[2]									596,887
Net loss from discontinued operations		(30,689)	[1],[2]	(779)	[1],[2]	(186)	[1],[2]	0	[1],[2]									0
Net income		$ 153,458	[1],[2]	$ 169,053	[1],[2]	$ 155,505	[1],[2]	$ 118,871	[1],[2]	$ 154,668	[2]	$ 160,622	[2]	$ 141,683	[2]	$ 129,441	[2]	$ 596,887	$ 586,414	$ 447,212
Net earnings per share from continuing operations—basic and diluted	[1],[3]	$ 2.21		$ 3.09		$ 2.78		$ 0.41
Net loss per share from discontinued operations—basic and diluted	[1],[3]	(0.56)		(0.01)		0		0
Net earnings (loss) per share - basic and diluted (in dollars per share)		$ 1.65	[1],[3]	$ 3.08	[1],[3]	$ 2.78	[1],[2]	$ 0.41	[1],[3]	$ 2.77	[3]	$ 2.88	[3]	$ 2.52	[3]	$ 2.23	[3]
[1]	Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Schroth as discontinued operations at September 30, 2017. See Note 22, “Discontinued Operations,” for additional information.
[2]	The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. See Note 2 “Acquisitions,” for additional details.
[3]	The sum of the earnings per share for the four quarters in a year does not necessarily equal the total year earnings per share.

SUPPLEMENTAL GUARANTOR INFORM97

SUPPLEMENTAL GUARANTOR INFORMATION - Narratives (Details)	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent	100.00%

SUPPLEMENTAL GUARANTOR INFORM98

SUPPLEMENTAL GUARANTOR INFORMATION - Supplemental Condensed Consolidating Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	$ 650,561	$ 1,586,994	$ 714,033	$ 819,548
Trade accounts receivable—Net	636,127	576,339
Inventories—Net	730,681	724,011
Assets held-for-sale	77,500	0
Prepaid expenses and other	38,683	43,353
Total current assets	2,133,552	2,930,697
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	0	0
PROPERTY, PLANT AND EQUIPMENT—Net	324,924	310,580
GOODWILL	5,745,338	5,679,452	4,686,220
OTHER INTANGIBLE ASSETS—Net	1,717,862	1,764,343
OTHER	53,985	41,205
TOTAL ASSETS	9,975,661	10,726,277
Current portion of long-term debt	69,454	52,645
Short-term borrowings—trade receivable securitization facility	299,587	199,771
Accounts payable	148,761	156,075
Accrued liabilities	335,888	344,112
Liabilities held-for-sale	17,304	0
Total current liabilities	870,994	752,603
LONG-TERM DEBT	11,393,620	9,943,191
DEFERRED INCOME TAXES	500,949	492,255
OTHER NON-CURRENT LIABILITIES	161,302	189,718
Total liabilities	12,926,865	11,377,767
Total stockholders’ deficit	(2,951,204)	(651,490)	(1,038,306)	(1,556,099)
TOTAL LIABILITIES AND STOCKHOLDERS’ DEFICIT	9,975,661	10,726,277
TransDigm Group
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	2,416	13,560	1,500	2,088
Trade accounts receivable—Net	0	0
Inventories—Net	0	0
Assets held-for-sale	0
Prepaid expenses and other	0	0
Total current assets	2,416	13,560
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	(2,953,620)	(665,050)
PROPERTY, PLANT AND EQUIPMENT—Net	0	0
GOODWILL	0	0
OTHER INTANGIBLE ASSETS—Net	0	0
OTHER	0	0
TOTAL ASSETS	(2,951,204)	(651,490)
Current portion of long-term debt	0	0
Short-term borrowings—trade receivable securitization facility	0	0
Accounts payable	0	0
Accrued liabilities	0	0
Liabilities held-for-sale	0
Total current liabilities	0	0
LONG-TERM DEBT	0	0
DEFERRED INCOME TAXES	0	0
OTHER NON-CURRENT LIABILITIES	0	0
Total liabilities	0	0
Total stockholders’ deficit	(2,951,204)	(651,490)
TOTAL LIABILITIES AND STOCKHOLDERS’ DEFICIT	(2,951,204)	(651,490)
TransDigm Inc.
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	439,473	1,421,251	659,365	782,648
Trade accounts receivable—Net	0	0
Inventories—Net	47,051	42,309
Assets held-for-sale	0
Prepaid expenses and other	4,746	8,209
Total current assets	491,270	1,471,769
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	10,263,999	9,671,019
PROPERTY, PLANT AND EQUIPMENT—Net	16,032	15,991
GOODWILL	85,905	68,593
OTHER INTANGIBLE ASSETS—Net	27,620	24,801
OTHER	20,316	10,319
TOTAL ASSETS	10,905,142	11,262,492
Current portion of long-term debt	69,454	52,645
Short-term borrowings—trade receivable securitization facility	0	0
Accounts payable	14,712	15,347
Accrued liabilities	180,916	159,909
Liabilities held-for-sale	0
Total current liabilities	265,082	227,901
LONG-TERM DEBT	11,393,620	9,943,191
DEFERRED INCOME TAXES	442,415	434,013
OTHER NON-CURRENT LIABILITIES	61,347	82,677
Total liabilities	12,162,464	10,687,782
Total stockholders’ deficit	(1,257,322)	574,710
TOTAL LIABILITIES AND STOCKHOLDERS’ DEFICIT	10,905,142	11,262,492
Subsidiary Guarantors
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	(203)	8,808	7,911	3,793
Trade accounts receivable—Net	25,069	26,210
Inventories—Net	571,712	586,648
Assets held-for-sale	6,428
Prepaid expenses and other	24,141	27,381
Total current assets	627,147	649,047
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	7,599,210	6,182,809
PROPERTY, PLANT AND EQUIPMENT—Net	261,434	250,544
GOODWILL	4,996,034	4,952,950
OTHER INTANGIBLE ASSETS—Net	1,438,006	1,483,285
OTHER	27,567	24,063
TOTAL ASSETS	14,949,398	13,542,698
Current portion of long-term debt	0	0
Short-term borrowings—trade receivable securitization facility	0	0
Accounts payable	137,948	120,455
Accrued liabilities	103,902	123,646
Liabilities held-for-sale	0
Total current liabilities	241,850	244,101
LONG-TERM DEBT	0	0
DEFERRED INCOME TAXES	(99)	(544)
OTHER NON-CURRENT LIABILITIES	73,245	70,124
Total liabilities	314,996	313,681
Total stockholders’ deficit	14,634,402	13,229,017
TOTAL LIABILITIES AND STOCKHOLDERS’ DEFICIT	14,949,398	13,542,698
Non-Guarantor Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	208,875	143,375	45,257	31,019
Trade accounts receivable—Net	652,807	561,124
Inventories—Net	114,018	96,229
Assets held-for-sale	71,072
Prepaid expenses and other	9,796	7,763
Total current assets	1,056,568	808,491
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	966,675	861,647
PROPERTY, PLANT AND EQUIPMENT—Net	47,458	44,045
GOODWILL	663,399	657,909
OTHER INTANGIBLE ASSETS—Net	252,236	256,257
OTHER	6,102	6,823
TOTAL ASSETS	2,992,438	2,635,172
Current portion of long-term debt	0	0
Short-term borrowings—trade receivable securitization facility	299,587	199,771
Accounts payable	37,667	31,560
Accrued liabilities	51,070	60,557
Liabilities held-for-sale	17,304
Total current liabilities	405,628	291,888
LONG-TERM DEBT	0	0
DEFERRED INCOME TAXES	58,633	58,786
OTHER NON-CURRENT LIABILITIES	26,710	36,917
Total liabilities	490,971	387,591
Total stockholders’ deficit	2,501,467	2,247,581
TOTAL LIABILITIES AND STOCKHOLDERS’ DEFICIT	2,992,438	2,635,172
Eliminations
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	0	0	$ 0	$ 0
Trade accounts receivable—Net	(41,749)	(10,995)
Inventories—Net	(2,100)	(1,175)
Assets held-for-sale	0
Prepaid expenses and other	0	0
Total current assets	(43,849)	(12,170)
INVESTMENT IN SUBSIDIARIES AND INTERCOMPANY BALANCES	(15,876,264)	(16,050,425)
PROPERTY, PLANT AND EQUIPMENT—Net	0	0
GOODWILL	0	0
OTHER INTANGIBLE ASSETS—Net	0	0
OTHER	0	0
TOTAL ASSETS	(15,920,113)	(16,062,595)
Current portion of long-term debt	0	0
Short-term borrowings—trade receivable securitization facility	0	0
Accounts payable	(41,566)	(11,287)
Accrued liabilities	0	0
Liabilities held-for-sale	0
Total current liabilities	(41,566)	(11,287)
LONG-TERM DEBT	0	0
DEFERRED INCOME TAXES	0	0
OTHER NON-CURRENT LIABILITIES	0	0
Total liabilities	(41,566)	(11,287)
Total stockholders’ deficit	(15,878,547)	(16,051,308)
TOTAL LIABILITIES AND STOCKHOLDERS’ DEFICIT	$ (15,920,113)	$ (16,062,595)

SUPPLEMENTAL GUARANTOR INFORM99

SUPPLEMENTAL GUARANTOR INFORMATION - Supplemental Condensed Consolidating Statement of Income and Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Sep. 30, 2017	[1],[2]	Jul. 01, 2017	[1],[2]	Apr. 01, 2017	[1],[2]	Dec. 31, 2016	[1],[2]	Sep. 30, 2016	[2]	Jul. 02, 2016	[2]	Apr. 02, 2016	[2]	Jan. 02, 2016	[2]	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Condensed Income Statements, Captions [Line Items]
NET SALES																	$ 3,504,286	$ 3,171,411	$ 2,707,115
COST OF SALES																	1,519,659	1,443,348	1,257,270
GROSS PROFIT																	1,984,627	1,728,063	1,449,845
SELLING AND ADMINISTRATIVE EXPENSES																	415,575	382,858	321,624
AMORTIZATION OF INTANGIBLE ASSETS																	89,226	77,445	54,219
(LOSS) INCOME FROM OPERATIONS																	1,479,826	1,267,760	1,074,002
INTEREST EXPENSE—Net																	602,589	483,850	418,785
REFINANCING COSTS																	39,807	15,794	18,393
EQUITY IN INCOME OF SUBSIDIARIES																	0	0	0
INCOME BEFORE INCOME TAXES																	837,430	768,116	636,824
INCOME TAX PROVISION (BENEFIT)																	208,889	181,702	189,612
Net income from continuing operations																	628,541	586,414	447,212
Net loss from discontinued operations																	(31,654)	0	0
NET INCOME																	596,887	586,414	447,212
Statement of Comprehensive Income [Abstract]
Other comprehensive loss, net of tax																	64,644	(53,778)	(70,838)
TOTAL COMPREHENSIVE INCOME (LOSS)																	661,531	532,636	376,374
TransDigm Group
Condensed Income Statements, Captions [Line Items]
NET SALES	$ 923,885		$ 897,655		$ 868,728		$ 814,018		$ 875,223		$ 797,692		$ 796,801		$ 701,695		0	0	0
COST OF SALES																	0	0	0
GROSS PROFIT	531,239		519,696		489,437		444,255		484,319		443,515		425,662		374,567		0	0	0
SELLING AND ADMINISTRATIVE EXPENSES																	69	0	0
AMORTIZATION OF INTANGIBLE ASSETS																	0	0	0
(LOSS) INCOME FROM OPERATIONS																	(69)	0	0
INTEREST EXPENSE—Net																	0	0	0
REFINANCING COSTS																	0	0	0
EQUITY IN INCOME OF SUBSIDIARIES																	(596,956)	(586,414)	(447,212)
INCOME BEFORE INCOME TAXES																	596,887	586,414	447,212
INCOME TAX PROVISION (BENEFIT)																	0	0	0
Net income from continuing operations	184,147		169,832		155,691		118,871										596,887
Net loss from discontinued operations	(30,689)		(779)		(186)		0										0
NET INCOME	$ 153,458		$ 169,053		$ 155,505		$ 118,871		$ 154,668		$ 160,622		$ 141,683		$ 129,441		596,887	586,414	447,212
Statement of Comprehensive Income [Abstract]
Other comprehensive loss, net of tax																	64,644	(53,778)	(70,838)
TOTAL COMPREHENSIVE INCOME (LOSS)																	661,531	532,636	376,374
TransDigm Inc.
Condensed Income Statements, Captions [Line Items]
NET SALES																	143,631	132,407	131,378
COST OF SALES																	79,403	75,521	79,174
GROSS PROFIT																	64,228	56,886	52,204
SELLING AND ADMINISTRATIVE EXPENSES																	97,677	114,546	72,792
AMORTIZATION OF INTANGIBLE ASSETS																	1,003	684	1,392
(LOSS) INCOME FROM OPERATIONS																	(34,452)	(58,344)	(21,980)
INTEREST EXPENSE—Net																	614,353	490,974	430,224
REFINANCING COSTS																	39,807	15,794	18,393
EQUITY IN INCOME OF SUBSIDIARIES																	(1,318,945)	(1,044,371)	(773,510)
INCOME BEFORE INCOME TAXES																	630,333	479,259	302,913
INCOME TAX PROVISION (BENEFIT)																	33,377	(107,155)	(144,299)
Net income from continuing operations																	596,956
Net loss from discontinued operations																	0
NET INCOME																	596,956	586,414	447,212
Statement of Comprehensive Income [Abstract]
Other comprehensive loss, net of tax																	31,603	6,381	(55,338)
TOTAL COMPREHENSIVE INCOME (LOSS)																	628,559	592,795	391,874
Subsidiary Guarantors
Condensed Income Statements, Captions [Line Items]
NET SALES																	2,911,950	2,580,091	2,262,842
COST OF SALES																	1,191,770	1,105,893	973,908
GROSS PROFIT																	1,720,180	1,474,198	1,288,934
SELLING AND ADMINISTRATIVE EXPENSES																	284,819	210,209	197,914
AMORTIZATION OF INTANGIBLE ASSETS																	80,053	65,299	45,337
(LOSS) INCOME FROM OPERATIONS																	1,355,308	1,198,690	1,045,683
INTEREST EXPENSE—Net																	(1,248)	259	(487)
REFINANCING COSTS																	0	0	0
EQUITY IN INCOME OF SUBSIDIARIES																	0	0	0
INCOME BEFORE INCOME TAXES																	1,356,556	1,198,431	1,046,170
INCOME TAX PROVISION (BENEFIT)																	156,251	285,887	315,017
Net income from continuing operations																	1,200,305
Net loss from discontinued operations																	(9,496)
NET INCOME																	1,190,809	912,544	731,153
Statement of Comprehensive Income [Abstract]
Other comprehensive loss, net of tax																	16,310	(9,598)	770
TOTAL COMPREHENSIVE INCOME (LOSS)																	1,207,119	902,946	731,923
Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
NET SALES																	535,129	486,198	324,675
COST OF SALES																	333,985	289,219	215,968
GROSS PROFIT																	201,144	196,979	108,707
SELLING AND ADMINISTRATIVE EXPENSES																	33,010	58,103	50,918
AMORTIZATION OF INTANGIBLE ASSETS																	8,170	11,462	7,490
(LOSS) INCOME FROM OPERATIONS																	159,964	127,414	50,299
INTEREST EXPENSE—Net																	(10,516)	(7,383)	(10,952)
REFINANCING COSTS																	0	0	0
EQUITY IN INCOME OF SUBSIDIARIES																	0	0	0
INCOME BEFORE INCOME TAXES																	170,480	134,797	61,251
INCOME TAX PROVISION (BENEFIT)																	19,261	2,970	18,894
Net income from continuing operations																	151,219
Net loss from discontinued operations																	(22,158)
NET INCOME																	129,061	131,827	42,357
Statement of Comprehensive Income [Abstract]
Other comprehensive loss, net of tax																	58,856	(39,461)	(29,147)
TOTAL COMPREHENSIVE INCOME (LOSS)																	187,917	92,366	13,210
Eliminations
Condensed Income Statements, Captions [Line Items]
NET SALES																	(86,424)	(27,285)	(11,780)
COST OF SALES																	(85,499)	(27,285)	(11,780)
GROSS PROFIT																	(925)	0	0
SELLING AND ADMINISTRATIVE EXPENSES																	0	0	0
AMORTIZATION OF INTANGIBLE ASSETS																	0	0	0
(LOSS) INCOME FROM OPERATIONS																	(925)	0	0
INTEREST EXPENSE—Net																	0	0	0
REFINANCING COSTS																	0	0	0
EQUITY IN INCOME OF SUBSIDIARIES																	1,915,901	1,630,785	1,220,722
INCOME BEFORE INCOME TAXES																	(1,916,826)	(1,630,785)	(1,220,722)
INCOME TAX PROVISION (BENEFIT)																	0	0	0
Net income from continuing operations																	(1,916,826)
Net loss from discontinued operations																	0
NET INCOME																	(1,916,826)	(1,630,785)	(1,220,722)
Statement of Comprehensive Income [Abstract]
Other comprehensive loss, net of tax																	(106,769)	42,678	83,715
TOTAL COMPREHENSIVE INCOME (LOSS)																	$ (2,023,595)	$ (1,588,107)	$ (1,137,007)
[1]	Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Schroth as discontinued operations at September 30, 2017. See Note 22, “Discontinued Operations,” for additional information.
[2]	The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. See Note 2 “Acquisitions,” for additional details.

SUPPLEMENTAL GUARANTOR INFOR100

SUPPLEMENTAL GUARANTOR INFORMATION - Supplemental Condensed Consolidating Statement of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ 788,733	$ 683,298	$ 520,938
Capital expenditures, net of disposals	(71,013)	(43,982)	(54,871)
Acquisition of business, net of cash acquired	(136,295)	(1,399,064)	(1,624,278)
Acquisition of Schroth, net of cash acquired	(79,695)	0	0
Net cash used in investing activities	(287,003)	(1,443,046)	(1,679,149)
Intercompany activities	0	0	0
Excess tax benefits related to share-based payment arrangements	0	0	61,965
Proceeds from exercise of stock options	21,177	30,112	61,674
Dividends paid	(2,581,552)	(3,000)	(3,365)
Treasury stock purchased	(389,821)	(207,755)	0
Proceeds from term loans, net	2,937,773	1,711,515	1,515,954
Repayments of Long-term Debt	(1,284,698)	(834,409)	(1,025,318)
Repayments of Senior Debt	528,847	0	0
Proceeds from senior subordinated notes, net	300,386	939,584	445,303
Proceeds from trade receivable securitization facility, net	99,471	0	0
Financing fees and other	(17,571)	(3,580)	(1,266)
Net cash (used in) provided by financing activities	(1,443,682)	1,632,467	1,054,947
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	5,519	242	(2,251)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(936,433)	872,961	(105,515)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	1,586,994	714,033	819,548
CASH AND CASH EQUIVALENTS, END OF PERIOD	650,561	1,586,994	714,033
Eliminations
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	475	(4,427)	3,154
Capital expenditures, net of disposals	0	0	0
Acquisition of business, net of cash acquired	0	0	0
Acquisition of Schroth, net of cash acquired	0
Net cash used in investing activities	0	0	0
Intercompany activities	(475)	4,427	(3,154)
Excess tax benefits related to share-based payment arrangements			0
Proceeds from exercise of stock options	0	0	0
Dividends paid	0	0	0
Treasury stock purchased	0	0
Proceeds from term loans, net	0	0	0
Repayments of Long-term Debt	0	0	0
Repayments of Senior Debt	0
Proceeds from senior subordinated notes, net	0	0	0
Proceeds from trade receivable securitization facility, net	0
Financing fees and other	0	0	0
Net cash (used in) provided by financing activities	(475)	4,427	(3,154)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	0	0	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	0	0	0
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	0	0	0
CASH AND CASH EQUIVALENTS, END OF PERIOD	0	0	0
TransDigm Group
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(69)	0	0
Capital expenditures, net of disposals	0	0	0
Acquisition of business, net of cash acquired	0	0
Acquisition of Schroth, net of cash acquired	0
Net cash used in investing activities	0	0	0
Intercompany activities	2,939,121	192,703	(120,862)
Excess tax benefits related to share-based payment arrangements			61,965
Proceeds from exercise of stock options	21,177	30,112	61,674
Dividends paid	(2,581,552)	(3,000)	(3,365)
Treasury stock purchased	(389,821)	(207,755)
Proceeds from term loans, net	0	0	0
Repayments of Long-term Debt	0	0	0
Repayments of Senior Debt	0
Proceeds from senior subordinated notes, net	0	0	0
Proceeds from trade receivable securitization facility, net	0
Financing fees and other	0	0	0
Net cash (used in) provided by financing activities	(11,075)	12,060	(588)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	0	0	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(11,144)	12,060	(588)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	13,560	1,500	2,088
CASH AND CASH EQUIVALENTS, END OF PERIOD	2,416	13,560	1,500
TransDigm Inc.
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(587,800)	(230,931)	(298,797)
Capital expenditures, net of disposals	(1,984)	(1,716)	(2,871)
Acquisition of business, net of cash acquired	(136,295)	(1,399,064)	(1,624,278)
Acquisition of Schroth, net of cash acquired	(79,695)
Net cash used in investing activities	(217,974)	(1,400,780)	(1,627,149)
Intercompany activities	(1,682,518)	580,487	867,990
Excess tax benefits related to share-based payment arrangements			0
Proceeds from exercise of stock options	0	0	0
Dividends paid	0	0	0
Treasury stock purchased	0	0
Proceeds from term loans, net	2,937,773	1,711,515	1,515,954
Repayments of Long-term Debt	(1,284,698)	(834,409)	(1,025,318)
Repayments of Senior Debt	528,847
Proceeds from senior subordinated notes, net	300,386	939,584	445,303
Proceeds from trade receivable securitization facility, net	99,471
Financing fees and other	(17,571)	(3,580)	(1,266)
Net cash (used in) provided by financing activities	(176,004)	2,393,597	1,802,663
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	0	0	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(981,778)	761,886	(123,283)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	1,421,251	659,365	782,648
CASH AND CASH EQUIVALENTS, END OF PERIOD	439,473	1,421,251	659,365
Subsidiary Guarantors
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	1,334,099	944,152	734,130
Capital expenditures, net of disposals	(63,305)	(32,608)	(44,564)
Acquisition of business, net of cash acquired	0	0	0
Acquisition of Schroth, net of cash acquired	0
Net cash used in investing activities	(63,305)	(32,608)	(44,564)
Intercompany activities	(1,279,805)	(910,647)	(685,448)
Excess tax benefits related to share-based payment arrangements			0
Proceeds from exercise of stock options	0	0	0
Dividends paid	0	0	0
Treasury stock purchased	0	0
Proceeds from term loans, net	0	0	0
Repayments of Long-term Debt	0	0	0
Repayments of Senior Debt	0
Proceeds from senior subordinated notes, net	0	0	0
Proceeds from trade receivable securitization facility, net	0
Financing fees and other	0	0	0
Net cash (used in) provided by financing activities	(1,279,805)	(910,647)	(685,448)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	0	0	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(9,011)	897	4,118
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	8,808	7,911	3,793
CASH AND CASH EQUIVALENTS, END OF PERIOD	(203)	8,808	7,911
Non-Guarantor Subsidiaries
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	42,028	(25,496)	82,451
Capital expenditures, net of disposals	(5,724)	(9,658)	(7,436)
Acquisition of business, net of cash acquired	0	0	0
Acquisition of Schroth, net of cash acquired	0
Net cash used in investing activities	(5,724)	(9,658)	(7,436)
Intercompany activities	23,677	133,030	(58,526)
Excess tax benefits related to share-based payment arrangements			0
Proceeds from exercise of stock options	0	0	0
Dividends paid	0	0	0
Treasury stock purchased	0	0
Proceeds from term loans, net	0	0	0
Repayments of Long-term Debt	0	0	0
Repayments of Senior Debt	0
Proceeds from senior subordinated notes, net	0	0	0
Proceeds from trade receivable securitization facility, net	0
Financing fees and other	0	0	0
Net cash (used in) provided by financing activities	23,677	133,030	(58,526)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	5,519	242	(2,251)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	65,500	98,118	14,238
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	143,375	45,257	31,019
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 208,875	$ 143,375	$ 45,257

Valuation and Qualifying Acc101

Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		$ 4,414	$ 3,801	$ 4,091
Charged to Costs and Expenses		(1,095)	(1,043)	(376)
Acquisitions		363	724	271
Deductions from Reserve	[1]	(2,053)	(1,154)	(185)
Balance at End of Period		3,819	4,414	3,801
Reserve for excess and obsolete inventory
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		80,039	64,158	55,586
Charged to Costs and Expenses		(17,361)	(26,407)	(15,554)
Acquisitions		4,254	0	0
Deductions from Reserve	[1]	(21,879)	(10,526)	(6,982)
Balance at End of Period		79,775	80,039	64,158
Valuation Allowance of Deferred Tax Assets
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		27,286	17,645	24,267
Charged to Costs and Expenses		(5,928)	(9,641)	(6,622)
Acquisitions		0	0	0
Deductions from Reserve	[1]	0	0	0
Balance at End of Period		$ 33,214	$ 27,286	$ 17,645
[1]	The amounts in this column represent charge-offs net of recoveries and the impact of foreign currency translation adjustments.