EXHIBIT 4.2(a)


                    FIRST SUPPLEMENTAL INDENTURE dated as of June 27, 1996 
            (this "Supplemental Indenture"), to the Indenture dated as of 
            February 29, 1996 (the "Indenture"), between HEXCEL CORPORATION, 
            a Delaware corporation (the "Company"), and FIRST TRUST OF 
            CALIFORNIA, NATIONAL ASSOCIATION, a national banking association, 
            as trustee (the "Trustee").  Capitalized terms used but not 
            defined in this Supplemental Indenture shall have the meanings 
            ascribed to them in the Indenture.

          WHEREAS, the Company desires to amend certain provisions of the 
Indenture, among other things, in respect of the Credit Agreement (as defined 
in Section 1(b) below) which is being entered into concurrently with this 
Supplemental Indenture;

          WHEREAS, the Company desires to issue up to $115 million of its 
Convertible Subordinated Notes due 2003;

          WHEREAS, Section 9.02 of the Indenture authorizes the Company and 
the Trustee to amend certain provisions of the Indenture with the consent of 
the Securityholders;

          WHEREAS, the Company has not issued any Securities under the 
Indenture as of the date of this Supplemental Indenture;

          WHEREAS, pursuant to the Strategic Alliance Agreement, dated as of 
September 29, 1995, and as subsequently amended (the "Strategic Alliance 
Agreement"), among Ciba-Geigy Limited ("Ciba"), Ciba-Geigy Corporation and 
the Company, all the Securities to be issued under the Indenture shall be 
issued to Ciba and its Subsidiaries (as defined in the Strategic Alliance 
Agreement); and

          WHEREAS, Ciba and the Company have agreed to modify the terms of 
the Securities as set forth in this Supplemental Indenture, and accordingly, 
Ciba consents to this Supplemental Indenture.

          NOW, THEREFORE, the Company and the Trustee hereby agree for the 
equal and ratable benefit of the Securityholders as follows:





                                                                             2


          SECTION 1.  AMENDMENT OF INDENTURE.  (a)  The definition of "Ciba" 
contained in Article I of the Indenture is hereby amended to read as follows:

               ""CIBA" means Ciba-Geigy Limited, a corporation organized 
            under the laws of Switzerland, together with its successors and 
            assigns, including, upon consummation of the merger or 
            combination of Ciba-Geigy Limited and Sandoz Limited, Novartis 
            Limited."

          (b)  The definition of "Credit Agreement" contained in Article I of 
the Indenture is hereby amended to read as follows:

               ""CREDIT AGREEMENT" means, collectively, the Credit Agreement 
            dated as of June 27, 1996, among the Company, certain of its 
            Subsidiaries, the institutions from time to time party thereto as 
            Lenders, Citibank, N.A. (or any successor thereto) in its 
            separate capacity as collateral agent for the Lenders and Credit 
            Suisse (or any successor thereto) in its separate capacity as 
            administrative agent for the Lenders, as the same may from time 
            to time be amended, renewed, supplemented or otherwise modified 
            at the option of the parties thereto, and any other agreement 
            pursuant to which any of the Indebtedness, commitments, 
            obligations, costs, expenses, fees, reimbursements and other 
            indemnities payable or owing thereunder may be replaced or 
            refinanced, in any such event having an aggregate principal 
            amount and availability not in excess of $310,000,000 LESS the 
            amount of any Indebtedness Incurred by Subsidiaries of the 
            Company pursuant to Section 13.1(j) of the Credit Agreement (or 
            any successor provision) PLUS amounts otherwise permitted 
            pursuant to Section 4.03(b)(i) of this Indenture."





                                                                             3


          (c)  The definition of "Specified Properties" contained in Article 
I of the Indenture is hereby amended to read as follows:

               ""SPECIFIED PROPERTIES" shall mean (i) the Company's 
            manufacturing plants located in (a) Lancaster, Ohio, (b) 
            Welkenraedt, Belgium and (c) Graham, Texas, (ii) the 
            manufacturing plants of Hexcel Omega Corporation located in 
            Anaheim, California, (iii) the outstanding capital stock of 
            Hexcel Omega Corporation and (iv) the outstanding capital stock 
            and intercompany obligations of Hercules Aerospace Espana, S.A., 
            a Spanish corporation, to the extent such properties are sold 
            pursuant to the letter agreement dated June 27, 1996, between the 
            Company and Hercules Incorporated."

          (d)  Section 4.03(b)(i) of the Indenture is hereby amended to read 
as follows:

               "(i)  Indebtedness under the Credit Agreement and any other 
            loan or other agreement in an aggregate principal amount 
            outstanding at any time not to exceed the sum of (A) the 
            outstanding Indebtedness under the Credit Agreement and the 
            unused commitments thereunder as of the date the Credit Agreement 
            first becomes effective and (B) $12,500,000."

          (e)  Section 4.03(b)(vi) of the Indenture is hereby amended to read 
as follows:

               "(vi)  Refinancing Indebtedness Incurred in respect of 
            Indebtedness Incurred pursuant to clause (iv) or (v) above or 
            Section 13.1(j) of the Credit Agreement as in effect on the date 
            the Credit Agreement first becomes effective (or any successor 
            provision having the same terms)."

          (f)  Section 4.03(b)(x) of the Indenture is hereby amended to read 
as follows: 

               "(x)(A)  Guarantees of any Subsidiary in respect of 
            obligations of the Company, (B) Guarantees of the Company in 
            respect of Indebtedness of any Subsidiary Incurred pursuant to 
            Section 13.1(j) of the Credit Agreement as in effect on the date 
            the Credit Agreement first becomes effective (or any successor 
            provision having the same terms) and (C) Guarantees of any 
            partnership or 




                                                                             4


            joint venture (other than Existing Joint Ventures) to the extent 
            that the Incurrence of such obligations shall not cause to 
            Maximum Partnership/Joint Venture Amount to exceed $15,000,000 at 
            any time; PROVIDED that no such Investment may be made as long as 
            any Default or Event of Default has occurred and is continuing or 
            would occur as a result of such Investment;"

          (g)  Section 4.03(b) of the Indenture is hereby amended by 
inserting the following new clauses (xv) and (xvi) at the end thereof:

               "(xv)  Indebtedness of the Company in respect of unsecured 
            standby and commercial letters of credit issued by Lenders under 
            the Credit Agreement in an aggregate face amount (including, 
            without limitation, any reimbursement obligations owing in 
            respect thereof) not to exceed $10,000,000; or

               (xvi)  Indebtedness represented by the Company's Convertible 
            Subordinated Notes due 2003 in an aggregate principal amount not 
            to exceed $115 million."

          (h)  The face of Exhibit A to the Indenture is hereby amended to 
state that the principal amount of the Securities is payable on March 1, 2003.

          (i)  The second sentence of Section 1 of Exhibit A to the Indenture 
is hereby amended to read as follows:

               "On the third anniversary of the date of the Closing (as 
            defined in the Strategic Alliance Agreement dated as of September 
            29, 1995, among Ciba-Geigy Limited, Ciba-Geigy Corporation and 
            the Company), the rate of interest then borne by the Securities 
            shall increase to 10.5%, and on each subsequent anniversary of 
            the Closing the rate of interest then borne by the Securities 
            shall increase by an additional 0.5%."

          (j)  Exhibit B to the Indenture is hereby amended and restated in 
the form of Exhibit B hereto.

          SECTION 2.  CONFIRMATION.  Except as hereby expressly amended, the 
Indenture is in all respects ratified and confirmed and all the terms, 
conditions and provisions thereof shall remain in full force and effect.

          SECTION 3.  EFFECTIVENESS.  This Supplemental Indenture shall take 
effect immediately upon its execution and delivery by the Company, the 
Trustee and Ciba.





                                                                             5


          SECTION 4.  COUNTERPARTS.  This Supplemental Indenture may be 
executed in any number of counterparts, each of which, when so executed, 
shall be deemed to be an original, but all of which shall together constitute 
but one contract. 

          SECTION 5.  EXECUTION.  Delivery of an executed counterpart of a 
signature page by facsimile transmission shall be effective as delivery of a 
manually executed counterpart of this Supplemental Indenture.

          SECTION 6.  APPLICABLE LAW.  THIS SUPPLEMENTAL INDENTURE SHALL BE 
GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW 
YORK.

          IN WITNESS WHEREOF, the parties hereto have caused this 
Supplemental Indenture to be duly executed by their duly authorized officers, 
all as of the date and year first above written.

                                   HEXCEL CORPORATION

                                     by
                                       ---------------------------------
                                       Name:
                                       Title:


                                   FIRST TRUST OF CALIFORNIA, NATIONAL
                                   ASSOCIATION

                                     by
                                       -----------------------------------
                                       Name:
                                       Title:






                                                                             6


CONSENTED AND AGREED TO BY:

CIBA-GEIGY LIMITED

  by
    ----------------------------
    Name:
    Title:


  by
    ----------------------------
    Name:
    Title: