Exhibit 12.1 TRANSDIGM INC. Computation of Ratio of Earnings to Fixed Charges Thirteen Weeks Ended Unaudited Unaudited ------------------------ Pro Forma Pro Forma December 26, January 1, January 1, 1994 1995 1996 1997 1998 1998 1997 1999 1999 ------ ------ ------ ------ ------ --------- ------------ ---------- ---------- Earnings: Total earnings (loss) $(5,323) $ (261) $1,175 $3,172 $14,137 7,169 4,118 (24,824) 2,113 Income tax provision (credit) (2,307) 134 2,045 5,193 12,986 4,350 2,590 (7,566) 1,406 Extraordinary Item 1,462 --------------------------------------------------------------------------------------------- Pre-tax earnings (loss) (7,630) (127) 3,220 9,827 27,123 11,519 6,708 (32,390) 3,519 --------------------------------------------------------------------------------------------- Fixed charges: Interest charges 4,823 5,193 4,510 3,463 3,175 25,419 1,046 2,276 5,980 Interest factor of operating rents 198 190 188 178 197 200 50 50 50 --------------------------------------------------------------------------------------------- Total fixed charges 5,021 5,383 4,698 3,641 3,372 25,619 1,096 2,326 6,030 --------------------------------------------------------------------------------------------- Earnings as adjusted (2,609) 5,256 7,918 13,468 30,495 37,138 7,804 (30,064) 9,549 --------------------------------------------------------------------------------------------- Ratio of earnings to fixed charges - - 1.7 3.7 9.0 1.5 7.1 -- 1.6 ---------------------------------------------------------------------------------------------