SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* SMALL ROBERT J (Last) (First) (Middle) C/O BERKSHIRE PARTNERS LLC 200 CLARENDON STREET, 35TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol TransDigm Group INC [ TDG ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X Director 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 05/12/2010
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	05/12/2010		P		15,000(1)	A	$55.94(5)	4,198,562	I	By Berkshire Entities(2)(3)(4)
Common Stock	05/13/2010		P		15,000(1)	A	$57(6)	4,213,562	I	By Berkshire Entities(2)(3)(4)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Represents shares acquired by one of the Berkshire Entities (as defined below), a passive investment fund (the "Fund"), consistent with its investment objective of achieving capital appreciation by investing primarily in marketable securities. This Form 4 has been filed because the Reporting Person is a director of the Issuer and a managing member of the general partner of the Fund. As such, the Reporting Person may be deemed to have a shared voting and/or dispositive power over the shares held by the Fund. However, the Reporting Person disclaims beneficial ownership of such shares except to the extent of his pecuniary interest therein.

2. Owned by Berkshire Fund VII, L.P., Berkshire Fund VII-A, L.P., Berkshire Investors LLC, Berkshire Investors III LLC and Stockbridge Fund, L.P. (collectively, the "Berkshire Entities"). Seventh Berkshire Associates LLC is the general partner of each of Berkshire Fund VII, L.P. and Berkshire Fund VII-A, L.P. Stockbridge Associates LLC is the general partner of Stockbridge Fund, L.P. The Reporting Person is a managing member of each of Seventh Berkshire Associates LLC, Stockbridge Associates LLC, Berkshire Investors LLC and Berkshire Investors III LLC. As such, the Reporting Person may be deemed to have a shared voting and/or dispositive power over the shares held by such entities. However, the Reporting Person disclaims beneficial ownership of these shares, except to the extent of his pecuniary interest therein.

3. The Reporting Person may also be deemed to indirectly beneficially own 103,500 shares of Common Stock held by Stockbridge Partners LLC on behalf of a managed account over which it has shared voting and sole dispositive power. The Reporting Person is a managing member of Stockbridge Partners LLC. As such, the Reporting Person may be deemed to have a shared voting and/or dispositive power over these shares. However, the Reporting Person disclaims beneficial ownership of these shares, except to the extent of his pecuniary interest therein.

4. The Reporting Person also directly beneficially owns 5,000 shares of Common Stock.

5. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $55.92 to $55.95. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote.

6. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $56.47 to $57.25. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote.

Remarks:

	/s/ Robert J. Small	05/14/2010
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.