TDG Transdigm Group Incorporated

[ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).         
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES                                                                                   
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940                       

1. Name and Address of Reporting Person * SMALL ROBERT J	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)
(Last)          (First)          (Middle) C/O BERKSHIRE PARTNERS LLC, 200 CLARENDON STREET, 35TH FLOOR	3. Date of Earliest Transaction (MM/DD/YYYY) 8/20/2019
(Street) BOSTON, MA 02116 (City)        (State)        (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)	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. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. 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	8/20/2019		S		8943	D	$534.0493 (4)	230651	I	By Stockbridge Partners LLC (1)
Common Stock	8/20/2019		S		60957	D	$534.0493 (4)	3176189	I	By Berkshire Entities (2)(3)
Common Stock	8/20/2019		S		7035	D	$535.0603 (5)	223616	I	By Stockbridge Partners LLC (1)
Common Stock	8/20/2019		S		47946	D	$535.0603 (5)	3128243	I	By Berkshire Entities (2)(3)
Common Stock	8/20/2019		S		2710	D	$535.9317 (6)	220906	I	By Stockbridge Partners LLC (1)
Common Stock	8/20/2019		S		18467	D	$535.9317 (6)	3109776	I	By Berkshire Entities (2)(3)
Common Stock	8/20/2019		S		653	D	$536.8040 (7)	220253	I	By Stockbridge Partners LLC (1)
Common Stock	8/20/2019		S		4447	D	$536.8040 (7)	3105329	I	By Berkshire Entities (2)(3)
Common Stock	8/20/2019		S		38	D	$537.7527 (8)	220215	I	By Stockbridge Partners LLC (1)
Common Stock	8/20/2019		S		262	D	$537.7527 (8)	3105067	I	By Berkshire Entities (2)(3)
Common Stock	8/21/2019		S		3931	D	$532.4256 (9)	216284	I	By Stockbridge Partners LLC (1)
Common Stock	8/21/2019		S		3189	D	$532.4256 (9)	3101878	I	By Berkshire Entities (2)(3)
Common Stock	8/21/2019		S		19333	D	$533.3710 (10)	196951	I	By Stockbridge Partners LLC (1)
Common Stock	8/21/2019		S		15685	D	$533.3710 (10)	3086193	I	By Berkshire Entities (2)(3)
Common Stock	8/21/2019		S		20925	D	$534.2587 (11)	176026	I	By Stockbridge Partners LLC (1)
Common Stock	8/21/2019		S		16978	D	$534.2587 (11)	3069215	I	By Berkshire Entities (2)(3)
Common Stock	8/21/2019		S		2092	D	$535.1179 (12)	173934	I	By Stockbridge Partners LLC (1)
Common Stock	8/21/2019		S		1697	D	$535.1179 (12)	3067518	I	By Berkshire Entities (2)(3)
Common Stock	8/21/2019		S		55	D	$536.5200 (13)	173879	I	By Stockbridge Partners LLC (1)
Common Stock	8/21/2019		S		45	D	$536.5200 (13)	3067473	I	By Berkshire Entities (2)(3)
Common Stock	8/21/2019		S		111	D	$537.5225 (14)	173768	I	By Stockbridge Partners LLC (1)
Common Stock	8/21/2019		S		89	D	$537.5225 (14)	3067384	I	By Berkshire Entities (2)(3)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. 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		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 of Derivative Security: 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 held by Stockbridge Partners LLC ("SP") on behalf of a managed account over which it has shared voting and sole dispositive power. This Form 4 has been filed because the Reporting Person is a director of the Issuer and a managing member of SP. As such, the Reporting Person may be deemed to share voting and dispositive power with respect to the shares of the Issuer's common stock held by SP. However, the Reporting Person disclaims beneficial ownership of these shares, except to the extent, if any, of his pecuniary interest therein, and the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of the reported securities for purposes of Section 16 or for any other purposes.
(2)	Represents shares held directly or indirectly by Berkshire Fund VII, L.P. ("VII"), Berkshire Fund VII-A, L.P. ("VII-A"), Berkshire Fund VIII, L.P. ("VIII"), Berkshire Fund VIII-A, L.P. ("VIII-A"), Berkshire Investors LLC ("Investors"), Berkshire Investors III LLC ("Investors III"), Berkshire Investors IV LLC ("Investors IV"), Stockbridge Fund, L.P. ("SF") and Stockbridge Absolute Return Fund, L.P. ("SARF") (collectively, the "Berkshire Entities"). Berkshire Partners Holdings LLC ("BPH") is the general partner of BPSP, L.P. ("BPSP"), which is the managing member of each of Berkshire Partners LLC, the registered investment adviser to VII, VII-A, VIII, VIII-A, Investors, Investors III and Investors IV ("BP"), and SP, the registered investment adviser to SF and SARF. Seventh Berkshire Associates LLC ("7BA") is the general partner of each of VII and VII-A. Eighth Berkshire Associates LLC ("8BA") is the general partner of each of VIII and VIII-A.
(3)	[Continued from Footnote 2] Stockbridge Associates LLC ("SA") is the general partner of each of SF and SARF. The Reporting Person is a managing member of each of BPH, BPSP, BP, SP, 8BA, 7BA, SA, Investors, Investors III and Investors IV. As such, the Reporting Person may be deemed to share voting and dispositive power with respect to the shares of the Issuer's common stock held by the Berkshire Entities. However, the Reporting Person disclaims beneficial ownership of these shares, except to the extent, if any, of his pecuniary interest therein, and the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of the reported securities for purposes of Section 16 or for any other purposes.
(4)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions within the range of $533.5250 to $534.5249. 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 purchased at each separate price within the ranges set forth in this footnote.
(5)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions within the range of $534.5250 to $535.5249. 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 purchased 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 within the range of $535.5250 to $536.5249. 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 purchased at each separate price within the ranges set forth in this footnote.
(7)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions within the range of $536.5250 to $537.5249. 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 purchased at each separate price within the ranges set forth in this footnote.
(8)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions within the range of $537.5250 to $537.8000. 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 purchased at each separate price within the ranges set forth in this footnote.
(9)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions within the range of $532.0000 to $532.9999. 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 purchased at each separate price within the ranges set forth in this footnote.
(10)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions within the range of $533.0000 to $533.9999. 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 purchased at each separate price within the ranges set forth in this footnote.
(11)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions within the range of $534.0000 to $534.9999. 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 purchased at each separate price within the ranges set forth in this footnote.
(12)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions within the range of $535.0000 to $535.9999. 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 purchased at each separate price within the ranges set forth in this footnote.
(13)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions within the range of $536.0000 to $536.9999. 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 purchased at each separate price within the ranges set forth in this footnote.
(14)	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions within the range of $537.0000 to $537.7450. 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 purchased at each separate price within the ranges set forth in this footnote.

Reporting Owners
Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
SMALL ROBERT J C/O BERKSHIRE PARTNERS LLC 200 CLARENDON STREET, 35TH FLOOR BOSTON, MA 02116	X

Signatures
/s/ Robert J. Small		8/22/2019
**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 control number.

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