Filing Details

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 TransDigm Group INC (Name of Issuer) Common Stock (Title and Class of Securities) 893641100 (CUSIP Number) December 31, 2017 (Date of Event which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: [X] Rule 13d-1(b) [_] Rule 13d-1(c) [_] Rule 13d-1(d) *The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page. The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 893641100 Page 2 1 NAMES OF REPORTING PERSONS Principal Global Investors, LLC 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) (b) 3 SEC USE ONLY 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware NUMBER OF 5 SOLE VOTING POWER 0 SHARES BENEFICIALLY 6 SHARED VOTING POWER 2,627,025 OWNED BY EACH 7 SOLE DISPOSITIVE POWER 0 REPORTING PERSON WITH 8 SHARED DISPOSITIVE POWER 2,627,025 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,627,025 10 CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See Instructions) 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.1 12 TYPE OF REPORTING PERSON (See Instructions) IACUSIP No. 893641100 Page 3 Item 1(a). Name of Issuer: TransDigm Group INC Item 1(b). Address of Issuer's Principal Executive Offices: 1301 EAST 9TH STREET SUITE 3000 CLEVELAND, OHIO 44114 Item 2(a). Name of Person Filing: Principal Global Investors, LLC Item 2(b). Address of Principal Business Office, or, if None, Residence: Principal Global Investors, LLC 801 Grand Avenue Des Moines, IA 50392 Item 2(c). Citizenship: Principal Global Investors, LLC - State of Delaware Item 2(d). Title of Class of Securities: Common Stock Item 2(e). CUSIP Numbers: 893641100 Item 3. If this statement is filed pursuant to section 240.13d-1(b) or 240.13d 2(b) or (c), check whether the person filing is a: (e) [X] An investment adviser in accordance with section 240.13d 1(b)(1)(ii)(E) Item 4. Ownership: (a) Amount Beneficially Owned 2,627,025 Shares Common Stock presently held by Principal Global Investors, LLCCUSIP No. 893641100 Page 5 Item 8. Identification and Classification of Members of the Group Not applicable Item 9. Notice of Dissolution of Group Not applicable Item 10(a). Certification By signing below I certify, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect. Signature After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. Principal Global Investors, LLC By /s/ Jill Hittner Jill Hittner, Chief Financial Officer Dated February 14, 2018 EXHIBIT 99.1 Principal Global Investors, LLC Item 3 Classification: (e) Investment Adviser in accordance with Section 240.13d-1(b)(1)(ii)(E)