TRANSDIGM INC., TRANSDIGM GROUP INCORPORATED, THE GUARANTORS NAMED HEREIN, AND THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A., as Trustee FOURTH SUPPLEMENTAL INDENTURE Dated as of September 14, 2012 to Indenture Dated as of December 14, 2010 by and...

Exhibit 4.1

TRANSDIGM INC.,

TRANSDIGM GROUP INCORPORATED,

THE GUARANTORS NAMED HEREIN,

AND

THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A.,

as Trustee

FOURTH SUPPLEMENTAL INDENTURE

Dated as of September 14, 2012

to

Indenture

Dated as of December 14, 2010

by and among

TRANSDIGM INC.,

TRANSDIGM GROUP INCORPORATED,

THE GUARANTORS NAMED THEREIN,

AND

THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A.,

as Trustee

7.75% Senior Subordinated Notes due 2018

of TransDigm Inc.

This FOURTH SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), dated as of September 14, 2012, by and among Aero-Instruments Co., LLC, an Ohio limited liability company (the “Guaranteeing Subsidiary”), TransDigm Inc., a Delaware corporation (the “Company”), TransDigm Group Incorporated, a Delaware corporation (“TD Group”), Xxxxx Rite Aerospace, Inc., a California corporation (“Xxxxx Rite”), MarathonNorco Aerospace, Inc., a Delaware corporation (“Marathon”), Champion Aerospace LLC, a Delaware limited liability company (“Champion”), Avionic Instruments LLC, a Delaware limited liability company (“Avionic”), Xxxxxx Aerospace Inc., a Delaware corporation (“Xxxxxx”), CDA InterCorp LLC, a Florida limited liability company (“CDA”), Aviation Technologies, Inc., a Delaware corporation (“ATI”), Avtech Corporation, a Washington corporation (“Avtech”), Transicoil LLC, a Delaware limited liability company (“Transicoil”), AeroControlex Group, Inc., a Delaware corporation (“AeroControlex”), Malaysian Aerospace Services, Inc., a Delaware corporation (“Malaysian”), Xxxxx Aerospace Inc., a Delaware corporation (“Xxxxx Aerospace”), Xxxxx Industries, Inc., a Colorado corporation (“Xxxxx Industries”), CEF Industries, LLC, a Delaware limited liability company (“CEF”), Aircraft Parts Corporation, a New York corporation (“APC”), Acme Aerospace, Inc., a Delaware corporation (“Acme”), Xxxxx Aerospace, Inc., a Delaware corporation (“Xxxxx”), Semco Instruments, Inc., a Delaware corporation, (“Semco”), Xxxxxxxx Corporation, a California corporation (“Xxxxxxxx”), XxXxxxxxx Aerospace DE, Inc., a Delaware corporation (“XxXxxxxxx Aerospace DE”), XxXxxxxxx Aerospace Holdings, Inc., a Delaware corporation (“XxXxxxxxx Aerospace Holdings”), XxXxxxxxx Aerospace Investments, Inc., a Delaware corporation (“XxXxxxxxx Aerospace Investments”), XxXxxxxxx Aerospace US LLC, a Delaware limited liability company (“XxXxxxxxx Aerospace US”), Texas Rotronics, Inc., a Texas corporation (“Rotronics”), Western Sky Industries, LLC, a Delaware limited liability company (“Western”), Xxxxxxxxx Holdings LLC, a Delaware limited liability company (“Xxxxxxxxx Holdings”), Xxxxxxxxx LLC, a Delaware limited liability company (“Xxxxxxxxx”), Xxxxxxxxx International Sales Corp., an Ohio corporation (“Xxxxxxxxx International”), Harco Laboratories, Incorporated, a Connecticut corporation (“Harco”), AmSafe Global Holdings, Inc., a Delaware corporation (“AmSafe Global”), AP Global Holdings, Inc., a Delaware corporation (“AP Global Holdings”), AP Global Acquisition Corp., a Delaware corporation (“AP Global Acquisition”), AmSafe Industries, Inc., a Delaware corporation (“AmSafe Industries”), Bridport Holdings, Inc., a Delaware corporation (“Bridport Holdings”), AmSafe, Inc., a Delaware corporation (“AmSafe Inc.”), AmSafe Aviation, Inc., a Georgia corporation (“AmSafe Aviation”), AmSafe Commercial Products, Inc., a Delaware corporation (“AmSafe Commercial”), AmSafe Bridport, Inc., a Delaware corporation (“AmSafe Bridport”), Bridport-Air Carrier, Inc., a Washington corporation (“Bridport-Air”), Bridport Erie Aviation, Inc., a Delaware corporation (“Bridport Erie”), and AmSafe – C Safe, Inc., a Delaware corporation (together with TD Group, Xxxxx Rite, Marathon, Champion, Avionic, Xxxxxx, CDA, ATI, Avtech, Transicoil, AeroControlex, Malaysian, Xxxxx Aerospace, Xxxxx Industries, CEF, APC, Acme, Xxxxx, Semco, Xxxxxxxx, XxXxxxxxx Aerospace DE, XxXxxxxxx Aerospace Holdings, XxXxxxxxx Aerospace Investments, XxXxxxxxx Aerospace US, Rotronics, Western, Xxxxxxxxx Holdings, Xxxxxxxxx, Xxxxxxxxx International, Harco, AmSafe Global, AP Global Holdings, AP Global Acquisition, AmSafe Industries, Bridport Holdings, AmSafe Inc., AmSafe Aviation, AmSafe Commercial, AmSafe Bridport, Bridport-Air and Bridport Erie, the “Existing Guarantors”), and The Bank of New York Mellon Trust Company, N.A., as trustee (the “Trustee”) under the Indenture referred to below. Capitalized terms used herein and not otherwise defined shall have the meaning assigned to them in the Indenture.

WITNESSETH:

WHEREAS, the Company and the Existing Guarantors have heretofore executed and delivered to the Trustee an indenture, dated as of December 14, 2010 (as supplemented by the First Supplemental Indenture thereto, dated as of September 22, 2011, the Second Supplemental Indenture thereto, dated as of December 9, 2011, and the Third Supplemental Indenture, dated as of February 15, 2012, the “Indenture”), providing for the issuance by the Company of 7.75% Senior Subordinated Notes due 2018 (the “Notes”) and the guarantees thereof by each of the Existing Guarantors;

WHEREAS, the Indenture provides that under certain circumstances described therein, newly created or acquired Domestic Restricted Subsidiaries shall execute and deliver to the Trustee a supplemental indenture to the Indenture providing for a senior subordinated guarantee of payment of the Notes by such Domestic Restricted Subsidiary (the “Guarantee”);

WHEREAS, all things necessary to make this Supplemental Indenture the legal, valid and binding obligation of the Company, the Existing Guarantors and the Guaranteeing Subsidiary have been done; and

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WHEREAS, pursuant to Section 9.01(g) of the Indenture, the Trustee is authorized to execute and deliver this Supplemental Indenture without the consent of the Holders of the Notes.

NOW, THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, the Guaranteeing Subsidiary covenants and agrees for the equal and ratable benefit of the Holders of the Notes as follows:

1. CAPITALIZED TERMS. Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

2. GUARANTEE, ETC. The Guaranteeing Subsidiary hereby agrees that from and after the date hereof it shall be a Guarantor under the Indenture and be bound by the terms thereof applicable to Guarantors and shall be entitled to all of the rights and subject to all the obligations of a Guarantor thereunder.

3. RATIFICATION OF INDENTURE; SUPPLEMENTAL INDENTURE PART OF INDENTURE. The Indenture is in all respects ratified and confirmed and all the terms, conditions and provisions thereof shall remain in full force and effect. This Supplemental Indenture shall form a part of the Indenture for all purposes, and every holder of Notes heretofore or hereafter authenticated and delivered shall be bound hereby.

4. EXECUTION AND DELIVERY. The Guaranteeing Subsidiary agrees that the Guarantee granted by it pursuant to the terms hereof shall remain in full force and effect notwithstanding any failure to endorse on each Note a notation of such Guarantee.

5. NO RECOURSE AGAINST OTHERS. No past, present or future director, officer, employee, incorporator, stockholder or agent of the Guaranteeing Subsidiary (or any successor entity) (other than the Company or the Existing Guarantors), as such, shall have any liability for any obligations of the Company, TD Group, the Guaranteeing Subsidiary or any other Guarantor under the Notes, any Guarantee, the Indenture or this Supplemental Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder of the Notes by accepting a Note waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Notes.

6. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW YORK SHALL GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE AND THE GUARANTEE GRANTED HEREUNDER WITHOUT GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

7. COUNTERPART ORIGINALS. The parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement.

8. EFFECT OF HEADINGS. The Section headings have been inserted for convenience of reference only, are not to be considered part of this Supplemental Indenture and shall in no way modify or restrict any of the terms or provisions hereof.

9. THE TRUSTEE. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Guaranteeing Subsidiary, the Existing Guarantors and the Company.

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IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed as of the date hereof.

TRANSDIGM INC.
By:		/s/ Xxxxxxx Xxxxx
		Name: Xxxxxxx Xxxxx
		Title:   Executive Vice President and Chief             Financial Officer
TRANSDIGM GROUP INCORPORATED
By:		/s/ Xxxxxxx Xxxxx
		Name: Xxxxxxx Xxxxx
		Title:   Executive Vice President and Chief             Financial Officer
ACME AEROSPACE, INC. XXXXX RITE AEROSPACE, INC. AEROCONTROLEX GROUP, INC. AERO-INSTRUMENTS CO., LLC AIRCRAFT PARTS CORPORATION AMSAFE – C SAFE, INC. AMSAFE AVIATION, INC. AMSAFE BRIDPORT, INC. AMSAFE COMMERCIAL PRODUCTS, INC. AMSAFE GLOBAL HOLDINGS, INC. AMSAFE, INC. AMSAFE INDUSTRIES, INC. AP GLOBAL ACQUISITION CORP. AP GLOBAL HOLDINGS, INC. AVIATION TECHNOLOGIES, INC. AVTECH CORPORATION BRIDPORT-AIR CARRIER, INC. BRIDPORT ERIE AVIATION, INC. BRIDPORT HOLDINGS, INC. XXXXX AEROSPACE INC. XXXXX INDUSTRIES, INC. XXXXX AEROSPACE, INC. XXXXXXXX CORPORATION HARCO LABORATORIES, INCORPORATED MALAYSIAN AEROSPACE SERVICES, INC. MARATHONNORCO AEROSPACE, INC. XXXXXXXXX AEROSPACE DE, INC. XXXXXXXXX AEROSPACE HOLDINGS, INC. XXXXXXXXX AEROSPACE INVESTMENTS, INC. XXXXXXXXX AEROSPACE US LLC By: XxXxxxxxx Aerospace DE, Inc., its sole member XXXXXXXXX INTERNATIONAL SALES CORP. SEMCO INSTRUMENTS, INC. XXXXXX AEROSPACE INC. TEXAS ROTRONICS, INC. TRANSICOIL LLC By: Aviation Technologies, Inc., its sole member WESTERN SKY INDUSTRIES, LLC By: XxXxxxxxx Aerospace Investments, Inc.,         its sole member
By:		/s/ Xxxxxxx Xxxxx
		Name: Xxxxxxx Xxxxx
		Title: Treasurer and Secretary

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AVIONIC INSTRUMENTS LLC CDA INTERCORP LLC CEF INDUSTRIES, LLC CHAMPION AEROSPACE LLC XXXXXXXXX HOLDINGS LLC XXXXXXXXX LLC
By: Xxxxxxxxx Holdings LLC, its sole member
By:		TransDigm Inc., its sole member
By:		/s/ Xxxxxxx Xxxxx
		Name: Xxxxxxx Xxxxx
		Title:   Executive Vice President and Chief Financial Officer

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THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A., AS TRUSTEE
By:		/s/ X. Xxxxxx
		Name: X. Xxxxxx
		Title:   Vice President

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