# STC SA5990NM-D - Type: Supplemental type certificate - Status: Current, Reissued - Holder: United Airlines Inc, United States - Description: Modifies the aircraft to install a one way check valve in the yaw damper actuator hydraulic return port. The installation is in accordance with DAS-1-WE Approved United Air Lines Drawing List No. 5990 dated April 27, 1994, or later FAA approved revisions. - Applied: April 1, 1994 - Status date: November 30, 2011 - Product: Aircraft, Large Multi-Engine - Certification basis: Part 21, Part 25 - Data sheets: [TCDS A1NM](https://openairdocs.org/tcds/A1NM) - Certificate PDF: https://openairdocs.org/files/sha256/7c/45/7c455d6553c7ae1a96df6d4facdfab52df5e31fe2731e6ed0b08a5e4e8609732 - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/FECBCEAF71FDE4D786257991006FC52E.0001 - DRS record last changed: December 6, 2025 - Page: https://openairdocs.org/stc/SA5990NM-D ## ADs that name it (0) None. ## Approved models (2) - The Boeing Company 767-200 Series ([TCDS A1NM](https://openairdocs.org/tcds/A1NM)) - The Boeing Company 767-300 Series ([TCDS A1NM](https://openairdocs.org/tcds/A1NM)) ## What the certificate says Read from the PDF's text layer, without the form's printed wording; the layout is lost and the order can differ. The PDF is the record. This Certificate issued to United Air Lines, Inc. 600 Jefferson Street Houston, Texas 77002 Part 25 of the Federal Aviation Regulations. See Type Certificate Data Sheet A1NM for Special Conditions Original Product Type Certificate Number : A1NM Boeing 767-200, 767-300 Series Description of Type Design Change: Modifies the aircraft to install a one way check valve in the yaw damper actuator hydraulic return port. The in stallation is in accordance with DAS-1-WE Approved United Air Lines Drawing List No. 5990 dated April 27, 1994, or later FAA approved revisions. Limitations and Conditions: Approval of this installation app lies to all 767-200, and 767-300 series aircraft. This approval should not ex tend to other aircraft unless it is determined by the installer that this modification is compatible with the configuration of the aircraft to be modified, and that the airworthiness of the aircraft is not compromised by the modifica tion. If the holder agrees to permit another person to use this certificate to alter the product, the holder shall give the other person written evidence of that permission. This certificate and the supporting data, which is the basis for approval, shall remain in effect until surrendered, suspended, revoked or a termination date is otherwise established by the Administrator of the Federal Aviation Administration. Date of application: April 1, 1994 Date of issuance: April 27, 1994 Date reissued: November 30, 2011 ( Signature) Haifa Haj-Eid Supervisor, Technical & Administrative Support Staff, Los Angeles Aircraft Certification Office (Title) NOTE: **DO NOT DELETE THIS PAGE.** **DO NOT ADD ANY DATA TO THIS PAGE.** **THIS PAGE IS FOR PAGE NUMBERING PURPOSES, PLEASE DISCARD PRINTED COPY.** ## Every issue (1) - November 30, 2011: Reissued, Current. [certificate](https://openairdocs.org/files/sha256/7c/45/7c455d6553c7ae1a96df6d4facdfab52df5e31fe2731e6ed0b08a5e4e8609732) --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.