# STC SR00135LA - Type: Supplemental type certificate - Status: Current, Issued - Holder: Yehnert Helicopters, Inc, United States - Description: Installation of Yehnert Tail Rotor Blades YH-278 as replacements for Hiller Tail Rotor Blades 55073. - Applied: November 22, 1994 - Status date: December 15, 1995 - Product: Aircraft, Rotorcraft - Certification basis: Part 21 - Data sheets: [TCDS 4H10](https://openairdocs.org/tcds/4H10), [TCDS 4H11](https://openairdocs.org/tcds/4H11) - Certificate PDF: https://openairdocs.org/files/sha256/0f/5f/0f5f468429ae5f84b6627b878439778984539ebcfb69e8532d7ee0676631ca02 - Approved model list and other attachments: [SR00135LA_AML.pdf](https://openairdocs.org/files/sha256/ff/35/ff35ff641117273eebca38e47557a690dbac0459740383d450069d6f4df3055d) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/A10D5A1B8E945DA485256CC20062249E.0001 - DRS record last changed: December 6, 2025 - Page: https://openairdocs.org/stc/SR00135LA ## ADs that name it (0) None. ## Approved models (3) - Hiller Aviation UH-12D (Army UH-23D) ([TCDS 4H10](https://openairdocs.org/tcds/4H10)) - Rogerson Hiller Corporation UH-12E ([TCDS 4H11](https://openairdocs.org/tcds/4H11)) - Rogerson Hiller Corporation UH-12E-L ([TCDS 4H11](https://openairdocs.org/tcds/4H11)) ## What the certificate says This is OCR from the scanned FAA certificate. OCR can misread letters and numbers. United States of America 8103 Department of Transportation Federal Aviation Administration Supplemental Type Certificate Number SR00135LA This certificate issued to: 1049 Airport Drive Yehnert Helicopter, Inc. Upland, California 91786 Part " of the " Regulations. Original Product - Type bertificale Number: * *See attached FAA Approved Model List (AML) No. Make: * SR00135LA for list of approved helicopter models and Model: * applicable airworthiness regulations. Description of Type Design Change: Installation of Yehnert Tail Rotor Blades YH-278 as replacements for Hiller Tail Rotor Blades 55073, in accordance with FAA approved Installation Instructions, as listed on AML No. SR00135LA, dated December 1, 1995, or later FAA approved revision. Limitations and Conditions: The service lives of the Yehnert tail rotor blades have been established in accordance with FAR 27.571 (e) at the specified time-in-service, with periodic inspections required, as listed in Table 1 of the AML. These inspections shall be conducted in accordance with Yehnert Report YH-307, dated December 1, 1995, or later FAA approved revisions. A copy of this Certificate and FAA Approved Model List (AML) No. SR00135LA, dated December 1, 1995, or later FAA approved revision, must be maintained as part of the permanent records for the modified aircraft. This approval should not be extended to aircraft of these models on which other previously approved modifications are incorporated unless it is determined that the relationship between this change and any of those other previously approved modifications, including changes in type design, will introduce no adverse effect upon the airworthiness of that aircraft. - END - 47 PAGE 30F 3PAGES FAA AC 82.03 ### SR00135LA_AML.pdf This is OCR from the scanned FAA attachment. OCR can misread letters and numbers. AML AMENDMENT DATE 12/1/95 12/1/95 12/1/95 12/1/95 NOTES: 1. Mandated maximum service lives and required periodic inspectionance anual for the un 122. For be thiel UH-120, the installation instructions in SUPPLEMENT NUMBER/DATE N/A N/A N/A N/A AS A REPLACEMENT FOR HILLER TAIL ROTOR BLADES P/N 55073 ON HILLER HELICOPTERS Rev. No. and Date* Rev. D, 11/29/95 11/29/95 Rev. D, 11/29/95 Rev. D, 11/29/95 the Hiller Maintenance Manual for the UH-12D, or in the Army Maintenance Manual for the H-23D may be used. FAA APPROVED MODEL LIST (AML) NO. SRO0135LA INSTALLATION OF YEHNERT TAIL ROTOR BLADES P/N YH-278 ISSUE DATE: December 1, 1995 INSTALLATION INSTRUCTIONS Number DL YH-300 See Note 2 DL YH-300 See Note 2 DL YK-300 See Note 2 DL YH-300 See Note 2 *or later FAA-approved revision Installation instructions are those given in the Hiller Maintenance Manual for the UH-12E. YEHNERT HELICOPTER, INC. FOR CERTIFICATION BASIS FOR ALTERATION CAR 6 with amendments listed in TCDS 4H10 CAR 6 with amendments listed in TCDS 4H11 CAR 6 with amendments listed in TCDS 4H11 CAR 6 with amendments listed in TCDS 4H11 TYPE CERTIFICATE NO. ORIGINAL 4H10 4H11 4H11 4H11 PAGE 1 OF 2 AIRCRAFT MODEL, BLADE P/N See Note 1 UH-12D (3 place) YH- 278-1 UH- 12E (3 place) YH- 278-1 UH- 12E (4 place) YH-278-2 UH-12E-L (3 place) YH-278-1 AIRCRAFT MAKE Hiller Hiller Hiller Hiller ITEM Note A: Mandated Inspection periods for the YH-278-1 blades are at: 1,000 hours, 2,000 hours, 3,000 hours, 4,000 hours, 4,500 hours, 5,000 hours; Note B: Mandated Inspection periods for the YH-278-2 blades are at: 600 hours; 1,200 hours, 1,800 hours, 2,400 hours, 2,700 hours, 3,000 hours; Bubuls Service Lives and Periodic Inspection Requirements for Yehnert Tail Rotor Blades YH-278 Manager, Table 1 Inspection Periods See Note A See Note A See Note A See Note B FAA Approved: ta- Service Life 5400 hours 5400 hours 5400 hours 3240 hours PAGE 2 OF 2 Replacement for Hiller Part No. 55073 55073 55073 55073 remove blade before 5,400 hours time in service. remove blade before 3,240 hours time in service. Model Eligibility Hiller Model UH-12D Hiller Model UH-12E (3 place) UH-12E-L (3 place) Hiller Model UH-12E (4 place) Yehnert Part No. YH-278-1 YH-278-1 YH-278-1 YH-278-2 ## Every issue (1) - December 15, 1995: Issued, Current. [certificate](https://openairdocs.org/files/sha256/0f/5f/0f5f468429ae5f84b6627b878439778984539ebcfb69e8532d7ee0676631ca02), [SR00135LA_AML.pdf](https://openairdocs.org/files/sha256/ff/35/ff35ff641117273eebca38e47557a690dbac0459740383d450069d6f4df3055d) --- 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.