Data / Federal rules / 2025-15839
Airworthiness Directives; Siam Hiller Holdings, Inc.
The Federal Aviation Administration published this final rule in the Federal Register on August 20, 2025. It took effect on September 24, 2025.
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What the agency says
The FAA is adopting a new airworthiness directive (AD) for certain Siam Hiller Holdings, Inc. (Siam Hiller), Model UH-12E (Army OH-23G and H-23F) and UH-12E-L helicopters. This AD was prompted by reports of cracks found in a main rotor (M/R) transmission drive shaft (drive shaft). This AD requires inspecting certain M/R drive shafts for a crack, prohibits installing certain M/R drive shafts unless the inspection is done, and prohibits using certain paint strippers. The FAA is issuing this AD to address the unsafe condition on these products.
Key facts
- Document number
- 2025-15839
- Type
- Final rule
- Action
- Final rule
- Agency
- Transportation Department; Federal Aviation Administration
- Published
- August 20, 2025
- Takes effect
- September 24, 2025
- Dates
- This AD is effective September 24, 2025.
- Docket
- Docket No. FAA-2024-2555; Project Identifier AD-2024-00214-R; Amendment 39-23089; AD 2025-15-02
- Regulation ID (RIN)
- 2120-AA64
- Code of Federal Regulations
- 14 CFR 39
- Topics
- Air transportation; Aircraft; Aviation safety; Incorporation by reference; Safety
- Pages
- 3
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Everything from the Federal Aviation Administration · Rules on air transportation · Rules on aircraft · Rules on aviation safety · Published in August 2025
Read from the Federal Register API, last updated 2026-10-23. The document on federalregister.gov is the official record; dates and dockets can change through later corrections. Free to reuse with credit to SpecStream under CC BY 4.0.