AD 61-05-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12D | Airworthiness Directives; Hiller Models UH-12D and UH-12E Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E | Airworthiness Directives; Hiller Models UH-12D and UH-12E Helicopters |
Unsafe Condition
Failures of the main transmission due to improper part numbers or heat treat lot numbers on planet spur gear, bevel ring gear, and tail rotor bevel gear shaft.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect and remove planet spur gear, bevel ring gear, and tail rotor bevel gear shaft with non-compliant part numbers or heat treat lot numbers. Replace with specified parts. Inspect oil nozzles and filters for obstructions or metallic particles, and inspect/overhaul first stage planetary system if wear or overheating is found. Incorporate specified bushings and planet gear shafts within 150 hours.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Prior to next flight, and for specific models and serial numbers, at intervals not exceeding 10 or 25 hours' time in service until modified. Incorporate specified parts within 150 hours' time in service.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Hiller Models UH-12D and UH-12E helicopters, serial numbers 942, 954, and 2001 through 2198 inclusive.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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