AD 64-11-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Siam Hiller Holdings, Inc. | UH-12E | Airworthiness Directives; Hiller Model UH-12E Helicopters |
| aircraft | Siam Hiller Holdings, Inc. | UH-12E-L | Airworthiness Directives; Hiller Model UH-12E Helicopters |
Unsafe Condition
Failures of the tail rotor pinion gear have been experienced with several different gear heat treat lots and on helicopters both with and without rotor brakes installed.
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Required Actions
Replace tail rotor pinion gears identified as Hiller P/N 23522 or P/N 23634 with P/N 23634-3. Gears with less than 50 hours total time by May 16, 1964 must be replaced before 100 hours time in service. Gears with 50+ hours must be replaced within next 50 hours time in service.
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Compliance Time
Prior to the accumulation of 100 hours' total time in service
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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