AD 82-15-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12D | Airworthiness Directives; HILLER AVIATION Model UH-12D, UH- 12E, UH-12E4, UH-12E-L, UH-12L and UH-12L4 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12L | Airworthiness Directives; HILLER AVIATION Model UH-12D, UH- 12E, UH-12E4, UH-12E-L, UH-12L and UH-12L4 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12L4 | Airworthiness Directives; HILLER AVIATION Model UH-12D, UH- 12E, UH-12E4, UH-12E-L, UH-12L and UH-12L4 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E | Airworthiness Directives; HILLER AVIATION Model UH-12D, UH- 12E, UH-12E4, UH-12E-L, UH-12L and UH-12L4 Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E-L | Airworthiness Directives; HILLER AVIATION Model UH-12D, UH- 12E, UH-12E4, UH-12E-L, UH-12L and UH-12L4 Series Helicopters |
Unsafe Condition
Loss of power to the main and tail rotors due to failure of the mercury clutch attachment bolts (P/N 21041) and washers (AN 960-716L).
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Required Actions
Remove four P/N 21041 bolts and four AN 960-716L washers, replace with new P/N 21041 bolts and P/N 21074-3 washers per Hiller Service Bulletin 21-2. Mark removed bolts as unairworthy.
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Compliance Time
Within 50 hours' additional time in service after July 16, 1982
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Affected Aircraft
Hiller Aviation/Siam Hiller Holdings, Inc. Models UH-12D, UH-12E, UH-12E4, UH-12E-L, UH-12L, UH-12L4, and military OH-23D, OH-23F, OH-23G series helicopters through serial No. 5187. Excludes turbine-converted models via STC SH178WE/SH177WE unless restored to original configuration.
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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