AD 82-13-04 R1
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12L | Airworthiness Directives; HILLER AVIATION Model UH-12E and UH-12L Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12L4 | Airworthiness Directives; HILLER AVIATION Model UH-12E and UH-12L Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E | Airworthiness Directives; HILLER AVIATION Model UH-12E and UH-12L Series Helicopters |
| aircraft | Hiller Aviation | Siam Hiller Holdings, Inc. | UH-12E-L | Airworthiness Directives; HILLER AVIATION Model UH-12E and UH-12L Series Helicopters |
Unsafe Condition
Possible loss of driving torque to the helicopter rotor system due to torsional couplings P/N 21047-9 and -11 serial numbers 497 through 766.
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Required Actions
Inspect torsional couplings P/N 21047-9 and -11 per Hiller Aviation Service Bulletin UH-12-21-1, revise inspection schedule if serviceable, replace if non-compliant, and use special flight permits as allowed.
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Compliance Time
Within the next 50 hours' time in service after September 13, 1982, or within 300 hours' time in service since September 8, 1980, whichever occurs earlier, and thereafter every 300 hours' time in service.
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Affected Aircraft
Hiller Aviation/Siam Hiller Holdings, Inc. Models UH-12E, UH-12E-L, UH-12L, UH-12L4 equipped with torsional couplings P/N 21047-9/-11 serial numbers 497-766, excluding turbine-converted models under 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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