AD 47-51-14
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Stolp-Adams Company | Army YR-6A | Airworthiness Directives; Sikorsky Models YR-6A, R-6A, and HOS-1 Helicopters |
| aircraft | Stolp-Adams Company | (Navy) HOS-1 | Airworthiness Directives; Sikorsky Models YR-6A, R-6A, and HOS-1 Helicopters |
Unsafe Condition
Failure of the pinion and ring gears in the main gearbox due to improper installation of the power takeoff assembly.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect and adjust backlash between ring gear and pinion (0.003 to 0.005 inch), check shims and gasket for damage, measure shim thickness, apply Prussian blue to pinion teeth, install gasket and shims, secure power takeoff housing, verify tooth pattern via manual operation, and ensure proper installation per specified procedures.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
At each removal and replacement of the power takeoff assembly.
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Affected Aircraft
Stolp-Adams Company Models YR-6A, R-6A, and HOS-1 Helicopters.
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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