AD 81-23-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-76A | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters |
Unsafe Condition
Failure of the splines between the main gearbox input pinion bevel (P/N 76351-09019 series) and the helical gear (P/N 76351-09020 series).
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect the input pinion bevel housing assemblies on both sides per Service Bulletin 76-66-14. Remove and replace assemblies with nut torque less than 100 foot pounds. Retorque nut to 500 foot pounds, conduct .001 inch feeler gage clearance and rotational drag inspections; replace if unsatisfactory.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within the next 100 hours time in service or before accumulation of 650 hours time in service since new or last overhaul, whichever occurs later.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Sikorsky Aircraft Corporation Model S-76A series helicopters with main gearbox assemblies 76351-09000-058 or prior dash numbers.
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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