AD 81-21-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-76A | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-76A Series Helicopters |
Unsafe Condition
Fatigue failures of the main rotor scissors assembly due to the use of P/Ns 76104-08020-044, -045, -046, and 76070-10005-042 main rotor rotating scissors assemblies.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Replace specified main rotor rotating scissors assemblies with serviceable parts before accumulating 500 hours time in service or within 25 hours after AD effective date, whichever is later. Conduct inspections within 50 hours after AD effective date (if not done in last 50 hours) and every 100 hours thereafter for hub/scissors bearings play/wear and scissors center pivot bolt fretting/scoring/corrosion pits per specified manuals.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
before further flight
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 certificated in all categories.
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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