AD 51-22-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-51 | Airworthiness Directives; Sikorsky Model S-51 Helicopters |
Unsafe Condition
Failures of Gear Shaft (Generator Drive-Tail Drive Transmission System) P/N S-10-35-1004 due to improper alignment of the taper pin hole relative to the splines and sharp radii at the intersection with the taper pin hole.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Replace all in-service gear shafts with jig-drilled shafts where the taper pin hole aligns squarely with the splines, and stone/polish to deburr and remove sharp radii at the intersection of the taper pin hole and splines.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
within the next 25 hours of operation, but not later than November 1, 1951
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Affected Aircraft
All Model S-51 Helicopters manufactured by Sikorsky Aircraft Corporation.
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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