AD 48-18-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-51 | Airworthiness Directives; Sikorsky Model S-51 Series Helicopters |
Unsafe Condition
Cracks caused by stress concentration at the corners of the internal splines on the bevel drive gear (Sikorsky P/N S-535360).
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Form a 1/32-inch radius relief at the lower end of each spline on the bevel drive gear. Follow the procedure in Sikorsky Aircraft Information Circular No. 40 and No. 40 Revision 'A'.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
at first main gearbox overhaul but in any event not later than the next 400 hours of operation
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Sikorsky Model S-51 Series Helicopters, Serial Numbers SS-51-01 through SS-5157.
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
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.