AD 73-16-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-55 | Airworthiness Directives; Sikorsky Model S-55 Series Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-55B | Airworthiness Directives; Sikorsky Model S-55 Series Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-55C | Airworthiness Directives; Sikorsky Model S-55 Series Helicopters |
Unsafe Condition
Possibility of engine overspeed and resultant third stage turbine failure.
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Required Actions
Install a fuel bypass system per AiResearch Service Bulletin No. TSE331-73-5004 and Aviation Specialties Service Bulletin No. AS55-01-1. Incorporate FAA-Approved Rotorcraft Flight Manual Revision 3 dated July 17, 1973. Equivalent modifications may be approved by the Chief, Aircraft Engineering Division, FAA Western Region.
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Compliance Time
prior to further flight
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Affected Aircraft
Sikorsky Model S-55 series helicopters modified with AiResearch TSE331-3U-303N engines under Supplemental Type Certificate No. SH125-WE or SH127WE.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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