AD 75-22-12
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
Inflight power loss due to potential fuel leakage from the deceleration bleed valve, restricted tee fitting orifice, improper operation of manual fuel flow control valve, or incorrect calibration of engine tachometer and underspeed governor adjustments.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect and functionally test the fuel deceleration valve, replace if defective; inspect and replace restricted tee fitting orifice; test manual fuel flow control valve and replace if malfunctioning; inspect wiring and electrical connections for damage; calibrate engine tachometer and generator; adjust underspeed governor and throttle linkage per maintenance manual; install fuel enrichment valve system per service bulletins; update rotorcraft flight manual; apply operating limitations until required actions are completed.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within the next 10 hours time in service after the effective date of this AD
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Affected Aircraft
Sikorsky Model S-55 series helicopters with AiResearch model TSE331-3U-303N engines under Supplemental Type Certificates SH125WE or SH127WE.
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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