AD 70-08-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-61A | Airworthiness Directives; Sikorsky Models S-61A, S-61L, S-61N, and S-61R Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61L | Airworthiness Directives; Sikorsky Models S-61A, S-61L, S-61N, and S-61R Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61N | Airworthiness Directives; Sikorsky Models S-61A, S-61L, S-61N, and S-61R Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61R | Airworthiness Directives; Sikorsky Models S-61A, S-61L, S-61N, and S-61R Helicopters |
Unsafe Condition
Combustion air inlet duct backfire check valve (Bobrick Co. P/N 9660-1-1 or 40064-32) may have distortion, missing flappers, or other obvious damage leading to fuel contamination or heater system failure.
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Required Actions
Inspect the combustion air inlet duct backfire check valve for distortion, missing flappers, or damage within the next 10 heater hours in service, and every 15 heater hours thereafter. Replace defective valves before further heater operation and inspect heater inlet ducting for fuel contamination, which must be eliminated before further heater use.
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Compliance Time
within the next 10 heater hours in service, and every 15 heater hours in service thereafter. Compliance time may be based on helicopter hours in service if heater operating time cannot be documented.
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Affected Aircraft
Sikorsky Models S-61A, S-61L, S-61N, and S-61R 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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