AD 79-06-05
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Rolls-Royce Corporation | 250-C28B | DETROIT DIESEL ALLISON Model 250-C28B and 250-C30 Engines |
| engine | Rolls-Royce Corporation | 250-C30 | DETROIT DIESEL ALLISON Model 250-C28B and 250-C30 Engines |
Unsafe Condition
Moisture in the overspeed control system could cause engine power loss.
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Required Actions
Before further flight, pull and secure the N2 overspeed circuit breaker, install placards indicating 'Eng Ovsp Circuit Deactivated' on specified rotorcraft panels. By September 1, 1979, replace overspeed controls with DDA P/N 23001750 (C28B) or 23001751 (C30), reactivate the circuit breaker, and remove the placards.
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Compliance Time
Before further flight and not later than September 1, 1979
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Affected Aircraft
DETROIT DIESEL ALLISON Model 250-C28B and 250-C30 engines with overspeed controls DDA P/N 6895582 and 6894611 respectively, installed in Bell 206L-1 and Sikorsky S-76 rotorcraft.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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