AD 85-25-12
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Rolls-Royce Corporation | 250-C28B | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28B and -C28C Engines |
| engine | Rolls-Royce Corporation | 250-C28C | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28B and -C28C Engines |
Unsafe Condition
Cracks in turbine-to-compressor coupling P/N 23008080 could progress to disconnect failure, resulting in an overspeed uncontained failure of the gas producer turbine rotor.
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Required Actions
Replace P/N 23008080 turbine-to-compressor-coupling with P/N 23032345 and install two P/N AS 3085-018 O-rings on the aft end of the spur adapter gearshaft in accordance with Allison Commercial Engine Alert Bulletin CEB-A-72-2127, Revision 1, or FAA approved equivalent.
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Compliance Time
Within the next 100 hours time-in-service after the effective date of this AD, or at the next turbine repair/inspection when access to P/N 23008080 coupling is gained, whichever occurs first, but not later than March 6, 1986
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Affected Aircraft
Allison Gas Turbine Division, General Motors Corp. Model 250-C28B and -C28C engines with P/N 23008080 turbine-to-compressor-coupling installed in rotorcraft certificated in any category.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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