AD 85-25-08
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Rolls-Royce Corporation | 250-C28B | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28 and -C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C28C | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28 and -C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30 | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28 and -C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30P | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28 and -C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30S | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28 and -C30 Series Engines |
Unsafe Condition
Failure of the compressor mount can cause misalignment and subsequent failure of compressor to turbine shafting spline joints which may lead to an inflight loss of power or disconnect of the gas producer turbine rotor with a subsequent inflight shutdown/overspeed uncontained turbine wheel failure.
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Required Actions
Within 100 hours time-in-service after the effective date, inspect the compressor mount assembly per Allison CEB-A-72-2080/3081 or equivalent. If cracks are found, follow continued service criteria: inspect every 25 hours if one crack not within 3/8 inch of edge, or remove before further flight if cracks are within 3/8 inch or multiple cracks. Replace the compressor mount with P/N 23007217 by November 30, 1986, during overhaul/repair.
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Compliance Time
Within the next 100 hours time-in-service after the effective date, unless already accomplished within the last 200 hours time-in-service, and thereafter at intervals not to exceed 300 hours time-in-service from the last inspection. Replace by November 30, 1986.
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Affected Aircraft
Allison Model 250-C28B (CAC 70011-70793, 70795), 250-C28C (CAC 28001-28021), 250-C30, -C30P, -C30S (CAC 90001-90822) engines with compressor mount assemblies P/N 6896021, 6898966, or 6898611 installed in rotorcraft.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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