AD 85-25-09
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
Carbon buildup on turbine shafts and couplings can cause shaft rub and subsequent shaft or coupling failures leading to possible overspeed and/or uncontained turbine wheel failures.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Within 50 hours time-in-service after the AD's effective date (or within the last 250 hours if already done), and every 300 hours thereafter, clean and inspect turbine shafting/couplings and replace specific O-rings. By November 30, 1987, modify spur adapter gearshaft, compressor/gearbox assemblies, turbine-to-compressor coupling, and turbine-exhaust-collector per specified CEBs during engine repair/overhaul.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within the next 50 hours time-in-service after the effective date of this AD, unless already accomplished within the last 250 hours time-in-service, and thereafter at intervals not to exceed 300 hours time-in-service from the last inspection. For modifications, by November 30, 1987, during next engine or module repair/overhaul shop visit.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Allison Model 250-C28B and -C28C engines with engine serial numbers CAE 860011-860787CAT (C28B) and CAE 280001-280039CAT (C28C), and turbine serial numbers 70011-70804 (C28B) and 28001-28039 (C28C), except those already incorporating specified Allison Commercial Engine Bulletins.
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
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.