AD 86-20-13
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-C30G | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28 and -C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30G/2 | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28 and -C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30M | 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-C30R (T703-AD-700) | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28 and -C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30R/1 (T703-AD-700B) | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28 and -C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30R/3 | ALLISON GAS TURBINE DIVISION, GENERAL MOTORS CORP. Model 250-C28 and -C30 Series Engines |
Unsafe Condition
Excessive wear and/or fretting damage on the external splines of the turbine spline adapter or the aft splines of the turbine-to-compressor coupling shaft can progress to a disconnect and subsequent overspeed gas generator turbine failure/uncontained failure.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Within five hours time-in-service after the effective date, but not later than December 20, 1986, inspect the gas generator turbine spline adapter locknut torque. For uninstalled affected turbine assemblies, inspect the locknut torque before initial flight.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within the next five hours time-in-service after the effective date of this AD, but not later than December 20, 1986, for in-service engines. Before initial flight, for uninstalled affected turbine assemblies.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Allison Model 250-C28B, 250-C28C, and 250-C30 Series engines with turbine serial numbers CAT 70001 thru 70802 and 70804 (C28B), CAT 28001 thru 28046 (C28C), and CAT 90001 thru 95436 and 95438 (C30 Series), except those incorporating specified Allison Commercial Engine Alert Bulletin or FAA approved equivalents.
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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