AD 68-22-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Rolls-Royce Corporation | 250-C10B (T63-A-5A) | ALLISON Model 250-C18, 250-C18A, and 250-C10B Engines |
| engine | Rolls-Royce Corporation | 250-C18 | ALLISON Model 250-C18, 250-C18A, and 250-C10B Engines |
| engine | Rolls-Royce Corporation | 250-C18A | ALLISON Model 250-C18, 250-C18A, and 250-C10B Engines |
Unsafe Condition
Compressor assemblies with serial numbers prior to specified limits may experience failure due to insufficient strength, leading to engine failure.
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Required Actions
Modify engines in accordance with Allison Commercial Engine Bulletins 250 CEB-51 and 250 CEB-52. Until modified, restrict N1 rpm to ≤96.5% except during takeoff (limited to 2 minutes), and limit generator load to ≤60 amps above 70% N1 rpm.
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Compliance Time
on or before May 1, 1969
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Affected Aircraft
Rolls-Royce Corporation Model 250-C18 (compressor assemblies serial numbers prior to CAC 21073), Model 250-C18A (compressor assemblies serial numbers prior to CAC 20202), and all Model 250-C10B engines.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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