AD 69-18-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Rolls-Royce Corporation | 250-C10 (T63-A-5) | ALLISON Models 250-C10 and 250-C18 Series Engines |
| engine | Rolls-Royce Corporation | 250-C10B (T63-A-5A) | ALLISON Models 250-C10 and 250-C18 Series Engines |
| engine | Rolls-Royce Corporation | 250-C10D (T63-A-700) | ALLISON Models 250-C10 and 250-C18 Series Engines |
| engine | Rolls-Royce Corporation | 250-C18 | ALLISON Models 250-C10 and 250-C18 Series Engines |
| engine | Rolls-Royce Corporation | 250-C18A | ALLISON Models 250-C10 and 250-C18 Series Engines |
| engine | Rolls-Royce Corporation | 250-C18B | ALLISON Models 250-C10 and 250-C18 Series Engines |
| engine | Rolls-Royce Corporation | 250-C18C | ALLISON Models 250-C10 and 250-C18 Series Engines |
Unsafe Condition
Torquemeter shaftgear failure
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Required Actions
Adjust N1 speed at ground idle so that N2 speed does not exceed 71% RPM. Avoid continuous operation at engine power turbine speeds (N2) below 98% or above 102% RPM. Revise Rotorcraft Flight Manual and powerplant instrument markings as necessary.
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Compliance Time
Effective October 18, 1969
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Affected Aircraft
Allison Models 250-C10 and 250-C18 Series Engines with Gearbox Serial Numbers CAG 20183; CAG 20185; CAG 20193 through CAG 20265; CAG 20508; CAG 21001 through CAG 21395; CAG 21600 through CAG 21706; CAG 21800 through CAG 21803, except those modified per Allison Commercial Engine Bulletin 250 CEB-90 or later FAA approved revision, or having P/N 6852085 nitrided helical torquemeter shaftgears.
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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