AD 59-18-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Rolls-Royce Corporation | 501-D13 | ALLISON Models 501-D13 and -D13A Engines |
| engine | Rolls-Royce Corporation | 501-D13A | ALLISON Models 501-D13 and -D13A Engines |
Unsafe Condition
Third stage turbine blade failures due to resonance at low speed ground idle, resulting in damage to fourth stage blades and vanes, and in one case, turbine inlet case-vane case split line bolt failure.
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Required Actions
Aircraft without vibration detection equipment must limit low speed ground idle to 4 minutes total and inspect fourth stage turbine blades before next departure and every 25 hours. Aircraft with vibration detection must use it to detect anomalies and inspect blades upon arrival at next maintenance base if issues are found. Engines modified with specified blades (P/N 6794773) are exempt.
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Compliance Time
Compliance required as indicated.
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Affected Aircraft
Allison Models 501-D13 and -D13A Engines.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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