AD 79-16-06
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Rolls-Royce Corporation | 250-C28 | DETROIT DIESEL ALLISON Model 250-C28 and 250-C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C28B | DETROIT DIESEL ALLISON Model 250-C28 and 250-C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C28C | DETROIT DIESEL ALLISON Model 250-C28 and 250-C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30 | DETROIT DIESEL ALLISON Model 250-C28 and 250-C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30G | DETROIT DIESEL ALLISON Model 250-C28 and 250-C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30G/2 | DETROIT DIESEL ALLISON Model 250-C28 and 250-C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30M | DETROIT DIESEL ALLISON Model 250-C28 and 250-C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30P | DETROIT DIESEL ALLISON Model 250-C28 and 250-C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30R (T703-AD-700) | DETROIT DIESEL ALLISON Model 250-C28 and 250-C30 Series Engines |
| engine | Rolls-Royce Corporation | 250-C30R/1 (T703-AD-700B) | DETROIT DIESEL ALLISON Model 250-C28 and 250-C30 Series Engines |
Unsafe Condition
Accessory drive gearbox failure due to the use of generator idler gearshaft P/N 6898980, 6898591, or 77 tooth spur idler gearshaft P/N 6898652, which could result in engine power loss.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Remove the referenced gearshafts from service prior to reaching 9000 cycles for 250-C28 series engines or 2000 cycles for 250-C30 engines. For gearshafts within 50 cycles of the limit on the effective date, comply within 100 cycles.
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Compliance Time
Prior to reaching the specified cycle limits (9000 cycles for 250-C28, 2000 cycles for 250-C30). For gearshafts within 50 cycles of the limit on the effective date, compliance required within 100 cycles.
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Affected Aircraft
Rolls-Royce Corporation Model 250-C28 (including variants) and 250-C30 (including variants) series engines equipped with generator idler gearshaft P/N 6898980, 6898591, or 77 tooth spur idler gearshaft P/N 6898652 installed in Bell 206L-1 and Sikorsky S-76 rotorcraft.
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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