AD 62-23-05
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Lycoming Engines | GO-435-C2 (O-435-17) | LYCOMING Model GO, IGO, GSO and IGSO Series Engines |
| engine | Lycoming Engines | GO-435-C2A | LYCOMING Model GO, IGO, GSO and IGSO Series Engines |
| engine | Lycoming Engines | GO-435-C2A2 | LYCOMING Model GO, IGO, GSO and IGSO Series Engines |
| engine | Lycoming Engines | GO-435-C2B | LYCOMING Model GO, IGO, GSO and IGSO Series Engines |
| engine | Lycoming Engines | GO-435-C2B1 | LYCOMING Model GO, IGO, GSO and IGSO Series Engines |
| engine | Lycoming Engines | GO-435-C2B2 | LYCOMING Model GO, IGO, GSO and IGSO Series Engines |
| engine | Lycoming Engines | GO-435-C2E | LYCOMING Model GO, IGO, GSO and IGSO Series Engines |
| engine | Lycoming Engines | GO-435-D1 | LYCOMING Model GO, IGO, GSO and IGSO Series Engines |
| engine | Lycoming Engines | GO-480-C1B6 | LYCOMING Model GO, IGO, GSO and IGSO Series Engines |
| engine | Lycoming Engines | GO-480-C1D6 | LYCOMING Model GO, IGO, GSO and IGSO Series Engines |
Unsafe Condition
Excessive wear of the propeller shaft oil seal rings may cause propeller oil leaks, leading to potential failure of the propeller system.
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Required Actions
Conduct propeller oil leakdown inspections per Lycoming Service Bulletin No. 290 until Lycoming P/N 67722 oil seal rings are installed. Install P/N 67722 seal rings in the reduction gear assembly and identify them with an 'M' stamp next to the reduction gear serial number.
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Compliance Time
Within 10 hours' time in service after the effective date; 25 hours' time in service after the first inspection; 25 hours' time in service after the second inspection; and every 100 hours' time in service thereafter.
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Affected Aircraft
Lycoming Engines: GO, IGO, GSO, and IGSO series models listed in Service Bulletin No. 290 when installed in twin-engine aircraft with full feathering Hartzell propellers. Specific models and serial ranges include GO-435, GO-580-B, GO-480-F, GO-480-D, GSO-480, GO-480-C/-G, IGSO-480, IGO-540, IGSO-540, and others as detailed in the AD. Includes remanufactured/overhauled engines from Lycoming between Feb 16, 1961, and Aug 31, 1962, and engines overhauled elsewhere with Service Instruction No. 1033.
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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