AD 74-13-05
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Lycoming Engines | IGO-540-A1A | AVCO LYCOMING Model IGO-540 Series Engines and IGSO-540 Series Engines |
| engine | Lycoming Engines | IGO-540-A1B | AVCO LYCOMING Model IGO-540 Series Engines and IGSO-540 Series Engines |
| engine | Lycoming Engines | IGO-540-A1C | AVCO LYCOMING Model IGO-540 Series Engines and IGSO-540 Series Engines |
| engine | Lycoming Engines | IGO-540-B1A | AVCO LYCOMING Model IGO-540 Series Engines and IGSO-540 Series Engines |
| engine | Lycoming Engines | IGO-540-B1B | AVCO LYCOMING Model IGO-540 Series Engines and IGSO-540 Series Engines |
| engine | Lycoming Engines | IGO-540-B1C | AVCO LYCOMING Model IGO-540 Series Engines and IGSO-540 Series Engines |
| engine | Lycoming Engines | IGSO-540-A1A | AVCO LYCOMING Model IGO-540 Series Engines and IGSO-540 Series Engines |
| engine | Lycoming Engines | IGSO-540-A1C | AVCO LYCOMING Model IGO-540 Series Engines and IGSO-540 Series Engines |
| engine | Lycoming Engines | IGSO-540-A1D | AVCO LYCOMING Model IGO-540 Series Engines and IGSO-540 Series Engines |
| engine | Lycoming Engines | IGSO-540-A1E | AVCO LYCOMING Model IGO-540 Series Engines and IGSO-540 Series Engines |
Unsafe Condition
Failures of connecting rod assemblies P/N 72606, P/N 73174, and P/N 75548.
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Required Actions
Replace connecting rod assemblies with new P/N 77450 within the next 50 hours in service if accumulated 400 hours or more since new or overhaul. Replace within the next 100 hours in service if less than 400 hours since new or overhaul. Compliance time may be increased by the FAA Chief, Engineering and Manufacturing Branch upon request with substantiating data.
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Compliance Time
Within the next 50 hours in service (for engines with 400+ hours) or within the next 100 hours in service (for engines with less than 400 hours), or as increased by FAA upon request.
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Affected Aircraft
AVCO Lycoming Model IGO-540 series engines except serials 311-49 and subsequent; IGSO-540 series engines except serial ranges 2558-50 through 2563-50, 2565-50 through 2582-50, 2584-50 through 2589-50, 2591-50 through 2602-50, 2606-50 through 2631-50, 2637-50, 2640-50, 2647-50 through 2652-50, 2657-50 through 2692-50, 2694-50 through 2713-50, 2718-50 through 2727-50, 2730-50 through 2750-50, 2752-50 and subsequent; and except engines overhauled by Lycoming after October 29, 1970.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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