The following information is derived from the FAA’s Service Difficulty Reports and Aviation Maintenance Alerts.
Beechcraft Model F33A Bonanza/IO-520
Cracked Magneto Impulse Coupling
Accident Probes
Aircraft Analysis
Avionics and Gear
Features
Instrument Flying
Learning Experiences
Squawk Box
IO-520s
Beechcraft Model F33A Bonanza/IO-520Cracked Magneto Impulse CouplingDuring a 500-hour magneto inspection, the impulse coupling was discovered to have cracks in its flyweight base plate. The cracks were detected using magnetic particle inspection and appear to have originated from the sharp-cornered feature of the base plate that forms the full advance stop. Slick p/n M3050.Part total time: 565.0 hours
Key Takeaways:
- Multiple service reports detail magneto-related issues in IO-520 engines, specifically cracked impulse couplings (Slick p/n M3050) discovered during 500-hour inspections, and a broken distributor gear causing in-flight failure.
- Other significant engine component failures include cracked cylinder heads in a Beechcraft Baron, a catastrophic crankshaft failure due to bearing issues in a Cessna A185F, and a starter drive adapter failure leading to oil contamination in a Cessna 207.
- All reported incidents involve IO-520 engines across various Beechcraft Bonanza/Baron and Cessna aircraft models, often resulting in engine replacement or significant repairs.
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