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
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Instrument Flying
Learning Experiences
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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 reports detail cracking of Slick p/n M3050 magneto impulse couplings on IO-520 engines, typically discovered during 500-hour inspections.
- Significant engine component failures on IO-520 powerplants include cracked cylinder heads and a catastrophic crankshaft failure due to bearing issues.
- Other incidents involved accessory failures, such as a broken starter drive adapter and a magneto distributor gear failure, leading to severe engine damage or replacement.
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