Nuts And Bolts

While changing an IO-520-BBs oil during an annual inspection, steel and red rubbery pieces were found in the filter. Metal determined to be coming from crankshaft gear driving alternator. Rubber was coming from alternator drive coupler. Four bolts holding crankshaft gear to crank were loose, allowing gear to slop around and cause wear of gears and coupler. Locking plates securing the four bolts were missing.

Key Takeaways:

• Critical mechanical failures were reported across various aircraft, including loose crankshaft bolts, cracked wheel hubs, and multiple starter-related defects.
• Hidden structural issues posed safety risks, exemplified by extensive corrosion found on Cessna 150 wing spars under fuel tanks and an internal electrical arc from a defective Cirrus SR20 starter.
• A Cessna 421C experienced a gear-up landing after both its main landing gear system and the emergency extension cable failed.
• Recurring problems with low-time starter adapter bearings were noted in Cirrus SR22 aircraft, suggesting a potential systemic issue.

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