Cessna 340 N5870M accident near Mckinney, Texas

Probable cause

The failure of the bell crank pivot bolt which resulted in the left main landing gear collapse. Contributing to the accident was the lack of landing gear inspections in accordance with the airplane manufacturer's maintenance manuals.

NTSB analysis

After a cross-country flight and during the landing roll at the destination airport, the airplane's left main landing gear collapsed, causing substantial damage to the aileron.

An examination of the landing gear found the bell crank pivot bolt and gear down-lock broken.

A review of the airplane's maintenance manual revealed that the landing gear system is to be disassembled/inspected every 10 years/5,000 landings, after an initial inspection after 20 years or 10,000 landings. Additionally, the maintenance manual indicates that the main landing gear bell crank pivot bolt is to be inspected for wear every 3 years (or 500 landings), after an initial inspection at 3 years or 1,000 landings. A review of the airplane maintenance records did not reveal an entry were the landing gear inspections had been accomplished. The records revealed the airframe had accumulated 5,799.3 hours at the time of the last annual inspection, that was dated September 1, 2016.

It's likely that the landing gear pivot bolt developed a crack over time, which then failed during landing, causing the gear to collapse.

Text from the NTSB. Open the NTSB docket for CEN17LA351 for the full record.