American Champion Aircraft 8KCAB N721SD accident near Knoxville, Tennessee

Probable cause

The inadequate maintenance of the left main landing gear through bolt, which resulted in a left main landing gear collapse and subsequent runway excursion during landing.

NTSB analysis

After performing maneuvers in the local area, the pilot receiving instruction and the flight instructor returned to the departure airport and performed two practice landings. During the third landing, the flight instructor heard a “bang” noise and the airplane veered left away from the runway centerline. The airplane came to rest in the grass next to the runway and the airplane’s fuselage and rudder were substantially damaged.

A Federal Aviation Administration inspector examined the airplane after the accident. The airplane’s left main landing gear had collapsed and the inspector found that the left main landing gear through bolt was fractured. The inspector further reported that the airplane’s most recent annual inspection had been completed more than 22 months before the accident. Additionally, the airframe manufacturer’s maintenance manual required that the through bolt be removed and inspected at every 100 hour/annual inspection and replaced as necessary, in addition to a mandatory replacement every 500 hours. The airplane’s maintenance records did not show when the last though bolt change had occurred. Based on this information, it is likely that the landing gear collapsed due to a failure of the left main landing gear through bolt, and that the through bolt had likely not been maintained in accordance with the airframe manufacturer’s requirements.

Text from the NTSB. Open the NTSB docket for ERA22LA296 for the full record.