Cessna 140 N73053 accident near Independence, Oregon

Probable cause

Fatigue failure of the right landing gear axle, which resulted in a loss of control during the landing roll.

NTSB analysis

According to the instructor, the accident landing was the second landing of the flight. As the tailwheel-equipped airplane was slowing down and they were exiting the runway, there was a loud "clunk." The airplane slid sideways, bounced, and then ground looped, resulting in substantial damage to the fuselage. The instructor reported that the right wheel assembly separated at the axle.

Examination of the fractured axle assembly revealed that the axle fractured at the transition radius between the longitudinal barrel (tube) portion and the plate portion. A fatigue crack emanated from multiple origins at the outer surface of the transition radius and extended circumferentially around the outer surface of the transition radius. The fracture features outside of the fatigue region showed features consistent with overstress separation. The maintenance history of the landing gear and axle could not be determined. The fatigue crack started at the transition radius most likely as the result of a hard landing or several hard landings. Once the fatigue crack started, the crack propagated during taxiing and additional takeoffs and landings.

Text from the NTSB. Open the NTSB docket for WPR19LA169 for the full record.