The private pilot was landing the Cessna 140 on a dry, hard-surfaced runway in Independence, Oregon.
He said the approach and touchdown were normal. Just after touchdown, he felt “something similar to a bump,” and the airplane started to drift to the left.
He thought that the plane possibly had a flat tire and tried to compensate with rudder input, but it continued drifting to the left, left the left side of the runway, and ground looped, resulting in substantial damage to the right wing and fuselage.
An on-scene examination revealed that the left main landing gear axle had fractured, resulting in the separation of the wheel assembly.
A detailed examination revealed that the axle was fractured near the inboard end, just outboard of the axle attachment flange.
Portions of the fracture surface at the upper and lower sides of the axle had relatively smooth features oriented perpendicular to the outer surface, consistent with fatigue. The fatigue cracks initiated at a fillet corner at a change in the axle’s outer diameter.
The manufacturer specified inspection intervals to check for cracks and corrosion of the main landing gear axle, however the airplane’s maintenance logs were not located, and the airplane’s maintenance history could not be determined.
Probable cause: The failure of the left main landing gear wheel axle due to a fatigue crack.
NTSB Identification: WPR16LA068
This February 2016 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.