On April 25, 2001, a Cessna 140A (registration N666TC) operated by George Lair was involved in an aviation accident near Greeley, CO. Investigators recorded the probable cause as: Fatigue cracking in one of the two holes used to attach the step assembly to the right main landing gear spring, leading to overload fracture. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a conventional full-stall landing, the right main landing gear failed, causing the aircraft to skid. Metallurgical examination revealed fatigue cracks in the step assembly attachment holes, leading to overload fracture.
Landing
The pilot performed a conventional, full-stall landing. Upon touchdown, the right main landing gear failed.
Failure
Following the gear failure, the airplane skidded to a halt. The fuselage and landing gear box were buckled, and the wing spar was damaged.
Metallurgical Examination
A metallurgical examination disclosed that cracks had initiated in one of two holes used to attach the step assembly to the landing gear spring. Chevron (or beach) marks on the fractured surface pointed back to the crack initiation site and were consistent with fatigue cracking. The adjacent area was characterized by dimples, indicating that the final breakage was due to a ductile fracture under overload.
Probable cause
Fatigue cracking in one of the two holes used to attach the step assembly to the right main landing gear spring, leading to overload fracture.