Incident Overview
During the landing roll of a tailwheel aircraft, the dual student allowed the aircraft to drift too close to the right side of the runway. The instructor applied left rudder and left brake as corrective action. At that moment, the left main gear leg fractured and separated from the aircraft.
Examination Findings
Subsequent examination by the National Transportation Safety Board (NTSB) of the fracture surface revealed that two fatigue cracks had initiated in corrosion pits. These pits were created where the gear leg rubbed against the gear leg clamping system. Over time, the two cracks combined into one. When loads were applied during the landing roll, an overstress separation occurred stemming from the fatigue fracture region.
Technical Details
The fracture of the left main gear leg was the direct result of fatigue cracking that originated from corrosion pits. The rubbing contact between the gear leg and the clamping system facilitated corrosion pit formation, which served as initiation points for the fatigue cracks. The propagation of these cracks, eventually merging, weakened the structure until the applied loads during landing caused a catastrophic failure.