What happened
An airline transport certificated pilot was operating a tailwheel equipped airplane on an on-demand air taxi flight. The flight was approaching an airstrip located near a remote cabin, a location the pilot had previously used.
As the aircraft reached the end of the landing roll, the left main landing gear strut fractured above the left wheel axle. This failure caused the wheel and the lower portion of the gear strut to separate from the aircraft. The remaining upper portion of the strut dug into the ground, causing the airplane to nose over. The incident resulted in damage to the propeller, the right wing, the rudder, and the vertical stabilizer. The pilot was not injured.
The investigation
Investigators examined the lower end of the landing gear strut, which features four holes drilled through the metal for the installation of the brake assembly and wheel axle. The examination revealed areas of cracking consistent with fatigue, originating from the inboard edge of the forward, upper bolt hole.
One crack was found in an area containing two small corrosion pits within the drilled hole. A second crack was identified in the fillet between the drilled hole and the inboard surface of the strut. These two cracks merged to form a single lateral crack that extended across the strut and through the aft, upper bolt hole. Additionally, the interior surfaces of the fillet regions and the forward, upper bolt hole showed pitting consistent with corrosion.
Findings
- Neither the FAA nor the manufacturer has established a specific life limit, measured in hours or cycles, for the main landing gear strut.
- Current annual inspection requirements do not necessitate the disassembly of the axle from the gear strut.
- There are no specified inspection procedures from the manufacturer or the FAA beyond a general visual inspection of the landing gear.