What happened
During an on-demand charter flight, a pilot and one passenger were departing from a 900-foot long gravel bar in a tail wheel equipped airplane. As the aircraft accelerated for takeoff and reached approximately 45 knots, the left main landing gear strut fractured above the left wheel axle. This failure caused the upper portion of the gear strut to dig into the ground, forcing the aircraft to swerve to the left. The aircraft continued off the left side of the site, at which point the right wing struck the ground. The accident resulted in substantial damage to the right wing and fuselage; both occupants were not injured.
The investigation
A visual inspection of the fractured landing gear strut revealed a fracture through the upper two holes in the strut. The design of the spring steel landing gear strut includes four holes drilled through the metal in a box pattern, with the axle attached to the outboard side of the strut. Investigators noted that neither the manufacturer nor the FAA had established a life limit for the main landing gear strut. Furthermore, an annual inspection does not require the disassembly of the axle from the gear strut, and no specific inspection procedures beyond a general visual inspection have been specified by the manufacturer or the FAA.
Findings
While the NTSB recommended in March 2001 that the FAA issue an airworthiness directive for nondestructive inspection techniques for these struts, the FAA determined that existing maintenance manual criteria were adequate. The NTSB maintained that visual inspections alone might not detect cracks, but acknowledged that statistical evidence did not warrant an airworthiness directive at that time.