Accident Details
An airline transport certificated pilot was conducting a personal cross-country flight. During the landing at a sod-covered, off-airport site, the left main landing gear collapsed. The pilot stated that a witness reported an initial bounce of 12 to 18 inches before the airplane settled onto the landing area a second time. The pilot indicated there were no known mechanical anomalies with the airplane prior to the accident.
Damage and Examination
The accident resulted in structural damage to the gear box, left wing, aileron, and horizontal stabilizer. Upon inspection, the pilot discovered that the left main landing gear strut attachment bolt had broken.
Metallurgical Analysis
An examination of the landing gear attachment bolt, along with new, exemplar bolts, was conducted by a metallurgist at the NTSB materials laboratory in Washington, D.C. The laboratory report stated that the bolt had broken in a "ductile overstress separation in bending and shear mode." The report also noted that the bolt was made of the appropriate material and was of the proper dimensions.