Aeronca O-58B N47185 accident near Bulverde, Texas

Probable cause

The failure of the left main landing gear wheel casting due to fatigue, which resulted in a loss of directional control during the landing roll.

NTSB analysis

The commercial pilot reported that, following a normal touchdown and during the landing roll, the airplane suddenly veered to the left. The pilot corrected for the left swerve with the application of right rudder and brake. The airplane subsequently entered a right swerve. The airplane did not respond to the pilot's application of left rudder and brake inputs. The pilot reported that there was a 15-ft descending embankment and trees off the right side of the runway and that, to avoid a runway excursion, he lowered the left wing and intentionally ground looped the airplane to the right. The left wing subsequently contacted the runway surface.

A postaccident examination revealed a fracture to the left main landing gear wheel casting. The wheel fracture was located along the inner bearing race shelf and resulted in the bearing being exposed. The bearing race flange had fractured circumferentially and radially in two places. Further examination of the fracture surfaces revealed areas of fatigue, which were the result of casting oxide imperfections that had been present since the wheel was cast and had developed under typical loading of the landing gear. Additionally, the observed alternating fracture features were consistent with spectrum loading, typical of those experienced by a landing gear wheel. Ultimately, the wheel failed as a result of progressive fatigue cracking. The wheel had been cast in 1942, and the owner reported that the airplane had accumulated 3,520 hours since new with 10 hours since the last inspection.

Text from the NTSB. Open the NTSB docket for CEN16LA101 for the full record.