Amateur-built Thorp T-18-C N118CK accident near Palm Springs, California

Probable cause

A loss of directional control due to the fatigue failure of a tubular steel gear leg along a corroded weld line.

NTSB analysis

The pilot of the tailwheel-equipped experimental airplane had just touched down for a full-stop landing when the airplane started veering to the left. Although the pilot applied rudder and brake inputs to correct the airplane's alignment, the airplane did not respond. The pilot then added power to help correct the veering, but the airplane departed the left side of the runway and impacted a runway/taxiway sign. A postaccident inspection of the tubular steel left gear leg revealed that it had partially failed along a corroded weld line, and had bent backwards from its normal position. Corrosion/rust was present on about one inch of the fracture face, and along a wider area of the interior wall of the gear leg adjacent to the fracture. The fracture itself continued around about 70 percent of the circumference of the tubular leg.

Text from the NTSB. Open the NTSB docket for WPR09CA134 for the full record.