Travel Air C 4000 N9952 accident near Williams, California

Probable cause

The failure of the elevator control tube due to corrosion, which resulted in a loss of elevator control and collision with terrain.

NTSB analysis

A witness reported that during takeoff, the airplane reached about 8 ft above ground level, then suddenly pitched down and descended to ground contact. Postaccident examination of the airplane revealed a fractured and separated elevator control tube. A viscous liquid was inside the fractured tubing. A mixture analysis found signatures for emulsifiers, surfactants, and amines, which are often found in combination in corrosion-inhibiting compounds. The tubing fracture surfaces had features consistent with torsional overstress. A cross-section of the tube away from the fracture was examined. Corrosion was observed on the inner surfaces of the control tube, as well as significant thinning of the control tube wall thickness, which was 1/2 to 2/3 of the thickness of the least-corroded sections. The thinner wall thickness resulting from the corrosion likely could not support the same loading conditions as the full wall thickness, and likely led to the overstress separation of the control tube.

Text from the NTSB. Open the NTSB docket for WPR14LA361 for the full record.