THORP T 18 N25VP accident near San Rafael, California

Probable cause

The pilot's delayed decision to abort the takeoff. Contributing to the accident are an inadequate modification to the seat position, and the pilot's failure to check flight controls for freedom and correct movement.

NTSB analysis

The pilot reported that prior to the flight in the experimental airplane, he unbolted and rebolted the pilot's seat from its middle position to the forward position. He did not check to see if the flight control stick movement would be restricted in this new configuration.

During the takeoff roll, the airplane would not rotate when he moved the flight control stick aft. Not realizing the seat prevented the flight control stick movement to the full aft position, the pilot adjusted the elevator trim and the airplane subsequently lifted off, however, it would not climb. The pilot then aborted the takeoff; however, the airplane did not have sufficient distance to stop. It departed the runway surface and traversed through a field, impacted trees, and came to rest inverted. The airplane sustained substantial damage to the wings, rudder, and vertical stabilator. The pilot reported no preimpact mechanical malfunctions or failures with the airframe or engine that would have precluded normal operation.

Text from the NTSB. Open the NTSB docket for WPR15CA066 for the full record.