Cessna 172 N734GM accident near Lewiston, Montana

Probable cause

The pilot's failure to ensure that his seat was adjusted and locked, which resulted in his seat sliding aft during the takeoff roll, and the subsequent loss of directional control and runway excursion.

NTSB analysis

According to the pilot, during the takeoff roll about 30 knots indicated airspeed, his seat slid back a few inches. He reported that, "The slight movement of the pilot seat aft during takeoff roll was inconvenient. Had I done nothing at this point, it most likely would have been a manageable situation." However, the pilot reported that, "My reaction to move the seat forward using the adjustment bar during takeoff roll acceleration is what caused the pilot seat to move to the full aft position." He reported that the full aft seat movement caused him to pull back on the yoke, the nose landing gear came off the ground, and the airplane veered left and exited the runway to the left, and struck a fence before coming to a halt. The airplane sustained substantial damage to both wings, horizontal stabilizer, and elevator.

The pilot reported that there were no mechanical malfunctions or anomalies with the airplane during the takeoff roll that would have prevented normal flight operations.

Federal Aviation Administration Aviation Safety Inspector's examined the pilot's seat, track and adjustment assembly and found that there were no failures or anomalies.

According to the manufacturer's Pilot Operating Handbook, item number three of the Before Start Checklist states: Seats/Belts –Adjusted and locked

Text from the NTSB. Open the NTSB docket for GAA16CA419 for the full record.