The private pilot reported that, during takeoff for a local personal flight in Xenia, Ohio, his seat unexpectedly moved rearward, and the seat back tipped rearward.
As the seat slid rearward, he inadvertently applied aft yoke and his feet came off the rudder pedals, which resulted in a loss of directional control. The Cessna 172 went off the left side of the runway and struck a ditch, which resulted in substantial damage to the airplane.
A postaccident examination of the seat revealed that the forward outboard metal tang on the seat base that retained the base to the track was deformed. The forward outboard position of the base also contained the locking pin mechanism that adjusted the seat fore and aft and locked the seat into position.
The deformation of the metal tang likely allowed the seat to become detached from the track and disengaged the locking pin, which allowed the seat to slide rearward.
The seat back structure would not lock in any position after the accident. The reason why the seat back could not lock in position could not be determined.
The FAA had previously issued an airworthiness directive (AD) that required repetitive inspections of the seat mechanism, including inspections of the tangs on the seat base. A review of airplane’s maintenance records showed that the inspections had been performed in accordance with the AD.
The deformation of the tang was consistent with a lateral deformation due to a sideways force, but it could not be determined if the deformation was present during the most recent inspection.
A review of the airplane maintenance discrepancy records showed that, the day before the accident, a different pilot had entered a maintenance discrepancy, which noted that the “left seat slid back three times during flight.”
The following day, a mechanic repaired the hold-down spring and returned the airplane to service. After that repair and before the accident flight, another pilot entered a maintenance discrepancy, which noted that the “left front seat was in the reclined position and would not lock in the upright position.”
The records showed that the discrepancy had not been corrected before the accident flight.
It could not be determined whether or not the accident pilot was aware of the previous discrepancy reports.
The National Transportation Safety Board determined the probable causeof this accident as the failure of the seat track mechanism, which led the pilot to inadvertently apply aft yoke and lift his feet off the rudder pedals and resulted in a loss of directional control during takeoff.
NTSB Identification: CEN15LA024
This October 2014 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.