WPR26LA159

The pilot reported that after conducting a preflight inspection he entered the airplane and adjusted the seat in accordance with the manufacturer's instructions. The pilot taxied for departure and performed an engine run-up. After receiving the takeoff clearance from the tower controller, he began the takeoff roll. However, as the pilot applied nose up control input, the seat slid back to the full aft position. The airplane pitched up, yawed to the left, and subsequently impacted terrain. The airplane sustained substantial damage to the right wing. The preflight inspection and airplane run-up revealed no anomalies. Post accident examination of the left seat, seat rails, and seat locking pins revealed no mechanical malfunctions or failures that would have precluded normal operation. The seat was able to slide from stop to stop without the locking pins engaged. When the seat locking pins were engaged in the seat rails, the seat locked in place. The seat movement described by the pilot during the accident sequence was unable to be duplicated. The Pilot’s Operating Handbook states in part, “Crew seats must be locked in position, and control handles fully down before flight.” A non-mandatory service bulletin was issued in August, 2024 by the airframe manufacturer which recommended the installation of a secondary seat latch and stop, which limits how far aft the crew seat can move if the seat pins are not fully engaged. A review of the airplane maintenance records revealed that this service bulletin had not been complied with on the accident airplane. Based on the available evidence, it is unknown if the pilot properly secured the seat or if the seat latching mechanism malfunctioned.