What happened
During the landing phase of flight, the pilot experienced a significant loss of control authority. Just prior to touchdown, the pilot reported being unable to apply full up elevator to the controls. Upon making contact with the runway, the aircraft bounced and began to yaw toward the right.
In an attempt to maintain directional control, the pilot applied full left rudder and braking; however, the aircraft continued moving toward a line of trees. The pilot then executed a maneuver involving right rudder and braking to intentionally ground loop the aircraft in an effort to avoid the obstacle. Despite this maneuver, the left wing struck the trees, causing the aircraft to spin to the left before coming to a complete stop. There were no injuries reported in the incident.
The investigation
An inspection of the aircraft was conducted following the collision. Investigators discovered that the rear seat cushion was mounted on a piece of plywood that was not securely fastened to the seat structure or the airframe. This mechanical failure allowed the seat cushion to slide forward during flight operations, which physically restricted the movement of the control yoke, preventing the pilot from achieving the necessary elevator deflection for the landing.