What happened
The accident occurred while the aircraft was engaged in a glider towing operation. During the initial climb phase, the tow aircraft suddenly pitched its nose upward. Recognizing the loss of control, both the pilot of the tow aircraft and the pilot of the glider initiated an emergency release of the tow rope. The glider pilot successfully executed a safe landing without incident. However, the tow aircraft maintained its nose-high attitude, resulting in an aerodynamic stall. The aircraft then entered an uncontrolled descent and impacted the ground.
The investigation
Post-accident examination of the wreckage revealed a critical mechanical failure within the control system. Investigators determined that the lower elevator control cable was not properly attached to the control horn. Specifically, the attachment bolt was found with only its tip inserted into the hole of the lower control horn, providing no secure connection. The associated nut and cotter pin required to secure the assembly were not located at the scene.
Review of the aircraft maintenance logs indicated that an annual inspection had been performed approximately 30 flight hours prior to the accident. During that service interval, the flight controls were lubricated and checked, and the airframe was re-covered with fabric. The pilot's last biennial flight review was recorded on February 7, 1982.
Findings
The primary factor leading to the loss of control was the failure of the elevator control system. The incomplete attachment of the lower elevator control cable prevented proper pitch control input from reaching the elevator surface. This mechanical disconnection occurred despite recent maintenance activities that included a general check of the controls.