What happened
During a flight training session at the Kingston, Ontario, airport, a student pilot and a flight instructor were performing stall practice in a Cessna 150. After the instructor demonstrated the maneuver, the student attempted a stall recovery. During this attempt, the student pushed the control column forward aggressively, causing the aircraft to enter a dive.
Upon taking control, the instructor discovered that the elevator movement was severely restricted. Despite applying significant force, the instructor could not move the control column beyond the neutral position. The aircraft accelerated to approximately 190 miles per hour during the descent. To recover, the instructor utilized a combination of full nose-up trim, high engine power at 2500 RPM, and continuous back pressure.
As the aircraft approached the airport for an emergency landing, the instructor deployed flaps to reduce speed. During this process, the elevator controls regained full range of motion, allowing for a normal touchdown. However, the high-speed excursion resulted in substantial damage to the aircraft's wings, flaps, and ailerons.
The investigation
Investigators examined the elevator control system and found no permanent binding, damage, or mechanical defects in the elevator components. The investigation focused on identifying a transient cause for the control restriction.
It was determined that the push-to-talk cord on the right side of the cockpit had been stretched to twice its standard length and was wrapped loosely around the control column. The investigation established that a single loop of this cord could snag on the cabin air control knob. During the student's aggressive forward input and the subsequent nose-low attitude, the cord likely swung forward and became entangled on the knob, preventing the aft movement of the column. The movement of the column forward during the flap deployment phase likely released the tension, freeing the controls.