What happened
On February 13, 2005, a Piper PA-18-150, registration CS-AQN, departed from Leiria Aerodrome for an instructional flight. The flight involved an instructor and a student pilot who was undergoing type adaptation for this specific aircraft. After approximately 35 minutes of flight time, the crew was performing their fifth touch-and-go maneuver.
As power was applied for takeoff, the aircraft began to veer to the left of the runway centerline. The instructor attempted to correct the deviation by applying rightward input. However, the student pilot, unaware of the instructor's maneuver, applied leftward input, effectively countering the correction. The instructor then applied further rightward input to compensate. These alternating and increasingly large control inputs caused the aircraft to deviate significantly from the runway axis. The aircraft eventually exited the runway to the right, striking an earthen embankment. The impact caused the main landing gear to collapse and the propeller tips to strike the ground.
Both occupants were uninjured.
The investigation
The GPIAAF investigation focused on the sequence of control inputs and the coordination between the two occupants. The investigation established that the student pilot had very limited experience in this specific aircraft, having completed only 1 hour and 45 minutes of flight time in the CS-AQN prior to the incident. The investigation also noted that no formal command transfer had been ordered during the period when the conflicting inputs occurred.