What happened
On May 10, 1998, a Cessna F 150 K was conducting a training flight at a specialized landing field. The flight was intended to introduce a pilot, who had experience in ultralight aircraft, to powered flight. Following a successful go-around on the 650-meter asphalt runway, the student pilot was primarily controlling the aircraft.
As the aircraft climbed over a wooded area at an altitude of approximately 40 to 50 meters, the student pilot noticed a significant reduction in forward airspeed. The flight instructor then took control of the aircraft and initiated a rapid left turn to avoid the approaching trees. During this maneuver, the aircraft entered a stall and plummeted vertically into the high forest. The impact with the trees and the ground destroyed the aircraft, though both occupants, who were wearing seatbelts, sustained only light injuries.
The investigation
An investigation by the BFU determined that there were no mechanical defects present in the aircraft. The engine was found to have been operating at low power immediately prior to impact, as evidenced by cut marks on a tree trunk. Sufficient fuel was available in the tanks, the flaps were retracted, and both the center of gravity and the takeoff weight were within permissible limits.
The investigation also noted that while the student pilot had 80 hours of experience in ultralight aircraft, the physical control forces required for the elevator in a Cessna F 150 K might have been higher than what they were accustomed to, particularly regarding trim adjustments.
Findings
- The pilot instructor's decision to execute a rapid left turn while the aircraft was already at a low airspeed caused the aircraft to drop below its minimum flying speed.
- The student pilot failed to consistently counteract increasing elevator pressure or properly trim the aircraft following the go-around.
- The stall occurred during the aggressive turning maneuver initiated by the instructor to avoid the forest.