What happened
On April 22, 1972, a student pilot was conducting a solo training flight at Birrfeld airfield in a Cessna 150 J, registration HB-CTV. Prior to the accident, the pilot had successfully completed several supervised circuits and his first solo flight without issue.
During the takeoff roll, the pilot noted difficulties with the aircraft's taxiing, which he attributed to the wet and bumpy condition of the grass runway. Upon receiving the takeoff clearance from the instructor, the pilot applied full throttle. However, perceiving that the aircraft was not gaining sufficient speed, the pilot decided to abort the takeoff. He reduced throttle and applied the brakes using both feet.
During the aborted takeoff, the aircraft drifted slightly to the left of the runway. It crossed a field path located approximately 30 meters beyond the end of the runway and entered soft, uncultivated soil. After traveling roughly 40 meters into the field, the nose gear became stuck in the loose earth, causing the Cessna 150 J to flip over. The pilot escaped the crash uninjured, though the aircraft sustained heavy damage.
The investigation
The investigation examined the pilot's experience, the mechanical condition of the aircraft, and the environmental factors present at the time of the accident. The pilot held a valid student pilot certificate with approximately 10 hours of total flight time.
Technical inspections of HB-CTV revealed no pre-existing mechanical defects. The engine was found to be in good working order, and the braking system was fully functional. The aircraft's weight and center of gravity were within prescribed limits.
Weather conditions on the day of the accident involved a low-pressure system, resulting in significant cloud cover and a wet, partially softened grass runway. While the pilot believed the aircraft was underperforming, the flight instructor estimated that the acceleration had been normal. Notably, no brake marks were found on the grass between the point of the aborted takeoff and the airfield boundary.
Findings
- The decision to abort the takeoff was appropriate given the perceived lack of airspeed.
- The lack of deceleration marks suggests that the pilot failed to apply the brakes effectively or immediately.
- The pilot's lack of flight experience likely led to an improper response during the emergency maneuver.
- Several factors could have contributed to the perceived lack of acceleration, including the carburetor heat being engaged, a momentary engine power drop, or the pilot unintentionally applying brakes during the initial roll.