What happened
On the afternoon of July 25, 1963, a student pilot was conducting a solo training flight at the Bern-Belpmoos airfield to prepare for an advanced flight examination. After an initial successful flight, a second takeoff was performed at 15:43 CEST. While the flight initially proceeded normally, a thunderstorm approaching from the Gürbetal valley caused the aircraft to encounter intense turbulence at an altitude of approximately 600 meters.
As the weather deteriorated, strong winds began blowing from the south. Due to the shifting wind conditions, the flight instructor changed the landing direction, setting the windsock for runway 14. However, the student pilot, preoccupied with maintaining control of the Piper Cub HB-ALP amidst the heavy turbulence, did not notice the change in landing direction.
Attempting to land on the original runway 32, the pilot encountered a significant tailwind of approximately 20 to 30 knots. This caused the aircraft to overshoot the paved runway and land in a grassy area. During the landing roll, the aircraft encountered a potato field, which led to a capsize. There were no injuries to the pilot.
The investigation
SUST examined the flight sequence, the meteorological conditions, and the actions of both the student and the instructor. The investigation established that the thunderstorm had moved in an unexpected direction, shifting from the northwest toward the airfield. The investigation also reviewed the pilot's experience level, noting that the student had approximately 12 hours of flight time at the time of the accident.
Findings
- The primary cause of the accident was the student pilot encountering severe thunderstorm turbulence, which compromised the ability to monitor ground signals and maintain precise aircraft control.
- The pilot failed to observe the change in the landing direction signaled by the instructor.
- A strong tailwind significantly extended the landing roll, making the available surface area insufficient to stop the aircraft before it reached uneven terrain.
- The presence of a potato field contributed to the loss of control and subsequent capsize.