What happened
On June 29, 1969, a private recreational flight through the Bernese Alps ended in a fatal accident near the Eiger Glacier. The flight departed from Bern-Belpmoos in a Piper J3 and C HB-OWZ carrying a pilot and one passenger. During the flight, the aircraft traversed several landmarks, including the Hohtürli pass and the Jungfraujoch, with the passenger documenting the scenery through photography.
As the aircraft approached the Eiger Glacier, witnesses at the Eiger Glacier hotel observed the plane flying at an unusually low speed and appearing unstable. The aircraft entered a steep right-hand turn, during which it lost lift and entered a vertical descent. The aircraft struck the glacier approximately 300 meters below the hotel. The impact resulted in one fatality (the passenger) and left the pilot with severe injuries. The aircraft was destroyed in the crash.
The investigation
The investigation examined the aircraft's condition, the pilot's experience, and the environmental factors at the time of the accident. Analysis of the passenger's photographic slides allowed investigators to reconstruct the flight path, revealing that the aircraft had lost significant altitude during its final approach toward the glacier.
Investigators also reviewed the aircraft's weight and balance. At the time of the accident, the Piper J3C was operating above its maximum allowable takeoff weight. Furthermore, the investigation looked into the pilot's flight experience, noting that while the pilot held a valid license, his experience in mountainous terrain was limited. The presence of a secondary control stick in the front seat was also noted, though it was not determined to have interfered with the pilot's control.
Findings
Several contributing factors led to the accident:
- Improper mountain flying tactics: The pilot likely lost visual reference to the horizon due to the complex terrain, leading to an unrecognized high angle of attack.
- Aerodynamic stall: The pilot executed a tight right-hand turn without sufficient airspeed margin, causing the aircraft to stall and slip into a dive.
- Overweight conditions: The aircraft was overloaded at takeoff, which reduces the margin between cruise speed and stall speed, especially during maneuvering.
- Reduced visibility of instruments: The pilot's position in the rear seat, combined with the passenger's physical presence, may have obstructed the pilot's view of critical airspeed instruments during the critical phase of flight.