What happened
On May 17, 1964, at approximately 17:10 CET, a DFS-Kranich glider, registration HB-481, departed from Mollis for a ridge soaring flight. The aircraft was carrying a pilot and one passenger. After performing several maneuvers to gain altitude, the aircraft flew near the Kerenzerberg slope at a speed between 70 and 80 km/h.
While attempting to execute a left turn to move away from the slope, the pilot encountered difficulties maintaining control. Despite attempting a full circle to reposition the aircraft, the glider continued to bank toward the terrain. During the subsequent attempt to recover, the aircraft failed to level out, eventually striking the treetops of a dense beech forest. The impact caused the aircraft to capsize and slide along tree trunks before coming to rest on its back. The pilot sustained minor facial injuries, while the passenger remained uninjured. The DFS-Kranich was destroyed in the accident.
The investigation
Investigators examined the wreckage and the flight control systems of the HB-481. The investigation focused on whether technical malfunctions, interference from the passenger via the dual controls, or pilot error were responsible for the loss of control. The inquiry also reviewed the pilot's flight experience, noting he had approximately 60 hours of total flight time and relatively limited experience with this specific aircraft model.
Findings
- The investigation found no evidence of technical defects in the flight controls or the airspeed indicator.
- There was no evidence that the passenger interfered with the pilot's control inputs.
- The aircraft's flight characteristics were noted as being prone to sudden stalling without warning if the stall speed is reached.
- The primary cause of the accident was a pilot error occurring during a turning maneuver, specifically involving improper use of the rudder during the attempt to exit the turn.