What happened
On March 30, 1969, a training flight involving a Rhönlerche II glider, registration HB-615, ended in a heavy impact at the Winterthur airfield. The flight began with a winch launch in the direction of runway 23. After reaching an altitude of approximately 700 meters via an updraft near Bertschikon, the pilot initiated a return to the airfield.
During the approach, the pilot performed a series of maneuvers, including a 90-degree right turn and a subsequent 90-degree left turn to align with the runway. To manage the remaining altitude, the pilot entered a right-hand glide at an indicated airspeed of approximately 110 km/h. During this maneuver, the aircraft's right wing suddenly dropped. Despite attempts to correct the bank angle, the aircraft failed to respond to control inputs. The pilot realized the aircraft had become too slow and attempted to increase speed, but the glider continued to break to the right. The aircraft struck the ground in a steep bank, causing the right wing to break at the strut attachment and the nose of the fuselage to impact the soft field. The glider came to rest approximately 40 meters right of the runway centerline.
The investigation
The investigation examined the flight path, the pilot's experience, and the aircraft's technical condition. The pilot, who had approximately 30 hours of total flight time, was flying a routine training mission. The investigation confirmed that the Rhönlerche II was properly maintained and that the aircraft's weight and center of gravity were within legal limits for solo flight. Weather conditions at the time included significant turbulence below 300 meters and wind gusts up to 20 knots.
Findings
- The primary cause of the accident was a loss of airspeed during the glide.
- The pilot may have failed to adequately account for the turbulent wind conditions, potentially leading to an aerodynamic stall or an exaggerated flight state following a gust.
- The heavy impact resulted in approximately 85% damage to the aircraft, though the pilot sustained no injuries.