What happened
On July 4, 1966, a pilot operating a Ka-8B glider, registration HB-824, departed from the Dittingen airfield with the goal of completing a 50 km distance flight to earn a FAI performance badge. After releasing from the tow plane at approximately 900 meters altitude, the pilot initially gained height but later encountered a lack of expected thermal lift near Mt. Raimeux.
As the aircraft steadily lost altitude, the pilot decided to terminate the flight and sought a landing spot near Delémont, specifically targeting a grassy area between two football pitches. During the final approach, the pilot deployed air brakes and entered a left slip. Upon realizing that wooden stakes marking the field corners were positioned closer than anticipated, the pilot attempted to adjust the flight path to land in an adjacent cultivated field. During this maneuver, the pilot attempted to transition from the left slip into a right turn, but lost control of the aircraft. The glider struck the ground with its right wing and the front of the fuselage, causing extensive damage to the airframe.
The investigation
The investigation examined the pilot's experience, the aircraft's condition, and the meteorological environment. The pilot had approximately 61 hours of total flight time, with limited recent experience in the Ka-8B. The aircraft was found to be in good mechanical condition, with the center of gravity within prescribed limits and no technical failures identified. Weather conditions at the time involved unstable air with developing cumulonimbus clouds over the Jura mountains.
Findings
- The pilot was performing his first landing in an open field.
- The presence of unexpected obstacles (wooden stakes) caused a sudden change in landing intentions.
- The primary cause of the accident was the loss of control during a sudden course correction intended to avoid obstacles.
- The pilot's attempt to transition from a left slip to a right turn resulted in an excessive bank angle and a loss of airspeed, leading to the impact.