What happened
On May 5, 1968, a Ka-8B glider, registration HB-849, was performing a local training flight after departing from Lausanne-Blécherette. Shortly after releasing from the tow plane at approximately 1,000 meters, the pilot began searching for thermals. Due to very weak rising air and increasingly strong downdrafts, the pilot determined that returning to the airfield was not possible and decided to perform a forced landing in a field near Villars-le-Terroir.
The pilot executed a series of maneuvers to approach the chosen landing site, including two 360-degree turns. While approaching the final leg with airbrakes partially extended, the aircraft cleared a 15-meter tree line. Immediately after passing the obstacle, the glider experienced a sudden loss of altitude and pitched forward. Despite the pilot's attempts to recover using the elevator, the aircraft struck the ground at an angle of approximately 30 degrees, impacting with the nose and the right wing. The aircraft bounced before coming to rest in a field.
The investigation
Investigators examined the aircraft and the flight conditions at the time of the accident. The Ka-8B was found to be in good mechanical condition, with no defects found in the flight controls. The investigation also reviewed the pilot's flight history and the meteorological conditions, which included moderate turbulence below 200 meters and a light wind.
Findings
The investigation established that the accident was caused by an insufficient approach speed. It is believed that the pilot, attempting to maintain enough clearance to clear the trees, likely pulled back on the elevator while keeping the airbrakes partially deployed. This maneuver caused the airspeed to drop to a critical level, leading to the sudden forward pitch and loss of control.
Additionally, the investigation noted that the landing approach did not follow standard procedures, which typically involve descending to a specific altitude over the landing area before executing turns to intercept the approach axis.