What happened
On May 11, 1961, a pilot was returning to the Neuchâtel airfield following a multi-hour flight that had taken the aircraft over the Plateau and near the Moléran region. While crossing Lake Neuchâtel, the pilot encountered downdrafts that caused a rapid loss of altitude. Realizing that returning to the original airfield was no longer possible, the pilot decided to perform an emergency landing in a field east of Concise.
Due to significant turbulence in the area, the pilot was unable to determine the precise wind direction. Based on observations of wave patterns on the lake surface, the pilot assumed a northerly wind and attempted a landing toward the northeast. During the final turn before the approach, the pilot experienced a sudden sensation of the aircraft sinking and the controls becoming unresponsive. Despite two attempts to push the stick forward to regain airspeed, the L-Spatz 55 struck the ground at an angle of approximately 30 degrees. The pilot sustained injuries including various contusions and a spinal injury, and the aircraft was destroyed.
The investigation
Investigators examined the wreckage and the surrounding meteorological conditions. While witnesses initially reported seeing what appeared to be structural damage to the left wing during the descent, technical analysis of the debris proved that the airframe was airworthy and that all structural damage, including the failure of the wing spar, was the result of the impact with the ground.
Meteorological data from the Zurich Airport weather center indicated that the region was experiencing unstable weather with localized showers and significant turbulence. Specifically, a sudden, violent wind from the Mont-Aubert—a phenomenon known locally as a 'coup de Joran'—had descended upon the area at the time of the accident.
Findings
- The pilot was unable to accurately identify the true wind direction due to heavy turbulence and the onset of rain.
- The aircraft was inadvertently positioned in a tailwind during the final turn.
- A sudden tailwind gust and downdraft caused the glider to enter a stall during the turn.
- The pilot's first corrective maneuver was insufficient because the aircraft was caught in a tailwind, and the second attempt occurred at too low an altitude to effectively regain flying speed.