What happened
On the afternoon of April 3, 1979, a Morane-Saulnier MS-893E, registration HB-EYL, departed from Porrentruy for a private flight to Môtiers with two passengers on board. Although the pilot had noted threatening weather to the west during a previous stop, no additional meteorological information was sought before departure. The flight was delayed by approximately one hour due to engine starting difficulties.
While flying near the La Chaux-de an area near the Ponts-de-Martel plain, the aircraft encountered an extensive and intense snow squall. In an attempt to maintain visual contact with the ground, the pilot attempted to cross a wooded ridge at an extremely low altitude. After two unsuccessful attempts to clear the ridge, a third attempt was made at an even lower altitude. During this final maneuver, the aircraft encountered a farm in very restricted visibility. The pilot executed a sudden, steep climb to avoid the obstacle, which caused the aircraft to stall and impact the ground at 17:20 local time. All three occupants were killed, and the aircraft was destroyed.
The investigation
The investigation established that the aircraft was in a valid state for flight, with the weight and center of gravity within permissible limits. There were no signs of mechanical failure or prior defects in the engine or airframe. The investigation focused on the pilot's decision-making and the environmental conditions during the final phase of flight.
Findings
- The primary cause of the accident was a loss of control resulting from continuing visual flight rules (VFR) operations in insufficient meteorological conditions at a very low altitude.
- A rapid deterioration in weather conditions, specifically heavy snow and localized fog, significantly reduced visibility.
- The pilot's blood alcohol level was measured between 1.05 and 1.08 ‰, which likely impaired his situational awareness, reaction capabilities, and potentially his visual field and sense of balance during the low-level maneuvers.
- The pilot's attempt to avoid a farm via a sudden upward pitch likely caused the aircraft to lose airspeed and stall at an altitude too low to recover.