What happened
On December 18, 1969, a Beechcraft Baron HB-GBS was attempting a solo departure from the Eplatures airfield in La Chaux-de a Fonds. The flight was planned as an IFR operation to Geneva. During the takeoff roll on runway 24, the pilot encountered deteriorating conditions. As the aircraft accelerated, wet snow and rain began to accumulate on the windshield, significantly obscuring the view. Simultaneously, the pilot lost visual contact with the ground due to the low cloud ceiling and poor visibility.
As the aircraft reached approximately 65 mph, the pilot noted a slight leftward deviation on the heading indicator. Fearing that an aborted takeoff would result in the aircraft sliding into the snowbanks at the end of the runway due to the slippery surface, the pilot continued the takeoff roll using instruments. During the maneuver, the left wing struck a snowbank approximately 410 meters from the runway threshold. The impact caused the left and right main landing gear to be torn from the aircraft, and the plane eventually slid into a ditch, coming to rest 9 meters from the left edge of the runway.
The investigation
Investigators examined the wreckage and the airfield conditions following the accident. The investigation confirmed that the aircraft was fully equipped for IFR flight and that all maintenance and airworthiness certificates were valid. The engines and propellers were found to be in good working order, and no technical malfunctions were identified as contributing to the event. The investigation also noted that while the runway had been cleared, a thin layer of melting snow remained, and high snowbanks, measuring between 1 and 1.5 meters, lined the runway edges.
Findings
Several factors combined to severely degrade visibility during the critical takeoff phase:
- The presence of heavy, wet snowfall.
- The accumulation of snow on the windshield, which was not cleared by the propeller slipstream.
- A lack of visual contrast on the runway surface due to the thin layer of melting snow.
- Advanced twilight conditions caused by the inclement weather.
Ultimately, the investigation concluded that the pilot attempted the takeoff in visibility conditions that were insufficient for a safe departure.