What happened
On January 14, 1962, at 16:36 HL, an Ercotupe 415-C, registration HB-ERG, departed from the La Chaux-de-Fonds aerodrome for a local flight with one passenger. During the return approach to runway 24, the pilot encountered significant visual difficulties. The setting sun in the southwest, combined with the reflective properties of the snow-covered terrain, created a blinding glare.
While attempting to maintain the approach, the pilot lost precise situational awareness regarding the aircraft's position relative to the runway centerline. At 16:48, the aircraft touched down on hard snow approximately 8 meters to the left of the runway. The impact sequence began with the right wheel, followed by the nose wheel, which deformed upon contact. The left wing subsequently struck the ground, causing the aircraft to capsize. The aircraft was 80% destroyed, though both occupants escaped without injury.
The investigation
The investigation examined the meteorological conditions, the aircraft's technical state, and the airfield's visual aids. At the time of the accident, the sky was partially covered with clouds, and the sun was low in the southwest. The runway was covered in a thin layer of snow, while the surrounding terrain had a snow depth of 15 to 20 cm.
Investigators noted that while the aircraft's weight was slightly above its maximum permitted takeoff weight, this was not a contributing factor. The investigation also reviewed the airfield's marking system, which consisted of wooden markers and small red flags. It was observed that a different pilot had landed successfully on a Piper Super Cub just three minutes prior, though a third pilot experienced sudden loss of visibility during a subsequent approach.
Findings
- The primary cause of the accident was the pilot's decision to continue the approach despite being blinded by the sun and snow glare, leading to a loss of visual reference to the runway.
- The glare caused the pilot to lose track of the aircraft's exact position relative to the runway centerline.
- The airfield's visual markers were insufficient to compensate for the intense light reflections caused by the sun and snow.