What happened
On May 20, 1971, a pilot and his passenger departed from the Bad Ragaz airfield in a Bölkow-Junior, registration HB-UXP, for a short local flight. The pilot, observing a limp windsock, elected to take off from runway 30 to avoid flying over the town of Bad Ragaz. Shortly after liftoff, the aircraft struggled to gain altitude. In an attempt to clear high-voltage power lines positioned roughly 600 meters from the end of the runway, the pilot initiated a right turn. However, the aircraft's climb rate was insufficient, and the propeller struck the lines, severing two cables. The Bölkow-Junior subsequently crashed, resulting in two serious injuries and the destruction of the aircraft.
The investigation
The investigation examined the meteorological conditions, the aircraft's mechanical state, and the pilot's actions. Investigators reviewed the local weather patterns, noting that a South Föhn wind was prevalent in the region that day. The inquiry also assessed the aircraft's maintenance and the pilot's flight experience and health. No technical defects were found in the HB-UXP, and the pilot was found to be in good health and properly licensed for the operation.
Findings
At the time of the accident, the area was experiencing Föhn winds, but local topography can create temporary pockets of calm or even westerly valley winds at very low altitudes. The pilot mistakenly believed the Föhn wind had subsided because the windsock appeared still. The investigation established that the aircraft encountered a strong tailwind immediately after takeoff. This sudden wind shear significantly reduced the aircraft's climb angle, making it impossible to clear the power lines located near the airfield.