What happened
On July 16, 1963, a Grunau Baby II glider, registration HB-246, was participating in a training flight near Bad Ragaz, Switzerland. The flight was being conducted via aero-tow, with a Chipmunk HB-TUE acting as the tug aircraft. During the second takeoff of the day, the pilot experienced a takeoff roll that felt unusually long. As the aircraft approached a high-voltage power line situated approximately 550 meters beyond the end of the runway, the pilot became concerned that the tow aircraft would strike the cables, which ran perpendicular to the takeoff path.
To avoid this perceived danger, the pilot released the tow rope and entered a steep dive in an attempt to fly underneath the power lines. While the pilot successfully avoided contact with the lowest cable, the maneuver resulted in a loss of altitude that could not be recovered. The glider struck the ground at a steep angle, resulting in the total destruction of the aircraft.
The investigation
The investigation examined the takeoff conditions at the Bad Ragaz airfield, noting that the runway length of 515 meters is quite short for a takeoff in that direction. Investigators analyzed the flight path and the positioning of the high-voltage lines, which stand approximately 30 meters high. Evidence from both the glider pilot and the tug pilot suggested that the tow aircraft actually possessed sufficient altitude to clear the obstacle safely. The investigation also reviewed the pilot's flight history, noting that the pilot had recently resumed training after a hiatus of more than one year and possessed limited flight experience.
Findings
- The pilot's misjudgment of the aircraft's clearance regarding the power lines prompted an unnecessary release from the tow rope.
- The pilot likely perceived the power lines as being aligned with the tow cable, creating a false impression of an imminent collision.
- The sudden steep dive initiated to fly under the cables made it impossible for the pilot to arrest the descent before impacting the ground.
- The pilot's limited flight experience and recent return to flying after a long break contributed to the error in situational assessment.