What happened
On September 1, 1973, during the Dittingen airshow, a pilot was performing a scheduled aerobatic routine in a Bücker Jungmann HB-UUH. The flight began at an altitude of approximately 500 meters above ground level and included a series of maneuvers such as loops, spins, and rolls.
While performing a left half-cuban eight (Renversement), the aircraft entered a left-hand spin immediately after passing the peak of the maneuver. Although the pilot managed to stop the rotation after approximately two to two and a quarter turns, the remaining altitude was insufficient to recover the aircraft. At 16:08, the plane struck sloping terrain north of the Dittingen runway at a shallow angle and subsequently collided with a telephone pole, which caused the aircraft to rotate 180 degrees before coming to a halt. The pilot sustained no injuries, but the aircraft was destroyed.
The investigation
The investigation examined the pilot's qualifications, the aircraft's technical condition, and the flight dynamics. The pilot held valid private and limited professional licenses, including specific authorization for aerobatic flight at low altitudes. Medical examinations confirmed the pilot was not under the influence of alcohol and showed no signs of health issues at the time of the accident.
Technical inspections of the Bücker Jungmann revealed the aircraft was airworthy, with the weight and center of gravity within permissible limits. Weather conditions at the time were favorable, with light winds and clear visibility. Analysis of film footage from the event showed that the final maneuver was initiated at a low airspeed. The footage also captured control surface movements, indicating significant elevator and aileron inputs during the spin.
Findings
- The pilot reported that his right foot had slipped and become jammed against the rudder pedal during the lateral banking of the final maneuver, triggering the left spin.
- The investigation determined that the aircraft's altitude was insufficient for a full recovery after the spin was arrested.
- The unintended initiation of a spin at low altitude was the primary factor, likely caused by a sudden, reflexive pull on the elevator control as the pilot realized the aircraft's low altitude after the maneuver's peak.