Accident Overview
On August 12, 1965, at approximately 0900 MEZ, a student pilot of the Swiss Air Transport School departed Hausen airfield in a Bücker 131 Jungmann (registration HB-URL) for a planned cross-country flight from Hausen to Pontarlier and back. Shortly after departure, the pilot deviated from the assigned route and flew to Zug, where he conducted low-altitude maneuvers over his former workplace.
Flight Details
The pilot, born in 1943, held a private pilot license since June 5, 1962, and a glider license since July 27, 1964. He had accumulated about 175 hours of motor flying experience, including approximately 50 hours on the accident type, and 26 hours of glider flight. He had joined the Swiss Air Transport School on April 1, 1965, and previously worked as a toolmaker in Zug from July 1964 to March 1965.
Witnesses observed the aircraft circling at an estimated height of 80–250 meters above ground over the "Gutsch" hill near Zug. The pilot performed about five irregular turns with bank angles of 45–60 degrees, occasionally accompanied by wing-wagging and nose-up maneuvers. The pilot reported that his view was partially obscured by the left wing, causing him to increase bank and pull the elevator, resulting in a stall. The aircraft then entered an almost inverted attitude and descended uncontrollably.
Impact and Damage
At around 0907, the left wing struck an apple tree crown on the northwest slope of the hill. The aircraft then rotated right and impacted the ground steeply next to the tree. The pilot sustained severe injuries, including a serious concussion and leg fractures, and remained hospitalized for at least six months. The aircraft was destroyed. Minor damage to the apple tree and meadow was estimated at 250 Swiss francs.
Investigation Findings
The investigation revealed that the pilot had previously expressed intentions to fly over his former workplace and had conducted similar maneuvers over the same location on August 10, 1965, at a higher altitude. Evidence from August 11 suggested another similar flight, but the pilot's involvement could not be confirmed.
The accident was determined to be the result of a show-off flight at low altitude, during which the pilot lost control due to a stall.