What happened
On July 18, 1979, during a gliding flight camp near Münster, Switzerland, two gliders were performing thermal soaring maneuvers in a strong updraft. The first aircraft, a Club Libelle 2 .05, registration HB-1262, was executing tight right-hand turns at approximately 110 km/h with a bank angle of 40 to 45 degrees. Shortly thereafter, a Ka 6 CR, registration HB-650, entered the same area approximately 200 meters to the west, performing wider right-hand turns at a 20-degree bank angle.
During the maneuvers, the two pilots lost visual contact with one another. At an altitude of approximately 2,500 meters, the pilot of the HB-1262 suddenly observed the HB-650 appearing directly ahead and to the left. Simultaneously, the pilot of the HB-650 noticed the HB-1262 approaching from behind. In an attempt to avoid the collision, the pilot of the HB-650 initiated an evasive maneuver involving forward elevator input and a turn. During this movement, the lower fuselage of the HB-12SB struck the horizontal stabilizer of the HB-650, and the left wing of the HB-1262 struck the rudder, causing damage to the rudder's trailing edge.
Following the impact, the pilot of the HB-650 reported vibrations in the control column and immediately deployed spoilers to attempt an emergency landing on a rocky slope below. At 11:30 local time, the HB-650 struck the slope with its left wing, causing the aircraft to pivot and slide 30 to 40 meters down the terrain. The aircraft was destroyed, and the pilot sustained one minor injury. The HB-1262 sustained damage to its left wing but was able to land safely at the Münster airfield.
The investigation
Investigators examined the wreckage of both aircraft and identified red paint transfers on the HB-650's horizontal stabilizer, which originated from the underside of the HB-1262's fuselage. Scratches were also found on the underside of the HB-1262's fuselage. The investigation confirmed that both pilots held valid licenses and were authorized for the flights, and there were no indications of medical issues or mechanical failures that contributed to the accident.
Findings
- The pilots were focused heavily on controlling their aircraft within the strong thermals, which led to a failure in maintaining visual contact.
- The pilots failed to alter their flight paths to re-establish visual contact after losing sight of each other.
- The primary cause of the collision was insufficient airspace observation by the pilots.