What happened
On July 27, 1959, at approximately 15:20, two gliders were operating in the vicinity of Muottas Muragl, Switzerland, during a gliding camp. The first aircraft, a Bergfalke II with registration HB-559, launched via an auto-winch with a pilot and one passenger on board. Shortly after, a single-seat S-18-IB glider, registration HB-219, also launched using a winch to gain altitude for a performance badge.
As the aircraft navigated the strong updrafts created by the Maloja wind, the pilot of HB-219 observed HB-559 flying approximately 70 to 80 meters above him. The pilot of HB-219 then initiated a left turn. Simultaneously, the pilot of HB-559 entered a wide left turn that brought the two aircraft back toward one another. The two gliders collided nearly head-on at an altitude of about 60 meters above the Muottas Muragl plateau.
The impact caused the left wing of HB-559 to break, sending the aircraft into a flat spin. The glider crashed on the western slope of the mountain, resulting in two fatalities. The HB-2 and 19 sustained significant damage to its wing and canopy, but the pilot managed to stabilize the aircraft and perform an emergency landing at Samedan airfield without injury.
The investigation
The investigation examined the flight paths, weather conditions, and the visibility from both cockpits. Investigators noted that the weather was clear with good visibility exceeding 30 km, and the sun did not pose a significant visual obstruction to either pilot. The investigation also reviewed the mechanical condition of both aircraft, finding no evidence of technical failure or defects in either the S-18-IB or the Bergfalke II.
Findings
- The primary cause of the collision was objectively insufficient airspace observation by both pilots.
- Both pilots had the opportunity to detect the other aircraft during their respective left turns prior to the impact.
- The pilot of HB-219 failed to account for the fact that the strong updrafts could allow the other aircraft to reappear at his altitude during his maneuver.
- There was no evidence that any third aircraft distracted the pilots from monitoring the surrounding airspace.