What happened
On August 12, 1982, two gliders departed from Samedan Airport in Switzerland for soaring flights. The first aircraft, a Speed Astir II with registration D-2904, took off at 14:27 local time. Approximately thirteen minutes later, at 14:40, a second glider, a Ka 6 CR registered as HB-836, also launched from the same airfield.
By mid-afternoon, both aircraft were operating in the thermal updrafts above Piz Tschierva, an area known for dense traffic during such conditions. At approximately 16:02, the Speed Astir II D-2904 approached the Ka 6 CR HB-836 from behind and to the left. The collision occurred at an altitude of 3,807 meters. The impact severed a 3.27-meter section of the right wing of the D-2904. The German-registered aircraft then rolled over the Swiss glider and entered a spiral dive, crashing into the western face of Piz Tschierva. The pilot of the D-2904 was killed instantly, and his aircraft was destroyed. The pilot of the HB-836 sustained only minor damage to the left wing and canopy but remained uninjured and managed to return safely to Samedan.
The investigation
The Swiss Transportation Safety Investigation Board (STSB) examined the circumstances surrounding the accident. Both pilots were experienced, holding valid licenses and medical certificates. Neither showed signs of health issues or fatigue; both had been acclimatized to the high altitude after several days in the region. The weather was clear with good visibility, and no technical defects were found in either aircraft prior to the flight.
Witnesses reported that the area above Piz Tschierva was crowded with 15 to 20 other gliders performing various maneuvers. The investigation determined that the pilot of the D-2904 had entered this congested airspace at high speed. Due to the density of traffic and the relative positions of the aircraft, the pilot of the HB-836 was in a blind spot and did not see the approaching D-2904 until impact.
Findings
The primary cause of the accident was the pilot of the D-2904 flying into a complex group of gliders at high speed without maintaining adequate visual separation. This resulted in the failure to see and avoid the HB-836. The relative angle of impact was approximately 65 degrees, indicating a significant lateral deviation by the D-2904 just before collision. The pilot of the HB-836 had no opportunity to evade the attack from his blind sector.
Safety action
The investigation highlighted the dangers of high-speed penetration into crowded thermal zones. It emphasized the need for pilots to exercise extreme caution and maintain heightened situational awareness when operating in areas with significant glider traffic density.