What happened
On August 1, 2000, two gliders were participating in an alpine soaring camp held at the former military airfield in Münster, Switzerland. The first aircraft, a Rolladen-Schneider LS7-WL with registration HB-3065, departed at 11:46 LT. After navigating through the Valais region and the Rhone Valley, the pilot continued toward the Lengtal region.
The second aircraft, another Rolladen-Schneider LS7-WL registered as HB-3066, departed at 12:31 LT. The pilot flew toward the Sanetsch Pass before turning back, eventually heading north toward the Furkapass.
While flying over the Aegenetal at an altitude of approximately 3,800 meters, the two gliders collided head-on. A witness in a third aircraft observed the two gliders traveling toward each other at a combined closing speed of approximately 64 m/s. During the impact, the right wing of HB-3065 struck the tail unit of HB-3066. The collision caused the loss of the wing on the first aircraft and the horizontal stabilizer on the second, leading both aircraft to crash. Both pilots successfully deployed parachutes but sustained serious injuries upon landing.
The investigation
SUST examined the flight conditions, the mechanical state of both aircraft, and the pilots' flight profiles. Both Rolladen-Schneider LS7-WL aircraft were found to be airworthy, with weight and balance within limits. The investigation noted that the white paint and slender aerodynamic profiles of the gliders made them difficult to distinguish against the sky and clouds, a difficulty potentially compounded by the sun's position.
Investigators also reviewed the flight durations, noting that the pilot of HB-3065 had been airborne for over six hours, while the pilot of HB-3066 had been flying for over five hours. While the aircraft were equipped with GPS and ELTs, the GPS data could not be retrieved for analysis, and the ELT on HB-3065 was destroyed upon impact.
Findings
- The primary cause of the collision was that the pilots failed to see each other.
- A contributing factor was diminished concentration resulting from the long duration of the flights at high altitude.
- The high closing speed made it nearly impossible to detect an oncoming aircraft from a distance of one kilometer.