What happened
On July 29, 2003, at approximately 14:40 local time, a mid-air collision occurred near the Walliser Wispile in the municipality of Gsteig. Two gliders, a DG-50 and/or 22 ELAN with registration HB-1994 and an ASW 20L with registration D-6805, were participating in an alpine soaring training camp. The HB-1994 had departed from Zweisimmen carrying two pilots, while the D-6805 had launched from Saanen.
The aircraft were flying on intersecting paths at an altitude of approximately 2,700 meters. The D-6805 was traveling on a course of roughly 210 degrees, while the HB-1994 was flying north from the direction of Spitzhorn. The two gliders collided head-on during straight-and-level flight. The impact was severe, causing the destruction of both aircraft. The pilot of the D-6CO5 and the rear occupant of the HB-1994 managed to deploy their parachutes and survive the accident, though the pilot of the D-6805 sustained a broken leg upon landing. Tragically, the pilot in the front seat of the HB-1994 was unable to exit the aircraft and died as a result of the collision or the subsequent crash.
The investigation
An investigation by the Swiss Transportation Safety Investigation Board (SUST) examined the flight paths, aircraft condition, and pilot visibility. Investigators found no evidence of mechanical failure or technical defects in either aircraft. Both gliders were fully airworthy and had been properly maintained. Medical examinations of the surviving pilots showed no presence of alcohol, drugs, or medication that could have impaired their abilities.
Findings
- The primary cause of the accident was that the pilots detected each other too late to take effective evasive action.
- The head-on approach meant that the pilots could only perceive the oncoming aircraft as a silhouette.
- Flying against a bright or white background, such as clouds or mountain terrain, significantly reduced the visibility of the white gliders.
- While both aircraft featured high-visibility warning colors on the wingtips and nose, these were found to be of limited effectiveness in preventing a collision at close range.
Safety action
- The investigation recommended that the Federal Office of Civil Aviation (FOCA) review methods to reduce collision risks in Swiss airspace, such as the implementation of warning systems.
- Following the accident, a recommendation was made to re-evaluate the requirement for glider pilots to wear parachutes, as the use of parachutes was a critical factor in the survival of the two pilots.