Factual Information
On 23 July 2008, at approximately 16:59 local time, the Robin DR400-RP aircraft, registration HB-KBM, owned and operated by Segelfluggruppe Oberaargau, crashed near Santiglais, about 1 km east of Münster, in the municipality of Geschinen, Valais, Switzerland. The accident occurred at an elevation of 1365 m (4478 ft AMSL). The aircraft was destroyed, and all four occupants sustained fatal injuries. No fire occurred, and only minor property damage was reported.
Accident Sequence
The aircraft had been used for glider towing at the Münster airfield since 15 July 2008. On the day of the accident, the pilot arrived in the morning and participated in a briefing. He completed 12 towing flights between approximately 11:00 and 16:00, totaling 106 minutes of flight time. At about 12:45, he refueled with 80 liters of AVGAS. After parking the aircraft, he was asked by a passerby to conduct an alpine sightseeing flight to the Matterhorn with three passengers. The flight service director approved the flight and reminded the pilot of strong winds. The pilot responded that he was aware and expected reduced turbulence above the terrain. He then refueled the auxiliary tank with 50 liters of AVGAS, bringing the total fuel on board to an estimated 135–145 liters.
The flight departed from Münster airfield shortly before 17:00, heading up-valley. About two minutes after takeoff, while executing a left turn down-valley, the aircraft entered an uncontrolled flight attitude and collided with terrain near the departure airfield.
Aircraft Information
The aircraft was a Robin DR400-RP, manufactured by S.A. Avions Pierre Robin, France. It was registered in Switzerland with the registration HB-KBM. The aircraft was powered by a single engine and was equipped with a constant-speed propeller. It was used primarily for glider towing due to its high engine performance.
Injuries and Damage
The accident resulted in fatal injuries to all four occupants. The aircraft was completely destroyed. There was no fire, and only negligible damage to the surrounding vegetation occurred.
Cause
The investigation determined that the accident was due to the aircraft entering a loss of control following an inadequate flight tactic. Incomplete flight preparation contributed to the accident.