According to the Swiss Transportation Safety Investigation Board (Sust), the pilot failed to observe several basic rules of safe mountain flying tactics. This led to the crash of the small aircraft near Château d'Oex VD with two fatalities in the summer of 2019 in the canton of Vaud.
The single-engine Remos GX light aircraft stalled on a mountain slope at low altitude at a slow airspeed and a high bank angle and crashed into rough, wooded terrain. The 24-year-old pilot and the 27-year-old passenger were killed.
The two-seater had taken off from the airfield in Epagny FR on June 27, 2019. It was part of a group of three aircraft that wanted to fly to Bex VD. The pilots of the other two aircraft were the father and brother of the pilot involved in the accident. The aircraft involved in the accident was out of sight of the other two planes when it crashed.
Too low and too slow
In order to reach Bex, the pilot wanted to fly over the Col de Sonlomont, according to the final report published by Sust on Friday. The flight into the valley to this pass took place at too low an altitude and with reduced engine power.
According to the accident experts, this indicates that the pilot was not aware that she still had to gain altitude. At a distance of 1.7 kilometers from the pass, she probably became aware of this, as she increased the engine power to maximum.
The hot summer weather with temperatures above 30 degrees meant that the engine developed less power than normal. In the following 30 seconds, the aircraft only gained just under 25 meters in altitude with maximum engine power. In addition, the nose of the aircraft continuously pointed upwards during this period and the speed of the aircraft decreased significantly.
According to Sust, the speed for best climb was clearly undercut. This shows that the pilot no longer paid attention to the speed and thus created the conditions for the subsequent stall.
Turn in the wrong direction
About 900 meters before the top of the pass, around 150 meters above the ground, the pilot initiated a U-turn. According to the Sust report, the pilot most probably realized at this point that it was not possible to fly over the pass. Contrary to mountain flight tactics, the turn was made to the left towards the rising slope and not to the right towards the open center of the valley.
In summary, according to Sust, flying into the valley without sufficient altitude reserve, approaching the terrain with insufficient speed and finally turning towards the slope contradict the recognized basic principles for flying over a pass.