What happened
On March 24, 2018, a Maule M-7-235 with registration N561LC was participating in a mountain fly-in event in Arosa, Switzerland. During the takeoff roll on a prepared snow runway, the aircraft failed to lift off before reaching the end of the available surface. The aircraft struck a pedestrian suspension bridge over the Welschtobelbach at approximately 80 knots. The impact caused the engine to separate from the fuselage and ignited a fire. The collision resulted in two fatalities, involving both the pilot and the passenger.
The investigation
Investigators examined the aircraft's configuration, the runway conditions, and the flight sequence. The investigation established that the aircraft was equipped with skis for the snow surface. While the aircraft's weight and center of gravity were within limits, several factors hindered its acceleration. The investigation also reviewed the pilot's use of control surfaces and the environmental conditions, including a light tailwind present at the time of the accident.
Findings
Several factors prevented the aircraft from reaching the necessary rotation speed:
- The flaps were set to -7°, which required a higher takeoff speed than the recommended 24° setting.
- Excessive and unevenly applied wax on the skis created significant drag during the acceleration phase.
- The pilot maintained a full back-pressure on the elevator, which caused the tailwheel to dig into the snow, creating further resistance.
A contributing factor was a light tailwind, which further extended the required takeoff distance.