What happened
On August 29, 2017, a private flight involving a Robin DR 400/180, registration HB-KFY, ended in a runway excursion at Raron airfield (LSTA) in Switzerland. The pilot, performing a visual flight rules (VFR) circuit, approached runway 28 from the east. While the aircraft initially appeared normal to observers, it failed to stop before the end of the paved surface. The aircraft subsequently collided with an earthen embankment located just beyond the runway threshold. While the two occupants escaped without injury, the aircraft sustained heavy damage, and nearby vehicles were struck by displaced earth during the impact.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the aircraft's technical systems, the pilot's flight profile, and the airfield's infrastructure. Investigators scrutinized the braking system following the pilot's report of brake failure; however, technical inspections revealed no mechanical defects in the hydraulic brakes or the airspeed indicator. Data from the aircraft's Flarm system provided a precise reconstruction of the flight path. The investigation also reviewed the airfield's status, noting that Raron was operating on a temporary western runway while awaiting a planned relocation to an eastern site.
Findings
Analysis of the flight data revealed that the approach to runway 28 was unstable. Specifically, the aircraft crossed the runway threshold at a ground speed of approximately 90 knots, which was roughly 20 knots above the recommended approach speed. This excessive landing speed, combined with a late touchdown, resulted in a landing roll that exceeded the available runway length. Furthermore, the pilot determined that a go-around was too risky due to the proximity of buildings located in the runway extension area.
Safety action
The investigation highlighted that the delayed implementation of the planned airfield relocation remains a safety risk. The current configuration, which includes industrial buildings and an earthen embankment in the runway extension, poses a hazard during runway excursions.