What happened
On the evening of January 22, 2020, a Piper PA-28-181, registration HB-PMH, departed Ecuvillens (LSGE) for a night flight under Visual Flight Rules (VFR). The flight was intended to follow a specific route involving several waypoints, including Yverdon, Lausanne, and Gruyères.
During the flight, the pilot deviated from the original flight plan after passing Lausanne. Instead of proceeding to the next planned waypoint, the pilot chose to fly along the northern shore of Lake Geneva toward Vevey. After passing Vevey at an altitude of 3,800 ft, the aircraft turned northeast toward Gruyères. At approximately 20:03, the aircraft struck a steep forested area in the Les Pléiades region. The impact destroyed the aircraft and caused the two fatalities of the pilot and the passenger.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) reconstructed the flight using Flarm data, radio communications from Payerne, and data recovered from an electronic tablet used by the passenger. The investigation also reviewed surveillance footage from a nearby building and analyzed the aircraft's technical condition.
Investigators found that the aircraft's engine and control systems were functioning normally prior to the impact. The weather conditions were clear but characterized by a very dark night with minimal lunar illumination, making terrain identification difficult. The investigation also noted that the pilot had a history of intensive use of electronic tablets for flight planning and real-time navigation.
Findings
- The accident was a controlled flight into terrain (CFIT) caused by maintaining an altitude lower than the surrounding terrain on the chosen route.
- The pilot failed to verify if the chosen altitude was sufficient for the terrain between Vevey and Gruyères.
- The use of an electronic tablet likely contributed to a loss of situational awareness. The pilot's reliance on these modern aids, combined with the need to look at illuminated screens, may have reduced night vision acuity and created a false sense of ease.
- The lack of lunar illumination made the mountainous terrain difficult to distinguish visually.
- The pilot was not in radio contact with the Geneva Flight Information Centre, which might have alerted the crew to the deviation or the insufficient altitude.