What happened
On 29 August 2018, a Van's Aircraft RV7, registration D-EIOI, departed Fribourg-en-Brisgau, Germany, for a cross-country VFR flight to southern France. The pilot, accompanied by a passenger, intended to meet a friend in formation flight. During the journey, meteorological conditions deteriorated significantly. After losing visual contact with the lead aircraft, the pilot of D-EIOI disconnected the autopilot and began a climb to navigate through the terrain.
As the aircraft climbed through the Alps, it encountered unstable weather characterized by a convective cell, high humidity, and turbulence. The aircraft's engine experienced three separate instances of carburettor icing. During the third and most severe icing event, the aircraft was in a right bank with a nose-down attitude. The sudden drop in manifold pressure led to a loss of control, during which the aircraft descended 4,600 feet in 35 seconds. The aircraft eventually collided with the terrain at an altitude of approximately 2,670 meters near the Italian border. The impact resulted in two fatalities and the destruction of the aircraft.
The investigation
The BEA investigation utilized data from the Geneva air traffic unit, the aircraft's Dynon Avionics D1000 EFIS, and witness statements from the pilot of the accompanying aircraft. Investigators examined the engine's carburettor system, the meteorological conditions at the time of the accident, and the pilot's flight management. The investigation also reviewed the aircraft's maintenance history and the presence of oxygen equipment, noting that the aircraft was not equipped for flight in icing conditions and lacked oxygen for high-altitude operations.
Findings
- The primary cause of the accident was the decision to continue the flight toward high mountain massifs in weather conditions incompatible with VFR flight.
- The aircraft encountered severe carburettor icing, which caused a critical drop in manifold pressure during a high-angle maneuver.
- An inadequate analysis of available weather forecasts during flight planning led to an inability to plan appropriate diversions.
- The pilot encountered heavy turbulence and cloud layers that necessitated maneuvering in a moist, cold air mass, increasing the risk of icing.