History of the Flight
The pilot took off at 10:15 from runway 04 of Grenoble Le Versoud aerodrome with two passengers. She intended to fly to Chamrousse, clearing the Pas de la Coche pass and then following the eastern slope of the Belledonne Massif. After initial climb, she turned right toward the southeast, reaching 4,500 ft and then executing a 360° turn, reaching 5,750 ft. She continued southeast, climbing for about three kilometers, entering the valley leading to the pass at 6,150 ft. She flew through the center of the valley below the ridge, reaching the valley bottom at 6,400 ft about thirty seconds later—lower than the pass altitude. The aircraft struck terrain approximately 100 m below the pass and caught fire.
Site and Wreckage Information
The wreckage was found flat and across the slope at 1,880 m (pass altitude 1,989 m / 6,525 ft), oriented northward. On the flight path before the wreckage, sparse vegetation showed no sign of being struck; after the wreckage, power lines and a pylon were present. Examination indicated a probable impact with a slight nose-down attitude during a left turn. The wreckage was not dispersed but largely destroyed by post-impact fire. Metal flight control cables were continuous; flap control rods were intact. Damage to ailerons, control surfaces, and flaps precluded determination of their positions. Propeller damage suggested the engine was providing power, but quantification was not possible. No pre-impact technical malfunction was found in the engine.
Examination of the Exhaust System
A detailed examination revealed a crack in the exhaust outlet pipe at its connection with the exhaust muffler. Metallographic and chemical analyses showed corrosion initiation that progressively developed, likely leading to an incipient crack that grew. The crack's appearance time and dimensions prior to impact were not determinable. This opening may have caused exhaust gas leakage into the engine compartment, possibly leading to a higher-than-normal carbon monoxide (CO) level.
Aeroplane Information
The aircraft was a Robin DR400-140B with a Lycoming O-320-D2A engine, maintained by the Aéroclub du Dauphiné maintenance workshop. Maintenance documentation indicated the exhaust system was maintained per manufacturer specifications. The last 100-hour inspection on 31 August 2020 did not mention exhaust damage. The exhaust system had been replaced in May 2016. A CO detection patch was installed on the instrument panel in January 2020; it burned in the post-impact fire. The maintenance program required CO level measurement after any operation warranting a check flight; the last such measurement was on 24 July 2018. Pilots and instructors of three flights the day before the accident reported no malfunctions or abnormal physical symptoms.
Meteorological Information
Météo-France estimated conditions at the time: light wind, visibility greater than 10 km, few clouds, sky locally veiled by cirrus-type high clouds with some clouds clinging to the Alps. The 10:30 METAR for Grenoble-Isère airport indicated variable wind 2–3 kt, CAVOK, temperature 22°C. A hiker's photograph minutes after the accident showed sunny weather with few clouds not hiding the terrain.
Pilot Information
The 48-year-old pilot held a Private Pilot Licence (Aeroplanes) issued in 1994 and had been a member of Aéroclub du Dauphiné since 2002. She had logged approximately 300 flight hours, mainly in a DR400. In 2019, she logged about 13 hours, last flight in November; in 2020, about 2.5 hours, including two instruction flights in July and solo runway circuits in August. She had not received specific mountain flying training. She flew regularly with her husband, who stated she knew the area well and had cleared Pas de la Coche several times as a pilot. He was surprised at the altitude she entered the valley, lower than recommended. She was a citizen reservist and president of the departmental section of ANORAA.
BIA Flight Context
The flight was a local flight. The BIA (Brevet d'Initiation Aéronautique) is a certificate delivered by the French national education system. BIA air experience flights can be offered as part of the programme. The Aéroclub du Dauphiné is affiliated with the FFA (French Aeronautic Federation) and had an agreement with the Isère Association for the Promotion of the BIA. The president of the flying club stated that pilots performing BIA flights must meet minimum experience requirements.