Cat. 2 investigation report: simplified-format report, adapted to the circumstances of the occurrence and the investigation stakes.
The pilot, accompanied by two passengers, one of whom was an instructor pilot sat in the front right seat, undertook a flight under VFR between Lognes-Émerainville aerodrome and Villefranche-Tarare aerodrome, for professional reasons.
The forecast and actual weather conditions compromised both a VFR flight carried out entirely under the cloud layer due to the terrain, and a “VFR on top” flight due to the conditions at destination which did not guarantee that a safe descent could be made. The continuation of the flight in adverse weather conditions required the pilot to adapt his strategy.
The first half of the flight was carried out under the cloud layer. About midway into the flight, the pilot started descending probably to stay in sight of the ground. The height of the terrain preventing him from continuing on his heading, the pilot passed above the cloud layer and climbed back to FL075. He continued the flight after the passenger in the right seat had obtained the weather conditions at Lyon-Bron and Saint-Yan aerodromes from the Clermont FIS controller. The latter had asked him to be prudent and the passenger in the right seat had replied that if it was not possible to continue, they would turn around and descend. The use of the autopilot during this first part of the flight suggests that the pilot mastered its different operating modes.
The passenger in the right seat then asked for the weather conditions at Valence-Chabeuil aerodrome. It is possible that the pilot and passenger had envisaged making a diversion.
At 48 NM from destination, the pilot started descending to FL045. The investigation was not able to determine the reason for this choice when the plane was above the cloud layer.
In the five minutes that followed, the pilot made a heading alteration and changed the autopilot settings several times (altitudes and vertical speeds selected). He probably flew through a cloud layer. In the space of 30 s, the pilot selected a descent to FL030 and then a climb to FL080 before entering a steep-bank turn, overriding the autopilot which he disconnected.
At an altitude of 4,500 ft, he made several turns in manual control. He very probably had had to deal with broken, indeed overcast cloud cover, accompanied by showers. During these manoeuvres, probably without external visual references, the plane’s attitude was not stabilized. During a turn, the pilot very probably lost control of the plane which collided with the ground with high energy, around 2,600 ft below.
During the flight, the plane was manually controlled several times, notably during turn manoeuvres which were tighter than those which would have been performed with the autopilot engaged. This could correspond to phases of skirting around cloud masses. In the second part of the flight, the path changes made with the autopilot engaged, in manual or by countering the autopilot were more frequent and could testify to the growing difficulties experienced by the pilot in managing the flight. The last part of the flight was entirely flown in manual, probably without external visual references. It was not possible to establish who was the pilot flying during the manual flight phases.