What happened
On May 14, 1997, an AS 350 B Ecureuil helicopter, registration F-GKHP, was performing a medical evacuation flight from Aurillac to the Clermont-Ferrand University Hospital. The flight, operated by Héli-Périgord, carried a pilot, a physician, and a patient.
After picking up the patient near Marcenat, the aircraft began its transit toward Clermont-Ferrand. During the flight, the pilot encountered deteriorating weather conditions. At approximately 22:16 UTC, the pilot contacted Clermont-Ferrand-Aulnat tower to request weather updates and radar assistance, noting that he was flying above a cloud layer. Following the exchange, the pilot descended to approximately 4,300 feet in an attempt to find a gap in the clouds to maintain visual flight rules (VFR) conditions.
At 22:22 UTC, the pilot requested radar assistance, reporting his altitude at 7,300 feet. However, by 22:24 UTC, the controller attempted to contact the aircraft to suggest increasing altitude due to a lack of radar contact, but the pilot did not respond. Shortly thereafter, witnesses in nearby villages reported hearing the aircraft flying at a very low altitude. At 22:25 UTC, the helicopter struck the ground in a field near Ludières, resulting in a post-impact fire. All three occupants were killed.
The investigation
The investigation focused on the flight path, the meteorological conditions, and the aircraft's final moments. Investigators examined the wreckage, noting that the main rotor blades had struck a tree shortly before impact and that the fuselage and engine were destroyed by fire. The investigation also analyzed cockpit instruments, which indicated a horizontal speed of 70 knots and a vertical descent rate of approximately 2,000 feet per minute at the time of impact.
Meteorological data and witness testimonies were used to reconstruct the visibility conditions. While the sky was clear over some areas, a layer of clouds and fog was present over the terrain. Investigators also reviewed radio communications between the pilot and the air traffic controller to establish the timeline of the descent.
Findings
- The pilot was attempting to descend through a cloud layer to regain visual contact with the ground.
- Local weather conditions included high humidity and patches of fog at ground level, which obscured the terrain.
- The pilot likely experienced a visual illusion caused by the lack of contrast between the dark plateau and the low-level fog.
- While the lights of the villages of Vernet Sainte-Marguerite and Ludières were visible, the pilot's focus on these light sources, combined with a high-speed descent and a right-hand turn, led to a failure to perceive the approaching terrain.