What happened
On Sunday, August 10, 1997, at 18:20, a Robin Jodel DR 220 A, registered F-BOKI, was performing a local flight from the Champagnole aerodrome. The aircraft departed from the grass runway 10, heading north. Shortly after takeoff, witnesses observed the aircraft becoming unstable while flying over a forest located approximately 450 meters from the end of the runway. The aircraft then veered to the right and crashed into a stand of fir trees. The impact resulted in three fatalities (the pilot and two passengers) and the total destruction of the aircraft.
The investigation
The investigation focused on the aircraft's performance capabilities relative to the terrain and environmental conditions. At the time of the accident, the temperature was 31 °C, with a light wind from the north at 6 to 10 knots and clear visibility. Investigators performed calculations based on the aircraft's flight manual, accounting for the grass runway surface, the aircraft's weight, the airfield elevation, and the high ambient temperature.
Analysis of the takeoff performance indicated that the distance required to clear a 15-meter obstacle was 620 meters. Based on the flight manual, the optimal climb gradient was 7.2%, which would allow for a maximum obstacle clearance height of 60 meters after a horizontal distance of 1250 meters. Measurements of the tree canopy indicated that the treetops were at an altitude of 590 meters, which is 60 meters above the runway elevation.
Findings
- The investigation established that the erroneous assessment of takeoff performance was the primary cause of the accident.
- While the mathematical maximum clearance height matched the height of the trees, the aircraft's ability to safely clear the obstacle was compromised by the specific environmental and operational factors.
- The airfield's aeronautical information specifically warned that the northern gap was poorly cleared and advised pilots to verify takeoff performance due to the forest of fir trees causing turbulence north of the aerodrome.