What happened
On July 21, 2009, a Bell 47 G 2 helicopter, registered F-BTGR, was performing agricultural spraying operations near Cuisles, France. The pilot was engaged in treating vineyard parcels heavily affected by parasites. After completing three refueling and chemical loading cycles, the pilot departed for a fourth rotation.
During the initial pass over the target area, the pilot was flying at a speed of approximately 20 knots and an altitude of 1.5 meters while ascending a slope. Before reaching the end of the field, the pilot realized the engine power was insufficient to maintain altitude, causing the aircraft to descend. In an attempt to perform an emergency landing on a nearby path, the pilot executed a right turn. During this maneuver, the spreading boom struck the vines, and the helicopter struck the ground, coming to rest on its landing gear.
The investigation
The investigation focused on the aircraft's performance limits and the pilot's operational environment. The pilot reported that there were no mechanical or fuel supply anomalies prior to the loss of altitude. However, the investigation noted that the aircraft's mass was near its maximum takeoff weight due to the 50 liters of fuel and 150 liters of phytosanitary product loaded for the mission.
Investigators examined the operational pressures and the pilot's physiological state. The pilot had completed 80 hours of spraying flights in the 30 days preceding the accident and had flown 7 hours and 40 minutes the previous day. Furthermore, the investigation looked into the lack of an emergency jettison system for the chemical load and the inherent difficulty in precisely measuring the weight of the payload due to imprecise gauging systems.
Findings
- The primary cause of the accident was the decision to operate the aircraft at the edge of its power limits at a low altitude.
- Significant fatigue and high commercial pressure contributed to the event, as the pilot was working under a fixed-term contract during an urgent period of agricultural treatment.
- The pilot's fatigue likely impaired the ability to detect subtle changes in aircraft parameters as the descent began.
- The lack of an emergency release mechanism for the chemical payload meant the weight could not be shed to regain altitude.
- The difficulty in accurately verifying the exact weight of the payload due to imprecise measurement systems increased the risk of operating near maximum weight limits.