What happened
On June 13, 2012, at approximately 10:30 local time, a Bell 47G-2 helicopter, registration F-GPTO, was performing aerial spraying operations near Saintes-Maries-de-la-Mer. The pilot had completed an initial flight earlier that morning and had taken off again at 10:20 after refueling with phytosanitary products to treat a rice paddy.
During a rollover maneuver—a technique used in spraying to fly close to the surface and minimize time between passes—the pilot experienced sudden jerks and a perceived engine overspeed at an altitude of roughly 10 meters. As the pilot attempted to recover the aircraft, they experienced a loss of engine power and a loss of tail rotor effectiveness. During the subsequent forced landing, the right skid struck the ground, causing the helicopter to capsize onto its right side. The aircraft was destroyed.
The investigation
Investigators examined the wreckage and found that the damage to the main and tail rotor blades was consistent with rotation at low power during the impact. Technical inspections of the engine and mechanical components revealed no anomalies that could account for the reported engine overspeed, the loss of power, or the loss of tail rotor effectiveness. The aircraft's weight and balance were within the manufacturer's specified limits.
Meteorological conditions at the time were favorable, with CAVOK visibility, a temperature of 20 °C, and a light 12-knot crosswind. The pilot, who had 2,500 total flight hours (including 2,000 on type), reported no significant fatigue, having flown for approximately two and a half hours that day.
Findings
- The accident was likely caused by inadequate coordination between power and collective pitch controls during the rollover maneuver.
- The perceived engine overspeed was likely triggered by an excessive reduction in collective pitch.
- In response to the overspeed, the pilot likely reduced power reflexively. When attempting to increase collective pitch to recover the flight path, the remaining power reserve was insufficient to maintain flight.
- The low altitude prevented the pilot from increasing rotor RPM sufficiently to transition back to level flight.