What happened
On August 19, 2002, an Aérospatiale SE 313 B Alouette 2, registration F-GVEE, was conducting a private flight from Marseille Provence to Aix-les-Milles. While approaching the helicopter parking area, the pilot completed a final approach parallel to runway 15 and was cleared to transition to a parking spot on the opposite side of the runway.
After hovering momentarily near the parking area, the pilot attempted to rotate the aircraft to the left to align with the existing parked aircraft, which were all facing north. During this leftward rotation, the helicopter experienced a rapid increase in left yaw accompanied by a rightward tilt. The pilot lost control of the aircraft, which entered a series of spins before striking the ground. The impact resulted in the destruction of the aircraft and left the pilot with serious injuries.
The investigation
Investigators examined the wreckage, including the airframe, blades, turbine, and various components. No mechanical malfunctions were identified prior to the accident, and evidence from the rotor blades on the ground confirmed the turbine was delivering power at the time of impact.
Physical evidence on the ground indicated a two-stage impact: an initial contact by the skids, followed by a more significant impact five meters away involving the skids, main rotor blades, and the airframe.
During the investigation, the pilot noted that the longitudinal seat adjustment had not been changed from a previous flight, and a box of grease and other small items had been placed in a carton under the rear seat. While this box shifted and momentarily obstructed the movement of the collective and throttle lever during the post-crash shutdown procedure, investigators determined it did not interfere with the flight controls during the accident itself.
Meteorological data from the Aix-les-Milles station indicated a wind from 210 degrees at 8 to 16 knots, with gusts up to 16 knots. Although the station was located away from the exact accident site, the flat, unobstructed terrain allowed investigators to assume the wind conditions at the site were at least equal to those recorded.
Findings
- The primary cause of the accident was the insufficient compensation for tailwind effects during the leftward rotation.
- As the aircraft rotated, it transitioned through varying wind angles (tailwind right, direct tailwind, and tailwind left), which increased the yaw rate due to the weathercock effect on the anti-torque rotor and increased the rightward tilt as wind flowed under the main rotor disk.
- The pilot's attempt to increase power via the collective to gain altitude actually increased the torque-induced yaw, exacerbating the loss of control.
- Improper seat and pedal adjustments likely hindered the pilot's ability to apply the precise pedal inputs required to counter the wind forces.