What happened
On April 12, 2003, an Eurocopter EC120B, registration F-GKHH, was performing a local sightseeing flight near the Pyrenees. After approximately 45 minutes of flight, the pilot initiated a return to the Tarbes Laloubère aerodrome. The approach was conducted on a 5% glide slope, and the aircraft was performing a flare to transition into a hover.
During the flare, the helicopter began an uncontrolled leftward yaw. The pilot was unable to arrest this rotation. As the aircraft continued to spin, the tail boom moved dangerously close to the ground. The helicopter subsequently experienced significant longitudinal attitude variations, tilted heavily to the left, and struck the ground. The impact resulted in one fatality (the front left passenger) and the total destruction of the aircraft.
The investigation
The investigation focused on the mechanical integrity of the anti-torque system and the flight controls. Investigators examined the fenestron's ball-type control linkage, finding that the rear command had been severed by the main rotor blades during the impact. Traces of main rotor paint were found on the control sheath, confirming that the rotor interacted with the tail boom during the crash.
Technical analysis of the engine and transmission showed that the turbine and main gearbox were still producing power at the moment of impact. The investigation also examined the cockpit configuration, noting that dual controls (left and right) were installed. Investigators considered whether the passenger in the front left seat might have inadvertently interfered with the pedals, potentially obstructing the pilot's ability to apply sufficient right pedal input.
Findings
- The primary cause of the accident was a loss of yaw control during the landing flare.
- The onset and continuation of the leftward rotation may have been caused by either insufficient right pedal input by the pilot or involuntary interference with the pedals by the front passenger.
- The pilot was relatively inexperienced on this specific type, having only 8 hours and 15 minutes of flight time in the EC120B.
- The pilot was unaware of an existing Eurocopter service letter regarding the specific handling characteristics of the fenestron during high-power maneuvers, as this information had not been adequately covered in his type rating training.
- The increase in yaw rate was exacerbated by the application of collective pitch, which increased engine power and the resulting torque reaction.