What happened
On Tuesday, February 18, at 09:00, a Robinson R44 helicopter, registration F-GNYC, was involved in a ground collision at the Toussus-le-Noble aerodrome. The pilot was performing a private flight, intending to travel to Strasbourg. The flight sequence began with the pilot moving from a parking position toward a helipad, intending to take off parallel to runway 07.
During the maneuver, the pilot performed a high-speed transition at an altitude of approximately 2.5 meters. This movement involved a change in heading that resulted in the aircraft entering a tailwind condition as the pilot attempted to position the helicopter for a hover and subsequent takeoff into the wind. As the aircraft approached within approximately 70 meters of the helipad, the pilot applied cyclic input to reduce the translation speed.
During this deceleration, the helicopter began to descend toward the ground. Despite the pilot's application of increased power, the descent continued. The aircraft struck the ground on the rear of the skids, bounced, and slid across the grass before pitching forward. The main rotor blades struck the ground, causing the helicopter to capsize onto its back before coming to rest on its left side. The pilot successfully shut down the engine, and all occupants evacuated the aircraft without reported fatalities.
The investigation
The investigation focused on the flight dynamics during the transition and the power availability of the aircraft. Investigators examined the aircraft's weight and balance, noting that the total mass was approximately 45 kilograms below the maximum allowable takeoff weight. The investigation also reviewed the meteorological conditions, which included a temperature of -1.4 °C and a wind from 060° at 8 knots.
Findings
- The primary cause of the accident was the inadequate management of translation speed in ground effect while encountering a tailwind.
- The pilot was operating the aircraft at the limits of available power.
- The high-speed transition at an altitude of only 1.5 meters while experiencing a tailwind and a slight lateral tilt of the main rotor required a power reserve that was not available.
- The pilot and two passengers reported that no audible power alarms were heard during the descent.