2018 Robinson R44 accident at Houdainville (F-GLYF)

Accident overview and flight sequence On 24 July 2018, at 19:30 local time, a privately operated Robinson R44, registration F-GLYF, collided with the surface of the Étang de la Sansonnière in Houdainville (60) during a local flight. The helicopter was destroyed. The pilot, accompanied by a passenger who was also a pilot and the previous owner of the aircraft, departed from the Plessis Belleville aerodrome. The passenger, familiar with the site, guided the pilot to the approach axis and landing point on the shore. After joining friends at the lakeside, the pilot conducted a first pleasure flight with two passengers to respect mass and centering limits. Following that flight, two female passengers boarded in the rear seats with the rotor turning. The pilot determined that mass and centering limits were also respected for the second flight. The previous owner installed them and provided safety instructions, particularly regarding the opening and closing of the doors and seatbelts. The pilot established a hover at approximately three meters above the ground and checked flight parameters. He stated that he was reading 21.5 hPa of power and would have liked more power reserve, and that there was no wind. He then moved laterally to position over the lake and moved forward to take off, along the shore and without stopping, aiming to reach the takeoff point offering the best obstacle-free axis while gaining speed. Upon acceleration, the pilot estimated that he did not have enough power and could neither gain speed nor maintain flight altitude. After traveling a few dozen meters beyond the hover point, the pilot, aware that he would strike the water, decided not to demand more power by pulling the collective pitch and to land on the water with as little violence as possible to avoid pitching forward. The helicopter contacted the water surface with the landing skids, then by the front of the cabin. It rolled onto its left side and then onto its back before sinking in six meters of water. The helicopter came to rest on the muddy bottom, lying on its left side. The four occupants evacuated by themselves through the right side of the helicopter. ## Investigation findings No person on board perceived any alarm, auditory or visual, any decrease in engine power, or any yaw movement. Witnesses on the shore observed the helicopter descend slowly during its acceleration phase and collide with the water surface at a low angle. All occupants evacuated the helicopter while underwater by opening the doors and freeing themselves from their harnesses or seatbelts. The two female passengers evacuated through the right side. The pilot, aged 62, held a PPL(H) license and a valid R44 type qualification renewed in 2017. He had approximately 1,130 flight hours, including three hours in the previous 24 hours, and was resuming flights after a nine-month interruption. He stated that he was not very familiar with flying over water and with restricted helipads such as a lake bordered by trees. Meteorological conditions included visibility greater than 10 kilometers, a ceiling above 5,000 feet, a temperature of 32°C, and average winds from nearby aerodromes of 060° at 5 to 10 knots. Examination of the wreckage after recovery showed that all damages and ruptures were consistent with abnormally high forces applied during rotor contact with the water. The engine was functioning and providing power when the blades touched the water, and the controls were continuous and functional at impact. The estimated remaining fuel quantity of 60 liters and some onboard effects placed the helicopter's mass at 1,020 kg, within mass and centering limits for ground effect and out of ground effect. The flight manual includes safety instructions warning that flying low over water is very dangerous and advises maintaining 500 feet AGL whenever possible and avoiding maneuvers below 200 feet AGL. The lake had a diameter of approximately 200 meters and was bordered by tall trees except for its northern part, which allowed a takeoff axis oriented to heading 330°. This opening allowed, from the south of the lake, to take off without being out of ground effect and to gain more speed during the takeoff roll. The distress beacon signal was not perceived by COSPAS-SARSAT at the time of the accident. During recovery, the signal was perceived, and COSPAS-SARSAT contacted the pilot. The coordinates were those of the previous owner, who was present at the recovery site and inhibited the beacon. ## Conclusion The accident resulted from an insufficient consideration of the helicopter's performance limitations. The pilot, not very familiar with operating in a confined site, had to manage several parameters related to the flight conditions: available power close to the helicopter's operating limits during a flight partly out of ground effect and in high temperature; nearby obstacles (trees); a takeoff in near-constant turn; low-altitude flight over water with few external references to control the helicopter's attitude and determine altitude precisely; and a water surface partially reflecting the trees bordering the lake. The briefing by the front-seat passenger, a pilot and previous owner, regarding door and seatbelt procedures enabled the two rear-seat passengers to evacuate the submerged helicopter quickly by themselves.