2011 Robinson R44 accident at Refuge de la Traie

Overview and Circumstances On July 11, 2011, at 14:15 local time, a private Robinson R44 helicopter, registration EI-MUL, departed Chambéry for the Méribel altiport. During the flight, the British pilot and his French passenger decided to attempt a landing in a confined area. The passenger, who was familiar with the region, suggested landing near the Refuge de la Traie in Les Allues (73), at an altitude of 1,650 meters (5,450 ft). Upon arrival, the passenger noted that the intended landing zone was unusable due to tall grass and proposed a cleared path upstream of the refuge. The pilot performed two reconnaissance turns and entered the final approach along a trajectory descending with the terrain. This path flew over a road bend at approximately one meter in height. Witnesses observed the helicopter arriving at a very low speed and sinking into the road bend. The left skid contacted a rock, causing the helicopter to roll to the right, collide with the ground, and catch fire. ## Technical and Environmental Factors The helicopter was equipped with a Lycoming O-540 carbureted engine, which is less powerful than the fuel-injected version. An examination of the wreckage did not reveal any technical failure. Estimated weather conditions at the accident site included a north-northwest wind of 8 kt with gusts to 20 kt, few clouds at 4,500 ft, visibility over 10 km, and a temperature of 19 °C (ISA + 14 °C). With a QNH of 1018 hPa, the pressure altitude was approximately 5,100 ft. The estimated mass of the helicopter at the time of the accident was 1,010 kg. Given the site altitude and ambient temperature, the helicopter could hover in ground effect (up to 7,100 ft) but could not hover out of ground effect (impossible above 4,100 ft). When the helicopter sank, it was at a low speed near a hover, requiring significant power. The pilot benefited from ground effect while flying low over the road bend but lost some or all of this effect as the altitude increased again during the approach. This situation likely caused the helicopter to sink and tip over when the left skid touched the ground. Wind instability may also have affected the main rotor's lift. ## Personnel The pilot, aged 56, held a PPL(H) license from 1993 and had 750 hours of helicopter flight time. The investigation could not determine his activity in the three months prior to the accident, except for two hours on the R44 in the last 24 hours. He had also recently flown an R66, a more powerful turbine version of the R44. His mountain experience could not be traced. The passenger, aged 69, held a PPL(A) from 1962 and a PPL(H) from 1973, along with numerous aeronautical qualifications, including FI(H), FE(H), TRI(H), and mountain qualifications for wheels and skis. He had 17,000 total flight hours, including 4,000 on helicopters, 240 on type, and 25 hours in the preceding three months, including two hours with this pilot in the last 24 hours.