AAIB Bulletin: 1/2017

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67 ©Crown copyright 2017 AAIB Bulletin: 1/2017 G-RFUN EW/G2016/08/02 ACCIDENT Aircraft Type and Registration: Robinson R44 Raven, G-RFUN No & Type of Engines: 1 Lycoming O-540-F1B5 piston engine Year of Manufacture: 2002 (Serial no: 1239) Date & Time (UTC): 5 August 2016 at 1135 hrs Location: Near Crowden, Glossop, Derbyshire Type of Flight: Private Persons on Board: Crew - 1 Passengers - 3 Injuries: Crew - None Passengers - 1 (Minor) Nature of Damage: Aircraft destroyed Commander’s Licence: Private Pilot’s Licence Commander’s Age: 43 years Commander’s Flying Experience: 87 hours (of which 9 were on type) Last 90 days - 1 hour Last 28 days - 1 hour Information Source: Aircraft Accident Report Form submitted by the pilot Synopsis The helicopter took off at close to its maximum weight. It then flew to a hilly area, where the pilot made a downwind approach, with full carburettor heat applied, to an Out-of- Ground-Effect (OGE) hover. The manufacturer’s performance figures show this to be outside the declared flight envelope of the helicopter. The helicopter was unable to sustain the hover and descended, probably entering a vortex ring state, before it landed heavily and rolled onto its side. The occupants escaped from the aircraft with one passenger sustaining a minor injury. History of the flight Following a successful start-up at the second attempt, the helicopter, with three passengers, lifted from Coal Aston Airfield (elevation 720 ft amsl), 5 nm south of Sheffield. The pilot reported that he flew a vertical takeoff, climbing to a height of around 50 ft, before he transitioned the helicopter into forward flight. Approximately 15 minutes later the helicopter arrived at a boar shooting ground where the pilot intended to hover, so they could wave at some friends. The boar shooting ground is in the Peak District National Park at approximately 1,000 ft amsl. The pilot flew over the selected site and circled whilst losing height. He then made an approach, with full carburettor heat applied, on an easterly heading, and reportedly came to a hover with 23 inches of power, at a height of 70 ft agl. 68 ©Crown copyright 2017 AAIB Bulletin: 1/2017 G-RFUN EW/G2016/08/02 The pilot reported that after 2 or 3 seconds in the hover, he looked inside the helicopter to check the instruments; when he looked back outside, the helicopter was sinking. He raised the collective lever, but this had little effect and they continued to sink. Realising he was now too low to fly away, the pilot made the decision to try and land, on uneven ground to his right. He lowered the collective lever and yawed the helicopter to face into the hill, then pulled the collective back up to cushion the touchdown. The helicopter landed heavily on the front of its skids and then rolled onto its right-hand side before coming to a halt. The pilot and his passengers, were able to vacate the helicopter by climbing through the left doors, although the passengers on the left (upper) side needed some assistance in undoing their seatbelts. The front seat passenger had a small cut to his head, but the rest of the occupants, though shaken, were unhurt. The pilot made the helicopter safe, by turning off the fuel and the electrics, and was then able to see ground marks which indicated to him that it had probably rolled onto its side when one of the main rotor blades had struck the ground. Meteorology The weather conditions were good with no significant cloud and good visibility. The Doncaster METAR at 1120 hrs showed the wind as 280°at 10 kt, the visibility was more than 10 km, the lowest clouds were at 4,000 ft, the temperature was 21°C and the QNH was 1020 hPa. At Manchester at 1150 hrs, the wind was 270° at 11 kt, more than 10 km visibility, the lowest cloud was 3,600 ft, the temperature was 19°C and the QNH was 1018 hPa. Weight and balance The loading calculations in the pilot’s initial accident report show a pilot and passenger combined weight of 770 lbs which would have meant the helicopter was 29 lb above its maximum takeoff weight of 2,400 lbs. The pilot’s calculations did not include an aircraft cover and several litres of oil, which were contained in one of the rear baggage compartments, and were reported to weigh 17 lb. The AAIB received a separate report that the weights used by the pilot for his loading calculation were incorrect, and detailed pilot and combined passenger weights of 182 lbs and 609 lb respectively; this would have made the aircraft’s takeoff weight 2,467 lb. The pilot was asked to reconfirm his weight and that of the passengers, and he provided new figures of 154 lb for himself and a combined weight of 574 lb for the passengers. The investigation also contacted the passengers individually for their weights, and established a combined weight of 595 lb, which would have placed the aircraft slightly above its maximum takeoff weight. Aircraft performance The pilot described the aircraft making a downwind transition to an OGE hover at the boar shooting ground (approximately 1,000 ft amsl). The performance section of the POH for 69 ©Crown copyright 2017 AAIB Bulletin: 1/2017 G-RFUN EW/G2016/08/02 the R44 shows at this altitude and temperature, in zero wind, the aircraft should be able to hover OGE at its max weight 2,400 lbs. There is a note in the performance section of the POH that all hover performance data is given with the carburettor heat off: ‘Full carburettor heat reduces hover ceilings by up to 2400 feet.’ With full carburettor heat applied, the maximum weight the aircraft should have been able to hover OGE at the boar shooting ground would be approximately 2,230 lbs. Pilot’s assessment of cause The pilot reported he did not see or feel anything unusual in entering the hover, but that the aircraft lost power. When asked why he had used full carburettor heat, the pilot stated he had been taught “you can never have too much carb heat”. He was unaware that