Robinson R22 F-GHHT accident at Bourg Ceyzeriat

Flight details and accident sequence On 18 August 2013 at about 13:30 local time, a Robinson R22 helicopter registered F-GHHT, operated by a club, was on a general aviation flight from Mâcon Charnay to Bourg Ceyzeriat. The pilot and one passenger were aboard. While over the aerodrome at 2,200 ft and 80 kt, preparing to land on runway 18, the pilot reported hearing the “LOW RPM” alarm. He pulled the carburetor heat control and noted that the warning lights were off. The helicopter yawed to the right; the pilot applied rudder, lowered the collective, and the audible alarm stopped. He checked that the governor switch was on and saw the engine tachometer needle at zero. He then felt the controls were no longer responding and initiated an autorotation toward the south. The helicopter landed hard and rolled onto its right side. The aircraft was destroyed. ## Pilot, weather, and aircraft information The pilot held a private pilot helicopter licence obtained on 18 June 2013 and had 102 total flight hours, including 101 hours on type. In the three months before the accident he had 51 hours, including 50 on type, and 2 hours 30 minutes in the preceding 24 hours, all on type. Since obtaining the licence, he had 33 hours as pilot-in-command, and had flown 12 hours between 15 and 18 August. Estimated weather at the accident site was wind from the south-southwest at 5 kt, CAVOK, temperature 29 °C, dew point 21 °C, and relative humidity 70%. The helicopter’s mass and centre of gravity were within manufacturer limits. The collective control was conventional and included a rotating power control handle; the controls were interlinked and operated the carburetor throttle. The governor automatically maintained engine speed in the normal operating range, with its switch at the end of the collective control and normally set to “ON”. If the pilot gripped the power control handle firmly and locked it, the governor’s automatic function was inhibited and pitch/power coordination became the pilot’s manual responsibility. In a degraded flight mode, if the pilot did not rotate the handle in coordination with collective movements, yawing and changes in main rotor speed could occur. The “LOW RPM” alarm sounded and lit when the minimum main rotor speed threshold was reached. To restore speed, the pilot was to increase power immediately by moving the rotating handle, lower the collective, and, in forward flight, move the cyclic aft. The alarms were inhibited when the collective was at the low stop. ## Investigation findings and conclusion Examinations, including of the engine, did not reveal a malfunction that could explain the accident. A witness on the aerodrome said he saw the helicopter arrive over the field and make a landing manoeuvre, and that the engine had continuously made a normal operating noise. The BEA concluded that the pilot probably gripped the power control handle tightly after increased stress from a higher workload when arriving over the aerodrome. This unintentionally inhibited automatic pitch/power coordination, and the pilot did not realise that coordination was then his responsibility. Without automatic coordination, the low rotor RPM alarm activated and yawing movements appeared. The pilot believed the controls and engine were no longer functioning normally. Seeing the engine power indicator in the lower part of the dial, he thought the engine had stopped and initiated an autorotation. A late flare was followed by a hard landing and the helicopter rolled over.