Aircraft Information
The accident involved a Robinson R44 Raven, registration G-CEDG, serial number 1639, manufactured in 2006. It was powered by a single Lycoming O-540-F1B5 piston engine. The helicopter was being used for a private flight with one pilot and two passengers on board. The pilot, aged 69, held a Private Pilot’s Licence and had accumulated 1,632 total flying hours, of which 902 were on the Robinson R44 type. In the previous 90 days he had flown 4.9 hours, and 2.7 hours in the last 28 days.
History of the Flight
The day before the accident, the owner/pilot collected the helicopter from Sywell Aerodrome to reposition it to a private strip near Salford, Bedfordshire. During the initial engine start, the governor increased the engine rpm above the normal value. The pilot shut down the engine and sought engineering advice. When the engine was restarted, it operated normally, and the pilot continued the uneventful flight to Salford.
On 25 February 2015, the pilot boarded the helicopter with two passengers and a small amount of baggage for a planned flight to a hotel near Forest Row, East Sussex. The engine start and takeoff were uneventful. The pilot established a cruise climb profile as he departed.
The Accident Sequence
At approximately 1050 UTC, while climbing through 800 ft, the governor caused the engine rpm to increase beyond the green arc on the gauge and began to hunt. The pilot responded by switching off the governor and attempting to control the rpm manually. He initiated a precautionary landing by lowering the collective lever and starting a descent. However, the low rotor rpm warning horn sounded, prompting him to lower the collective fully. When he attempted to raise the collective again, the horn sounded once more. Believing the engine had failed, he entered autorotation towards a field located about 2 km south of his departure point.
During touchdown, the helicopter slid forward approximately 3 m before the skids dug into the ground, causing it to roll onto its left side. The pilot and one passenger exited through the right-side doors; the other passenger kicked a hole in the windscreen to escape.
Post-Accident Observations
The pilot stated that he believed the accident involved a governor failure followed by an engine failure. At the time of the AAIB report, no hard evidence of an engine or governor fault had been found. However, it was noted that the weather conditions were consistent with a risk of serious carburettor icing at any power according to the CAA’s official chart. The pilot did not recall whether he had applied carburettor heat when reducing power, but indicated that he probably had not due to the rapid development of events.
Damage to the helicopter was assessed as beyond economic repair. The pilot sustained no injuries; one passenger received minor injuries.