History of the Flight
The pilot of Robinson R44 Raven, registration G-EVEE, was conducting a private cross-country flight from Perranporth, Cornwall, to a private site in Oxfordshire near the Stokenchurch mast, with a stop at Dunkeswell Airfield. The first leg of approximately 80 nm took 20 minutes longer than planned. For the next leg of 100 nm, the pilot estimated a flight time of one hour, planning on a fuel consumption of 16 USG per hour. Weight and balance calculations allowed a maximum of 25 USG of fuel with passengers aboard. After dipping the tanks at Dunkeswell, 7 USG remained, and the pilot requested an uplift of 18 USG, which airfield records confirm was provided. The pilot believed 25 USG would be sufficient for the route plus about 40 minutes of reserves.
During the flight, the pilot noted a groundspeed of 90 kt on the GPS, slower than planned, and estimated the headwind would add about six minutes to the flight time. As the helicopter passed south abeam RAF Benson, the pilot considered diverting to Chiltern Park airfield for fuel but decided to continue to the original destination. Shortly afterward, the low fuel warning light illuminated, indicating slightly over 3 USG of fuel remained, allowing at most 10 minutes of flight time.
Forced Landing and Damage
The pilot chose to land at a farm recently passed and selected a field. During a right turn with approximately 25° of bank, the engine ran down to about 50% power, rotor rpm drooped, and the rotor rpm warning horn sounded. The pilot entered autorotation and conducted a forced landing. The helicopter touched down heavily in a field of standing crop, damaging the skid assembly. All four occupants were uninjured.
Fuel Planning and Operating Advice
The Robinson R44 Pilot's Operating Handbook does not provide fuel consumption figures. The pilot's planned consumption of 16 USG per hour was considered appropriate by experienced instructors. The handbook includes Robinson Helicopter Safety Notice SN-15, which cautions against fuel exhaustion and recommends landing if the hour meter or fuel gauges indicate low fuel, never allowing fuel to become low enough to activate the low fuel warning light. The CAA General Aviation Safety Sense Leaflet 17 also advises planning to land by the time tanks are down to the greater of 1/4 tank or 45 minutes, and not relying solely on gauges or low fuel warnings.
Survivability
The damage to the skids was consistent with design features intended to improve crashworthiness in a heavy landing and minimize occupant injury.
Conclusion
The pilot considered that he may have misjudged the amount of fuel on board and underestimated the effects of the headwind. When the low fuel warning illuminated, manoeuvring towards the landing site momentarily starved the engine of fuel.