Accident Overview
On 2 January 2006 at 1530 UTC, a Hughes 369HS helicopter, registration G-LINC, suffered an engine flameout while on final approach to land at Sywell Aerodrome in Northamptonshire. The helicopter was being operated on a private flight with one pilot and one passenger on board. Both occupants vacated the helicopter uninjured.
Flight History
The flight originated from Sywell Aerodrome earlier that day. The pilot flew approximately 16 nautical miles to Catthorpe, near Rugby, to pick up a passenger, then continued to Folkestone Race Course in Kent, a point-to-point distance of 113 nautical miles. The helicopter was not refuelled at Folkestone because no fuel was available. The return flight was uneventful until north of Luton Airport, when the FUEL LOW caution light flickered intermittently. The pilot attributed this to fuel movement in the tank due to air turbulence and did not perform a fuel burn check en route. About 10 nautical miles from Sywell, the FUEL LOW light illuminated steadily. The pilot believed he had 15 minutes of flying time remaining and was six minutes from the airport.
Due to microlight aircraft in the circuit, the pilot joined the downwind leg instead of a straight-in approach. At approximately 400 feet above ground level on final approach, the engine flamed out. The pilot initiated an autorotation and landed firmly short of Runway 23's threshold. The helicopter's tail boom was struck by the main rotor, and the landing skids were splayed by the heavy landing.
Fuel Planning and Usage
The helicopter had been refuelled to the brim before the preceding flight a few days earlier, indicating full at start-up. The usable fuel at departure was 435 lb of AVTUR. The pilot's fuel planning used a consumption rate of 150 lb per hour, based on previous experience. No allowance was made for start-up, taxi, and takeoff. The pilot calculated 200 lb of fuel remained at Folkestone, with a planned reserve of 57 lb upon return to Sywell. However, the actual fuel consumption rate appeared higher, as the indicated fuel at Folkestone was 200 lb but the trip consumption implied 185 lb per hour.
Information from a commercial operator of similar helicopters indicated that an allowance of 30 lb for start-up, taxi, and takeoff is typical, and they use a trip fuel consumption rate of 200 lb per hour for flight planning. The helicopter's Flight Manual states that the FUEL LOW caution light illuminates when approximately 35 lb of fuel remains, and the procedure is to land as soon as possible. The manual also notes that 4.9 lb of fuel is unusable; post-accident drainage recovered 4.5 lb.
Post-Accident Actions
Because the aerodrome was unlicensed on the bank holiday, no fire tender was available. However, a fire crew member who was present ran to the helicopter with a fire extinguisher and ensured safety as the occupants disembarked.
Fuel Gauge and Manufacturer Information
The fuel gauge uses a float resistance measuring system marked in 100 lb increments. The manufacturer advised that a full tank provides sufficient fuel for 1 hour 48 minutes of flight, with a reasonable allowance of 30-40 lb for start-up, taxi, and takeoff. Fuel consumption on a standard day can vary from 150 to 220 lb per hour. The volumetric capacity is 242 litres, with 2 litres unusable.
The AAIB's investigation noted that the pilot's failure to perform an in-flight fuel check deprived him of situational awareness. The source concluded that by continuing the flight to the intended destination when an immediate precautionary landing was required, the engine fuel supply was exhausted, leading to the flameout and subsequent damage during the forced landing.