Irish investigators believe fuel exhaustion on a Cessna U206G caused a power loss which prompted the pilot to order a mid-air evacuation of parachutists at Clonbullogue airfield last month.

The aircraft was carrying a pilot and four parachutists - two sets of tandem jumpers - when it suddenly lost power while climbing through 9,000ft.

Its pilot instructed the parachutists to jump from the aircraft. The pilot then attempted to return to the airfield but the Cessna landed in a field short of the runway, and flipped over.

Air Accident Investigation Unit inspectors found that, while the fuel tanks were undamaged, the left-hand tanks were empty and the right-hand tanks contained only two litres of fuel.

The Cessna was fuelled through outboard bladder tanks - a modification to the airframe - which bled fuel into the main tanks.

But a relatively slow transfer rate from the bladders to the main tanks meant that an immediate fuel measurement, using a calibrated dipstick, would have given an "erroneous and exaggerated" indication of the quantity of fuel on board. The AAIU says a dipstick, if used before the fuel was allowed to settle, would have overestimated the true figure by as much as 100%.

While the investigation into the 15 March accident has yet to conclude, the AAIU states that the aircraft, operated by the Irish Parachute Club, had been on its sixth flight, following refuelling, and that fuel starvation was the "probable cause" of the engine failure.

Source: Flight International