Norwegian investigators are still struggling to understand why a top Swedish display pilot overshot the threshold of an airfield runway in a Supermarine Spitfire, which subsequently overturned, killing him.

Pilot Bertil Gerhardt, who was aged 68 and had logged nearly 31,600h to become one of the country's most experienced airshow pilots, was at the controls of the 1945 Spitfire Mk XVIII as it arrived at Tynset, south of Trondheim, to participate in a display.

As the aircraft approached runway 23 it crossed the threshold high and continued for 100m (330ft) before the throttle closed and the flare began.

The Spitfire did not touch down on its main wheels until 350m past the threshold, moving in a straight line towards the left runway edge and crossing it at 590m.

"It gradually drifted left into the adjacent barley field and flipped over onto its back after travelling 95m through 1m-tall crop," says the Norwegian air accident investigation board SHT, in a preliminary report on the 21 August 2010 crash.

SHT says there is evidence the pilot tried to brake, outside of the runway, while image recordings indicate the rudder stayed neutral during the whole roll-out. Winds were light, 5kt, from 255°.

There was no evidence of malfunction of the flight controls, landing-gear or brakes.

 Crashed Spitfire

But SHT notes that the pilot was aware that Tynset's grass runway 23, normally 30m wide, had been newly re-turfed on its right-hand half. The new section, he was told, was usable but might be slightly softer than the older left-hand half.

"Further, the left, old, part of the runway clearly stood out as a runway compared to the much fresher green part to the right. The actual touchdown point might indicate that the pilot decided to land along the centreline of the old turf section and thus had to stay within the edges of a 16.5m-wide runway."

SHT also says the threshold, marked by red cones either wide, might have been difficult to see from the air.

"These two factors, [plus the] limited forward view from the Spitfire cockpit, might to some extent explain the accident," it says, but states that it has "not yet found a conclusive explanation" for the late touchdown and failure to maintain directional control.

Source: Flight International