Safety fears over RAF helicopter fleet after crash

They saw the aircraft apparently lose power at low level, roll on to its side and drop "like a sack of potatoes".

Flight safety experts said the description suggested a catastrophic mechanical problem.

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Crewman Sergeant Phillip Burfoot (left) and Flight Lieutenant David Sale were killed in the crash

As accident investigators tried to find the cause of the crash near Catterick Army Camp in North Yorkshire on Wednesday evening, the Ministry of Defence named the two RAF men who were killed.

They were Flight Lieutenant David Sale, 28, the pilot, and 27-year-old Sergeant Phillip Burfoot, both from 33 Squadron based at RAF Benson in Oxfordshire.

Colleagues of Flight Lieutenant Sale remembered his "cheerful manner and dry wit" while Sergeant Burfoot was described as a "highly capable aviator" whose love of life was "infectious".

The Puma had a three-man crew and was carrying nine soldiers taking part in an exercise. Two servicemen were fighting for their lives in hospital last night, with another six being treated for less serious injuries.

The crash sparked renewed concerns over the state of the Puma fleet. The machine entered service 36 years ago and is the oldest helicopter being operated by UK forces.

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Military personnel at the scene where the RAF Puma helicopter crashed on MoD land in North Yorkshire

It is also one of the busiest, facing a gruelling workload ferrying troops and supplies around the desert battlefields of Iraq and Afghanistan, where harsh conditions take their toll on men and machines.

Despite its age - and nine crashes which have claimed eight lives in the past ten years - the Ministry of Defence plans to keep the Puma flying at least until 2022.

A wide area around the crash site, on Defence Ministry land outside Catterick Camp, was cordoned off yesterday. The fuselage of the Puma had broken into three sections and wreckage was scattered across a field. Local coach driver Andrew Pavey, 39, described how he was watching two low-flying helicopters when he heard a "distinctive misfiring sound".

He added: "I told my nephew, 'That doesn't sound right. It's going to crash'.

"It climbed and then went on to its side. All of a sudden, it went down like a sack of potatoes. There was no explosion, no flames or smoke."

Five years ago, the National Audit Office warned that ageing military helicopters, including the Puma, were so badly hit by mechanical problems and shortages of spares that pilots could not fly enough hours to maintain their essential skills.