DESPERATE rescuers used a tractor in a vain bid to free a boy trapped in the wreckage of a crashed helicopter, a court heard yesterday.

The helicopter had tried to land in a field when its windscreen had misted up, but it was full of sheep. Pilot Robert Hobson headed for another field but crashed when his helicopter landing skids caught a wire fence, witnesses told Forfar Sheriff Court, Angus.

Earlier that morning the vintage car extravaganza, at which the pleasure flights were based, attended by 25,000 people at Glamis Castle had been hit by a 20-minute deluge of rain.

Captain Hobson, 56, from Penicuik, has pleaded not guilty to two charges following a crash at Glamis on July 13 last year killing passenger Garry Malley, nine, from Dundee.

The pilot denies endangering passengers by flying his Bell Jet Ranger with visibility restricted by a misted-up windscreen. He further denies overloading the craft by carrying a total of six people instead of a maximum five.

Farm director David Soutar, 45, of Deanbank House, Glamis, was working in a field when he saw the helicopter, the court heard. He described seeing it descend to head height, sending sheep scattering, before it pulled away.

Mr Soutar thought it had come low to get out of the way of another helicopter.

He then heard a bang and discovered the helicopter had come down in a field nearby.

Mr Soutar described how he at first felt ''a great sense of relief'' when saw three children and two adults get out safe. But the pilot told him someone was still trapped in the wreckage. He and the pilot tried to lift the helicopter by its landing skids to free the trapped boy, but to no avail.

He found a tractor and loader at a farm. By the time he returned to the accident, police and emergency services were ''pouring in''.

''We then proceeded to lift the helicopter to allow the police to recover the little chap,'' he said. Police then freed the trapped boy by cutting his seatbelt.

Police Sergeant John Milne said the pilot told him at the scene he had been carrying three children and one adult as passengers.

The court heard that Mr Hobson told police who interviewed him the the next day that he had been flying helicopters since 1978 and had 2,000 hours flying experience on that type of aircraft.

He had been employed as a pilot by Kwik-Fit since 1982 and that company had become associated with the Noel Edmonds Airborne charity three years before the crash. Airborne had asked Kwik-Fit for helicopter rides at its events, and Mr Hobson said he had taken part in these on two previous occasions.

He said that at the Glamis event the windows began to mist and he radioed to his control that he was returning to base. But he heard another aircraft was taking off and for safety reasons decided to look instead for another site to land.

He told police he brought the aircraft down to a height of three or four feet, became aware there were cattle nearby and decided to air taxi slowly to another area of grass. When he noticed the helicopter's forward movement was being arrested, he put the craft into a climb but it tipped over on its nose.

He said he believed the ''cause of the crash was the aircraft snagging on the wire fence.''

The trial continues.