The Bell 206 Jet Ranger helicopter, owned by Air Hanson, came down on Forestry Commission land a few miles from Blackbushe airport in Hampshire shortly after midday.
Captain Colin Bates, Air Hanson's chief pilot, 46, and his son, Nicholas, 12, were certified dead at the scene.
Nigel Whiteman, 33, Air Hanson's chief engineer, suffered severe chest and abdominal injuries. He and Capt Bates's other son, Christopher, 9, were taken to Frimley Park Hospital in Camberley, Surrey, where both were said to be in a serious but stable condition after surgery.
James Coulter, 12, a friend of the Bates family, suffered serious head injuries and multiple injuries and was taken by the London Ambulance helicopter to the London Hospital in Whitechapel, east London. His condition was said to be very serious.
The aircraft was en route from Newmarket, Suffolk, to Blackbushe airport, where Air Hanson is based. A spokesman for the company said that Capt Bates had taken the boys on a day out. They had flown to Newmarket with a replacement battery for another helicopter in which they were flying back to Blackbushe. The spokesman said that the crash was not, however, caused by a battery fault.
Lord Hanson, chairman of Hanson Trust, of which Air Hanson is a subsidiary, said last night that Capt Bates was 'a highly experienced helicopter pilot' who had worked for the company for many years. 'We regret this tragedy very much,' he said.
Air traffic controllers raised the alarm after receiving a mayday call from Capt Bates, who reported problems with his tail rotor. The helicopter crashed on land used as a firing range by the nearby Royal Military Academy Sandhurst.
Dave Peters, a Ministry of Defence land warden, said it appeared possible that the pilot had been attempting an emergency landing in a forest clearing when he clipped the top of an 80ft pine tree. The top of the tree was sliced off by one of the rotor blades.
Mr Peters said that a man walking his dog saw the aircraft come down. 'It was a million-to-one chance that someone happened to be there and see it,' he said. 'Otherwise it could have taken hours to find it.'
Inspector Peter Windle of Thames Valley Police, one of the first at the scene, said: 'It was an absolute wreck - unrecognisable as an aircraft. It could not have gone down in a worse place for the emergency services.
'We had to abandon our cars and climb through nearly a mile of gorse and fern to get there. One of the little boys was thrown clear.'
The wreckage was spread across 20 yards, with one piece of twisted metal caught 50ft up on the branch of a pine tree. Investigators from the Civil Aviation Authority went to the scene.
Malcolm Bailey, Divisional Officer with the Royal Berkshire Fire Brigade, said that rescue crews had to drive through dense undergrowth to reach the crash site. Firemen used hydraulic equipment to cut through the wreckage and reach the casualties.Reuse content