Private Christopher Game, 21, suffered severe injuries when he was knocked off a crane by the transport aircraft while taking part in a pallet-dropping exercise at South Cerney Army Camp near Cirencester in Gloucestershire.
The Hercules swooped low during the manoeuvre and hit Pte Game, who was unmarried and serving with the Royal Logistics Corps based at RAF Brize Norton, Oxfordshire.
Yesterday, an RAF Board of Inquiry was being formed to investigate the tragedy, which happened last Thursday.
Pte Game, from Poole, Dorset, was at first thought to have been crushed by a crated motorcycle, which was being parachuted to the ground. But investigators have since discovered that he was hit by the aircraft that dropped it.
A Ministry of Defence spokesman said: 'A Hercules was engaged in load-dropping trials. It carried out two passes - the first to clear the drop zone and the second to undertake the drop.
'As the Hercules returned for a third pass to check the accuracy of the drop, the ground reception team had started to recover the load. The aircraft struck a man on the recovery team who, it is believed, had climbed on top of a crane.'
The mobile crane was being used to pick up heavy crates containing vehicles.
The inquiry will be carried out by three senior officers. An RAF spokesman said that the board would investigate why the soldier was on the crane and how the Hercules had managed to hit him.
'Reports indicate that the plane hit him,' he said. 'The accident happened during a pallet-dropping exercise. However, the inquiry will have to look into the precise details of this unfortunate incident.'
An inquest is due to be opened and adjourned in Gloucestershire today while inquiries continue.