On March 1, 1994, at about 1535 eastern standard time, a Bell 47G5 Helicopter, N7043J, owned and operated by Plymouth Copters, was substantially damaged during a refueling operation while the helicopter was idling at the Plymouth Airport, Plymouth, Massachusetts. The pilot at the controls was not injured, but the instructor pilot operating the fuel truck received serious injuries. Visual meteorological conditions prevailed. A flight plan had not been filed for the flight operating under 14 CFR 91. The rated student pilot (RSP), John Christopher, was receiving instruction in the Bell 47G5, to qualify him for insurance purposes for the Bell 47G2 that he had recently purchased. The flight instructor/owner of Plymouth Copters Robert Dumas, and the RSP, departed the Plymouth Airport (PYM) in N7043J about 1400, for a local training flight. After a 1 1/2 hour flight, they returned to PYM to refuel the helicopter, and were planning to depart again for another 1 1/2 hour training flight. In his statement, the RSP stated: "...[Mr. Dumas] said that he would pull up along side of the helicopter, and re-fuel it without shutting it down. I gave him a look of disapproval to which he responded, 'We do this all the time'. I landed on the pad, the helicopter well centered...Mr. Dumas left the helicopter. I began applying collective friction. Before I engaged cyclic friction Mr. Dumas had already pulled along side of the helicopter and re-entered the cabin. He said to move the cyclic forward slightly and to hold it there, which I did. I watched ...the re-fueling, and the stowing of the hose. The fuel truck had side boards along its length approximately 6 feet above the ground. To stow the hose, Mr. Dumas fed the hose with his left hand over the top of the side boards while holding the nozzle with his right hand...My glance turned to the gauges when I felt an extreme shock through the cyclic accompanied by a loud bang. The helicopter turned to the right as in a tail rotor failure, I immediately chopped the throttle...." According to the Flight Instructor's statement, after landing, he exited the helicopter to drive the fuel truck into position to refuel the helicopter while it was idling. He returned with the fuel truck and positioned it outside of the main rotor tip path plane. The flight instructor observed that the tip path plane had drifted down, and went to the RSP at the controls and told him to level the main rotor tip path plane. The flight instructor further stated: "...I refueled the helicopter and turned my back toward the helicopter, returning the fuel hose to the truck...The main rotor tip path plane must have been permitted to dip down by the pilot, low enough to hit the fuel hose as I carried it back to the truck, which in turn struck me and began the sequence of events that resulted in the...damage to the helicopter." In the Federal Aviation Administration (FAA) Inspector's report he stated that interviews with Plymouth Copters employees revealed that company policy mandates a minimum of a 10 foot clearance between the fuel truck and the turning rotor blades. With the helicopter centered on the helipad, the tip path plane clearance with the fuel truck was 3.44 feet. The FAA Inspector's report further stated: "...Robert Dumas is seventy four inches tall. The distance from the ground to the top of the side boards on the fuel trick is seventy one and a half inches. The optimum height of the main rotor disc is 111.66 inches...Under the best of conditions, the clearance available can be predicted at 30.16 inches. We re- enacted the stowage of the hose assembly using an employee of Plymouth Copters who is seventy four inches in height. Even under this controlled environment, the tendency was for the hose to deflect up from the top of the truck in excess of thirty inches...."