On Monday, February 14, 1994, at 1135 eastern standard time, a Hiller UH-12E helicopter, N4495M, owned, operated, and piloted by James E. Stevens of Lovingston, Virginia, lost engine power and was substantially damage after colliding with trees during the emergency descent. The pilot and passenger were not injured. Visual meteorological conditions prevailed at the time of the accident. The aerial observation/powerline patrol flight was conducted under 14 CFR Part 91. According to personnel in the Fixed Base Operator's (FBO) facility at the Farmville Municipal Airport, on February 14, 1994, about 1120 eastern standard time, a passenger from N4495M got out of the helicopter and walked into the FBO facility and inquired about fuel. The FBO personnel reported that the passenger was asked what kind of fuel they needed, "Jet A or AVGAS?" and the passenger responded "Jet." The FBO personnel walked the passenger out of the facility and pointed to the Jet A fuel tank. The fueling area was cleared and the pilot of the helicopter flew the helicopter to the refueling area. The FBO personnel stated that he started to ground and fuel the helicopter, but in both instances the pilot took over. The passenger of the helicopter stated that when he was asked about the type of fuel needed, he responded that he did not know and that they would have to ask the pilot. According to the pilot, during the refueling process of the helicopter, he told the line boy that "...I needed 100 [low lead fuel]..." and the line boy handed him a fuel nozzle. The pilot stated that he proceeded to put the fuel into the fuel tank. The pilot stated that the "...wind was blowing 16 M.P.H. and gusting to 23 kts [knots] so no smell was present." He also stated that the fuel pump area was under construction and new fuel tanks were being installed. He stated that the fuel line and the fuel tank were unmarked. During the refueling of the helicopter, the pilot noticed that the fuel nozzle and the fuel flow were "different." The pilot said that he questioned the line service person about the fuel nozzle and fuel flow and the line service person told him "... that was what was required." The pilot stated that he finished the refueling and prepared for takeoff. He stated that he did not take fuel samples after the helicopter was refueled and that he did not get a fuel receipt because he had an open fuel tab for the day. He said he had about 12 gallons of 100 low lead fuel in the fuel tank when he refueled. The pilot stated that about four minutes after takeoff, the "...aircraft started to miss and shake violently then lose power." He stated that there were no suitable landing areas so he made a descent into the trees. A post accident examination of the fuel in the helicopter's fuel tank revealed that the fuel tank contained Jet A fuel. The manager of the Farmville Municipal Airport stated that on the day of the accident, the fuel tanks at the airport were being worked on and that the 100 low lead tanks were marked/placarded, but were out of service. He stated that because the Jet A fuel tanks were new, the placards/labels for the tanks were ordered and had not yet arrived.