On February 28, 1994, about 0800 hours Hawaii standard time, an Aerospatiale AS350-D, N5771L, experienced a loss of engine power and made an emergency landing Huelo, Maui, Hawaii. The pilot was conducting a visual flight rules (VFR) sightseeing flight in the local area under Title 14 CFR Part 135. The helicopter, operated by Papillon Helicopters Inc., sustained minor damage. Neither the certificated commercial pilot nor his four passengers sustained any injuries. Visual meteorological conditions prevailed. The flight originated at the Kahului Airport, Kahului, Maui, about 0745 hours. In the accident report, the pilot said that about 12 minutes into the flight, at 8,000 feet mean sea level, the helicopter's main rotor rpm began to bleed off. The pilot was unable to maintain the altitude and elected to land in an unsuitable area at a zero airspeed touchdown. A Federal Aviation Administration (FAA) airworthiness inspector, Honolulu Flight Standards District Office, conducted the on-scene investigation. He said that the pilot stated the helicopter experienced a loss of engine power (down to 58 percent engine power) and was unable to maintain normal main rotor rpm. The pilot entered an autorotation and during the landing, a tree stump penetrated the lower left fuselage section of the helicopter. The FAA inspector examined the helicopter and could start the engine. The engine would only accelerate to 58 percent power. Further inspection revealed a fuel leak in the fuel line inlet of the fuel control unit. The operator provided the National Transportation Safety Board excerpts of the pertinent maintenance and pilot records. The maintenance records examination revealed that the company's maintenance personnel completed the required annual inspection on October 17, 1993; the helicopter had accrued 8,178.6 hours at the time of the inspection. The engine had accrued 7,770.5 hours. The operator completed a 100-hour inspection on February 23, 1994; the helicopter and engine accrued 7.4 hours since the inspection at the time of the accident. Safety Board investigators found an entry in the maintenance records that showed the fuel control unit was replaced on February 26, 1994. The maintenance records also showed that the operator's maintenance personnel performed a postreplacement engine run-up and found no leaks. The operator told Safety Board investigators that he sent the fuel control unit to the manufacturer for examination. He said that the examination revealed no evidence of any preexisting malfunctions or failures.