DEN99LA040
DEN99LA040

On February 15, 1999, approximately 1715 mountain standard time, a Hughes 369D, C-GDCM, operated by Peace Helicopters of Edmonton, Alberta, Canada, was substantially damaged after impacting terrain following a loss of engine power while maneuvering nears Baggs, Wyoming. The Canadian registered commercial pilot, the sole occupant aboard, was seriously injured. The aircraft was being operated under Title 14 CFR Part 91, and a company VFR flight plan was filed. The flight originated from a local staging area approximately 10 minutes before the accident. Visual meteorological conditions prevailed.

According to the pilot, the flight was being conducted as a seismic survey operation, and he was repositioning supplies for ground team members with a long line hook up. While flying at 200 to 250 feet above the ground (agl) at approximately 40 knots airspeed, the pilot observed that the engine's automatic re-ignition system caution light had illuminated, followed by an immediate loss of main rotor rpm. The helicopter yawed to the left, followed by a sudden turbine deceleration. The pilot stated that he attempted to perform an autorotation, but was unsuccessful due to the helicopter's low altitude and airspeed. The aircraft impacted the ground, causing structural distortion to the underside of the fuselage due to landing gear overload fractures, and damaging the upper fuselage due to the downward flexing of the tail boom. The elapsed time between first engine warning and impact with the ground was approximately 4 to 5 seconds.

A postaccident examination of the turboshaft engine was performed by the FAA, with the assistance of engineering representatives from Rolls-Royce Allison and the Boeing Company. The inspection revealed that the PC line "B" nut between the fuel control unit (FCU) and the power turbine governor (PTG) was not connected at the FCU. The nut had completely backed off the threads of the fitting, resulting in a loss of engine pneumatic pressure. All additional oil and fuel lines were intact. During the investigation, air at 40 psi was supplied to the system, revealing the PC line leak. When the PC line fitting was connected and torqued, air was again supplied to the system. No additional leaks were observed.

According to aircraft maintenance records supplied by the operator, the turbine section of the engine was removed by company maintenance personnel on February 12, 1999, and replaced with a rental turbine. The PC line and various pneumatic and fuel system lines had been removed to facilitate removal and replacement of the engine's turbine section. The helicopter had flown 6.1 flight hours since the installation which occurred 3 days prior to the accident.

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