Accident Summary
On July 29, 2013, at about 1140 eastern daylight time, a McDonnell Douglas 369D helicopter (registration N31HM) impacted a power pole during a descent following a total loss of engine power. The accident occurred near Center Point, West Virginia, while the helicopter was conducting tree trimming operations as an external load flight under 14 CFR Part 133. The commercial pilot, the sole occupant, sustained minor injuries. The helicopter was substantially damaged. It was owned and operated by DAH Aircraft, LLC. Visual meteorological conditions prevailed, and no flight plan was filed. The flight had originated from a remote landing zone about 1.5 nautical miles northwest and was returning to the same zone.
Pilot Narrative
The pilot reported that after trimming the top portion of a tree overhanging a power line, he noticed a gradual loss of power without any noticeable yaw. Rotor rpm began to decrease, triggering an "Engine Out" alarm both visually and audibly. He lowered the collective to preserve rotor rpm and nosed the helicopter forward and to the right to avoid landing directly onto the power line. During the descent, the rotor blades struck the power line pole, and the helicopter impacted the ground on its right side in a densely wooded area.
Damage and Examination
Initial examination by a Federal Aviation Administration (FAA) inspector found substantial damage to all five main rotor blades and the left landing skid. Further inspection revealed extensive damage to the right side of the cabin section frame, both landing skids, the main rotor system, and the tail boom.
Engine and Maintenance
The helicopter was powered by a Rolls-Royce 250-C20B turbo-shaft engine (serial number CAE-821945F). The engine logbook showed a total time of 19,082.8 flight hours, with 29 hours since the last annual inspection and 4,266.4 hours since overhaul. The airframe's most recent annual inspection was completed on September 27, 2013, at a total airframe time of 10,446 hours. After the accident, a fuel vacuum check of the engine and airframe fuel supply system revealed no discrepancies. Checks of engine air, fuel, and oil systems were normal, and flight control continuity was verified. The engine was removed and sent to the manufacturer for testing; multiple power settings in a test cell showed no anomalies. A review of the helicopter's weight and balance indicated it was within the manufacturer's designed limits.
Weather Conditions
Weather recorded at North Central West Virginia Airport in Clarksburg, West Virginia, at the time included wind variable at 5 knots, visibility 10 statute miles, few clouds at 3,900 feet above ground level, temperature 21°C, dew point 12°C, and an altimeter setting of 30.15 inches of mercury.