WPR12LA328

The operator reported that the helicopter was in an 80-ft hover and had begun lifting and dragging the ends of winch lines used to pull power cables across sloping terrain when the engine lost power. The pilot jettisoned the external load as the helicopter began to descend rapidly. The helicopter's tail boom contacted the ground first and was then cut by the main rotor system, the skids separated from the fuselage, and the helicopter then came to rest on its right side. Several witnesses reported that the engine was still running on the ground after the impact. Postaccident examination and operational testing of the engine revealed no anomalies that would have precluded normal operation. During previous investigations of similar accidents, it was determined that the fuel tank supply pickup can become unported with a fuel load of less than 151 lbs when pitch-and-roll attitudes approach 20 degrees; the operator reported that about 117 lbs of fuel was recovered from the helicopter. It is likely that the fuel tank supply pickup unported while the helicopter was maneuvering, which led to fuel starvation and the subsequent loss of engine power.

In 2008, the Australian Transport Safety Bureau investigated a helicopter accident involving a MD369ER (Aviation Occurrence Investigation AO-2008-025) that was conducting power line stringing operations. The investigation found through testing that it was possible to introduce air into the fuel system through the fuel tank pick-up point when fuel quantity was less than 85L (151 lbs) and subjected to a 20 degrees nose up and 20-degree right roll attitude. In 1990, the National Transportation Safety Board investigated a helicopter accident involving a MD368D that was conducting external long line operations (LAX91LA054). The investigation stated that by duplicating the helicopter's pitch attitude and fuel load it was found that the fuel pick-up point is unported at fuel quantity levels at or below 115 lbs. The two-seat, conventionally configured, single engine helicopter, serial number 0188E, was powered by a Rolls Royce M250-C20B 420-hp turboshaft engine. The operator reported in the NTSB Form 6120 that the total airframe time at the time of the accident was 2,757 hours, and the last inspection was a 100-hour inspection conducted under the manufacturer's inspection program on June 21, 2012. The engine, serial number CAE835944, had a total time of 4,923 hours, time since overhaul was 286 hours, and time since last inspection was 47 hours. TESTS & RESEARCH Engine Functionality Test Rolls-Royce conducted an engine functionality test of M250-C20B engine CAE 835944 at the Rolls-Royce Indianapolis Plant 5 production test stand on September 13, 2012, under the supervision of the NTSB investigator-in-charge (IIC). The engine shipping container was sealed prior to departing the operator's facility, and the seals were intact prior to engine removal at Rolls-Royce. The engine was removed from the container and installed in a Rolls-Royce certified production test stand. In order to facilitate the test, 4 components were replaced due to damage that occurred during the event impact sequence. The outer combustion case, combustion liner, igniter, and igniter lead were replaced with serviceable factory components. The engine started and functioned per specification during the test run with the following exceptions: - The predicted power at the Cruise-C (300hp, 1261°F MGT) setting was 273hp, which was 9% below specified power. -The predicted power at the Normal Cruise (370hp, 1360°F MGT) setting was 347hp, which was 6.2% below specified power. - The predicted specific fuel consumption at the Cruise-C (300hp, 1261°F MGT) setting was 3.5% above specification. -The predicted specific fuel consumption was at the Normal Cruise (370hp, 1360°F MGT) setting was 1.5% above specification. No flame outs were noted during the engine acceleration and deceleration test points and the power turbine governor functioned per specification. The predicted power at the Maximum-Take Off setting (420hp, 1490°F MGT) was 453hp, which was 7.9% above specification. The engine performed asdesigned during the testing with performance deviations noted above. No anomalies which would contribute to a power loss were observed during the testing. On July 26, 2012, at 1445 Pacific daylight time, while conducting external load operations, a Hughes 369E helicopter, N427WC, experienced a partial loss of engine power and landed hard, 8 miles east of The Dalles, Oregon. Wilson Construction Company operated the helicopter under 14 Code of Federal Regulations, Part 133. The commercial pilot was seriously injured, and the helicopter was substantially damaged. Visual meteorological conditions prevailed, and a flight plan had not been filed. The operator reported in the NTSB Pilot/Operator Accident Report (Form 6120) that the helicopter was in an 80-foot hover and began to lift the ends of winch lines and dragging them across sloping agricultural terrain ground when the helicopter lost power. The external load was jettisoned as the helicopter began to descend rapidly. Witnesses said they heard a change in the sound of the helicopter, and one witness saw the helicopter impact the ground. The helicopter's tail boom contacted the ground first then was cut by the main rotor system. The skids spread and separated from the fuselage. The helicopter came to rest on its right side. Several witnesses said that the engine was still running on the ground after the impact. On-scene examination of the helicopter was conducted by a Federal Aviation Administration (FAA) inspector. The FAA inspector reported that the main rotor blades were coned upward, the tail boom had been separated from the fuselage, landing skids were sheared off, and control continuity was established from the cyclic to the main rotor swash plate. The helicopter was positioned upright into a flying attitude and the battery turned on. No fuel was observed to have leaked from the fuel system. The fuel gage read 125 lbs, and a stick was placed into the fuel tank to visually measure the fuel level, which measured 9 inches from the lower lip of the fuel filler flange to the fuel level. The operator drained the fuel from the helicopter and reported that 117 lbs (17.2 gal) was recovered. The pilot, age 64, held a commercial pilot certificate with ratings for airplane single-engine land, and rotorcraft helicopter, and a second-class medical certificate with the limitation that the pilot wear lenses for distant vision and possess glasses for near vision, issued on March 5, 2012. The operator reported on the NTSB Form 6120 that the pilot has 27,900 hours of total flight time; 27,650 hours in rotorcraft, and 9,000 hours in the Hughes 369.