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On January 5, 2009, about 1045 Hawaiian standard time, a Eurocopter AS 350 BA helicopter, N141MK, sustained substantial damage when it rolled over during a forced landing following a loss of engine power during approach to landing on a ridge top about 10 miles east of Honolulu, Hawaii. The commercial pilot and the passenger were not injured. The helicopter was being operated by Makani Kai Helicopters as a 14 Code of Federal Regulations Part 135 on demand charter flight. Visual meteorological conditions prevailed and a company flight plan was filed for the local flight that departed from Honolulu International Airport about 1030.
The purpose of the flight was to transport a worker to an antenna located on Wiliwili Nui Ridge at an elevation of about 2,400 feet. The pilot reported that the flight to the location was uneventful, and he completed his prelanding checklist and noted nothing abnormal. Just prior to landing, there was a “power decay.” According to the pilot, “the engine felt and sounded like it was winding down and rotor RPM was starting to bleed off.” At this point the helicopter was less than 10 feet from the landing site. The helicopter was not holding altitude, and the pilot maneuvered the helicopter so that it touched down and rolled over onto its right side, which prevented the helicopter from falling down the steep slope of the ridge. After the helicopter came to rest, he shut down the engine by pulling the fuel control lever and the emergency fuel shut off valve to the closed position.
The pilot, age 55, held a commercial pilot certificate with helicopter, single and multi-engine airplane, helicopter instrument, and airplane instrument ratings. He also held a flight instructor certificate with the same ratings. The pilot’s most recent second-class medical certificate was issued on March 19, 2008, with the limitation: must wear corrective lenses and possess glasses for near and intermediate vision.
The pilot reported that he had accumulated 13,000 total flight hours of which 6,500 hours were in the accident make and model of helicopter. In the past 90 and 30 days, he had flown 187 and 48 hours, respectively, in the accident make and model of helicopter.
The single-engine helicopter was manufactured as an AS 350 B in 1990 and converted to an AS 350 BA in 1997. A Heli-Lynx “AS 350 FX” conversion in accordance with Supplemental Type Certificate (STC) SR02295NY was performed in 2007, which included installation of a Honeywell LTS101-600A-3A engine, S/N LE-46021CE. Review of the maintenance records revealed that the most recent 100-hour inspection was completed on December 23, 2008, at an airframe total time of 14,250.3 hours. At the time of the annual inspection, the engine had accumulated 9,496.0 hours since new and 1,634 since overhaul. When the accident occurred, the helicopter had accumulated 14,290.7 hours.
At 1035, the reported weather conditions at Honolulu International Airport were winds from 070 degrees at 14 knots with gusts to 19 knots; visibility 10 miles; few clouds at 3,400 feet above ground level (agl), scattered clouds at 4,500 feet agl, scattered clouds at 5,500 feet agl; temperature 26 degrees Celsius (C); dew point 17 degrees C; and altimeter setting 30.12 inches.
WRECKAGE AND IMPACT INFORMATION
The wreckage was examined under the supervision of an NTSB investigator on January 21, 2009, at the operator’s facility in Honolulu. The main rotor system exhibited rotational damage. Two of the three blades exhibited significant impact damage. The transmission had shifted to the left and rear, and the engine had shifted forward. The engine-to-transmission drive shaft was compressed and torsionally separated near the transmission input coupling. The tail rotor drive shaft was disengaged from the engine output coupling. There was rotational scoring through 360 degrees on the forward tail rotor drive shaft section. The forward to aft tail rotor drive shaft coupling was also disengaged. Both tail rotor blades separated near the hub, and the remaining stubs displayed broomstrawing.
Electrical power was applied to the helicopter for the purpose of checking fuel system continuity and fuel pressure. The fuel filter light did not illuminate on the caution warning panel. When the fuel boost pumps were turned on, the fuel pressure indicator displayed normal fuel pressure and the fuel pressure light on the caution warning panel extinguished. No fuel leaks or breaches were observed. The impending bypass button on the airframe fuel filter was not extended. The fuel filter was removed and appeared to be clean. Fuel consistent in color, clarity, and smell with Jet A, along with a small amount of debris was observed in the filter container.
Engine continuity was established. The power turbine rotor was intact with no leading edge damage to the blades. No debris was found on any of the three engine oil chip detectors. A pneumatic leak check was performed and leaks were identified at the temperature compensator and at the PX acceleration bellows. The engine was removed from the helicopter and crated for shipping to Honeywell Aerospace, Phoenix, Arizona, for a test cell run.
TESTS AND RESEARCH
A test cell run of the engine was completed under the supervision of an NTSB investigator on March 5-6, 2009, at Honeywell Aerospace in Phoenix. During the test cell run, the engine achieved maximum continuous, takeoff, and thermodynamic shaft horsepower. The engine did not surge during transient deceleration and acceleration runs, and was responsive to commanded throttle inputs. None of the pneumatic fittings were tightened before the test cell run. No pre-existing condition was identified on the engine that would have interfered with normal operation or explain the reported loss of engine power.