History of Flight
On January 5, 2009, at approximately 1045 Hawaiian standard time, a Eurocopter AS 350 BA helicopter, registered as N141MK, sustained substantial damage during a forced landing after experiencing a loss of engine power while approaching a ridge top about 10 miles east of Honolulu, Hawaii. The commercial pilot and the passenger were not injured. The helicopter was 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, which had departed from Honolulu International Airport about 1030.
The flight's purpose was to transport a worker to an antenna on Wiliwili Nui Ridge at an elevation of about 2,400 feet. The pilot reported an uneventful flight to the location and completion of the prelanding checklist with no abnormalities. Just prior to landing, a "power decay" occurred. The pilot described that "the engine felt and sounded like it was winding down and rotor RPM was starting to bleed off." The helicopter was less than 10 feet from the landing site and was not holding altitude. The pilot maneuvered the helicopter so that it touched down and rolled over onto its right side, preventing it from falling down the steep slope of the ridge. After coming to rest, the pilot shut down the engine by pulling the fuel control lever and the emergency fuel shutoff valve to the closed position.
Personnel Information
The pilot, aged 55, held a commercial pilot certificate with ratings for helicopter, single-engine and multi-engine airplane, and helicopter and airplane instrument. He also held a flight instructor certificate with the same ratings. His most recent second-class medical certificate was issued on March 19, 2008, with the limitation that he must wear corrective lenses and possess glasses for near and intermediate vision. The pilot reported 13,000 total flight hours, including 6,500 hours in the accident make and model. In the preceding 90 and 30 days, he had flown 187 and 48 hours, respectively, in the same helicopter model.
Aircraft Information
The single-engine helicopter was originally manufactured as an AS 350 B in 1990 and converted to an AS 350 BA in 1997. A Heli-Lynx "AS 350 FX" conversion under Supplemental Type Certificate (STC) SR02295NY was performed in 2007, which included installation of a Honeywell LTS101-600A-3A engine, serial number LE-46021CE. Maintenance records showed 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 annual inspection, the engine had accumulated 9,496.0 hours since new and 1,634 since overhaul. At the time of the accident, the helicopter's total time was 14,290.7 hours.
Meteorological Information
At 1035, weather conditions at Honolulu International Airport were reported as 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 and 5,500 feet agl, temperature 26 degrees Celsius, dew point 17 degrees Celsius, and altimeter setting 30.12 inches.
Wreckage and Impact Information
An NTSB investigator examined the wreckage on January 21, 2009, at the operator's facility in Honolulu. The main rotor system exhibited rotational damage, with two of the three blades showing 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, with 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, with the remaining stubs displaying broomstrawing.
Electrical power was applied to check 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 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 appeared clean, and 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 identified leaks at the temperature compensator and the PX acceleration bellows. The engine was removed and crated for shipping to Honeywell Aerospace in Phoenix, Arizona, for a test cell run.
Tests and Research
A test cell run of the engine was completed under NTSB supervision on March 5-6, 2009, at Honeywell Aerospace in Phoenix. The engine achieved maximum continuous, takeoff, and thermodynamic shaft horsepower. It 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 explained the reported loss of engine power.