Kahuku, HI, USA
N911FT
HUGHES 369D
During an aerial surveillance flight, the helicopter's engine chip light illuminated, and the pilot headed towards a nearby heliport to make a precautionary landing. The pilot established a steep fast approach in case of engine failure while on approach. At approximately 100 feet above the ground and an airspeed of 65 knots, he applied power and began to slow the helicopter. At this point, the engine lost power, and the pilot entered an autorotation. The helicopter landed hard breaking both forward landing gear struts and spreading the rear struts. The main rotor blades impacted the tail boom, and the tail boom separated from the fuselage. Examination of the helicopter revealed heavy deposits of oil on the inner surfaces of the engine compartment as well as on the exterior surfaces of the engine. There was no oil in the airframe engine oil reservoir. The oil line leading from the engine gearbox to the oil pressure gauge was found cracked beneath the "B" nut securing it to the fitting on the engine gearbox. The N2 (power turbine) drive could not be rotated. Partial disassembly of the engine revealed damage to the number six, seven, and eight bearings consistent with a lack of adequate lubrication. Laboratory examination of the cracked oil line found fatigue cracking had propagated through an estimated 90 percent of the cross-sectional area of the tube. The cracking allowed lubricating oil to leak from the line resulting in oil starvation to the bearings leading to seizure of the power turbine.
On April 19, 2007, approximately 1405 Hawaii standard time, a Hughes 369D helicopter, N911FT, landed hard during an autorotation following a loss of engine power on final approach to Turtle Bay Heliport, Kahuku, Hawaii. The helicopter, which was registered to and operated by K&S Helicopters of Kailua Kona, Hawaii, sustained substantial damage. The commercial pilot and one passenger were not injured, and two passengers received minor injuries. Visual meteorological conditions prevailed and no flight plan was filed for the 14 Code of Federal Regulations Part 135 on demand air taxi flight conducted for the Honolulu Police Department. The purpose of the flight was aerial surveillance. The flight departed from Honolulu International Airport about 1305. According to the pilot, the flight proceeded from Honolulu to the North Shore area without incident. While in the vicinity of the town of Kahuku, the "engine chips" light illuminated, and he headed towards the Turtle Bay Heliport to make a precautionary landing. The pilot established a steep fast approach in case of engine failure while on approach. At approximately 100 feet above the ground and an airspeed of 65 knots, he applied power and began to slow the helicopter. At this point, the engine lost power, and the pilot entered an autorotation. The helicopter landed hard breaking both forward landing gear struts and spreading the rear struts. The main rotor blades impacted the tail boom, and the tail boom separated from the fuselage. Examination of the helicopter by a representative of the engine manufacturer, conducted under the supervision of a Federal Aviation Administration (FAA) inspector, revealed heavy deposits of oil on the inner surfaces of the engine compartment as well as on the exterior surfaces of the engine. There was no oil in the airframe engine oil reservoir. The oil line leading from the engine gearbox to the oil pressure gauge was found cracked beneath the "B" nut securing it to the fitting on the engine gearbox. The N2 (power turbine) drive could not be rotated. Partial disassembly of the engine revealed damage to the number six, seven, and eight bearings consistent with a lack of adequate lubrication. Laboratory examination of the cracked oil line by the NTSB Materials Laboratory found fatigue cracking had propagated through an estimated 90 percent of the cross-sectional area of the tube. Under the supervision of an FAA inspector, the oil pressure gauge was bench tested through its full indicating range and no discrepancies were noted.
Fatigue cracking of the oil line from the engine gearbox to the oil pressure gauge, which resulted in loss of engine lubricating oil, leading to seizure of the power turbine.
Source: NTSB Aviation Accident Database
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