Sunday, April 9, 2017

Hughes 369D, Olympic Air, N50713: Accident occurred November 24, 2015 in Carlisle, Washington

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Renton, Washington 
Boeing Helicopter; Mesa, Arizona
MD Helicopters; Mesa, Arizona

Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf

Aviation Accident Factual Report - National Transportation Safety Board: https://app.ntsb.gov/pdf

Docket And Docket Items - National Transportation Safety Board: https://dms.ntsb.gov/pubdms

http://registry.faa.gov/N50713

NTSB Identification: WPR16LA032
14 CFR Part 91: General Aviation
Accident occurred Tuesday, November 24, 2015 in Carlisle, WA
Probable Cause Approval Date: 06/20/2017
Aircraft: HUGHES 369D, registration: N50713
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The commercial pilot reported that, while relocating the helicopter to a staging area to refuel, the engine experienced a total loss of power. He initiated an autorotation to a partially-wooded area, where the helicopter touched down and rolled onto its right side. The pilot stated that, before the loss of engine power, he noticed that the fuel quantity indication was not decreasing as he would have expected. Postaccident examination revealed that the fuel quantity gauge indicated more fuel in the fuel tank than the amount that was physically present. This erroneous fuel level indication led the pilot to believe that more fuel was available than what was in the fuel tanks, and subsequently resulted in a total loss of engine power due to fuel exhaustion.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
A total loss of engine power during cruise flight due to fuel exhaustion. Contributing to the accident was the improper calibration of the fuel quantity gauge.

On November 24, 2015, about 0945 Pacific standard time a Hughes 369D, N50713, sustained substantial damage during a forced landing following a loss of engine power near Carlisle, Washington. The helicopter was registered to and operated by Olympic Air, Shelton, Washington, under the provisions of Title 14 Code of Federal Regulations Part 91. The commercial pilot, sole occupant of the helicopter, was not injured. Visual meteorological conditions prevailed and no flight plan was filed for the repositioning flight. The flight originated from Hoquiam, Washington, about 5 minutes prior to the accident, with an intended destination of a staging area near Carlisle.

The pilot reported that he originally departed a staging area near Francis, Washington, where he was parked on a hillside, waiting for improving weather. Prior to departing, he added about 50 pounds of fuel, noting he had 250 pounds of fuel total on board. The pilot departed and decided to land at Hoquiam, after noticing that the fuel gauge quantity indication was not decreasing as he would have expected for the flight. The pilot landed uneventfully at Hoquiam, noted he had about 140 pounds of fuel on board according to the fuel gauge, which was consistent with his estimations of how much fuel should have been on board. The pilot decided to depart and relocate the helicopter 12 nautical miles to a staging area where he was planning to refuel the helicopter prior to conducting external load operations in the area. The pilot stated that during the flight, the engine lost total power. He initiated an auto rotation to a partially open wooded area. Subsequently, the helicopter landed and rolled onto its right side.

Postaccident examination of the helicopter by the pilot revealed that the tailrotor and tailrotor gearbox were separated from the tail boom. The helicopter was recovered to a secure location for further examination.

Examination of the recovered wreckage revealed that the main rotor blades were removed to facilitate wreckage transport. The tailboom had contact damage from main rotor blade strike(s) and was fractured into multiple segments. The tail rotor system was still attached to the tailboom's aft frame. The tail rotor blades were damaged but exhibited little rotational damage. All main rotor blades exhibited various areas of bends, leading edge and trailing edge damage.

Control continuity was established for the collective and cyclic controls. Except for breaks in the area of the tailboom damage, tail rotor control continuity was verified. The drive system was functional from the engine through the main transmission to the main rotor hub. The tail rotor driveshaft had multiple fractures aft of FS 150 due to impact damage. The tail rotor transmission and tail rotor controls functioned normally. The upper flight controls and main rotor hub sustained minimal damage.

Electrical power was applied to the airframe and the N2 warning horn was found functional. The caution light panel was tested and all normal lights illuminated, including the low level fuel light. At this time, the fuel gauge indicated zero pounds of fuel. The fuel cell access covers were removed and the cells inspected. Only a small amount of fuel was found in the sump area below the start pump.

The engine and related systems sustained little visible damage. A fuel system vacuum check was successfully completed. The airframe fuel filter was removed from the housing. The filter and housing exhibited a slight amount of foam-like debris. Similar debris was observed in the fuel boost pump and in both the left and right fuel tanks.

In order to examine the fuel gauge quantity accuracy, 20 gallons of fuel was added in intervals utilizing 5-gallon fuel cans. With electrical power applied to the helicopter, the fuel quantity indicated on the fuel gauge were measured. When 4, 5, 7.5, 10, 12.5, 15, and 20 gallons of Jet A, which weighs about 6.8 pounds per gallon, was added to tank, the fuel quantity gauge indicated about 40-45, 80, 100, 150, 155-160, 175, and 245 pounds of fuel respectively.

While removing the fuel which was previously added, the low level fuel light illuminated at which time the fuel gauge displayed about 70 pounds of fuel. After the low level fuel light illuminated, the remaining fuel within the tank was removed and measured at about 5 gallons.

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