Accident Sequence
On November 24, 2015, at about 0945 Pacific standard time, a Hughes 369D helicopter, registration N50713, sustained substantial damage during a forced landing following a loss of engine power near Carlisle, Washington. The helicopter was operated by Olympic Air of Shelton, Washington, under Title 14 Code of Federal Regulations Part 91. The commercial pilot, who was the sole occupant, was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the repositioning flight. The flight had originated from Hoquiam, Washington, about five minutes earlier, with an intended destination of a staging area near Carlisle.
The pilot reported that he had originally departed a staging area near Francis, Washington, where he had been parked on a hillside awaiting improving weather. Prior to departure, he added about 50 pounds of fuel, for a total of 250 pounds on board. During that flight, he noticed the fuel gauge quantity indication was not decreasing as expected, so he decided to land at Hoquiam. After an uneventful landing, the fuel gauge indicated about 140 pounds, consistent with his fuel consumption estimate. The pilot then departed to relocate the helicopter 12 nautical miles to a staging area where he planned to refuel before conducting external load operations. During this flight, the engine lost total power. The pilot initiated an autorotation to a partially open wooded area; the helicopter landed and rolled onto its right side.
Postaccident Examination
Postaccident examination revealed that the tail rotor and tail rotor gearbox had separated from the tail boom. The helicopter was recovered to a secure location for further examination. The main rotor blades were removed to facilitate transport. The tailboom exhibited contact damage from main rotor blade strikes and was fractured into multiple segments. The tail rotor system remained attached to the tailboom's aft frame; its blades were damaged but showed little rotational damage. All main rotor blades had various bends and leading- and trailing-edge damage.
Control continuity was established for the collective and cyclic controls, and tail rotor control continuity was verified except for breaks in the area of the tailboom damage. 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 station 150 due to impact damage. The tail rotor transmission and controls functioned normally. The upper flight controls and main rotor hub sustained minimal damage.
Fuel System Examination
Electrical power was applied to the airframe; the N2 warning horn was functional, and the caution light panel illuminated all normal lights, including the low fuel level light. The fuel gauge indicated zero pounds of fuel. The fuel cell access covers were removed; 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 and 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.
To evaluate fuel gauge accuracy, 20 gallons of Jet A fuel (weighing about 6.8 pounds per gallon) was added in 5-gallon increments. With electrical power applied, the fuel gauge indicated approximately 40–45 pounds at 4 gallons, 80 pounds at 5 gallons, 100 pounds at 7.5 gallons, 150 pounds at 10 gallons, 155–160 pounds at 12.5 gallons, 175 pounds at 15 gallons, and 245 pounds at 20 gallons.
While removing the added fuel, the low fuel level light illuminated when the gauge indicated about 70 pounds. After illumination, the remaining fuel in the tank was measured at about 5 gallons.