Accident Summary
On November 2, 2015, at about 1424 Pacific standard time, a Bell 206B helicopter, registration N22743, was substantially damaged during an autorotation landing following a partial loss of engine power near Dallas, Oregon. The helicopter was registered to and operated by Applebee Aviation under 14 CFR Part 133 for an external load flight. The commercial pilot, the sole occupant, sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed. The local flight originated from a staging area about 15 minutes before the accident.
Pilot Report
The pilot reported that before the accident flight, the helicopter was refueled with 30 gallons of Jet-A fuel. The pilot departed from a staging area and began lifting Christmas trees from a field to a nearby loading zone. After about 5 to 10 loads, the pilot released a load of trees in the loading zone and shortly after, at an altitude of about 50 feet above ground level, the engine seemed to go to a reduced power setting. An abnormal noise was heard from the helicopter, and the aircraft began to spin to the right while a low rotor RPM light illuminated. The pilot jettisoned the external load line and rolled the throttle towards a closed position to counteract the yawing motion, with no response. The pilot initiated an autorotation, and during landing, the helicopter impacted a tree. The helicopter came to rest upright in a nose-high position. After the helicopter came to rest, the pilot noted the engine was at a "very slow idle" and shut it off.
Postaccident Examination
A Federal Aviation Administration inspector examined the helicopter and found that the tailboom forward of the tailrotor gearbox was twisted about 90 degrees. The helicopter was recovered to a secure location for further examination.
On December 2, 2015, the recovered helicopter was examined at AvTech Inc. in Auburn, Washington, by the National Transportation Safety Board investigator-in-charge and representatives from Rolls Royce and Bell Helicopters. The skids had been removed for transport. Flight control continuity was established throughout the airframe to the main rotor head and aft to the tailrotor. Impact damage was observed just forward of the tailrotor gearbox. Continuity of engine controls from cockpit to engine was established. The airframe fuel filter was removed; its element was dark, almost black. The fuel removed was dark, charcoal-like in color, and debris was observed within the fuel filter bowl. Samples of debris and fuel were retained. Power was applied to the helicopter, and fuel boost pumps were turned on. Fuel expelled from the engine supply fuel lines; a sample appeared fairly clear with no debris. Visual inspection of the fuel tanks revealed about 10 to 20 gallons of fuel present.
The engine was visually intact, with all fuel and air lines secure. N1 and N2 rotated freely, and continuity from the engine to the gearbox was established. The engine fuel filter was removed from its housing; a fuel sample was dark in color and contained unknown sediment. The filter was dark in color. Fuel from the fuel nozzle supply line was clear. The engine was removed and shipped to Rolls Royce for further inspection. Fuel samples were retained for testing.
Engine Examination
On April 6, 2016, the engine was examined at Rolls Royce in Indianapolis, Indiana. It was placed on an engine stand and visually examined. Compressed air was applied to the port where the PC line connects to the compressor scroll, and air was found leaking from the PC line that connects to the fuel control unit. The engine was then installed in an engine test cell and run for about 90 minutes at various power settings. During a governor droop test, when the load was removed to test the governor's ability to maintain RPM, N2 RPM increased to the limit for the test cell. Throughout the run, the engine produced rated power at cruise and takeoff power settings.
The power turbine governor and fuel control unit were removed and examined at Honeywell, Inc. in South Bend, Indiana, under NTSB supervision. Bench tests of the power turbine governor revealed it was "sluggish" but would not result in a loss of engine power. The fuel control unit functioned normally in bench tests.
Fuel Analysis
The fuel sample from the accident helicopter's fuel filter housing was submitted to a third-party laboratory for analysis. A small amount of unknown debris was visible in the sample. Three tests—Freezing Point, Flashpoint, and Distillation—were performed, and all results were within specification for Jet A fuel. The debris was retained and sent to the NTSB Materials Laboratory for further examination. Tests found higher elemental levels of calcium, copper, iron, magnesium, nickel, potassium, silver, and zinc. The source of the debris could not be determined.