History of Flight
On July 1, 2015, at about 1000 Pacific daylight time, a Hughes 269C helicopter, registration N9490F, collided with powerlines while flying in a canyon near Asotin, Washington. The helicopter was consumed by fire and destroyed. The pilot was operating under 14 Code of Federal Regulations Part 91 as a personal local flight. The flight originated from the Lewiston-Nez Perce County Airport, Lewiston, Idaho, about 0930. Visual meteorological conditions prevailed, and no flight plan was filed.
The pilot had spoken with his father earlier that morning, stating he planned to fly with a passenger, his cousin. Multiple witnesses in the area reported observing a helicopter in an adjacent canyon. A fire was reported just before 1000, and during suppression efforts, a firefighter discovered the wreckage. The post-impact fire spread primarily south, burning numerous acres of canyon terrain and fields. A Clear Water Power Co. employee later reported a temporary disruption in powerline service.
Personnel Information
The pilot, age 17, held a private pilot certificate issued in December 2014 with a rotorcraft-helicopter rating and a third-class medical certificate issued in December 2013 with no limitations. According to his personal flight logbook, he had accumulated 55.5 total flight hours, all in rotorcraft and all in the same make and model as the accident helicopter. He had about 22 hours as pilot-in-command. The majority of his flying hours were logged around the Lewiston area.
Aircraft Information
The Hughes 269C, serial number 1030243, was manufactured in 1973. Maintenance records indicated the airframe had accumulated about 12,725 total hours in service. The most recent annual inspection was completed in February 2015. The Lycoming HIO-360-D1A engine underwent an annual inspection on the same date at an engine total time of about 435 hours.
Meteorological Information
A routine aviation weather report (METAR) for the Lewiston-Nez Perce County Airport, issued minutes before the accident, reported sky clear, visibility 10 miles, wind calm, temperature 86°F, dew point 50°F, and altimeter 29.98 inHg.
Wreckage and Impact Information
The accident site was located in Ayres Gulch Canyon, about 6 nautical miles long and oriented north-south, with the site midway. The canyon was surrounded by wheat fields; a large barn was about 1.7 nm south. Elevation at the site was about 2,225 feet msl, with surrounding hills about 2,660 feet msl. The main wreckage, comprising the fuselage and engine, came to rest on a flat dirt area on the east canyon wall.
Powerlines were located 350 ft south of the wreckage. Two 35-ft wood support structures were positioned on either side of the canyon, 1,452 ft apart. Two 5/16-inch diameter guy wires ran east-west horizontally parallel. Additional powerlines ran north-south along the west canyon wall. Under the powerlines, a portion of the canopy frame was found, including the mid-left horizontal and center vertical sections. A bend on the vertical frame corresponded to the top of the cockpit panel. Red rub marks on the frame were consistent with tail rotor blade contact. Nearby was a portion of the mid-right horizontal canopy. Numerous pieces of tinted and clear plexiglass were observed. A headset holder, portions of the upper canopy slat, frames of both headsets, and the upper tail boom light-clip were located on the hill between the wires and the main wreckage.
Medical and Pathological Information
The Spokane County Office of the Medical Examiner performed autopsies on the pilot and passenger. The FAA Toxicology Accident Research Laboratory conducted toxicological testing, which was positive for ethanol; however, the report noted evidence of putrefaction in the specimens.
Tests and Research
The wreckage sustained significant thermal damage. Examination of the airframe revealed that most control push-pull tubes and fuselage structure were consumed by fire, with thermally damaged remnants of bellcranks, cyclic, collective, and anti-torque pedals remaining.
Both skids were separated near midspan. The drag strut signatures and forward skid fractures indicated the helicopter was in forward motion at impact. The skid toes were the first contact point, causing upward deformation and concentrated load on the forward support strut. The drag struts were relatively straight with little bending, primarily exhibiting crushing from contacting the frame. The main frame steel tubing showed bowed deformation and numerous fractures consistent with a nose-down vertical attitude.
The stationary scissors link that holds the non-rotating portion of the swashplate was fractured. The blue main rotor blade exhibited significant arcing spatter on its bottom inboard end; the other two blades had minor arcing. The rotating scissors links remained intact and attached. Given the damage orientation, it is likely the powerlines contacted the swashplate area, causing electrical arcing and fracturing the stationary scissors and non-rotating swashplate.
The tail boom came to rest in front of the cabin. The tail rotor assembly was in the dirt, with the blue main rotor blade's leading edge near the vertical fin. The tail boom exhibited a fracture just aft of the vertical fin attachment on the left side; no main rotor blade strike indications were on the boom. A red rub mark indent on the tail was consistent with tail rotor blade contact during rotation. The vertical fin showed signatures of a main rotor blade strike on the right side, consistent with blade contact after the boom was on the ground, with enough energy to fracture the boom tube at the vertical fin attach area.
The tail rotor blades and horizontal stabilizer exhibited arcing marks; the stabilizer also had bending of the forward inboard sheet metal and spar. It is likely that electrical transmission wires contacted the tail rotor blades and stabilizer.
According to the helicopter manufacturer, in level flight the helicopter is about 18° nose-down (depending on airspeed). Under accident conditions, estimating the wires spaced about 6 feet apart, the angle would orient both wires on top of each other at cabin impact. Assuming maneuvering at 60 mph, 0.11 seconds would elapse between contact with the first wire (canopy) and second wire (slat and mast). Based on the damage and rub marks, after the second wire impact, the helicopter likely pitched up and yawed left, then contacted the horizontal stabilizer, exited the wires, and continued in a right rotation with a nose-low descent. The tail boom was likely partially separated during wire contact.
Examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.