History of Flight
On June 23, 2016, about 1425 mountain standard time, a Robinson Helicopter Company R66, registration N117TW, broke up in flight near Wikieup, Arizona. The commercial pilot and the pilot-rated passenger sustained fatal injuries; the helicopter was destroyed. Guidance Air Service LLC operated the helicopter under 14 CFR Part 91 as a cross-country positioning flight. The flight departed Prescott, Arizona, about 1338 with a planned destination of Riverside, California. Visual meteorological conditions prevailed, and no flight plan was filed.
The pilot, seated in the right seat, was traveling to Riverside for a Part 135.293 check ride with an FAA inspector. The pilot-rated passenger, in the left seat, was the operator's Part 141 chief pilot.
The helicopter was reported overdue when it did not arrive at its destination, and the wreckage was located about 0430 on June 24. No witnesses, radar data, or radio transmissions were recorded. A SPOT GPS tracking device provided location fixes, with the last data point at 1425 near the accident site.
Meteorological Information
The National Weather Service surface analysis showed a thermal low pressure system west of the accident site. The upper air sounding from Yuma, Arizona, indicated strong thermals through 8,500 ft. The lifted and K-indices suggested conditions conducive to significant updrafts and dust devils. Other weather products supported strong thermals to 11,000 ft.
Two individuals near the accident site reported numerous large dust devils. An airframe and powerplant mechanic observed up to five dust devils simultaneously. A pilot performing aerial survey work north of the site reported increasing wind gusts from 1130 onward, numerous dust devils, and a significant updraft exceeding 1,000 ft/min. He discontinued operations around 1515 and encountered a wind shift while returning to base. Dust devils are common in Arizona, especially between June and August.
Wreckage and Impact Information
The helicopter came to rest in hilly desert terrain. The debris field measured about 750 yards long and 150 yards wide. The outboard 5 ft of a main rotor blade afterbody had separated from its leading edge spar, with black paint transfer marks near the tip, located on a small ridgeline. The inboard section of this blade was about 600 yards into the debris field and 85 yards left of the centerline.
The left side of the helicopter was more fragmented than the right. Left side cabin pieces and instruments were distributed throughout the early debris field. The tail boom was about midway. The left side/nose cabin had a straight separation line with accordion-crushed floor panels and came to rest inverted about 600 yards into the field; a postcrash fire destroyed it. The engine remained attached to the cabin.
The transmission, mast, and second main rotor blade separated as a unit about 100 yards past the cabin area. The coning bolt of the separated blade was bent, and the teeter stops had impact marks. The attached blade was bent midspan about 10° to 20° opposite the direction of rotation. The main rotor driveshaft was bent about 15° at the swashplate.
Medical and Pathological Information
The Mohave County Medical Examiner's Office completed autopsies of both occupants. The pilot's cause of death was multiple injuries due to the helicopter crash; toxicology was negative for ethanol and tested drugs. The pilot-rated passenger's cause of death was also multiple injuries; toxicology detected 80 mg/dL ethanol in muscle and propanol, but no ethanol in the brain, noting putrefaction had occurred.