History of Flight
On December 10, 2015, about 1347 mountain standard time, an experimental amateur-built RV-7 airplane, registration N307AB, broke up in flight and impacted terrain about 3 miles west of General Dick Stout Field Airport, Hurricane, Utah. The airline transport pilot and passenger were fatally injured, and the airplane sustained substantial damage. The airplane was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions existed near the accident site, and no flight plan had been filed. The local flight departed from an unknown airport at an undetermined time.
Several witnesses near the accident site reported hearing the airplane's engine and hearing power changes. They observed airplane debris floating in the air. One witness stated that the engine was running during the entire descent and that the airplane was spiraling and descending in a cork-screw maneuver. Another witness reported seeing the airplane inverted at low altitude just before impact.
Personnel Information
The pilot held an airline transport pilot certificate with multi-engine land, single-engine land, instrument, and instructor single-engine land ratings. He was issued a first-class FAA medical certificate on October 22, 2015, with the limitation that he must have glasses available for near vision. On his most recent medical certificate application, the pilot reported 17,359 total flight hours, 403 of which were accumulated in the previous 180 days.
Aircraft Information
The two-seat, low-wing, fixed-gear airplane was assembled in 2011 and issued an airworthiness certificate certified for aerobatic maneuvers in March 2011. It was powered by an experimental 180-horsepower ECI/Titan IO-360 reciprocating engine equipped with a Whirlwind 200RV propeller. The last documented inspection was a conditional inspection on May 15, 2015, at an airframe time of 258.9 hours. The kit manufacturer listed the maximum load factor as +6 g, the minimum as -3 g, and the never-exceed speed as 230 mph. The maximum aerobatic gross weight was 1,600 lbs.
Meteorological Information
Weather observation at Saint George Regional Airport, about 12 miles west-southwest of the accident site, at 1355 reported calm wind, visibility 10 statute miles, clear skies, temperature 12°C, dew point -2°C, and altimeter 29.87 inches of mercury. The accident site was between a cold front and a high-pressure area, with strong pressure gradient. A model sounding estimated surface wind from 220° at 8 knots, increasing with height and veering west. Mean 0–18,000 ft winds were from 250° at 52 knots. Light-to-moderate clear air turbulence was suggested from 6,400 to 8,000 ft, and mountain wave development from 10,000 to 12,000 ft. Pilot reports noted mountain wave activity with moderate-to-severe turbulence near the accident site at 6,500 ft. An AIRMET for moderate turbulence below 18,000 ft was active; no SIGMET was active.
Wreckage and Impact Information
The wreckage was located about 4.2 miles southwest of Hurricane, Utah, on flat sagebrush terrain on a mesa. The debris path was about 1,460 ft long and 450 ft wide, containing all major components. The main wreckage, including fuselage, engine, right wing, half of the left wing, most elevators, and lower half of rudder, was at the northern extent. The vertical stabilizer with upper rudder was about 1,420 ft south-southwest. The left and right horizontal stabilizers were 850 ft and 790 ft south, respectively. The left aileron was 430 ft south-southwest, and the left outboard wing 320 ft south-southwest.
The main wreckage was inverted with no ground scars. The fuselage was intact but upper half crushed. The canopy frame was separated and located about 55 ft northeast. Most acrylic canopy was fractured. The engine remained attached; one propeller blade was fractured from the hub and the other missing the tip. Debris consistent with propeller material was found. Engine examination showed no mechanical malfunctions precluding normal operation. Main landing gear remained attached with some deformation.
The entire right wing remained attached with flap and aileron. The flap was up. The outboard half was deformed downward 15°–20° at the flap/aileron junction about 57 inches outboard. Upper and lower wing skins buckled. The fiberglass wingtip was splayed open at the trailing edge.
The inboard half of the left wing remained attached with flap up. The outboard half separated at the flap/aileron junction. The main spar fractured where upper and lower spar caps decreased in net section. The outboard half was mostly intact with minimal damage.
Medical and Pathological Information
The Utah Department of Health autopsy determined the cause of death as blunt force trauma. FAA toxicology testing was negative for carbon monoxide, cyanide, and volatiles. Doxylamine was detected in the liver but not blood; ibuprofen was detected in blood.
Tests and Research
Structural examination showed the vertical stabilizer separated mostly intact, with forward spar fractured above attachment to horizontal stabilizer front spar, and rear spar fractured and twisted. The rudder was fractured spanwise below the center hinge, with counterweight separated. Horizontal stabilizer spars and elevators were deformed down and aft. Left wing fractures were consistent with downward separation. Control continuity was established for elevators and right aileron; left aileron control rod was fractured. Rudder cables were jammed. All fractures exhibited overstress separation with no pre-existing fractures.
Flutter analysis performed by Van's for the RV-8 and applied to the RV-7 (a derivative with wider cabin) concluded the airplane was free from flutter above the design envelope with control surface balance weights. Ground vibration tests accounted for variations. Electronic devices recovered included a GoPro camera with images from the accident flight. Based on terrain features, the airplane initially headed south, then the pilot rolled right to inverted and executed a split-S maneuver returning northbound. As the airplane nearly returned to wings level, the vertical stabilizer appeared missing. Between later photos, the airplane went from nearly wings-level to inverted with apparent substantial negative g load.
Weight and balance could not be accurately assessed due to debris distribution. An estimated calculation, assuming 42 gallons of fuel and occupant weight of 306 lbs, indicated the airplane was about 72 lbs above its maximum aerobatic gross weight of 1,600 lbs.