N307AB

HISTORY OF FLIGHTOn December 10, 2015, about 1347 mountain standard time, an experimental amateur built, RV-7 airplane, N307AB, experienced an in-flight break up and then 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 was being operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions existed near the accident site about the time of the accident, and no flight plan had been filed. The local flight departed from an unknown airport at an undetermined time.

Several witnesses located near the accident site stated that they heard the airplane's engine and that it sounded like it was making power changes. The witnesses added that they saw airplane debris floating in the air. One witness stated that the engine was running during the entire descent and that he also observed the airplane spiraling and descending in a cork-screw type maneuver. Another witness reported seeing the airplane inverted at a low altitude just before impact. PERSONNEL INFORMATIONThe pilot, held an airline transport pilot certificate with airplane multi-engine land, single-engine land, instrument, and instructor single-engine land ratings. The pilot was issued a first-class Federal Aviation Administration airman medical certificate on October 22, 2015, with the limitation that he must have glasses available for near vision.The pilot reported on his most recent medical certificate application that he had accumulated 17,359 total flight hours, 403 of which were accumulated in the previous 180 days. AIRCRAFT INFORMATIONThe two-seat, low-wing, fixed-gear airplane, was assembled in 2011, and it was 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.The engine was 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 airplane's kit manufacturer listed the maximum load factor as +6 g, the minimum load factor as -3 g, and the never exceed speed (VNE) as 230 mph in Section 15 of the RV-7/7A Construction Manual. Additionally, the kit manufacturer listed a maximum aerobatic gross weight of 1,600 lbs in Section 14 of the Construction Manual. METEOROLOGICAL INFORMATIONThe 1355 recorded weather observation at Saint George Regional Airport, Saint George, Utah, located about 12 miles west-southwest from the accident site, reported calm wind, visibility 10 statute miles, clear skies, temperature 12° C, dew point -2° C, and an altimeter setting of 29.87 inches of mercury.

The accident site was located between a cold front to the northwest and a high-pressure area to the southwest, in an area of strong-pressure gradient. A model sounding, which included a wind profile, for the area over the accident site about the time of the accident estimated that the surface horizontal wind speed was 220° at 8 knots, with winds increasing in speed with height and veering to the west. The mean 0-to-18,000 ft mean sea level (msl) winds were from 250° at 52 knots. The model supported light-to-moderate clear air turbulence from 6,400 through 8,000 ft msl, and mountain wave development from 10,000 to 12,000 ft msl.

Pilot reports noted evidence of mountain wave activity in the region but with moderate-to-severe turbulence near the accident site, at 6,500 ft msl, consistent with the model sounding. An AIRMET for moderate turbulence below 18,000 ft was active over the accident site at the accident time. No SIGMET was active for the accident site at the accident time. AIRPORT INFORMATIONThe two-seat, low-wing, fixed-gear airplane, was assembled in 2011, and it was 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.The engine was 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 airplane's kit manufacturer listed the maximum load factor as +6 g, the minimum load factor as -3 g, and the never exceed speed (VNE) as 230 mph in Section 15 of the RV-7/7A Construction Manual. Additionally, the kit manufacturer listed a maximum aerobatic gross weight of 1,600 lbs in Section 14 of the Construction Manual. WRECKAGE AND IMPACT INFORMATIONThe airplane wreckage was located about 4.2 miles southwest of Hurricane, Utah, on flat sagebrush-covered terrain on top of a mesa. The debris path was about 1,460 ft long and 450 ft wide. All major components of the airplane were located in the debris path.

The main airplane wreckage was located almost at the northern extent of the debris field and included the fuselage, engine, right wing, half of the left wing, a majority of the left and right elevators, and the lower half of the rudder. The vertical stabilizer with the upper half of the rudder attached was located at the southern extent of the debris field, about 1,420 ft south-southwest of the main wreckage. The left and right horizontal stabilizers were located about 850 ft and 790 ft, respectively, south of the main wreckage. The left aileron was located about 430 ft south-southwest of the main wreckage, and the left outboard wing was located about 320 ft south-southwest of the main wreckage.

The main wreckage was found inverted. There were no noticeable ground scars leading up to the wreckage. The fuselage was intact, but the upper half was crushed. The canopy frame was separated from the airframe and located about 55 ft northeast of the main wreckage. Most of the acrylic canopy was fractured from the frame and found in many pieces in the debris field. The engine remained attached to the fuselage. One of the composite propeller blades was fractured from the hub and the other blade was missing the tip portion. Debris consistent with propeller material was found around the main wreckage. The examination of the engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The main landing gear remained attached to the lower fuselage, and there was some deformation at the attachment points.

The entire right wing remained attached to the fuselage with the flap and aileron attached. The right flap was in the "up" position. The outboard half of the right wing was deformed downward about 15º to 20º at the flap/aileron junction, located about 57 inches outboard of the wing attachment point. The upper and lower wing skins were buckled around the area where the wing was deformed downward. The right fiberglass wingtip remained attached to the wing but was splayed open at the trailing edge.

The inboard half of the left wing remained attached to the fuselage with the flap attached. The left flap was in the "up" position. The outboard half of the left wing had separated at the flap/aileron junction located about 57 inches outboard of the wing attachment point. The main spar fractured at the location where the upper and lower spar caps undergo a net section decrease from inboard to outboard. The outboard half of the left wing was mostly intact with minimal damage noted. MEDICAL AND PATHOLOGICAL INFORMATIONThe Utah Department of Health, Office of the Medical Examiner, conducted an autopsy on the pilot. The medical examiner determined that the cause of death was "blunt force trauma."

The Federal Aviation Administration's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological testing of specimens from the pilot. Test results were negative for carbon monoxide, cyanide, and volatiles. The testing detected doxylamine in the liver but not in the blood and ibuprofen in the blood.

Doxylamine is an over-the-counter antihistamine medication that can be used in combination with decongestants and other medications to relieve sneezing, runny nose, and nasal congestion caused by the common cold. It can be sedating. Ibuprofen is used to reduce fever and to relieve minor aches and pains from headaches, muscle aches, arthritis, the common cold and other such ailments. TESTS AND RESEARCHStructures Examination

The vertical stabilizer separated mostly intact from the airplane during the accident sequence and had the upper portion of the rudder attached. The forward spar was fractured just above its attachment to the horizontal stabilizer front spar. The rear spar was fractured and twisted just above the stabilizer shelf, consistent with the vertical stabilizer separating leading edge left. Most of the upper half of the rudder remained attached at the upper and center hinge points. The lower half remained attached to the empennage. The rudder trailing edge was splayed open, and the trailing edge strip remained attached to the left rudder skin on both halves. There was evidence of sealant between the rudder skins and trailing edge strip. The rudder was fractured spanwise just below the center hinge. The rudder counterweight was separated from the upper end of the rudder just above the upper skin stiffeners (see figure).

Figure. Vertical stabilizer and attached rudder.

The center portion of the horizontal stabilizer forward spar, most of the horizontal stabilizer rear spar, and most of the left and right elevators remained attached to the fuselage. The horizontal stabilizer forward and rear spars were deformed down and aft. The elevators were deformed down and aft matching the spar deformation. The left and right horizontal stabilizers were found in the debris field. There was buckling damage on the lower skin of both horizontal stabilizers consistent with the stabilizers separating downward.

Examination of the inboard and outboard left wing s...