Accident Overview
On April 11, 2023, at 1132 eastern standard time, an experimental amateur-built RV-12 airplane, registration N543GM, was destroyed when it struck an overpass and impacted terrain inverted near Climax, North Carolina. The left-seat commercial pilot was fatally injured and the right-seat commercial pilot sustained serious injuries. The flight was conducted under 14 CFR Part 91 as a test flight for Phase 1 flight testing.
History of Flight
According to the surviving right-seat pilot, the purpose of the accident flight was to perform aerodynamic stall testing. The airplane had 12 gallons of 93 octane automotive fuel on board. After a normal takeoff from runway 35, the airplane climbed to about 400 feet above ground level, at which point the engine rpm dropped and the engine lost partial power. The left-seat pilot made two left turns to fly southbound over US Highway 421, which ran parallel to the runway. Both fuel pumps were on, and the surviving pilot adjusted the mixture and throttle. The engine continued to produce partial power as they flew over the highway. An overpass bridge ahead, a stopped semi-truck under it, and multiple powerlines spanning the highway forced the pilots to attempt flying below the powerlines but above the overpass. During this maneuver, the airplane collided with the overpass and subsequently hit the ground inverted. A post-impact fire ignited, and motorists pulled the right-seat pilot, who was already partially outside the cockpit, away from the wreckage.
Witness Observations
Surveillance video from the airport showed the airplane back-taxiing after an initial takeoff where acceleration slowed and no rotation occurred. A second takeoff at 1131 was followed by a climb that lasted about 30 seconds before the airplane stopped climbing and entered an abrupt left turn. It then flew over the highway at treetop level. Multiple witnesses on the highway saw the airplane flying low. One witness reported seeing the airplane about 50 feet above ground level over northbound lanes, then crossing the median to fly over southbound lanes. Another witness observed a sharp turn where the wing tips were vertical before it struck the overpass; she could not recall engine noise or whether the propeller was turning. Photographs provided by the witness showed the airplane low over the highway about 500 feet from the overpass.
Aircraft Information
The airplane, an experimental amateur-built RV-12, had been issued a special airworthiness certificate on August 30, 2021, requiring 40 hours of Phase 1 flight testing within prescribed geographic areas. According to the airplane owner/builder, there were several-month gaps in engine operation between 2021 and 2023. A log showed 8.6 hours of ground and flight activity from October 2021 to August 2022, with only 3 flight hours logged in 2021. The right-seat pilot reported about 14 additional hours flown by the two pilots, bringing the total flight time to about 22 hours. The owner stated he used 87 octane automotive gasoline in the engine, which was a modified Honda Fit car engine (Viking Aircraft Engine Model 110). The pilot’s operating handbook specified that approved fuel types were 89 octane or higher automotive fuel with up to 10% ethanol, and that 100LL could be used when automotive fuel was not available. The Viking engine operating handbook stated to use 89 octane or higher and never lower-grade fuels, warning that lower octane could destroy the engine. The engine had been stored for over a year with about half a tank of automotive fuel, with an additive added for preservation. The owner performed an engine run-up in October 2022 without issues.
Wreckage and Impact
The airplane came to rest inverted in a compact area. A post-crash fire consumed significant portions of the fuselage, cockpit, and left wing. Flight control continuity was confirmed for rudder and elevator; aileron push-pull rods had multiple breaks consistent with impact and thermal damage. The engine exhibited extensive thermal damage but no evidence of catastrophic failure. The gear reduction box rotated freely. The oil filter was clean. Pistons and valves showed normal combustion signatures. The three-bladed composite propeller had all blades splintered from the hub. The Nos. 1 and 2 cylinder spark plugs had obliterated ground electrode tips and blackening, while the Nos. 3 and 4 plugs were blackened but intact. Bench testing showed that the Nos. 1 and 2 plugs lost continuous spark at pressures between 70 and 80 psi, while the other plugs functioned normally. No evidence was found that the airplane impacted the powerlines, but impact marks were found on the overpass railing.
Personnel Information
The surviving right-seat pilot had flown 6 hours in the airplane, and the left-seat pilot (pilot flying) had 8 hours. Both were commercial pilots. No further personnel details were provided in the source.