N543GM

HISTORY OF FLIGHTOn April 11, 2023, at 1132 eastern standard time, an experimental amateur-built RV-12 airplane, N543GM, was destroyed when it was involved in an accident near Climax, North Carolina. The commercial pilot seated in the left seat was fatally injured, and the commercial pilot in the right seat sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 test flight.

According to the surviving pilot, the accident airplane was undergoing Phase 1 flight testing. On the morning of the accident, he flew one solo flight and returned to the departure airport. Shortly after, the other pilot boarded the airplane for the accident flight, the purpose of which was to perform aerodynamic stall testing. The airplane had 12 gallons of fuel on board, which was 93 octane fuel the pilot purchased from a gas station near the departure airport.

The surviving pilot reported that the left-seat pilot was the pilot flying and the takeoff from runway 35 was normal. The airplane climbed to 400 ft above ground level, where the engine rpm dropped, the engine lost partial power, and the pilot made two left turns to fly southbound over the highway parallel to the runway (US Highway 421). While flying over the highway, both fuel pumps were on, and the surviving pilot reported that he was adjusting the mixture and throttle. The engine continued to produce partial power while they overflew the highway; however, an overpass bridge was located ahead of the airplane, along with a semi-truck that had stopped under the overpass. Additionally, multiple powerlines spanned across the highway.

The surviving pilot reported that he knew they would not be able to gain sufficient altitude to fly above the powerlines, nor fly under the overpass due to the semi-truck, so they attempted to fly below the powerlines, but above the overpass. During this maneuvering, the airplane collided with the overpass, and subsequently impacted terrain inverted. A post-impact fire ignited after the impact with terrain. Motorists pulled the right-seat pilot, who was already partially outside the cockpit, away from the wreckage area.

Review of surveillance video provided by the airport revealed that the airplane departed on the accident flight at 1127. The airplane accelerated down runway 35 and, shortly before reaching the runway midpoint, the acceleration slowed, and no rotation was observed. The airplane back-taxied to the start of runway 35 and a takeoff was observed at 1131.

The airplane climbed after takeoff, gained altitude for about 30 seconds, and then immediately stopped climbing and entered an abrupt left turn. The airplane turned left again and began flying over US Highway 421 southbound near treetop level. The airplane came in and out of camera view near treetop level as it paralleled the full length of runway 35, before exiting the camera view south of the airport.

Multiple witnesses on the highway reported observing the airplane flying low over the highway. One witness described that she first saw the airplane about 50 ft above ground level over the northbound lanes near the airport, then observed the airplane cross over the grass median to fly over the southbound lanes.

Another witness observed the airplane flying low over the southbound lanes. She observed the airplane enter a sharp turn and “tilt sideways” immediately before striking the overpass and stated that the “wing tips were straight up in the air.” She could not recall hearing engine noise, or whether the propeller was turning.

The witness provided three photographs from her position on the northbound lanes of the highway, which shows the airplane low over the highway about 500 ft from the overpass (see figure 1).

Figure 1 - Witness provided photographs of the airplane flying low over the highway about 500 ft from the overpass bridge.

Impact marks were observed on the overpass bridge railing. The airplane subsequently came to rest inverted just past the overpass on a hill next to the highway about .40 nautical mile south of the departure airport. About 40 ft past the overpass, multiple low-voltage powerlines spanned the entire distance across the highway, paralleling the overpass. There was no evidence the airplane impacted the lines.

Figure 2 below provides an overview of the estimated flight track of the airplane as reported by the surviving pilot, surveillance video, and witnesses. The total distance the airplane traveled over the highway, from abeam the north end of runway 35 to the overpass, was about 4,300 ft. US Highway 421 was a 4-lane highway with a sloping grass median that was about 60 ft wide. Photographs reviewed at the time of the accident and witness reports found that the traffic was not heavy in either direction.

Figure 2 - Overview of the airplane’s estimated flight track, witness location, and accident site. PERSONNEL INFORMATIONAccording to the surviving pilot, he had flown the airplane 6 hours, and the pilot seated in the left seat, who was the pilot flying, had 8 hours in the airplane. AIRCRAFT INFORMATIONAccording to Federal Aviation Administration (FAA) airworthiness records, the airplane was issued a special airworthiness certificate on August 30, 2021. The airworthiness certificate outlined multiple limitations during Phase 1 flight testing. One limitation required a total of 40 hours to be flown within certain prescribed geographic areas, which included the departure airport.

According to the airplane owner, who was also the builder of the airplane and was not onboard the airplane for the accident flight, there were several-month gaps in engine operation between 2021 and 2023. Review of an airplane log found entries denoting ground engine operation and flight activity from October 5, 2021, through August 27, 2022. A total of 8.6 hours was logged, and within those hours 3 hours were flight hours logged in 2021. According to the log and the owner, he did not fly the airplane in 2022 or 2023. The right-seat pilot reported that he and the other pilot flew about 14 hours in the airplane, which resulted in about 22 hours of total flight time for the airplane.

According to the owner, in March 2023, he and the right-seat pilot had an agreement to complete the remainder of the 40 hours required to complete Phase 1 flight testing.

The airplane owner reported that he recalled there being about 1/2 of a tank of fuel onboard the airplane for the more than a year that it did not fly. He recalled that he added an additive to the tank to help preserve the automotive gas. He recalled performing an engine run-up in October 2022 and did not experience any issues.

The airplane owner further reported that he used automotive gasoline with the engine. He reported specifically that he used 87 grade octane and that the engine was a small car engine from a Honda Fit, and he “felt comfortable” using the “lower grade” 87. He never used 100 low lead (100LL) aviation fuel with the airplane. The owner also reported that he never had any discussions with either accident pilot on what type of fuel they should use for the test flights.

Pilot’s Operating Handbook

The pilot’s operating handbook (POH) stated that the airplane’s aerodynamic stall speed with flaps extended was 41 knots and 45 knots with flaps retracted. The published landing distance was estimated to be 525 ft at maximum gross weight.

The fuel capacity was 19.8 gallons. According to the POH, approved fuel types were 89 octane or higher automotive fuel with 10% ethanol as a maximum. It further stated that 100LL could be used when automotive fuel was not available.

Engine

The engine was a 110-horsepower fuel-injected Viking Aircraft Engine, Model 110. Viking Aircraft Engines produce experimental aircraft engines from originally manufactured Honda Fit car engines.

The Viking Aircraft Engines operating handbook, Chapter 5, Engine Operation, stated to use only 100LL when 90 or higher octane fuel is not available. The handbook further stated:

FUEL: These are high compression, high performance engines! Use 89 or higher octane fuel. Up to 10% ethanol is permitted. Never run lower grade fuels! It can and will destroy your engine.

The manual further stated, “the engine should never be left with auto type fuel in the fuel rail or fuel pumps for longer than 3 month intervals. The approved storage fuel is 100LL aviation fuel. 100LL was used to test run the engine at the factory, prior to shipping.”

According to a representative with Viking Aircraft Engines, the normal compression for a Viking 110 engine was 180 to 210 psi. The spark plugs to be used were NGK brand Iridium Spark Plugs. The representative further reported that the engine may exhibit detonation should 87 octane be used.

Maintenance Records

Review of the airframe logbook revealed that the most recent condition inspection was recorded on September 1, 2022; however, the endorsement was not signed.

The engine and propeller logbook were not located; however, they were later shipped by the airplane owner to the NTSB for review. The engine logbook contained one entry, dated July 8, 2021, denoting that the engine was inspected in accordance with 14 CFR Part 43 Appendix D. The inspection was signed by the airplane owner/builder. There were no other entries noted in the engine logbook.

The propeller logbook contained one entry, dated July 8, 2021, denoting that the propeller was inspected in accordance with Part 43 Appendix D. The inspection was signed by the airplane owner/builder. There were no other entries noted in the propeller logbook. There were no entries to indicate that the spark plugs had been inspected or replaced since 2021. AIRPORT INFORMATIONAccording to Federal Aviation Administration (FAA) airworthiness records, the airplane was issued a special airworthiness certificate on August 30, 2021. The airworthiness certificate outlined multiple limitations during Phase 1 flight testing. One limitation required a tot...