History of Flight
On December 16, 2023, about 1150 Pacific standard time, an experimental amateur-built Vans RV-8 airplane, N6948L, was substantially damaged when it was involved in an accident near Corona, California. The pilot and passenger were fatally injured. The airplane was operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
The pilot had flown the airplane to Corona Municipal Airport (AJO) on November 13, 2023, to have it painted. The accident flight was the first flight after painting. The paint shop required the pilot to disassemble and reassemble the airplane because it was experimental amateur-built. Prior to flying to AJO, the pilot had drained and repaired the left fuel tank to address fuel leaks.
Witnesses reported hearing the airplane during takeoff and noted that the engine sounded like it was “missing” and producing partial power.
Airport security camera footage showed that at 1149:23, the airplane was midway down runway 7 with all landing gear on the surface. The airplane continued down the runway and rotated about 4 seconds later. Video analysis determined the speed at rotation was 71 knots, and a sound spectrum analysis indicated engine rpm was about 2,500. The airplane climbed slightly, passing over a berm at the airport’s perimeter, reaching a maximum altitude of about 95 feet above the runway. Estimated ground speed was 58 knots. The airplane then descended and made a left turn, disappearing from the camera’s field of view.
Aircraft Information
A review of maintenance logbooks found no evidence of maintenance after the airplane received a Special Airworthiness Certificate on May 11, 2023. The pilot purchased the airplane kit in April 2022. The tachometer was consumed by fire.
Invoices showed the pilot had recently purchased two-part sealant Flamemaster CS-3204 B2 and Pro Seal Fuel Tank Sealant PS 890 (part A & B), and on January 31, 2023, a quart of Bill Hirsch alcohol-resistant gas tank sealer. The sealer manufacturer stated that if the tank is not dry or has foreign matter, the sealer may not adhere and could come loose, potentially entering the fuel system and blocking the fuel pump.
The pilot/builder deviated slightly from the original RV-8 fuel plan design and used several automotive parts. The left fuel tank was likely empty and the right tank likely contained about 10 gallons, but quantities could not be verified due to severe fire damage. The fuel source at AJO indicated the pilot did not purchase fuel at the airport.
Wreckage and Impact
The accident site was in soft dirt about 3,650 feet from the departure end of runway 7. The airplane came to rest upright under a tree, and surrounding terrain (5–10 feet) was burned. The wreckage was consumed by postimpact fire; most of the fuselage, wings, and skin panels were charred, with areas of ash and resolidified puddled aluminum. The fuselage was on a heading of about 55°. The entire airplane was at the accident site except portions of wheel pants and outboard left wing found in the debris path.
First identified points of contact were on the west side of a flat paved road at the west end of the debris field. A divot in a concrete wall with paint transfers and paint chips was consistent with the left wing tip. About 85 inches south of the divot was a black smudge on the road surface, continuing toward the wreckage and making a left track. Grooves and indentations on the road made a parallel right track. About 12 feet from the road’s western edge were two 18-inch gouges in concrete perpendicular to and between the parallel tracks, consistent with propeller slashes. The witness marks were consistent with the left wing impacting first, followed by the left wheel and then the right wheel.
Postaccident airframe examination established partial control continuity. Control cables were continuous to molten bellcranks and airframe portions. The cockpit was completely thermally consumed. The canopy appeared in the unlocked and open position. Main landing gear remained with the airframe, folded aft and under the wings. Left and right wheel rotors were shaved down with flat areas, consistent with sliding against pavement.
Engine examination revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. The crankshaft rotated freely by hand in both directions; thumb compression was observed on all four cylinders. The complete valvetrain operated properly. Normal lift action was observed at each rocker assembly, and clean, uncontaminated oil was present in all rocker box areas. Mechanical continuity was confirmed throughout rotating, reciprocating, valvetrain, and accessory sections. Combustion chambers examined via borescope showed no foreign object ingestion or detonation. All valves were intact with no valve-to-piston contact. Gas path and combustion signatures were consistent with normal operation.
Fuel system examination revealed substantial thermal damage; fuel tanks were consumed. Fuel lines from tanks to selector were looped before attaching to valve inlet fittings. The fuel line from selector valve outlet to filter was kinked at a loop bottom; it could not be determined if crushing was impact-related. Trace amounts of liquid from fuel selector valve tested positive for water, consistent with fire suppression. Disassembly revealed white material on inner surfaces of fittings. The 40-micron fuel filter outlet fitting was loose; the entire fitting assembly could be moved in and out. The electric boost pump contained solid white, glossy material between two curved plate magnets, with a groove consistent with molded and melted plastic. The 10-micron cylindrical pleated filter and firewall elbow fittings contained tan and bubbled material; hard, shiny, off-white, bubbled material was in filter housing and between pleats. Engine-driven fuel pump had hard, glossy white material adhered inside both chambers; water flow tests showed slow dripping through check valves, with no appreciable flow to outlet chamber. The fuel flow transducer was not mounted; surrounding lines unsecured. Disassembly revealed white material adhered internally and pooled in fittings, with the internal wheel partially embedded and immovable. The fuel injection servo filter fitting had hard white material filling and protruding from the screen; interior of fitting was obstructed.
Tests and Research
The NTSB Materials Laboratory analyzed specimens from fuel system components. Samples from fuel selector matched polyimide or polyacrylic polymers; electric fuel pump sample was consistent with nylon-based material. Samples from firewall elbow fitting, 10-micron filter screen and housing, engine-driven fuel pump, fuel flow transducer, and fuel injector servo filter were consistent with polyvinyl chloride or polyvinyl acetate-based polymers. The 10-micron filter screen displayed a composite profile.
Thermal testing of white material from the engine-driven fuel pump showed that heating to 100°C caused softening and tackiness; continued heating darkened the material; upon cooling, it returned to a hardened state, characteristic of thermoplastic polymers and inconsistent with thermoset or chemically cured materials.
Comparative analysis against materials reportedly used in the build (polysulfide-based sealants, Bill Hirsch alcohol-resistant tank sealer, epoxy primer, polyurethane topcoat) showed fuel system deposits inconsistent with polysulfide, epoxy, or polyurethane. The Bill Hirsch sealer (containing VMCH resin) displayed chemical compatibility with deposits found in firewall elbow, 10-micron filter screen and housing, engine-driven fuel pump, fuel flow transducer, and fuel injector servo filter.