HISTORY OF FLIGHTOn June 07, 2021, about 1420, a Vans RV-6A experimental airplane, N94PJ, was substantially damaged when it was involved in an accident in Porterville, California. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot departed from his home airport in Fresno, California about 1320 and landed at Porterville shortly thereafter. A witness at the airport observed the pilot and airplane before the accident. They stated that the pilot refueled the airplane with about 17.5 gallons at the self-serve fuel tanks located mid-field. A witness observed the pilot, positioned in the right seat, start the airplane after refueling. The start-up was abnormal and sounded as though it was a “hot start” with the engine rpm’s immediately accelerating to a near-maximum setting. The airplane then continued to the departure end of the runway and proceeded to takeoff. The airplane began to climb and the engine was making “popping” sounds while continuing left of centerline. The nose pitched down and the engine momentarily sounded normal as the airplane then climbed to about 300 ft above ground level (agl). The “popping sounds” continued and some witnesses observed that the engine then experienced a loss of power (see Figure 1 below). Figure 1: Visual of Witness Reports Video footage was obtained from a fixed security camera at the airport. A review of the footage revealed that the airplane made a hard right bank, with the wings near perpendicular to the ground.,. The witnesses further stated that the airplane then momentarily maneuvered to a wings-level attitude and then rolled left. The airplane then rapidly descended in a left-wing-low attitude nearly perpendicular to the terrain before impacting the ground and immediately erupted into flames. AIRCRAFT INFORMATIONThe two-seat, low-wing, fixed-gear experimental amateur-built airplane, serial number 23286, was completed in 2004. The pilot purchased the airplane on May 19, 2021. The fuel receipt from the last known fueling was the day of the accident at 1341. The invoice showed the pilot added 17.53 gallons of 100LL AvGas. The airplane was powered by a Superior XP-IO-360-B1CC2 engine and was equipped with a Catto two-bladed constant speed propeller. Partially burned maintenance logbooks were found at the accident site. It is unknown when the most recent maintenance was performed because the pages were burned. AIRPORT INFORMATIONThe two-seat, low-wing, fixed-gear experimental amateur-built airplane, serial number 23286, was completed in 2004. The pilot purchased the airplane on May 19, 2021. The fuel receipt from the last known fueling was the day of the accident at 1341. The invoice showed the pilot added 17.53 gallons of 100LL AvGas. The airplane was powered by a Superior XP-IO-360-B1CC2 engine and was equipped with a Catto two-bladed constant speed propeller. Partially burned maintenance logbooks were found at the accident site. It is unknown when the most recent maintenance was performed because the pages were burned. WRECKAGE AND IMPACT INFORMATIONThe accident site was located about 250 ft from the approach end of runway 12 on flat terrain composed of hard, dry dirt and short vegetation. The wreckage was found distributed over an approximate 40-ft distance with the nose pointed on a median magnetic bearing of about 350°. The fuselage and inboard sections of the wings had been consumed by fire. The first identified pieces of debris were fragments of red lens, consistent with the tip of the left wing contacting the ground at the beginning of the accident sequence. From the lens fragments was pieces of propeller blades and pieces of the skin (see Figure 2 below). Figure 2: Main Wreckage The fuselage came to rest upright and was partially consumed by fire, with only the outboard right wing and tail not thermally damaged. After collection and examination of the flight control system components, control continuity was established from the flight controls in the cockpit to the breaks in the system, which displayed evidence of tensile overload and from the breaks in the system to the flight control surfaces. The cockpit was consumed by fire and the gauges and switches were unreliable. The keys were found loose in the wreckage. An external examination of the engine revealed that the crankcase had fractures in numerous areas around the casing. There was no oil visible seeping around the engine, nor was the evidence of oil on the windscreen. Investigators were able to rotate the engine by exerting force on the remaining propeller blades. The airplane was equipped with a dual ignition system. A Light Plasma III electronic module provided ignition to the upper spark plugs and a Slick magneto was used for the lower spark plugs. The electronic modules found were partially burned and could not be tested. Disassembly of the magneto revealed the internal mechanisms were thermally destroyed. The spark plugs were removed revealing a No. 4 massive-electrode style plug exhibiting a fractured insulator at the electrode area. It is unknown if the cracked insulator led to a pre-ignition or detonation event since the piston dome had deposits similar to the other pistons. Investigators removed the cylinders, which revealed no evidence of foreign object ingestion or detonation. All valves were intact and the internal cylinder domes and piston crowns exhibited similar combustion deposits, with the No. 2 and No. 4 exhaust appearing to be more reddish in color, consistent with hot operation. The valves and guides were examined and no evidence of material transfer was visually apparent. The crankshaft, idler gear, and camshaft gears were all aligned with their respective marks aligning. The oil pump was disassembled revealing intact gears; the pump rotated freely. The crankshaft was intact and the connecting rods remained secured with a dark coloration consistent with thermal damage. The bearings were free of wear and no fretting was observed. The fuel selector handle was attached and found in the “OFF” position. The selector position plate was affixed to the structure and bent over on the handle. There was a divot in the plate metal consistent with the selector handle being in the “OFF” position at the time of impact. Continuity and functionality of the fuel system could not be ascertained due to the thermal damage incurred following the impact. TESTS AND RESEARCHThe ground track, ground speed, and altitude of the airplane were estimated based on a video recorded by an airport camera in a Video Study. When the airplane climbed to about 158 ft, the ground speed at that time was about 62 knots. This speed is above the stall speed of the Van’s RV-6A and near the typical takeoff speed of the airplane. The climb rate estimated during the first two analyzed seconds was about 1,500 ft per minute (fpm). The airplane continued climbing for about 8 seconds past, but its ground speed was decreasing. When the airplane reached its maximum agl altitude of about 240 ft, its ground speed was down to about 14 knots, well below the stall speed. Thereafter, the speed was increasing because the altitude was decreasing. The descent speed was increasing rapidly, reaching about 3,850 fpm at the time of ground impact.