History of Flight
On June 7, 2021, at approximately 1420, a Vans RV-6A experimental airplane, registration N94PJ, was substantially damaged during an accident in Porterville, California. The pilot sustained fatal injuries. The flight was operated as a personal flight under Title 14 Code of Federal Regulations Part 91. The pilot had 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. The pilot refueled the airplane with approximately 17.5 gallons of fuel at the self-serve fuel tanks located mid-field. After refueling, the pilot, positioned in the right seat, started the engine. The start-up was abnormal, sounding like a “hot start” with the engine rpm immediately accelerating to near-maximum. The airplane then taxied to the departure end of the runway and took off. During the initial climb, the engine emitted “popping” sounds, and the airplane continued left of the runway centerline. The nose pitched down, and the engine momentarily sounded normal as the airplane climbed to about 300 ft above ground level. The popping sounds persisted, and some witnesses observed a subsequent loss of engine power.
Video footage from a fixed security camera at the airport showed the airplane making a hard right bank with wings nearly perpendicular to the ground. The airplane then momentarily leveled its wings before rolling left. It rapidly descended in a left-wing-low attitude, nearly perpendicular to the terrain, struck the ground, and immediately erupted in flames.
Aircraft Information
The 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 last known fueling occurred on the day of the accident at 1341, with an invoice showing the addition of 17.53 gallons of 100LL AvGas. The airplane was powered by a Superior XP-IO-360-B1CC2 engine and equipped with a Catto two-bladed constant speed propeller. Partially burned maintenance logbooks were found at the accident site; it was unknown when the most recent maintenance was performed due to fire damage.
Wreckage and Impact Information
The accident site was located approximately 250 ft from the approach end of runway 12 on flat terrain composed of hard, dry dirt and short vegetation. The wreckage was 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 were consumed by fire. The first identified pieces of debris were fragments of red lens, consistent with the left wing tip contacting the ground at the beginning of the accident sequence. Adjacent were pieces of propeller blades and skin.
The fuselage came to rest upright and was partially consumed by fire, with only the outboard right wing and tail undamaged by heat. Examination of the flight control system revealed continuity from the cockpit controls to breaks in the system, which showed evidence of tensile overload, and from the breaks to the control surfaces. The cockpit was fire-damaged, making gauges and switches unreliable; keys were found loose in the wreckage.
The engine crankcase exhibited fractures in numerous areas. No oil was visible seeping from the engine or on the windscreen. Investigators could rotate the engine by exerting force on the remaining propeller blades. The airplane had a dual ignition system: a Light Plasma III electronic module for the upper spark plugs and a Slick magneto for the lower plugs. The electronic modules were partially burned and could not be tested; the magneto’s internal mechanisms were thermally destroyed. One spark plug (No. 4) had a fractured insulator at the electrode area, but it was unknown if this caused pre-ignition or detonation, as piston dome deposits were similar to others. Cylinders showed no evidence of foreign object ingestion or detonation. All valves were intact. Cylinder domes and piston crowns had similar combustion deposits, except the No. 2 and No. 4 exhaust valves appeared more reddish, consistent with hot operation. The crankshaft, idler gear, and camshaft gears were aligned. The oil pump rotated freely with intact gears. The crankshaft was intact, and connecting rods had dark coloration consistent with thermal damage. Bearings showed no wear or fretting. The fuel selector handle was in the “OFF” position, with a divot in the selector plate consistent with that position at impact. Fuel system continuity and functionality could not be determined due to thermal damage.
Tests and Research
A video study used airport camera footage to estimate ground track, ground speed, and altitude. At about 158 ft altitude, the ground speed was approximately 62 knots, above the stall speed and near typical takeoff speed. The climb rate during the first two seconds was about 1,500 ft per minute. The airplane continued climbing for about 8 seconds but with decreasing ground speed. At the maximum altitude of about 240 ft, the ground speed was about 14 knots, well below stall speed. Thereafter, altitude decreased and speed increased, with a descent rate reaching about 3,850 ft per minute at impact.