N74MS

HISTORY OF FLIGHTOn June 15, 2021, about 1031 eastern daylight time, an experimental amateur-built Vans RV-6A airplane, N74MS, was substantially damaged when it was involved in an accident in Buckingham, Pennsylvania. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

About 0817 on the morning of the accident, the pilot departed Doylestown Airport (DYL), Doylestown, Pennsylvania, for Sky Manor Airport (N40), Pittstown, New Jersey, arriving about 0827. About 30 minutes later, the pilot departed N40 for South Jersey Regional Airport, VAY, Mount Holly, New Jersey, arriving there about 0913. About 1 hour later, the pilot departed VAY to return to DYL.

About 1020, the pilot transmitted over the common traffic advisory frequency for DYL that he had an emergency and was making a straight-in landing to runway 5. About 1021, the pilot transmitted that the airplane had an in-flight fire, would be landing on runway 5, and was inbound, to DYL. The pilot made no further intelligible transmissions.

According to witnesses, the airplane was flying in a northwest direction just before the accident. The engine sounded rough and sputtered, and then a “pop” sound was heard. The airplane appeared to be on fire with trailing smoke. The airplane then appeared to bank right and left and then appeared to follow a flightpath toward DYL while losing altitude quickly. The airplane was later observed striking the tops of trees, which was followed by the sound of impact. Flames were observed emanating from the airplane.

Review of video camera footage from a home security system indicated that a fire was present on the airplane near the engine and that smoke, which was bluegray in color, was trailing from the airplane. Review of another video from a home security camera system indicated that the airplane struck a large tree and that a fire around the engine was present before ground impact. A photograph taken by the Township of Buckingham Fire Marshall after the accident also showed that the area near the engine was on fire. PERSONNEL INFORMATIONAccording to Federal Aviation Administration (FAA) records, in addition to the pilot’s airmen certifications, he held a mechanic certificate with ratings for airframe and powerplant, and a repairman experimental aircraft builder certificate with an inspection certificate for the Vans RV-6A. The pilot also held type ratings on the B757, B-767, DC-6, DC-7, DC-9, and L-1011. The pilot reported, at the time of his most recent FAA third-class medical certificate, that he had a total of 12,225 hours of flight experience. AIRCRAFT INFORMATIONThe RV-6A was a two-seat, single-engine, low-wing airplane that was sold in kit form. According to FAA and airplane maintenance records, the airplane’s experimental airworthiness certificate was issued in 2008. The airplane's most recent condition inspection was completed by the pilot on September 21, 2020. At the time of the inspection, the airplane had accrued a total of about 484 hours.

A review of the National Transportation Safety Board’s (NTSB) accident database indicated that the engine in the airplane had been involved in a previous accident on August 8, 1998, in Bainbridge, Georgia (NTSB case no. ATL98LA108); at that time, the engine was installed in an experimental amateur-built Vans RV-6, N245DF. During the 1998 accident, the pilot was seriously injured, and the airplane was substantially damaged.

Review of maintenance records indicated that the engine was removed from the wreckage of N245DF on November 6, 1999. The maintenance records also indicated that an “engine inspection” was conducted due to a “propeller strike” and that the crankshaft, bearings, gear bolt, rod bolts, fuel pump, and the No.1 cylinder stud and rings were replaced. The records further stated that the vacuum pump was rebuilt and that the engine case and camshaft were inspected, with the ferrous parts undergoing non-destructive testing (magnafluxed). AIRPORT INFORMATIONThe RV-6A was a two-seat, single-engine, low-wing airplane that was sold in kit form. According to FAA and airplane maintenance records, the airplane’s experimental airworthiness certificate was issued in 2008. The airplane's most recent condition inspection was completed by the pilot on September 21, 2020. At the time of the inspection, the airplane had accrued a total of about 484 hours.

A review of the National Transportation Safety Board’s (NTSB) accident database indicated that the engine in the airplane had been involved in a previous accident on August 8, 1998, in Bainbridge, Georgia (NTSB case no. ATL98LA108); at that time, the engine was installed in an experimental amateur-built Vans RV-6, N245DF. During the 1998 accident, the pilot was seriously injured, and the airplane was substantially damaged.

Review of maintenance records indicated that the engine was removed from the wreckage of N245DF on November 6, 1999. The maintenance records also indicated that an “engine inspection” was conducted due to a “propeller strike” and that the crankshaft, bearings, gear bolt, rod bolts, fuel pump, and the No.1 cylinder stud and rings were replaced. The records further stated that the vacuum pump was rebuilt and that the engine case and camshaft were inspected, with the ferrous parts undergoing non-destructive testing (magnafluxed). WRECKAGE AND IMPACT INFORMATIONExamination of the accident site revealed that the airplane came to rest upright in a field on a 148° magnetic heading and about 0.5 nautical miles from runway 5. The airplane struck a tree that was about 50 ft above ground level; impacted, in a nose-down attitude, a tree limb that was about 36 ft above ground level; and pivoted to an upright position before coming to rest on top of a standpipe-mounted sprinkler head, which had vertically punctured and traveled through the right wing.

The wing flaps and ailerons remained attached to their respective wings, but the left aileron displayed bending and impact damage. The vertical stabilizer, rudder, horizontal stabilizers, and elevators also remained attached, but the left stabilizer and elevator displayed impact damage and wrinkling. Control continuity was established for pitch, roll, and yaw. Most of the instrument panel had been consumed by fire, and the forward portion of the cabin back to the front of both seats, had been exposed to the fire, with portions of the right seat displaying fire damage on the upper surface of the bottom seat cushion. The canopy displayed thermal, and impact damage, and was almost completely separated from the fuselage. The exterior of the fuselage and wings also displayed sooting, on the sides and top surfaces, along with more delineated areas which displayed heavy thermal and fire damage toward the front of the airplane, both near, and adjacent to the firewall, and on the sides and bottom of the fuselage

Examination of the propeller and engine revealed that the propeller remained attached to the crankshaft flange and that the engine remained attached to the engine mounts. The propeller displayed minimal damage, and the spinner displayed crush and compression damage primarily on one side. The propeller governor also remained attached along with the governor oil line, which had no oil. The governor could not be rotated by hand, and the gasket installed did not have an oil screen.

The engine was damaged by fire. A crack was observed in the crankcase above the No.1 cylinder, and a large hole appeared in the crankcase above the No. 4 cylinder. The No. 4 connecting rod was separated from the connecting rod cap. The large end of the connecting rod was laying against the camshaft, and the tappets for the No. 4 cylinder were exposed. A borescope inspection of the cylinders noted no abnormalities. A portion of the cap of the dislocated connecting rod was found in the crankcase below the crankshaft.

The carburetor remained attached to the bottom of the engine with the mixture and throttle cables attached. The carburetor displayed minimal impact damage but displayed signs of thermal damage. The fuel inlet screen was found to be contaminated in a manner consistent with thermal exposure, and the floats in the unit were melted. The fuel pump remained attached to the accessory housing but was destroyed by fire. The remaining part of the fuel pump was removed and actuated by hand.

The magneto and the electronic ignition system on the accessory pad were both thermally damaged. The spark plugs remained installed in their cylinder heads with minor thermal signatures noted. The ignition harness was damaged due to impact and fire.

The oil suction screen remained safety-wired into the oil sump. The suction screen contained ferrous and nonferrous metal debris. The oil filter remained attached to the accessory housing but displayed thermal damage. The oil pump displayed thermal damage and remained safety wired in place. The torque on the oil pump body nuts appeared loose. The oil pump body and gears displayed rotational scoring, and a small amount of metal was found in the pump. The oil sump contained ferrous and nonferrous metal, and portions of the connecting rod cap material and connecting rod bolts from the No. 4 connecting rod were present. The oil quick drain was not seating properly, allowing fluid to exit the sump.

The crankshaft was rotated, and thumb compression and valvetrain continuity were established on cylinders Nos. 1, 2, and 3. Compression on the No. 4 cylinder could not be established because of the damage to the connecting rod and valvetrain in that area. The crankshaft displayed damage and heat signatures on the No. 4 connecting rod journal, and a portion of the connecting rod bearing was melted to the crankshaft journal. The faces of the No. 3 exhaust tappet and both tappets for the No. 4 cylinder were fractured.

Oil passages in the crankshaft and crankcase were checked with compressed air for any ...