ERA23LA065

In preparation for the instructional flight, the flight instructor primed the engine with fuel several times and attempted to start it; each time the engine would get close to starting but would not run. On the fourth start attempt, he did not prime the engine and white smoke started to emanate from the engine compartment. The flight instructor then shut off the fuel valve and electrical equipment and then exited the airplane to investigate. He discharged a fire extinguisher into the air intake without effect. The smoke increased in intensity before a fire broke out and within minutes engulfed the engine compartment and cockpit area before eventually being extinguished by airport fire rescue. Postaccident examination of the airplane revealed electrical arcing damage to an alternator wire and surrounding structure. Pitting consistent with electrical arcing was discovered on the engine mounts and the alternator wire displayed features consistent with electrical arcing damage that was located near a fuel line. The clamp that affixed the wire was severely damaged and melted. Based on this information, the wire likely chafed over time until metal-to-metal contact was made as the wire was energized, which resulted in a fire that was fed by fuel from a nearby fuel line.

On November 18, 2022, about 0745 eastern standard time, a Piper PA28-181, N8129M, was substantially damaged when it was involved in an accident near Manassas, Virginia. The flight instructor and a student pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor and student were preparing for a flight at Manassas Regional Airport/Harry P. Davis Field (HEF), Manassas, Virginia. The flight instructor reported that he primed the engine with fuel several times and attempted to start the engine in the cold weather; the engine got close to starting but did not maintain power and stopped. He attempted another start with the same result. After waiting several minutes, he primed it once and attempted to start it again, but it shut off after about 4 seconds. During the fourth attempt, he did not use any primer, but white smoke started emanating from the engine compartment. He shut off the fuel valve and electrical equipment and then grabbed the fire extinguisher before exiting the airplane. The smoke continued to increase and a mechanic who was nearby told him to aim the fire extinguisher into the engine air intake and attempt to suppress any developing fire; he did so to no effect. The smoke continued to increase in severity followed quickly by fire emanating from the engine compartment. The fire increased in intensity and engulfed the front of the airplane in about 5 minutes before airport fire rescue services arrived and extinguished the fire. A Federal Aviation Administration (FAA) inspector examined the wreckage. The fire consumed the engine compartment and entire cockpit and cabin. There was additional thermal damage to the wings. Further examination revealed electrical arcing damage to the alternator wire. Electrical pitting was discovered on the engine mounts and the alternator wire displayed features consistent with electrical arcing. The clamp that affixed the wire was severely damaged and melted and appeared to be oversized. There was damage to the wire and clamp where they joined and was in close proximity to a fuel line. A review of maintenance records for the preceding 36 months did not yield any items associated with the alternator or wires.