ERA23LA347

When the flight instructor initiated a takeoff roll, the engine rpm initially increased to 2,200, then decreased to 800, followed by flames emanating from the engine cowling. The flight instructor rejected the takeoff, secured the engine, and exited the airplane on the runway; however, the fire continued in the engine compartment until airport personnel were able to extinguish it. Postaccident examination of the engine compartment revealed that about a 25 to 30-in length of starter motor electrical lead was not clamped and had drooped down on top of the fuel primer line. Metal beads on top of the fuel primer line were consistent with chaffing and welding due to contact from the electrical lead. It is likely that arcing from the lead ignited fuel in the fuel primer line. The airplane had been operated for 73 hours during a 1-month period following its most recent 100-hr inspection. The electrical lead drooping down and resting on top of the fuel primer line was contrary to Federal Aviation Administration (FAA) and aircraft manufacturer maintenance instructions regarding proper routing and should have been identified and corrected during the most recent 100-hr inspection.

On July 27, 2023, about 1441 eastern daylight time, a Piper PA-28-180, N15417, was substantially damaged when it was involved in an accident near Knoxville, Tennessee. The flight instructor and student pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor reported that the accident flight was the student pilot’s first flight (discovery flight). The flight instructor added that the preflight inspection, engine start, taxi, and run-up were normal. He initiated a takeoff roll on runway 26 by letting the student pilot advance the throttle. The engine rpm initially increased to 2,200, then decreased to 800, followed by flames emanating from the engine cowling. The flight instructor rejected the takeoff, advanced the throttle lever, retracted the mixture level, and turned off all electrical equipment, including the master switch. He also instructed the student pilot to turn the magnetos and fuel selector to off, which he did. They then exited the airplane on the runway and called the fixed based operator for assistance. Examination of the engine compartment by a Federal Aviation Administration inspector revealed substantial damage to an engine mount tube. The inspector also noted that about a 25 to 30-in length of starter motor electrical lead was not clamped and had drooped down on top of the fuel primer line. He also observed metal “beads” on top of the fuel primer line, consistent with chaffing and welding due to contact from the electrical lead. Review of maintenance records revealed that the airplane had been operated for 73 hours during a 1-month period following its most recent 100-hr inspection. FAA Advisory Circular AC 43-13-1, Section 2 Fuel Systems, revealed: “…b Routing. Make sure that the line does not chafe against control cables, airframe structure etc., or come in contact with electrical wiring or conduit…In no case should wiring be supported by the fuel line…” Review of Piper Cherokee Service Manual, Table III-I Inspection Report, B. Engine Group, revealed: “…39. Inspect engine compartment wiring for condition (chafing, cracked insulation, general deterioration), security, proper routing, and correct installation…”