N25144Luscombe 8A · 1939

On September 10, 2022, about 1530 central daylight time, a Luscombe 8A airplane, N25144, sustained substantial damage when it was involved in an accident near Kingsbury, Texas. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot, who is also the mechanic, he had not flown the airplane “for some time.” The pilot performed the preflight inspection with no anomalies noted. The fuel tank was full of fuel, the fuel vent was checked, and he “sumped” the fuel tank. The pilot started the airplane, taxied to the north end of the runway, and performed the run-up procedure with no anomalies noted. As part of the run-up procedure, both magnetos, the carburetor heat, and the fuel system were all checked.

The airplane took off from the runway and the pilot noticed the engine was “performing very well.” The airplane climbed to about 400 ft agl and the pilot initiated a left turn. About halfway through the turn, the engine sustained a total loss of engine power. The pilot reported there was “no cough” or “no sputter” and the engine “just died.” The pilot attempted to troubleshoot the loss of engine power to no avail. The pilot maneuvered the airplane for a forced landing to an open field. The pilot then realized the airplane would not make the open field and maneuvered the airplane for a wooded area. The airplane came to rest in trees. The pilot was able to egress from the airplane without further incident.

The pilot reported that at the time of the loss of engine power the engine was operating at full power. The pilot assessed that perhaps a short occurred in the ignition switch, that resulted in the loss of engine power. The airplane sustained substantial damage to the fuselage, both wings, and the empennage.

A postaccident examination revealed that the airplane was not equipped with a starter. The ground to the key-operated ignition switch (Bendix, part number 10-357290-1A) was found disconnected. The pilot surmised that he may have pulled off the ground lead when he removed the ignition switch from the panel.

The p-leads for the left, right, and both positions were checked with a multimeter. The readings for the p-leads varied from open to closed, along with varied ohm, or resistance, readings. The ignition switch was then disassembled, and carbon tracking, a buildup of carbon that interfered with electrical continuity, was observed. A substantial amount of carbon tracking was found inside the ignition switch, particularly on the contacts. The contacts in the ignition switch were then cleaned and the ignition switch was reassembled. The p-leads were checked again with a multimeter, the varied ohm readings were no longer present, and the ignition switch appeared to function normally with the multimeter.

There were no issues noted with the magnetos, the ignition harness, and the spark plugs. The magnetos are electrically independent, except at the ignition switch, and both magnetos produced spark when checked.

The pilot reported that while the ignition switch was not originally installed by the manufacturer, but it had been in the airplane for over 40 years. He additionally reported that he had no previous issues with the ignition switch, the ignition switch was never overhauled, nor was he aware of an overhaul schedule for the ignition switch. According to the manufacturer, the maintenance requirements for the ignition switch are based on condition.

The Federal Aviation Administration has published the Aviation Maintenance Technician Handbook – Powerplant Volume 1. This document defines carbon tracking for an ignition system and states in part:

Flashover can lead to carbon tracking, which appears as a fine pencil-like line on the unit across which flashover occurs. The carbon trail results from the electric spark burning dirt particles that contain hydrocarbon materials. The water in the hydrocarbon material is evaporated during flashover, leaving carbon to form a conducting path for current. When moisture is no longer present, the spark continues to follow the carbon track to the ground.