Accident Overview
On September 10, 2022, at about 1530 central daylight time, a Luscombe 8A airplane, registration 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 personal flight under Title 14 Code of Federal Regulations Part 91.
Flight Sequence
According to the pilot, who is also the mechanic, he had not flown the airplane for some time. He performed a preflight inspection with no anomalies noted. The fuel tank was full, the fuel vent was checked, and the tank was sumped. The pilot started the airplane, taxied to the north end of the runway, and performed a run-up procedure with no anomalies. During the run-up, both magnetos, carburetor heat, and the fuel system were checked.
The airplane took off, and the pilot noticed the engine was performing very well. The airplane climbed to about 400 ft above ground level, and the pilot initiated a left turn. About halfway through the turn, the engine sustained a total loss of power. The pilot reported no cough or sputter; the engine just died. He attempted to troubleshoot the power loss but could not restore power. He maneuvered for a forced landing to an open field, then realized the airplane would not reach it and headed for a wooded area. The airplane came to rest in trees. The pilot egressed without further incident.
Postaccident Examination
The pilot reported that at the time of the power loss, the engine was at full power. He assessed that perhaps a short occurred in the ignition switch, resulting 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 wire 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. Readings varied from open to closed, with varied ohm (resistance) readings. The ignition switch was 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 switch, particularly on the contacts. The contacts were cleaned, the switch was reassembled, and the P-leads were checked again. The varied ohm readings were no longer present, and the switch appeared to function normally with the multimeter.
No issues were noted with the magnetos, ignition harness, or spark plugs. The magnetos are electrically independent except at the ignition switch, and both produced spark when tested.
Ignition Switch Condition
The pilot reported that the ignition switch was not originally installed by the manufacturer but had been in the airplane for over 40 years. He had no previous issues with it, it was never overhauled, and he was not aware of an overhaul schedule. According to the manufacturer, maintenance requirements for the ignition switch are based on condition.
The Federal Aviation Administration has published the Aviation Maintenance Technician Handbook – Powerplant Volume 1, which defines carbon tracking for an ignition system. It states that flashover can lead to carbon tracking, which appears as a fine pencil-like line across which flashover occurs. The carbon trail results from electric sparks burning dirt particles containing hydrocarbon materials; water in the hydrocarbon evaporates during flashover, leaving carbon to form a conducting path. When moisture is no longer present, the spark continues to follow the carbon track to ground.