What happened
On 10 April 2019, a Colomban MC-3li Luciole, registration G-CIBJ, was involved in an accident at a farm strip in Thankerton, South Lanarkshire. Following a routine local flight, the pilot began taxiing the aircraft toward the hangar. The taxi route required several sharp turns. During a left turn, the pilot applied full left rudder pedal and noticed a physical restriction. Shortly after this movement, smoke began to fill the cockpit. The pilot evacuated the aircraft immediately; however, because the aircraft had not yet come to a complete stop and the engine and fuel systems remained active, a fire broke out. The fire destroyed the aircraft, though the pilot escaped without any injuries.
The investigation
The investigation focused on the aircraft's electrical and fuel systems. The cockpit of this single-seat, ultra-lightweight aircraft features a compact footwell where the battery is located on the left side, with the starter solenoid mounted on the engine bulkhead. The fuel supply pipes run along the right side of the cockpit and pass through the engine bulkhead directly beneath the starter solenoid. At the time of the accident, the rudder pedals had been adjusted to their most forward position.
Investigators examined the electrical components and found evidence of heat damage on the engine bulkhead near the solenoid. It was determined that the metal rudder pedal had made contact with the starter solenoid's terminals. While the aircraft's construction plans require these terminals to be perfectly isolated, the investigation found that the terminals on G-CIBJ were uninsulated. This contact created an electrical short circuit to the earth, causing the battery to discharge rapidly and the electrical system to overheat. This intense heat likely melted the nearby fuel pipe, allowing fuel to escape and ignite.
Findings
- The fire was caused by an electrical short circuit resulting from the metal rudder pedal contacting the exposed terminals of the starter solenoid.
- The rudder pedals were adjusted to the fully forward position, making contact possible during tight taxiing manoeuvres.
- The starter solenoid terminals on G-CIBJ lacked the insulation required by the aircraft's design plans.
- The overheating of the electrical system caused the fuel pipe to fail, leading to the ignition of fuel.