What happened
On December 12, 2005, at approximately 14:00, a Robin DR 400-140 B aircraft, registered F-BTZY, was involved in an aircraft fire at Langres aerodrome. The aircraft, operated by a flying club, was being prepared for a local flight. Following refueling, the pilot moved the aircraft away from the fuel pump and attempted to start the engine. After several unsuccessful priming attempts, the pilot observed smoke emerging from the area between the engine cowling and the firewall.
In response to the smoke, the pilot immediately deactivated the electrical circuits and evacuated the aircraft. Despite the pilot's efforts to alert the fire services, the fire spread rapidly, resulting in the total destruction of the aircraft.
The investigation
The investigation focused on the origin of the fire and the condition of the electrical components. Investigators examined the wreckage and discovered that approximately 20 centimeters of the starter motor power cable strands had been welded together. The internal components of the battery were also found to be melted.
Examination of the engine compartment revealed that the insulation on the starter cable had been damaged due to friction and crushing against the upper metal plate of the nose landing gear strut. At the point of failure, the cable was not properly secured. The investigation also noted that the cable's routing, positioned beneath a structural tube of the engine mount, made it susceptible to such mechanical wear.
Records indicated that the aircraft had undergone significant maintenance following a runway excursion in 2003, which included work on the nose gear and an engine overhaul. The battery had been replaced during a 100-hour inspection, and the aircraft had flown only seven hours since that service.
Findings
- The fire was caused by a short circuit resulting from the degradation of the starter cable's insulation.
- The insulation was compromised by friction and pressure against the nose gear strut metalwork.
- The cable was not properly secured in place, and its specific installation path under a structural tube facilitated the rubbing action that led to the failure.