What happened
On 3 July 2017, a Cessna 206G, registration F-GAMJ, was performing a parachute drop flight near Granville–Mont Saint-Michel when an electrical fire broke out in the cockpit. The aircraft, operated by Vendée Aviation, was descending through 3,000 ft after dropping four passengers when smoke began appearing at the instrument panel.
In response to the smoke, the pilot deactivated the electrical equipment and the battery. As the smoke thickened, primary flight instruments—including the airspeed indicator, alt/altimeter, and vertical speed indicator—ceased to function. The pilot, experiencing significant breathing difficulties, attempted to manage the situation by opening a window and air vents. Despite the thick smoke and reduced visibility, the pilot successfully performed an emergency landing on runway 07. Upon landing, the pilot observed flames originating from the engine cowling and the instrument panel, which were subsequently extinguished using on-board and external fire extinguishers.
The investigation
The BEA examined the aircraft's electrical system, specifically focusing on the alternator and the wiring harness behind the control panel. Investigators found that components such as glass wool, flexible sheaths, and various instruments had been exposed to temperatures exceeding 300 °C.
Technical examinations of the electrical system revealed that the cable connecting the alternator to the busbar had a significant defect. At the alternator connecting lug, the metal shielding, insulation, and conductive material were in continuous contact. This defect was likely the result of a previous modification or repair that did not meet Cessna's quality standards. Furthermore, investigators found evidence of arcing at the firewall feedthrough, where the metal shielding and insulation had been destroyed.