Accident to the Cessna - U206G registered F-GAMJ on 03/07/2017 at Granville-Mont Saint-Michel (50)

Investigation progression Closed
Progress: 100%

The pilot took off at 15:20 from runway 25 of Granville–Mont Saint-Michel aerodrome with four parachutists. On descending through an altitude of 3,000 ft after dropping the parachutists at FL100, smoke appeared at the instrument panel. The pilot made an emergency call on the aerodrome’s A/A frequency. He set the switches of the electrical equipment to OFF and then a few seconds later, the battery switch to OFF. When the primary instruments such as the airspeed indicator, altimeter and vertical speed indicator ceased operating, the smoke became thicker. The altitude was estimated at around 2,000 ft and the pilot experienced difficulties in breathing. On final approach, at a height considered sufficient, he commanded the shut-down of the engine and managed to land on runway 07 despite the thick smoke and breathing difficulties. He quickly evacuated the aeroplane and observed that it was on fire at the instrument panel and engine cowling.

The fire was rapidly put out using two fire extinguishers, one from the aircraft and a second one brought by a person who had come to help.

The electrical fire probably broke out due to contact at the alternator terminal between the metal shielding and the conductive material of the cable connecting the alternator to the bus bar. This abnormal contact was the result of a modification or repair, the origin of which was not determined. With a potential corresponding to that of the alternator, the shielding may have touched a surface with a lower potential (structure ground) when routed between the firewall and the instrument panel. The cable then probably became hot which damaged the cable harness behind the control panel.