Incident Overview
On 25 August 2016, at approximately 17:17 local time, a Robin DR 400/180 aircraft (registration HB-KEE) operated by Groupe de Vol à Moteur Sion, Aéro-Club du Valais, experienced smoke in the cabin during takeoff from Sion Airport (LSGS). The aircraft was engaged in a private flight under visual flight rules (VFR). The pilot, a French citizen born in 1980, held a Private Pilot Licence (PPL(A)) issued by the European Aviation Safety Agency (EASA) and had accumulated 95 total flight hours, all on the same type.
Flight Details
After boarding the aircraft, which had been parked on the ramp during a particularly hot afternoon, the pilot waited for traffic on final approach to Runway 25 before taxiing via Taxiway Bravo. During the takeoff roll at full power, a light white smoke appeared in the cabin. The pilot continued the takeoff, which proceeded normally. At approximately 1000 feet above ground, a more substantial wave of white smoke appeared, accompanied by the smell of oil. The pilot immediately informed the control tower of the issue and requested to rejoin the downwind leg for a quick circuit and an expedited landing on Runway 25. Firefighting services stood by as the aircraft landed, exited the runway via Taxiway Bravo, and the occupants disembarked without delay. Firefighters confirmed the absence of flames or fire traces, and the aircraft was towed to the parking area.
Post-Flight Inspection
An inspection conducted the following day identified overheating of two electrical cables (see figure 1 in original report) that were part of the power supply to various switches in section 21 of the DR400/160/180 maintenance manual electrical diagram. The defective components were replaced. No injuries to the pilot or passengers were reported, and the aircraft sustained no damage.