What happened
On August 25, 2016, a Robin DR 400/180, registration HB-KEE, was preparing for departure from Sion Airport (LSGS) following a period of parking on the apron during particularly high temperatures. While taxiing to runway 25 via taxiway Bravo at full power, the pilot observed a light amount of white smoke entering the cabin.
Despite the initial smoke, the pilot proceeded with the takeoff. However, upon reaching an altitude of approximately 1,000 feet, a second, more significant wave of white smoke appeared, accompanied by the smell of oil. The pilot immediately notified the control tower of the situation and transitioned to a downwind pattern to perform an urgent landing on runway 25.
Following the landing, the aircraft exited the runway via taxiway Bravo. Emergency services met the aircraft, and the occupants evacuated the cabin. After firefighters confirmed there were no active flames or signs of fire, the aircraft was towed to the parking area.
The investigation
An inspection of the aircraft was conducted the following day to identify the source of the smoke. Investigators focused on the electrical systems and identified that two electrical cables, which provided power to various switches, had overheated. These specific cables were part of the electrical supply system detailed in the maintenance manual for the DR400/160/180 series.
Findings
- The primary cause of the smoke and odor was the overheating of two electrical cables.
- The incident occurred following a period of the aircraft being parked in high ambient temperatures.
- The aircraft sustained no structural damage, and the occupants suffered only minor injuries.