What happened
On July 31, 2020, at 19:30 UTC, an ATR 72-202, registration SP-SPE, operated by SprintAir, was performing a commercial cargo flight from Brnik Airport (Ljubljana) under IFR rules. Shortly after takeoff, the flight crew received a warning via the cockpit panel indicating the presence of smoke. The crew also detected a distinct, unpleasant odor within the flight deck.
Recognizing the emergency, the crew immediately decided to cancel the flight and execute a 180-degree right turn to return to the departure airport. The aircraft performed a visual approach to runway 30. During the descent and approach, the crew continued to experience smoke and an electric smoke warning on their displays. The aircraft landed safely at Ljubljana Airport, and the fire and rescue services met the aircraft on the maneuvering surface. Upon stopping and shutting down the engines, firefighters inspected the cockpit using a thermal camera.
The investigation
The Slovenian Safety Investigation Authority examined the aircraft's flight trajectory, maintenance records, and communication data. The investigation focused on identifying the source of the smoke and evaluating the crew's response to the emergency. Investigators also reviewed the maintenance history of the avionics compartment and the manufacturer's prescribed emergency procedures for smoke in the cockpit.
Findings
- The source of the smoke and odor was identified as a failing cooling fan located in the avionics compartment under the cockpit floor panel.
- The fan was equipped with a temperature sensor that had malfunctioned.
- There was no damage to the aircraft or other equipment resulting from the incident.
- The flight crew followed the operator's manual and manufacturer's instructions regarding the return to the airport.
- The meteorological conditions at the time of the incident were favorable (CAVOK) and did not contribute to the event.
- The airport's fire service and air traffic control responded promptly and appropriately to the emergency.