What happened
On 6 January 2011, an Airbus A319-111, registration G-EZFI, was operating a commercial flight from Liverpool to Madrid via Belfast. After landing at Belfast International Airport, the aircraft vacated Runway 25 and turned onto Taxiway D. During the landing roll, the crew utilized idle reverse thrust. Shortly after turning onto the taxiway, a dark, smoke-like substance began emerging from the overhead air conditioning vents, filling the cabin. The substance had a smell described by those on board as similar to electrical burning or a bonfire.
Upon noticing the smoke, the cabin manager notified the flight crew via the interphone. As the smoke density increased, the cabin manager issued an evacuation command over the public address system. The commander, hearing the forward cabin doors being opened, immediately shut down the engines to protect passengers from potential jet blast. During the evacuation, one passenger sustained minor injuries.
The investigation
The AAIB investigation focused on the source of the smoke and the effectiveness of the aircraft's systems. Engineers inspected the aircraft's bleed air and air conditioning systems, finding no mechanical defects. Laboratory analysis of seat headrest covers and air filters revealed significantly higher concentrations of potassium and acetate compared to other aircraft, suggesting these chemicals had been present in the cabin environment.
Investigators also examined the airport's maintenance logs, which showed that the runway and taxiways had been treated with potassium acetate and urea. The investigation noted that the urea pellets had not been thoroughly wetted prior to application. Furthermore, the investigation reviewed the crew's use of reverse thrust and the communication protocols between the flight deck and cabin crew during the emergency.
Findings
- The smoke was caused by the ingestion of de-icing chemicals into the engine compressors, which then entered the cabin through the air conditioning system.
- The volume of smoke was likely increased by the prolonged use of reverse thrust, which helped deliver the chemicals into the aircraft's air supply.
- The presence of un-wetted urea pellets on the taxiway contributed to the chemical mist formation.
- A lack of clear communication was noted, as the cabin manager used the standard interphone rather than the emergency call function, and the commander's audio panel was not set to receive the initial notification.