What happened
On 10 September 2023, an Air China A320NEO, registration B-305J, was descending toward Singapore Changi Airport from Chengdu, China, when the flight crew detected an unusual odor in the cockpit. Shortly thereafter, the smell intensified into a burning odor, and dense smoke began filling both the cockpit and the passenger cabin. The crew donned oxygen masks and declared a MAYDAY to Air Traffic Control (ATC).
As the situation progressed, the crew received multiple smoke warnings from the aircraft's systems, including indications of smoke in the avionics compartment, the forward cargo area, and the lavatories. Despite a brief period of uncertainty regarding the landing runway, the aircraft landed on Runway 20L. Upon stopping on the runway, the crew initiated an emergency evacuation. While all 155 people on board escaped safely, nine passengers sustained minor injuries during the egress. Following the landing, the Airport Rescue and Fire Fighting Service identified and extinguished a fire located at the left engine tailpipe.
The investigation
The investigation focused on the source of the smoke and the subsequent engine fire. Technical examinations, including borescope inspections and engine disassembly, revealed that the front carbon seal of the No. 3 bearing had fractured. This failure allowed engine oil to leak into hot engine zones, creating smoke that entered the cabin via the bleed air system and causing a localized fire at the tailpipe.
The investigation also examined the communication chain between the flight crew and ATC. It was noted that the Tower Coordinator had not been alerted to the MAYDAY declaration by the Approach Coordinator. Additionally, the investigation looked into the delay in deploying emergency services, which was attributed to unclear communication from the flight crew regarding their intention to evacuate on the runway.