What happened
On 10th December 2018, an IndiGo Airbus A320neo, registration VT-ITR, was operating a scheduled flight from Jaipur to Kolkata when smoke began to permeate the aircraft. During the descent, cabin crew first noticed smoke in a rear lavatory and alerted the flight crew. As the aircraft descended through 21,000 feet, the smoke became denser, eventually entering the cockpit.
As the situation progressed, the flight crew received a series of ECAM warnings, including lavatory smoke, avioness smoke, and smoke in both the forward and aft cargo compartments. At approximately 40 nautical miles west of Kolkata, the pilot declared a "MAY DAY" to Air Traffic Control. The aircraft was vectored via the shortest possible path and performed an emergency landing at Kolkata Airport. Following the landing, the aircraft was moved to an isolation bay, where all 139 passengers and 6 crew members were safely evacuated using slides and ladders. There were no injuries reported.
The investigation
AAIB India examined the aircraft and its engines following the incident. Post-flight inspections revealed a significant drop in the oil quantity of engine number two, which had decreased from 18 quarts to 13 quarts during the flight. Ground runs confirmed that smoke was present in the cabin when the engine was running with the packs engaged.
A detailed teardown inspection of the PW1127G-JM engine conducted by the manufacturer revealed that the No. 3 bearing rear carbon seal had failed. This failure caused oil to leak into the engine's gas path and secondary air systems. The leaked oil then entered the aircraft's bleed air system, allowing fumes and smoke to be distributed throughout the cabin and cockpit via the ventilation valves.
Findings
- The primary cause of the smoke was the wear and failure of the No. 3 bearing rear carbon seal.
- This seal failure led to internal oil leakage into the compressor secondary air systems and the engine bleed air system.
- The loss of pressurized sealing allowed oil fumes to be released into the passenger and flight compartments through the bleed valves.
- The wear on the seal was attributed to exposure to high temperatures during standard operations.
- The aircraft's airworthiness and crew qualifications were all found to be in order at the time of the incident.