What happened
On 18 May 2024, an Air India Express Airbus A320 (registration VT-ATF) departed Bengaluru International Airport for Cochin. Shortly after takeoff, while the aircraft was climbing through approximately 600 feet, the crew experienced loud bangs and severe jolts from the right-hand engine. While the flight deck instruments did not initially trigger a fire warning, cabin crew reported seeing fire emanating from the right engine.
As the aircraft continued its climb, the right engine experienced a stall, accompanied by fluctuations in engine parameters and a momentary hydraulic system fault. The pilot in command declared a "Mayday" and initiated an emergency return to Bengaluru. Upon landing, the crew attempted to extinguish the fire using onboard extinguishers, but the flames persisted until airport crash fire tenders arrived to suppress the fire with foam. Due to the ongoing fire, an emergency evacuation was ordered. All 185 people on board were evacuated via the aircraft slides. While most passengers exited safely, 10 passengers sustained minor injuries during the evacuation process.
The investigation
AAIB India examined the aircraft' and engine components to determine the origin of the fire. The investigation focused on the right-hand engine's internal mechanics and the recent maintenance history of the Center Vent Tube (CVT). Investigators analyzed flight data recorder information, which confirmed a recoverable engine stall and significant vibrations in the right engine during the initial climb phase.
Findings
- The fire was caused by lubricating oil leaking into the engine exhaust system, where it ignited due to high temperatures and airflow.
- The oil leak originated from the failure of the No. 4 bearing.
- The primary cause was a maintenance error at a repair shop, where an out-of-tolerance repair to the Center Vent Tube caused metal particles to be released into the lubrication system.
- These particles migrated to the No. 4 bearing, causing the bearing rollers to seize and the bearing cage to deform.
- This mechanical degradation led to rotor imbalance and the subsequent failure of the aft sump sealing, allowing oil to escape into the exhaust.
- No fire warning was triggered in the cockpit because the fire was contained within the engine exhaust area rather than the nacelle.