What happened
On October 23, 2023, an Airbus A321neo, registration CS-TJL, was operating a scheduled commercial flight from Milan, Italy, to Lisbon, Portugal. While cruising at FL370 over the Barcelona area, the aircraft encountered moderate turbulence, which was recorded by the flight data recorders.
Shortly after the turbulence, the captain received an ECAM message indicating an engine shutdown (ENG2 SHUTDOWN). The flight crew declared an emergency and descended to FL220. During the descent, the crew attempted to relight engine #2 twice, but both attempts were unsuccessful. The crew subsequently diverted to Barcelona (LEBL), where the aircraft landed without further incident. Upon parking the aircraft, the crew discovered that the engine #2 fire pushbutton switch (PB-SW) had disengaged and its guard was open.
The investigation
The GPIAAF investigation analyzed flight data, including vertical, lateral, and longitudinal acceleration parameters. The data revealed that the triggering of the fire switch and the subsequent crew alert occurred immediately following the recorded variations in acceleration caused by the turbulence. The investigation also examined the aircraft's maintenance history and the physical condition of the fire panel.
Findings
- The engine shutdown was triggered by the mechanical disengagement of the engine #2 fire pushbutton switch due to turbulence.
- The fire switch was sensitive to mechanical handling and the impact of turbulence.
- Because there was no actual fire condition, the fire switch did not illuminate when it moved from its normal position, meaning the crew was not visually alerted to the switch's movement until the ECAM message appeared.
- The aircraft sustained no damage, and the crew and all 194 passengers remained unharmed.
- Airbus has since initiated actions, including an inspection service bulletin for the A320 fleet and an update to the Aircraft Maintenance Manual (AMM) regarding the sensitivity of the fire panel component.