What happened
On July 25, 2022, Airblue flight ABQ-412, an Airbus A321 NEO (registration AP-BOCT), departed from Allama Iqbal International Airport (AIIAP) in Lahore for a scheduled service to Sharjah. Shortly after takeoff at 19:51 UTC, the crew received a 'SMOKE AFT CARGO' warning.
In response to the alert, the pilot discharged both cargo fire bottles. The aircraft subsequently returned to Lahore and landed safely on runway 36L at 20:01 UTC. Upon arrival, an inspection of the aft cargo compartment revealed no evidence of actual fire, smoke, or heat damage. There were no injuries to the 233 occupants on board.
The investigation
The Aircraft Accident Investigation Board (AAIB) of Pakistan examined the circumstances surrounding the warning. Investigators found that approximately 3,200 kg of frozen animal meat had been loaded into the aft cargo compartment. This meat was contained in fabric bags that showed traces of fluid and blood, indicating they were not adequately sealed.
At the time of the incident, meteorological reports for Lahore indicated high ambient humidity levels (between 79% and 87%). The investigation also reviewed the technical specifications of the aircraft's smoke detectors (P/N PPC1100-00), noting that their single optical measurement design cannot always distinguish between actual smoke particles and condensation or moisture.
Findings
- The smoke warning was a spurious event caused by inadequately packed animal meat generating high humidity levels within the sealed cargo compartment.
- This internal moisture, combined with high external humidity, led to condensation droplets that the smoke detectors misidentified as smoke particles.
- The airline's Airside Operations Manual lacked detailed instructions regarding the specific packing and loading requirements for perishable goods such as meat.
- The design of the installed smoke detectors possesses a limitation in discriminating between smoke and heavy condensation.