What happened
On 3 January 2021, an Airbus A321-251NX, registration G-UZMI, was prepared for a commercial flight from Bristol Airport to Edinburgh. Due to a technical issue with the originally scheduled aircraft, the operator substituted an A320 with the A321. Because the initially rostered crew were not qualified on the larger type, a new crew was called from standby.
During the boarding process at Bristol, the flight crew used load figures provided by the Turnaround Coordinator (TCO). While the load sheet indicated the center of gravity (CG) was near the forward limit, it remained within the calculated operational boundaries. The flight proceeded to Edinburgh without incident.
However, during the subsequent boarding process at Edinburgh, the Cabin Manager noticed that passenger seating did not match the Loading Form and Certificate (LFC). Upon performing a manual zone count, the crew discovered that the passenger distribution data was incorrect, as it had been based on the seating configuration of an A/320 rather than the A321. Re-calculating the figures revealed that the aircraft CG was forward of the permitted operating envelope. The crew immediately moved passengers to correct the distribution before departure.
The investigation
The operator's investigation established that the initial flight from Bristol to Edinburgh had been flown outside the operational CG envelope. This occurred because, while the aircraft management system had been updated to reflect the A321, the departure control system—which generates the LFC—had not synchronized the change.
Technical analysis revealed that code errors in the Batch Interaction Layer (BIL) prevented the automated data transfer from completing. This was exacerbated by a high volume of schedule changes due to the COVID-19 pandemic, which caused the validation process to lag. Furthermore, the manual update of the aircraft type occurred after boarding had already commenced at Bristol, and the system provided no alert to ground staff regarding the discrepancy.
Additionally, the investigation found that pandemic-related biosecurity measures had altered communication protocols. The TCO delivered the loading documents to the Cabin Manager rather than directly to the flight deck, reducing the opportunity for the pilots to query last-minute changes with ground personnel.
Findings
- The primary cause was a failure in the IT system's ability to synchronize aircraft type changes between the management and departure control systems.
- A manual update to the aircraft type triggered a seating algorithm that incorrectly allocated passengers based on the previous aircraft's configuration.
- The operational CG envelope was exceeded during the first sector because the flight crew accepted load data that had not been verified against the actual passenger distribution.
- COVID-19 biosecurity protocols had reduced direct communication between the TCO and the flight crew, limiting the crew's ability to identify discrepancies during the turnaround.