What happened
On 29 August 2019, an Airbus A319-111, registration G-EZBI, was preparing for a commercial passenger flight at Nice Côte d’Azur Airport. During pre-flight preparations, the flight crew intended to calculate takeoff performance based on the most restrictive available intersection, known as Bravo 3. However, both pilots inadvertently selected the Quebec 3 intersection in their electronic flight bag (EFB) software.
As the aircraft taxied, the crew was cleared to depart from intersection Alpha 3. Because the crew believed they had already calculated performance for the more limiting Bravo 3, they accepted the clearance without recalculating their parameters. During the takeoff roll, the commander noted that the end of the runway appeared closer than anticipated, though no immediate danger was perceived. The aircraft successfully lifted off, but subsequent flight data monitoring revealed that the takeoff calculations were based on a runway length significantly greater than what was actually available at the departure point.
The investigation
The investigation focused on how the error escaped detection during the crew's independent performance cross-checks. It was established that both pilots had made the exact same mis-selection of the intersection in the performance software. This simultaneous error meant that the standard validation process, which relies on the assumption that two pilots will not make the same mistake, failed to identify the discrepancy.
Investigators also examined the user interface of the EFB software. The commander noted that the data entry process was cumbersome and that the proximity of the B3 and Q3 labels on the interface contributed to the error. Furthermore, the investigation looked into the effectiveness of existing safety barriers, such as the takeoff distance available (TODA) cross-check against airfield charts.
Findings
- The primary cause of the incident was the simultaneous independent error by both pilots in selecting the incorrect runway intersection.
- The error went undetected because the takeoff performance cross-check was invalidated by the identical nature of the two mistakes.
- The software user-interface was considered a contributing factor, as the text-based representation of runway characteristics made the mis-selection easy to make and difficult to detect.
- The aircraft was not equipped with the enhanced automatic takeoff surveillance system (TOS2) which could have acted as a safety barrier by verifying that the entered data was compatible with the actual runway distance.