What happened
On 2 October 2019, an Airbus A3CO19-131, registration G-EUOG, was preparing for a commercial passenger flight from London Heathrow Airport to Leeds Bradford Airport. During the taxi phase, the Pilot Monitoring requested a departure from intersection N4E, rather than the originally planned N2W. Air Traffic Control granted this request quickly.
Because the new intersection provided a takeoff run available that was 678 m shorter than the original plan, the takeoff performance data required updating. However, due to the rapid nature of the clearance, the crew did not update the Flight Management Guidance Computer (FMGC) with the new parameters. As the aircraft lined up, the Pilot Flying questioned if the Pilot Monitoring was satisfied with the departure; the Pilot Monitoring, believing the question referred to the completion of engine start and checklists, responded affirmatively. The aircraft subsequently departed the runway without incident, as the light payload and limited fuel requirements meant the existing performance calculations remained sufficient for the actual conditions.
The investigation
The investigation established that the crew had calculated their takeoff performance based on the longer runway length available at N2W. The investigation found that the crew's familiarity with Heathrow as their home base, combined with the pressure of a rapid departure, led to a lack of shared mental model regarding the change in takeoff position. The post-flight debrief revealed that the Pilot Monitoring was unaware that his request for a different intersection had invalidated the previously entered performance data.
Findings
- The aircraft departed from intersection N4E using performance data calculated for intersection N2W.
- The crew failed to update the FMGC with the correct takeoff performance figures for the new intersection.
- The rapid approval of the new intersection by ATC left the crew with insufficient time to complete pre-departure duties.
- A lack of communication and a breakdown in the shared mental model between the two pilots contributed to the error.
- The incident was mitigated by the fact that the aircraft was operating with a light load and minimal fuel for a short sector.