What happened
On 24 November 2019, an Airbus A321-231, registration G-EUXJ, was performing a scheduled passenger flight from Glasgow Airport to London Heathrow. During the takeoff roll, the flight crew noticed that the aircraft was not accelerating at the expected rate. As the aircraft approached V1, the commander applied full TOGA power to compensate. The aircraft eventually rotated near the end of the runway, crossing the upwind end at 2D76 ft, and continued to its destination without further incident.
Following the flight, the crew identified that a flex temperature of 79°C had been entered into the flight management guidance computer, rather than the required 49°C. There were no fatalities and no injuries during the event.
The investigation
The AAIB examined the flight data and interviewed the crew to determine why the incorrect performance data was entered and why it went undetected. The investigation focused on the period during which the takeoff performance figures were being programmed into the MCDU. The crew reported that during the data entry process, they were briefly distracted by a request from a cabin crew member regarding a flight deck visitor.
Investigators also reviewed the standard cockpit procedures used during the pre-flight and before-takeoff phases. It was noted that while the crew performed several checks, these procedures involve verifying the displayed values rather than cross-referencing them against the original printed performance calculations.
Findings
- The flight crew entered an incorrect flex temperature of 79°C instead of 49°C.
- The error was likely caused by distraction during the data entry process and the crew's focus on a non-standard acceleration altitude.
- The incorrect entry was not caught because the subsequent checklist items only required the crew to read the displayed temperature rather than verify it against the source document.
- The error was harder to detect because a 79°C flex temperature, while unusual for an A321, is a common value for the A319 aircraft the crew had been operating earlier in their duty period.