What happened
On 25 June 2015, an Airbus A319-111, registration G-EZAA, was prepared for a commercial passenger flight from Belfast Aldergrove Airport to Luton Airport. During the pre-departure phase, the flight crew used an Electronic Flight Bag (EFB) to calculate takeoff performance. While the initial calculation was set for a wet runway, the crew decided to update the runway state to 'dry' to utilize a reduced engine thrust setting, as the surface appeared dry.
During the takeoff roll from Intersection Bravo on Runway 25, the commander noticed at approximately 115 kt that the end of the runway was becoming visible. He realized that a rejected takeoff at the calculated V1 speed would likely result in insufficient stopping distance. Consequently, the commander elected to continue the takeoff. The aircraft became airborne with roughly 200 meters of runway remaining. Post-flight analysis revealed that the performance figures used were actually calculated for Runway 07 rather than the intended Runway 25B.
The investigation
The AAIB investigation focused on how the incorrect runway was selected in the EFB. While the crew believed they had only modified the runway condition, the commander later discovered that the runway field in the software had changed to Runway 07.
Investigators identified a software anomaly within the FlySmart application used on the EFB. On touchscreen devices, if a user touches the screen anywhere outside the specific drop-down menu or keyboard after interacting with a menu, the software can automatically revert the runway selection to the lowest available number for that airport. In this instance, the selection switched from 25B to 07. The investigation also noted that the crew's standard operating procedures involved a cross-check of specific speeds rather than an independent, full-field verification of all EFB entries.
Findings
- The takeoff performance was based on incorrect runway data due to an unintended change in the EFB input.
- A software anomaly in the FlySmart version used allowed for an involuntary runway selection change when the touchscreen was touched.
- The flight crew did not perform an independent review of all EFB performance entries, focusing instead on a gross error check of specific speeds.
- The aircraft manufacturer's software was not optimized for touchscreen use at the time of the incident.
- Had a rejected takeoff been attempted at the calculated V1, a runway overrun at approximately 75 kt was theoretically possible.