What happened
On 14 April 2016, an Airbus A3/111, registration G-EZFJ, was preparing for a scheduled passenger flight from Malaga Airport, Spain, to Liverpool International Airport. During the pre-flight phase, the flight crew utilized the Multiple Runway Computation (MRC) function on their Electronic Flight Bag (EFB) to calculate takeoff performance.
While the crew intended to prepare for Runway 31, a software anomaly caused the EFB to display detailed runway information for Runway 31 alongside takeoff performance data actually calculated for Runway 13. Although the commander performed a cross-check of the critical data entry, the discrepancy was not identified. The crew noted that the takeoff speeds appeared lower than usual, but they attributed this to potential recent changes in the airline's performance algorithms. The aircraft subsequently departed from Runway 31 using the incorrect parameters. During the cruise phase, the commander reviewed the EFB and discovered that the performance results were tied to the wrong runway.
The investigation
The AAIB investigation focused on the software behavior of the FlySmart EFB and the crew's verification procedures. Investigators established that a specific sequence of actions—switching to the load sheet screen to update takeoff weight just before computing performance—triggered the anomaly. This allowed the screen to show the 'details' for one runway while the 'results' section remained linked to another.
The investigation also examined the operator's Standard Operating Procedures (SOPs). While the crew followed the existing protocols for cross-checking, the investigation found that the crew's familiarity with the single runway calculation method made them less likely to look for the runway selection in the secondary drop-down menu used by the MRC function. The manufacturer confirmed that the software should not have been capable of displaying conflicting runway information simultaneously.
Findings
- The flight crew used takeoff performance data for Runway 13 while operating from Runway 31.
- A software anomaly in the EFB allowed the display of mismatched runway information.
- The crew's cross-check was unsuccessful because the runway selection in the results section was located in a different area of the screen than the primary runway verification box.
- The crew's observation of lower-than-expected speeds was dismissed due to an assumption of unannounced changes to performance algorithms.
- The error was triggered by a specific sequence of data entry involving the load sheet and the MRC function.