Incorrect takeoff performance data calculated, Belfast Aldergrove Airport, 25 June 2015.
The flight crew planned to perform a takeoff from Runway 25 using Intersection Bravo at Belfast Aldergrove Airport. The initial performance figures, calculated using the Electronic Flight Bag (EFB), were computed for a wet runway; this produced a full power thrust setting. Just before pushback, as the runway was dry, the crew elected to change the runway state on the EFB from wet to dry to see if this would produce a reduced engine thrust setting, which it did.
During the takeoff roll, as the end of the runway became visible at about 115 kt, the commander felt that a rejected takeoff would not provide sufficient stopping distance and thus became ‘Go’ minded. The aircraft subsequently got airborne with about 200 m of runway remaining.
After departure, analysis by the crew revealed that an incorrect runway was used to calculate the dry runway performance figures, resulting in erroneous figures being generated. The reason for this could not be confirmed but subsequent investigations revealed that in one scenario, an involuntary runway change could occur on the EFB. This anomaly was not known by the operator or manufacturer at the time of the event and is likely to have been the reason for the incorrect runway selection. These figures were not identified as erroneous and were subsequently used for takeoff.