An EFB software anomaly likely caused incorrect takeoff performance data be calculated by the crew of an easyJet Airbus A319 at Belfast Airport, according to an AAIB report.
The flight crew were scheduled to fly from Belfast Aldergrove Airport to Luton Airport. The co-pilot was the Pilot Flying (PF) and the commander was the Pilot Monitoring (PM) for the sector.
In preparation for the sector the commander entered the available data into his Electronic Flight Bag (EFB).
This included the meteorological data recorded from the ATIS, the runway for departure (runway 25 from Intersection Bravo) and the flap setting for takeoff. At this point he selected a wet runway, from the drop-down menu as, despite the runway appearing to be dry, there were showers in the vicinity. He did this to account for a possible degradation in the weather conditions. The crew recorded ATIS Information Alpha, issued at 1720 hrs, which stated: wind was from 160° at 12 kt, the visibility was in excess of 10 km, the temperature was 17°C, the dew point 15°C and the QNH 1015 hPa.
Prior to pushback the crew reviewed the performance inputs made into the EFB in accordance with the operator’s standard operating procedures (SOPs). So that the co-pilot could have a clearer view, the commander removed his EFB from its stowage, by his left window, and placed it on his table in front of him. At this point the co-pilot noticed that the computed engine thrust setting was toga/full power. As the runway was dry, and was forecast to remain so, the crew agreed to see if selecting a dry runway would give a flex/reduced engine thrust takeoff. The commander changed the runway condition box from wet to dry, using the drop-down menu, with the co-pilot monitoring his actions, and then pressed compute. The new performance figures produced a flex takeoff as expected.
After mentally assessing the generated speeds to see if they appeared sensible, they were input into the Flight Management and Guidance Computer (FMGC). As a gross error check the crew crosschecked the ‘Green Dot’ speed and the engine out acceleration altitude in the FMGC with the EFB, but they did not conduct an independent review of all the EFB performance figure entries. The aircraft was then pushed back, and taxied out to Intersection Bravo of runway 25.
The end of the runway is not visible from the start of the takeoff roll, due to a hump. Consequently, the commander became visible with the end of the runway at about 115 kt.
Although the aircraft’s acceleration appeared normal after takeoff thrust was set, it became apparent to him that, should there be a requirement to discontinue the takeoff at the calculated V1 speed of 130 kt, there would be insufficient stopping distance available. He therefore committed to continuing the takeoff. At this point he believed there was an error in the entry of V1 into the FMGC. He continued to monitor the aircraft’s performance and satisfied himself that there was sufficient runway remaining for the aircraft to accelerate, rotate and take off at the calculated speeds. He also planned that, had there been an engine problem during the takeoff roll, he would have selected toga and taken control, rotating within the paved surface. He decided to maintain the flex thrust to avoid distracting the co-pilot.
The commander estimated that he called to “rotate” approximately 600-700m before the end of the runway with the aircraft becoming airborne soon thereafter. The rest of the departure was uneventful with the crew briefly acknowledging that something was likely to have been incorrect with the performance figures.
Later in the flight the commander opened his EFB to try to determine what may have been incorrect. He was surprised to notice that runway 07 was in the runway drop-down box.
A review of the EFB software revealed that the selected runway can be changed involuntarily. When the pilot uses the touch-screen to select the runway dropdown menu, the selected runway will blank and the menu will open to display a list of the available runways which can then be selected. A blue box will frame the first entry in the drop-down menu which will be the lowest numbered runway, in the case of Belfast, this is runway 07.
If the user then touches the screen anywhere other than the drop-down menu or keyboard, the runway selected in the rwy box will switch to the lowest number in the list of those at the airport selected, which will then be displayed. In the case of Belfast Aldergrove Airport, if runway 25B was initially selected and the same process is applied, the drop-down menu would switch to runway 07.
The incident was caused by the use of incorrect takeoff performance data. The data was most likely calculated using runway 07 instead of Runway 25B. The most likely reason for using runway 07 was an involuntary runway selection by an anomaly within the EFB software which went undetected by the crew. They did not conduct an independent check of the selected runway when their recollection was of changing only the runway condition.
Operators have been informed of the anomaly and the EFB software will be corrected in future standards.
The commander recognised the limited stopping distance available just before V1 but the potential seriousness of the event is highlighted by the theoretical result of a runway overrun at 75 kt if the takeoff had been rejected at that stage. A number of international, European and national initiatives are underway to consider and address the safety risks posed by using erroneous takeoff performance parameters.