Easyjet A319 at Nice on Aug 29th 2019, takeoff with insufficient thrust, both pilots made same error
Last Update: April 10, 2020 / 10:24:41 GMT/Zulu time
On Apr 9th 2020 the UK AAIB released their bulletin concluding:
This incident resulted from identical independent errors not being trapped by a TORA cross-check or by EFB output validation. While revised software with a graphical runway presentation could have helped reduce the likelihood of this occurrence. Automated systems, such as TOS2, could, in the future, provide an effective barrier to incidents of this nature.
The AAIB stated:
A takeoff performance calculation error was detected after flight by the operator's flight data monitoring (FDM) programme. Cross-checking FDM information with electronic flight bag (EFB) calculations indicated that both pilots had inadvertently selected the Quebec 3 (Q3) intersection, rather than B3, in their performance software. The mis-selection was not detected during an initial data validation 'departure distance check' and cross-checking EFB calculation outputs did not trap the error.
The AAIB further stated:
An indicative calculation conducted by the AAIB revealed that outputs from takeoff calculations based on B3 and Q3 differed significantly. For a departure from B3 rather than Q3, takeoff speeds were >=Ý13 kt slower (V1=Vr=125 KIAS, V2=130 KIAS instead of V1=Vr=139 KIAS, V2=143 KIAS), the thrust reduction (flex) temperature was 57° (8° lower) and flap 2 setting (instead of flap 1) was required. From A3 the speeds were 8 kt slower (V1=Vr=131 KIAS, V2=135 KIAS) than from Q3, the flex temperature was 61° and Flap 2 was the optimum setting. Meaningful comparisons of takeoff run required could not be drawn because all three calculations used different settings to achieve balanced-field performance.
The AAIB summarized the crew testimonies: "The flight crew considered that the performance calculation software's user-interface was a factor in the intersection selection error being made and missed. It was the aircraft commander's view that 'EFB Toughbook data entry is clumsy and often requires re-entering especially runway details and, at NCE, B3 and Q3 appear next to each other and are easy to mis-select'" and reported the operator was already in the process of updating the software.
The AAIB analysed:
Comparison of indicative takeoff performance parameters for B3 and Q3 departures indicated that the only credible explanation for the calculation error was mis-selection of Q3 by both pilots. It was not determined why the 'departure point distance confirmation' check referred to by the commander did not alert the crew to the mis-selections. This incident showed that simultaneous independent errors were possible and that an EFB output cross-check and TORA cross-check would not necessarily trap them.
The aircraft commander reported that the EFB software user-interface was "clumsy" and prone to errors which, once made, were difficult to detect. The operator's proposed EFB software update would bring an improved graphical user-interface. The limitations of human performance mean that any system relying on user-entered data is unlikely to be infallible.
An independent automated check, such as the Airbus TOS2 function, could provide an additional barrier to prevent a performance calculation error contributing to an accident.
This article is published under license from Avherald.com. © of text by Avherald.com.
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