Old Facts, New Insights – Lessons from A-320

Automation surprises result from an imbalance between ‘autonomy’ and ‘authority’ of advanced automated systems and the gaps in the operator’s mental model of the system and its interactions. The vital factor at play in such cases could be low observability interfaces in novel (“nonroutine elements”) situations with operator caught in a bind while trying to track and anticipate the actions by the system in his hands! Simply put, when he (rather, they, being multi crew environment) is loosing the grip of the unfolding situation and finds himself inadequately prepared for the fast unwinding situation, which was chillingly evident in Air France Flight AF 447 as brought out in the final report [1]:-

“The accident resulted from the following succession of events:

  • ˆTemporary inconsistency between the measured airspeeds, likely following the obstruction of the Pitot probes by ice crystals that led in particular to autopilot disconnection and a reconfiguration to alternate law,
  • ˆInappropriate control inputs that destabilized the flight path, ˆ
  • The crew not making the connection between the loss of indicated airspeeds and the appropriate procedure, ˆ
  • The PNF’s late identification of the deviation in the flight path and insufficient correction by the PF, ˆ
  • The crew not identifying the approach to stall, the lack of an immediate reaction on its part and exit from the flight envelope, ˆ
  • The crew’s failure to diagnose the stall situation and, consequently, the lack of any actions that would have made recovery possible.”

Does it mean that the training of commercial pilots flying autonomous automated aircraft needs to be reviewed? To answer this, there is a need to look at the findings of an earlier study on automation ‘surprises’ on the Airbus A-320, as reported by the pilots [2]. Before delving further, use of term ‘automation surprises’ reflects a lack of mode awareness, which is “a misunderstanding of the current and future status and behaviour of the automation” [2, 5]. Such ‘lack of mode awareness’ can occur due to various factors, including [2, 4]:-

  • “Inadequate feedback on system activities.
  • Gaps or misconceptions in pilots’ knowledge and understanding of the automation.”

The referred study [2] used Airbus A-320, representing advanced automated aircraft, as a “natural laboratory”, with questionnaire based feedback obtained from sample of 167 line pilots of an American carrier. The participating pilots were asked open-ended questions about Airbus A-320 on the following aspects:-

  • Specific cases of automation surprises,
  • Their approach to monitoring the automation on this advanced flight deck, and
  • Their attitude toward and experiences with the unique design of fight controls on the Airbus A-320.”

Automation Surprises [2]

It was reported that 80% (n = 133) pilots had experienced automation surprises at least once during line operations. When asked about learning value from such an experience, of the 56 pilots responding, 22 did not find an explanation for the reported surprises, while 24 benefitted from an explanation offered by an experienced crew member; it was 11 of them who figured out the cause of ‘surprise’ on their own whereas an explanation was found in the aircraft’s operating manual by 6 pilots.

The list of surprises are as follows [2]:-

    • Failure to activate the approach (n = 21)
    • Loss of constraints after entering change (n = 20)
    • Indirect mode transitions (n = 14)
    • Exceeding an airspeed of 250 knots below 10000 feet (n = 9)
    • Automation strategies in managed vertical navigation (n = 6)
    • Failure to immediately detect a failure of the flight management and guidance computer (n = 6)
    • Unexpected airspeeds during a go-around (n = 5)
    • Decrease in airspeed when leveling off in the “open descent’ mode (n = 5)


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Acknowledgement  Image courtesy Wikipedia

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