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Evidence for an Issue 8 pieces of evidence for this issue.

mode transitions may be uncommanded (Issue #44) - Automation may change modes without pilot commands to do so, possibly producing surprising behavior.

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  2. Evidence Type: Excerpt from Accident Review Study
    Evidence: If we combine this understanding of the FCU with the events of flight F-GGED, we can identify two pivotal human 'failures' in the causal chain leading to the accident. Firstly, the pilot entered a seemingly correct parameter value on the correct entry dial, whilst the panel was in an unappreciated mode. Subsequently, both the pilot and co-pilot failed to notice the (unintended) rapid descent of the aircraft until shortly before impact. In other words, they were surprised by the performance of the system (plane) – an example of the phenomenon described in section 1. These errors are summarised in the schematic outline of events in Figure 2. (page 4)
    Strength: +1
    Aircraft: A320
    Equipment: autoflight FCU
    Source: Hourizi, R. & Johnson, P. (2001). Beyond Mode Error: Supporting Strategic Knowledge Structures to Enhance Cockpit Safety.. In A. Blandford, J. Vanderdonkt & P. Gray (Eds.): People and Computers XV - Interaction without frontiers. Joint Proceedings of HCI2001 and ICM2001, Lille, 10-14th Sept. 2001, Springer Verlag, 229-246. See Resource details

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  4. Evidence Type: Excerpt from Survey
    Evidence: The following comment was made in response to the questionnaire statement, "Describe a problem you know of or a concern you have about flightdeck automation.": "As identified in recent research, unanticipated mode changes are a concern, particularly when transitioning from climbing/descending to level flight. Complicating this picture is that - in the ... fleet - we have 3 different glass cockpits (757, 737-300, A320) each with a particular philosophy and design . There are vexing differences even between the 757and 737, both Boeings." (B757 Captain) In response the questionnaire statement, "To your knowledge, has this ever contributed to an accident or incident? Describe.", this B757 captain stated: "The situation described above for the 757 results in missed crossing restrictions on virtually every descent ! Error can range from 50 to 200 feet and 10 to 30 knots. Many pilots compensate by building a 2 or more mile "pad" into the LNAV course, i.e. creating a waypoint ahead of the crossing restriction to reach the altitude early."
    Strength: +1
    Aircraft: various
    Equipment: automation
    Source: Lyall, B., Wilson, J., & Funk, K. (1997). Flightdeck automation issues: Phase 1 survey analysis. Available: http://www.flightdeckautomation.com/ExpertSurvey/e_report.aspx. See Resource details

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  6. Evidence Type: Excerpt from Survey
    Evidence: 26 of the 30 (87%) respondents reported a 4 (= agree) or 5 (= strongly agree) with pc44 mode transitions may be uncommanded
    Strength: +4
    Aircraft: unspecified
    Equipment: automation
    Source: Lyall, E., Niemczyk, M. & Lyall, R. (1996). Evidence for flightdeck automation problems: A survey of experts. See Resource details

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  8. Evidence Type: Excerpt from Survey
    Evidence: 2 of the 30 (7%) respondents reported a 1 (=strongly disagree) or a 2 (=disagree) with pc44 mode transitions may be uncommanded
    Strength: -1
    Aircraft: unspecified
    Equipment: automation
    Source: Lyall, E., Niemczyk, M. & Lyall, R. (1996). Evidence for flightdeck automation problems: A survey of experts. See Resource details

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  10. Evidence Type: Excerpt from resource
    Evidence: From the A320 accident in Habsheim, France ... "the DFDR [Digital Flight Data Recorder] listings of the early part of the flight [showed] that autothrust went into 'speed' mode on passing 460ft radion altitude , without any command from the crew, and stayed in that mode from then on until the final request for 'go-around' (TOGA) thrust." (page 32-33)
    Strength: +1
    Aircraft: A320
    Equipment: automation
    Source: Mellor, P. (1994). CAD: Computer-Aided Disaster. High Integrity Systems, 1(2), 101-156. See Resource details

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  12. Evidence Type: Excerpt from Incident Study
    Evidence: In our review of 282 automation-related ASRS incident reports, we found 14 reports (5%) supporting issue044 (mode transitions may be uncommanded).
    Strength: +1
    Aircraft: various
    Equipment: automation
    Source: Owen, G. & Funk, K. (1997). Flight Deck Automation Issues: Incident Report Analysis. http://www.flightdeckautomation.com/incidentstudy/incident-analysis.aspx. Corvallis, OR: Oregon State University, Department of Industrial and Manufacturing Engineering. See Resource details

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  14. Evidence Type: Excerpt from Survey
    Evidence: "Pilots were asked to describe instances where FMS behavior surprised them and to indicate modes/features of FMS operation that they did not understand. There were no sharp boundaries between the incidents elicited by the two questions. Pilot reports are categorized according to their underlying theme." ... There were 28 reports [28 / 135 = 20.7%] in the category: "Uncommanded Mode Transitions ... Pilots report that they are surprised by 'uncommanded' mode transitions which occur upon reaching a target state or for protection purposes. Most often, the reports refer to the automatic reversion from Vertical Speed Mode (V/S) to Level Change mode (LVL CHG) which occurs if the airspeed deviates from the target range due to an excessive rate of climb or descent." (page 307, 311)
    Strength: +1
    Aircraft: B737-300
    Equipment: autoflight
    Source: Sarter, N.B. & Woods, D.D. (1992). Pilot interaction with cockpit automation: Operational experiences with the Flight Management System. International Journal of Aviation Psychology, 2(4), 303-321. Lawrence Erlbaum Associates. See Resource details

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  16. Evidence Type: Excerpt from resource
    Evidence: "Indirect mode transition: 14 cases. Another source of surprises is the "indirect" mode transisition, in which the automation changes its behavior without an explicit instruction by the pilot. In some cases such uncommanded transitions result in automation behavior that runs contrary to pilot's intentions and may even be unsafe." (page 560)
    Strength: +1
    Aircraft: A-320
    Equipment: automation
    Source: Sherry, L. & Polson, P.G. (1999). Shared models of flight management system vertical guidance. International Journal of Aviation Psychology, 9(2), 139-153. Lawrence Erlbaum Associates. See Resource details
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