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Evidence for an Issue 7 pieces of evidence for this issue.

automation may use different control strategies than pilots (Issue #122) - Automation may use a different strategy of control or control logic than the pilot, possibly leading to the pilot's loss of situation awareness and pilot errors.

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  2. Evidence Type: Excerpt from Incident Study
    Evidence: "4.1.2.2 FMS Algorithmic 'Behavior' ... In many of the reports, an altitude excursion was the result of the FMS not performing as expected, or the flight crew not recognizing that the FMS was not working properly or was misprogrammed. It is likely that these incidents occur because the FMS algorithms are designed to level off the aircraft at the last minute. If the flight crew missed the 900-foot and 300-foot cues that signal approaching the selected altitude, this leveling off is the major cue to the crew that the desired altitude will be acquired. The last-minute nature of the leveling-off process, coupled with missing the altitude alert cues, means that the crew knows a problem has occurred only when the airplane does not [emphasized] level off, at which time it is probably too late to perform any actions that can prevent the altitude deviation. One pilot described the experience this way: [ASRS Report #125410] ... 'On departure, we were cleared to climb to 12,000 feet, but we had an altitude deviation and climbed to 12,450 before returning to our assigned altitude of 12,000. At 11,000, I called 1,000 to go and then looked back outside to clear for traffic in the turn. I looked back inside and saw that we were at 11,800 climbing at 4,000 feet per minute (fpm). I pushed forward the yoke the same time I said '12,000' ... This aircraft is a popular modern transport with an excellent thrust to weight ratio, glass cockpit, autothrottles, FMC's, the works. With this aircraft's power it has quite a good climb rate and the automated systems fly the aircraft exceptionally well, but they do not climb or descend the aircraft according to the Airman's Information Manual (AIM). It is not at all unusual to approach within 300-400 feet of an altitude at 4,000 fpm. The computer will capture the altitude with about a 1.25 G pull or a .75 G pushover so that the passengers don't really feel it... I feel that if the AIM descent and climb rates were programmed into the computer that would be a better system. That way, high vertical speed in the last 1,000 feet would be the exception and not the rule and much more likely to result in a timely level off instead of an altitude bust. After all, it would take more that [in sic] 30 seconds to overfly/underfly an altitude by the magic 300 feet at 500 fpm as opposed to only slight more that [in sic] 4 seconds it would take at 4,000 fpm.' This type of algorithm can encourage the occurrence of altitude excursion since it does not leave much room for error compensation." (page 4.7-4.8)
    Strength: +1
    Aircraft: unspecified
    Equipment: FMS
    Source: Eldredge, D., Mangold, S., & Dodd, R.S. (1992). A Review and Discussion of Flight Management System Incidents Reported to the Aviation Safety Reporting System. Final Report DOT/FAA/RD-92/2. Washington, DC: U.S. Department of Transportation, Federal Aviation Administration. See Resource details

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  4. Evidence Type: Excerpt from Survey
    Evidence: "Q.59. Do you feel that aircraft designers' logic differs from pilot-users' logic?" 88.0% of the respondents answered either 'yes, absolutely' or 'yes, on the whole', 4.8% answered 'No, not at all' or 'No, on the whole not', and 7.2% answered 'Neither yes nor no' or gave no response. (page 37)
    Strength: +4
    Aircraft: unspecified
    Equipment: automation
    Source: Gras, A., Moricot, C., et. al. (1994). Faced with automation. Publications de la Sorbonne. See Resource details

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  6. Evidence Type: Excerpt from Survey
    Evidence: 13 of the 30 (43%) respondents reported a 4 (= agree) or 5 (= strongly agree) with pc122 automation may use different control strategies than pilots
    Strength: +2
    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: 10 of the 30 (33%) respondents reported a 1 (=strongly disagree) or a 2 (=disagree) with pc122 automation may use different control strategies than pilots
    Strength: -2
    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: "56 pilots provided comments on Automation Surprises. These responses were coded into categories based on the primary thrust of the pilot’s response. Five categories were created with ten of the responses not fitting into one of the five categories. The categories, numbers of responses in each category, and a brief summary of the comments are provided below:...Speed (18) -- The plane slows too early. FMS Speed mode causes surprises. This plane places a priority on airspeed over altitude, which is a problem when you have speed and altitude-constrained waypoints." (page 437)
    Strength: +1
    Aircraft: MD11
    Equipment: automation & FMS
    Source: Parasuraman, R., Mavor, A., Wickens, C.D., Danaher, J.W., & Aalfs, C. (1998). Managing the future national airspace system: Free flight or ground-based control with increased automation (panel session). In Proceedings of the 42nd Annual Meeting of the Human Factors and Ergonomic Society, 62-66. See Resource details

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  12. Evidence Type: Excerpt from resource
    Evidence: Automation strategies in managed vertical navigation: 6 cases... The automation is designed to improve fuel efficiency by minimizing thrust variations. It therefore compensates for any deviations from its target airspeed by allowing the airplane to deviate to some extent from the target altitude. This is not the way pilots manually fly the airplane, and therefore the automation behavior surprises them and sometimes leads to unnecessary pilot interventions. (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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  14. Evidence Type: Excerpt from Experiment
    Evidence: "It is also important to realize that the performance benefits of the NAV condition were achieved without noticeably altering the 'style' in which the aircraft flew the circuit. The tracks produced by the FMS appeared 'normal', i.e., not unlike the intended track or the tracks produced when the pilots flew in the STANDARD condition. There was no apparent cause for concern that flight tracks flown with the FMS in command would differ materially from those flown by aircraft not equipped with an [in sic] FMS." (page 11.14)
    Strength: -1
    Aircraft: A310
    Equipment: FMS & autopilot
    Source: Speyer, J.J., Monteil, C., Blomberg, R.D., & Fouillot, J.P. (1990). Impact of New Technology on Operational Interface: From Design Aims to Flight Evaluation and Measurement. Advisory Group for Aerospace Research and Development No. 301, Vol. 1. See Resource details
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