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(
Autoflight Mode AwarenessIssues: An Overview
Beth Lyall
Presented to the FAA Mode Awareness Workshop
Seattle, July 14-16, 1998
( Mode Awareness Workshop
Outline
• Definitions– Mode error
– Mode awareness
• Types of modes and mode transitions
• Mode-related issues
• Summary for workshop
( Mode Awareness Workshop
Why are we interested in modeawareness?
• Flight crew confusion about autoflight modes hascontributed to some accidents
• Pilots have reported incidents in which modeawareness was an issue
• Flight test pilots and others in aircraft oroperations certification have identified problems
• Human factors researchers have identified issuesrelated to flight crew mode awareness
( Mode Awareness Workshop
Assumptions
• Flight crew performance of their tasks willbe enhanced by increasing their awarenessof autoflight modes
• The flight crew / aircraft systemperformance will benefit from increasingflight crew awareness of autoflight modes
• Increasing the mode awareness of flightcrews will increase flight safety
( Mode Awareness Workshop
Definitions
• Mode
• Mode error
• Mode ambiguity
• Mode awareness
• Types of modes
• Mode transitions
• Mode structure
( Mode Awareness Workshop
Definition of Mode
• A machine configuration that correspondsto a unique behavior
• A manner of behaving
• A device state which controls or displaysfunctions in a distinct way or has a distinctmeaning
( Mode Awareness Workshop
Mode Error
When a situation is falsely classified, theresulting action may be one that wasintended and appropriate for the perceivedor expected situation, but inappropriate forthe actual situation (Norman, 1981)
( Mode Awareness Workshop
Mode Ambiguity
A state in which the mode of the systemcannot be determined based on theinformation available
( Mode Awareness Workshop
Mode Ambiguity and Errors
If distinguishing between modes is not apart of the user's task, no meaningful errorswill occur due to mode ambiguity (Degani,Shafto, & Kirlik, 1998)
( Mode Awareness Workshop
Mode Awareness
• The ability of the user to track andanticipate the behavior of the automatedsystems (Sarter & Woods, 1995)
• An abstract level of vigilance required tomanage the operation of multiple modesconcurrently with other tasks (Callentine,1997)
( Mode Awareness Workshop
Mode Awareness
Factors for maintaining mode awareness(Sarter & Woods, 1995)
• knowledge of how the system works
• tracking of environment states and events andpast instructions given to the automation
• monitoring, integration, and interpretation ofnumerous indications of the active modeconfiguration
( Mode Awareness Workshop
Mode Awareness
To maintain mode awareness, pilots ofautomated aircraft must know:• who/which system is in charge of controlling
the aircraft,
• what the active target values are, and
• whether they can anticipate the status andbehavior of the FMS (Sarter and Woods, 1994).
( Mode Awareness Workshop
Types of Modes
• Control modes
• Format/data-entry modes
( Mode Awareness Workshop
Control Modes
• The purpose of control modes is to providethe human operator with options forcontrolling the behavior of automation.
• Some have further divided these into– functional modes that specify the behavior of
the various functions of a machine, and
– supervisory modes that specify the level of theuser and machine involvement in supervisingthe process
( Mode Awareness Workshop
Control Modes
Control modes have• engagement conditions
• arming conditions
• disengagement conditions
• control properties- subsystems used by or controlled by the mode,
- the specific set of parameters that the mode controls,
- the manner in which the mode controls them
• allowable modifications to operation
( Mode Awareness Workshop
Format / Data-Entry Modes
• The purpose of format/data-entry modes isto provide increased functionality of asystem while using the same inputmechanism and display space
• Control mode interfaces often incorporateformat/data-entry modes
( Mode Awareness Workshop
Mode Transitions
• Manual - can only be commanded by the humanoperator
• Automatic - only occur automatically as a resultof some target state being attained
• Automatic/manual - occur either as a result ofpilot input or attainment of a specific target state
• Conditional - can be armed for later engagementor engaged immediately if the target stateconditions are already met at the time of inputfrom the human operator
( Mode Awareness Workshop
Mode Structure
Degani et al. (1995) use the term “modestructure” to refer to• the hierarchy of modes in a system,
• the transitions among modes and associatedtransformations in the controlled system, and
• the interactions between modes of differentsubsystems
( Mode Awareness Workshop
Evidence forMode-Related Issues
• Accidents
• Incident report reviews
• Surveys
• Operations and training observations
• Experiments
( Mode Awareness Workshop
Accidents withMode-Related Contributors
• China Airlines 747 Upset
• A320 in Bangalore
• Aeromexico DC-10 over Luxembourg
• A320 at Strasbourg
• L-1011 in the Everglades
( Mode Awareness Workshop
Mode-Related Issues(Eldredge, Dodd, & Mangold, 1992)
• Mode transition difficulties
• Problems understanding VNAV logic
• Insufficient information on FMA
( Mode Awareness Workshop
Mode-Related Issues(Vakil et al., 1995)
• AFCS failures
• Database errors
• Confusing mode transitions
• Data entry problems
• Insufficient knowledge of mode behavior
• Crew coordination problems
( Mode Awareness Workshop
Mode-Related Issues(Wiener 1985, 1989)
• Mode-mode interactions cause unexpectedtransitions
• Insufficient information on the FMA
• Difficulty after a mode has been requested(armed), but conditions for a transition havenot been met
• Mode and reference value interactionsaffect when pilots can intervene
( Mode Awareness Workshop
Mode-Related Issues(Sarter & Woods, 1992, 1994, 1995)
• Mode availability
• Mode disengagement
• Tracking automatic mode transitions
• VNAV mode target values and logic
• Infrequently used modes
• Selecting from multiple modes
• Automation surprises (taking unexpected actions, failing totake expected actions)
• Preparing a mode, but forgetting to engage it
• Increasing errors of omission (failure to detect undesiredbehavior)
( Mode Awareness Workshop
Mode-Related Issues(FAA HF Team Report, 1996)
• Difficulty understanding control algorithms ofmodes
• Incomplete or wrong expectations of systembehavior
• Situations unforeseen by designer lead tounexpected mode behaviors
• Difficulty anticipating the next system state whendifferent levels of supervisory modes are usedconcurrently
( Mode Awareness Workshop
Other Certification Issues
• Number of modes prohibits testing of allpossible operational situations
• Challenge lies in defining scenario set fortesting to best represent entire set and mostsafety critical situations
( Mode Awareness Workshop
Summary of Mode Awareness Issues
• Different locations of mode control interface andmode annunciations
– may result in conflicting information availableabout the system
• Salience of cues indicating mode transitions
• Availability of information about when a modewill not engage
• Multiple modes to accomplish the same tasks
• Complexity of mode behavior is sometimesdifficult to understand
( Mode Awareness Workshop
Summary
• Humans behave/perform in a mannerconsistent with their view of the situation
• For supervisory performance this viewincludes their expectations aboutperformance of all agents involved in taskperformance
• For flight crews this includes performanceof the automated systems
( Mode Awareness Workshop
Summary
Flight crew expectations of automatedsystem performance result from:• their knowledge of the way the system is
designed to perform
• their experience with the system
• information available on the interface aboutsystem intentions (mode, parameters, referencevalues, limitations)
( Mode Awareness Workshop
Summary
• A representation of these flight crewexpectations related to automated systemperformance has been called modeawareness or mental models of the system
• There have been issues documented frommany domains related to mode awareness
( Mode Awareness Workshop
Summary
• We are concerned with flight crew modeerror because it represents performance thatis not consistent with the actualsituation/mode in which the flight crew wasperforming
• We assume that being more aware of themode of the system would decrease thiserror
( Mode Awareness Workshop
Workshop Challenge
• The challenge faced by members of theworkshop is to make recommendations thatwill close the gap between pilotexpectations and actual system performance
• This can be done with– training
– procedure design
– system design and certification