Guidance in Choosing Among Levels of Automation
Human Factors in Aircraft Automation - issue #1
SECOND REPORT from the Human Factors Committee, Automation Subcommittee, Air Transport Association
prevThe FAA team recommended that carriers "provide guidance to crews concerning circumstances where autoflight should be engaged, disengaged, or engaged in modes with greater or lesser authority, conditions under which autoflight systems will not engage, will disengage, or revert to another mode, and appropriate combinations of automatic and manual control." However, the subcommittee concurs with the position advocated by most member carriers that operating manual guidance and initial and recurrent training should lead to application of pilot judgment rather than provide highly specific guidance on when to use what level.
The Subcommittee noted two types of guidance provided by carriers on this issue:
- Authorization to choose levels of automation — Each carrier has emphasized that proficiency is required in each level of automation, and has explicitly authorized pilots to choose the most appropriate level for each flight situation. Statements of this type appear today in most policy manuals.
- Training for choosing among levels — Some carriers have begun to offer guidance in training for when to choose what level, and this is a significant further step beyond simply authorizing such choices. However, these training statements have not been documented in policy or operating manuals. Such guidance would include activating versus deactivating automated systems for specific/special recovery maneuvers. For example, one member carrier has specified in training to disconnect autopilot and autothrottles to maintain control and extract maximum aircraft performance for: unusual attitude recovery, windshear/microburst, high altitude upset, GPWS terrain warning, engine failure at low altitude/energy state, flight instrument malfunctions, and mid-air collision avoidance. Though the subcommittee does not necessarily endorse this specific statement, we do believe this level of guidance is warranted.
While training has begun to expand guidance regarding levels of automation, little more has been written into policy or operating manuals as a part of the carrier’s operating philosophy. Most of these statements remain limited to authorization to choose levels appropriate to each situation.
Supporting Evidence
Significantly, several member carriers participated in the research conducted by the FAA Team in 1995. Despite the efforts described above, the Team found evidence leading to automation management and situation awareness concerns. Similarly, reports to ASRS and Partnership programs continue to reflect two tendencies consistent with the Team’s concerns:
- Tendency to choose an inappropriate level of automation – Even though carriers have explicitly authorized pilots to choose appropriate levels, pilots often attempt to program when it creates additional workload, or alternatively, to turn automation completely off even though some intermediate mode would relieve workload. This is exactly the issue to which automation philosophy statements were written. Further documentation to guide these choices is warranted.
- Tendency to attempt to correct an "automation-induced" deviation by manipulating the automated system, rather than the controls of the aircraft — a situation where manual control is clearly most appropriate, yet reports show preference for mode control over manual control. (The FAA Team pointed out that in some accidents, pilots have turned to an autoflight system to correct flight attitudes beyond the capability of the system -- in contrast to guidance in some member carriers’ training that immediate control requires manual control.) Again while carriers are highlighting this issue in training, publication of more detailed guidance is warranted.
Policy Guidance for Pilot Action
Application of pilot judgment is the immediate target of guidance on this issue. The subcommittee offers the following prototypical statement for publication in policy manuals:
Pilots will be proficient in operating their aircraft in all levels of automation. However, the level of automation used at any time should be the most appropriate to enhance safety, passenger comfort, schedule, and economy. Pilots are specifically authorized to choose what they believe to be an appropriate level of automation. In general, choices among levels can be guided by their functionality and the demands of the situation.
- Where immediate, decisive, and correct control of aircraft path is required, the lowest level of automation — hand-flying without flight director guidance — will be necessary. Such instances would include escape or avoidance maneuvers and recovery from upset or unusual attitudes. With the exception of visual approaches and deliberate decisions to maintain flying proficiency, this is essentially a non-normal operation for flight guidance or FMS-generation aircraft. It should be considered a transitory mode used when the pilot perceives the aircraft is not responding to urgent aircraft demands. The pilot can establish a higher level of automation as soon as conditions permit.
- When used with flight director guidance, hand flying is the primary takeoff and departure mode. It is also the primary mode for landings, except for autolands.
- Where short-range tactical planning is needed (i.e., radar vectors for separation or course intercept, short-range speed or climb rate control, etc.), Mode Control or Flight Guidance inputs may be most effective. This level should be used predominantly in the terminal environment when responding to clearance changes and restrictions, including in-close approach/runway changes.
- Autoflight coupled to the FMS/GPS is the primary mode for non-terminal operations and should be established as soon as "resume own navigation" or similar clearance is received. This level exploits programming accomplished pre-flight. Where the longer-range strategic plan is changed (i.e., initial approach and runway assignment, direct clearances, etc), Flight Management inputs remain appropriate. However, when significant modifications to route are issued by ATC, the pilot should revert, at least temporarily, to lower levels of automation.
The subcommittee believes a statement like this represents significant and needed guidance beyond what appears in carrier manuals today.
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