Automation and the ATCO – Human Factors Consideration

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Automation and the ATCO – Human Factors Consideration

30TH ANNUAL CONFERENCE, Port of Spain, Trinidad & Tobago, 22-26 April 1991

WP No. 74

Automation and the ATCO – Human Factors Consideration


The Subject of Mode S Operation was put on the Work Programme of SC4 at the 1989 Frankfurt Conference. The reason for raising this subject was the concern of several MAs at the way Mode S was being considered for use within the ATC System.


i)  as a means of Automating ATC;

ii)  as a means of promoting an Airborne Collision Avoidance system, rather than the provision of a satisfactory ATC Service;

iii)  as a means to improve airborne data to enable airlines to take over aspects of existing ATC Services, such as Flow Control management;

Whilst recognising the positive advantages of Mode S, there is concern that the involvement of the ATCO is being ignored during the considerations for the operational use of Mode S transponders. Specifically, the use of Mode S could be developed to devolve certain responsibilities from the controller and reduce the participation of the controller in the ‘control’ process of Air Traffic Control.

A Working Paper was prepared for the 1990 Acapulco Conference, but this was withdrawn during the proceedings of Committee C. Although the working papers was prepared for information purposes only, certain objections to the content of the paper resulted in it being withdrawn and the subject retained on the Work Programme of SC4 for further consideration. During further discussion on this subject, SC4 decided to broaden the topic to include all aspects of Automation and the Controller, rather than focus specifically on Mode S implications. Although the subject of Automation and the ATCO involves Technical and Legal aspects, this Working Paper, prepared by SC4, concentrates on the Human Factors considerations.


The similarities between ATC Operations and Aircrew working with electronic Flight-decks presentations may seem remote, but there are signs that aircrew operating in such an environment are identifying problems associated with automated controls and data. Aircrews are becoming passive monitors rather than active fliers and there have been numerous reports of pilots trying to ‘fix’ the computer, rather than fly the aeroplane. Is this the way ahead for the ATCO? Will ATCOs become so reliant on automated systems that active participation is reduced to a monitoring status? And will the ATCO be expected to pick up the pieces, and take over, if the computer cannot provide the appropriate solution to the problem?

There are already areas where ATC is being automated in some way or another. In these cases data exchange is being enhanced by computerised Databases and electronic data displays. The introduction of colour radar, for instance, allows for a greater measure of enhancement than monochrome. The computerisation of ATFM is seen as an essential element to efficiently deal with the various flow control rates and increases in traffic demand. However, in the case of the Shanwick OATCC computer there is a radical move towards a computerised ‘control’ function, with computer assigned Oceanic clearances being issued. This system has not proved to be fail- safe, nor is it seen as being able to deal with all clearance requests. If is was not for the fact that an ATCO is still needed to provide a clearance that the computer cannot cope with, then it would be quite possible that this system could operate without any ATCO involvement, at all. Air Traffic Control Assistants would input clearance requests and the computer would provide the answer. ATCOs would no longer be necessarily required.

Mode S transponders are already being seen as solution to resolving many ATC problems and difficulties, around the world. Not only to supply the ATCO with seemingly limitless amounts of data, but also to provide a Conflict Alert and Resolution system for aircraft so equipped.

IFATCA policy already exists on Airborne Collision Avoidance Systems (ACAS):

“IFATCA recognises that the development of airborne collision avoidance systems should be encouraged. However, it must be accepted that the primary means of collision avoidance within a controlled airspace environment must continue to be the Air Traffic Control System that should be totally independent of airborne emergency devices such as ACAS. Autonomous airborne devices should not be a consideration in the provision of adequate Air Traffic Services”.

(IFATCA Manual p. 3211)

IFATCA also draws attention to the compatibility between a controller’s responsibility for providing positive separation and with the controller’s ability to discharge them.

IFALPA also highlights the inherent requirements of a data-link system, such as Mode S.

“The integrity of information should be assured by system design, together with automatic warning in the event of malfunction. The system should be capable of growth and also be standardised. Data link should not supersede the use of voice where this is the optimum medium and voice communication should remain available as a back-up.”

(IFALPA Annex 10 (COM) Polstat (April 1987)

Electronic data screens may replace Flight Progress Strips, but when the TV monitor fails all the data is immediately lost. The need for a fail-safe system, or immediate access to duplicated standby equipment, is paramount. Human Factor research has already identified that automation does not always reduce ATCO workload, in fact it can increase it. Certain aspects of an ATCOs’ tasks need to remain a manual type operation to maintain job satisfaction. Automation can reduce awareness and alertness. The man-machine interface is extremely important and Psychologists highlight the need for the system to fit the man, rather than the other way around. Human response involves the use and co-ordination of eyes, ears and speech, together with a little common sense. Computers rely on the ‘right’ button being pressed and the ‘right’ programme installed to ensure the ‘right’ action is taken. One of the difficulties facing computer programming of ATC Systems is the ability to engineer a programme that can deal with every eventuality and situation. If the computer is faced with a problem that it cannot solve, it will fail, but ATCOs are expected to provide solutions to every problem they face.


Human Factors research has shown that automated tabular lists of aircraft data impose a major search task when traffic becomes heavy. Alphanumeric labels (SSR) encounter serious difficulties when label overlap occurs in high density traffic. Because it cannot all be displayed at once, some information will have to be requested from the computer. This requires ATCOs to undertake extra tasks to use keyboards, or other methods, to retrieve data. In automated systems, in addition to extra data entry and retrieval tasks, the ATCO may have more to remember, because less information is permanently displayed. This may well lead to multi-data displays or extensive data ‘menus to find the information that is required.

It may still be right to introduce an automated aid, but it should be justified on it’s own merits, rather than implying benefits purely in workload terms. There is a need to specify exactly how new and updated data is imputed into the system. If done automatically, there is a need for correct data, as well as a means of highlighting when data changes. If undertaken manually, there must be keyboard and data entry skills to maintain accuracy. Errors can easily occur if personnel are distracted or fail to enter the data correctly. In any such system, whether the data input is automatic or manual, there must be a means of cross checking the data to ensure absolute reliability and confidence.


It is often suggested that by automating a system, you can reduce peak workloads, or can increase system capacity. This is often far from the truth. Additional working practices, such as data entry/retrieval methods can actually increase workload. When ATCOs are working at peak levels of workload, this is usually due to them exercising positive control over the maximum number of aircraft in the constraints of limited airspace. Merely by automating certain aspects of an ATC system will not enable the ATCO to necessarily handle more traffic. Any automation should be directed in removing non-essential tasks allowing the ATCO to concentrate on more important tasks. It is not correct to assume that, because workload of one kind can be reduced by an automated aid, a commensurate increase in workload of another selected kind must be possible. A reduction in speech does not necessarily lead to more time for decision making. A relative consistent finding in ATC studies, is that an automated aid, such as SSR labelling on a display, may lead to substantial reduction of essential verbal messages, without producing a corresponding improvement in any other measurable aspect of an ATCO’s performance.

Job satisfaction

It is generally recognised that educated personnel with higher levels of skill and status (which includes ATCOs) find that their main source of satisfaction in a job lies in its intrinsic interest to them (Herzberg, 1957). A satisfying job should require effort, provide a challenge and make use of the person’ skills. Automation may well reduce the effort of certain tasks and the stress associated with them, but may lead to loss of job satisfaction by taking away some of the intrinsic interests of the job, and the perceived ‘control’ over certain functions. It is widely accepted that the challenges of the ATCO’s job is one of the main reasons that ATCOs enjoy their profession. Even working under difficult circumstances, sometimes with inadequate equipment and with high traffic levels, ATCOs may well perceive they are working very hard, possibly under great stress, but afterwards they will generally accept that they have achieved a great deal in dealing with a complex and busy situation – and will find an element of satisfaction. A reduction of workload, to the point that job satisfaction is reduced, can lead to boredom and general discontent.

System integrity and ATCO responsibility

When undertaking their duties, ATCOs are generally fully aware of the responsibilities they carry. They continually check their own and other’s work so that safety is not compromised. An ATCO is usually encouraged to be self-critical and to embrace self-analysis of their methods of operation. Because of the inherent safety factors that are associated with the task, ATCOs are trained to expect the unexpected. They are generally cautious with the data they handle. Pilots do not always do what is expected of them and ATCOs are continually forming alternative solutions to problems. The nature of the job requires an ATCO to be able to react quickly and calmly to ‘unusual’ events.

Automation requires great confidence from the operator. Operators must be able to trust the data they are dealing with. With greater levels of automation, the more reliant the operator becomes in the system to provide accurate and trustworthy data. In any field of automation, the data-links must be fail-safe and totally accurate. Otherwise the operator will not trust the system and will feel uncomfortable working with it. In the ATC world there can be no element of doubt in a controller’s mind to the accuracy of the data being handled. Safety depends on it.

The question of responsibility in automated systems needs to be looked at closely. If the controller is going to retain the ‘control’ function, then the responsibility remains with him, or her. It is no good at all suggesting that an error in the computer input is the reason for an airmiss, or that the data that the ATCO was using was corrupt or inaccurate.

The Legal implications of automated ATC systems need to be identified and responsibilities determined. ATCOs may hold the responsibility, at least in the legal sense, without retaining the means to exercise the responsibility that they possessed when the system was manual. The reliance that will be naturally placed on automated systems should be balanced by alternative methods of handling the workload should the system fail and ‘manual reversion’ takes over. Does ‘Fail-Safe’ actually exist and should ATS Authorities ensure that the manual type of ATC procedures are maintained to cope with failures of an automated system?


Automation is, in many instances, desirable and beneficial. In some cases it can be considered essential. Automation should only be introduced when there is a full awareness of all the associated Human Factor implications.

Automation sometimes brings extra tasks, as well as benefits, and many functions cannot be automated entirely. Automated aids should also be trustworthy. When automation is extended to problem solving and decision making, it affects job satisfaction and the exercise of skills and responsibilities.

Computer assistance can alter the nature of the task and new information is of no use unless it is presented in an easily understandable form. There are no equivalents of job satisfaction, stress, status, morale or professional pride in machines.

A fall back system of ATC skills should be maintained, despite the ability to do away completely with some aspects of the ATC task. Automation carries implications, both real and perceived, of status and responsibility. As automation evolves, certain automated functions in the system become relatively fixed and inflexible. This reduces the ability of the controller to implement different strategies to solve individual problems. The nature of the ATC task allows individual controllers to apply differing strategies that result in similar solutions and efficiency of operation.

Automation may limit the freedom of choice for the individual and ATCOs may perceive a loss of control or a reduction in skills to perform their tasks. In efficiency terms, it may be possible to identify and assume that there is only one particular way to complete a task. Though convenient, this will require all ATCOs to be trained in one particular way. If there is no such optimum way, then the machine should not be designed as though there is.

Studies in other safety critical industries, such as nuclear power and the cockpit, have identified undesirable human factors trends within the design and operating philosophy of these systems, as a result, the current human factors preference should be to retain the controller as the primary decision maker in future ATC systems, in order to maintain the controller’s interest, motivation and skill levels.

There are genuine needs for automation to assist ATCOs, to improve performance and reduce workload, to increase efficiency, to remove non-essential tasks, and to enhance job satisfaction.

There is also a need for ATCOs to be involved as an essential part of any future ATC system. The man-machine interface needs to be examined closely so that the system fits the man, rather than the other way around.

There is a requirement for ATCOs to be involved with evaluations of equipment design and purchase. It is essential that automation works for the benefit of the controller.


Automation must improve and enhance the data exchange for controllers. Automated systems must be fail-safe and provide accurate and incorruptible data. These systems must be built with an integrity factor to review and crosscheck the information being received.

Automation must assist and support ATCOs in the execution of their duties, to improve performance and reduce workload, to remove non-essential tasks, to increase efficiency, to enhance not only the job satisfaction of the controller, but also the safety element of the controller’s task.

The Human Factors aspects of Automation must be fully considered when developing Automated systems and should include the maintenance of essential manual skills and controller awareness.

The controller must remain an essential element of the ATC system and must retain the overall control function of the system. Safeguards must be established to ensure that the controller remains an active, rather than a passive, monitor of an automated system.

The legal aspects of a controller’s responsibilities must be clearly identified when working with automated systems. Limits of responsibility must be established when electronic data is being handled automatically without controller input or control.


Human Factors in ATC: David Hopkin – NATO AGARDograph no 275.

The controller versus Automation: David Hopkin.

MMI Problems in designing ATC systems: David Hopkin (I.E.E. 1989).

Automation – Implications for Knowledge Retention as a Function of Operator Control Responsibility: C S Narborough Hall (RAF. IAM).

Research in Automation for ATC: UK work and Associated European Projects – A.G. Thorning (1987).

Report on ASI Conference – Automation and Systems Issues in ATC. – J. Levesley UK Guild of Air Traffic Control Officers (1990).

The Future Position of the controller – K. Brauser & R. Seifert.

Last Update: September 20, 2020  

December 4, 2019   818   Jean-Francois Lepage    1991    

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