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HMI Aspects of Support Tools for Air Traffic Management
Copyright 0 IFAC Analysis, Design and Evaluation of Human-Machine Systems, Kassel, Germany, 2001
HMI ASPECTS OF SUPPORT TOOLS FOR AIR TRAFFIC MANAGEMENT
Dipl.-Ing. Ralf Beyer
delair Air Traffic Systems Lilienthalplatz 5 D-38J08 Braunschweig Federal Republic a/Germany
Abstract: Air traffic is growing but the resources of airspace and real estate for airports are rather limited. Therefore, a better utilisation of given resources is needed to achieve the necessary capacity enhancement. This in turns leads to more complex operational procedures and to the requirement of better support of the human operator in air traffic management by intelligent machines. Some examples of operational support tools are presented and future development areas for machine-based support in air traffic management are discussed with particular respect to the human-machine interface aspects involved. Copyright @200] IFAC Keywords: air traffic control, automation, continuous speech recognition, co-operation, decision support systems, ergonomics, human-centred design, human factors, manmachine interaction, man-machine systems.
Operations research has shown that operations in the terminal area of an airport can be regarded as a system of interacting processes that are often not optimised with respect to air traffic capacity and to the more general requirements of energy conservation, protection of the environment, and integration of air traffic with other modes of transport. Capacity gains can be expected, therefore, from a more efficient design, integration, and implementation of these interacting processes. This applies in particular to the control of the arriving, taxiing, and departing air traffic as well as to all types of operations on the ground. However, human operators will not be capable to achieve this process optimisation without the help of intelligent machines for situation monitoring, diagnosis, planning, plan selection, and plan execution.
1. INTRODUCTION Air traffic is growing and so are the delays in air traffic. A flight is said to be not on time if it is delayed by more than 15 minutes. In the United States, over 300,000 flights annually experience such delays. In Europe the situation is even worse because of the dense infrastructure, national regulations, and ecological constraints. Lufihansa, for instance, reported for the year 2000 that (only) SI% of its flights were on time and that the current goal is to increase this rate to 90%. While in 1997 about 7.5 million flights used the European airspace, S.6 million flights were counted in the year 2000, and about 12 million flights are expected by the year 2010. Germany with its central geographic position in Europe is particularly affected by this growth of air traffic resulting in about SOOO flights per day over Germany.
2. PAST EXPERIENCES WITH MACHINEBASED SUPPORT SYSTEMS
The bottlenecks of air traffic are still the airports and the surrounding terminal areas. However, the chance to extend existing airports in terms of real estate and thus larger infrastructures including more runways is rather limited. On the other hand capacity enhancements are needed in the light of the expected air traffic growth. Capacity enhancements must concentrate, therefore, on a better utilisation of given infrastructures and human resources.
To support human operators working in air traffic management, the concept of a machine-based system that manages the increasingly complex air traffic at large airports has been pursued for almost two decades. Although billions ofU.S. dollars were spent for research and development - the largest project being the Advanced Automation Suite (AAS) in the U.S. - no such comprehensive support system is in operation today. Major reasons are:
549
no need for national or regional agreements on their (local) introduction
sensory, algorithmic, and computational difficulties to compute and to predict aircraft trajectories with high accuracy in real-time, -
problems of conflict resolution in real-time,
-
operational difficulties to integrate a rather autonomous machine-based system for air traffic management into the overall system of airspace, airports, handling agents, airlines, and others in form of a collaborative decision making (CDM) process, and
-
lack of acceptance by the human operator.
The design, development, prototyping, and introduction of early sets of support tools less complex than the much needed assistant systems also required a significant effort. For support tools like the Computer Oriented Metering, Planning and Advisory System (COMPAS) developed by DLR and DFS in Germany or the Center-TRACON Automation System (CTAS) developed by NASA in the U.S. this cycle took up to 15 years. However, some of the support tools developed for air traffic controllers are operational today.
-
relatively short development cycle
-
non-intrusive to current airport operations
-
configurable to the particular needs of an individual airport
-
easy interaction among support tools for different operational areas
-
almost no safety risks
-
good expected/demonstrated acceptance by the human operator
Therefore and with the experiences of the past two major development areas for machine-based support and assistance of those working in air traffic and airport management exist today: 1. An increasing number of developments of support tools is foreseen that are needed for operations on the ground in the short run. Relevant products exist and more products will become available shortly because of low safety risks, because these tools are well accepted as responsibility remains with the human operator, and because an attractive return of investment can be expected from their introduction. With these tools significant capacity enhancements of airport operations on the ground can be achieved rather rapidly. These tools form the basis for the conception and the fUture development of human operator assistant systems that later may assume certain responsibilities extending from operational areas with low human operator interaction into areas which are currently the sole responsibility of the human operator.
COMPAS, for instance, estimates arrival times of aircraft, determines the required separation between aircraft of same or different weight classes, and suggests an optimum sequence of aircraft. It supports air traffic controllers in their task to produce a smooth flow of the arriving traffic into an airport while making best use of the existing airport capacity. The tool unburdens air traffic controllers from recurring tasks, leaves responsibility with the air traffic controllers, and does not involve safety risks: if the tool is turned-off air traffic controllers return to their previous operating practice at the expense of operational efficiency. COMPAS is ofa non-intrusive nature and has led to a smooth workflow in the management of the arriving air traffic at an airport. It is in operation since 1989 at the airport of FrarUkfUrtn\1ain.
2. On the other hand it becomes evident that support tools alone are inadequate to solve the bottlenecks in the departing, en-route, and arriving air traffic. Human operator assistant systems are required, therefore, which assume some of the responsibilities of the human operator. However, at current the chances are rather low that those working in air traffic management accept such systems and that a large-scale introduction needed to be efficient - can be agreed mid-term. Much more research on human factors, on the interaction of operational processes in air traffic, on safety related issues, and on human operator selection and training is required to achieve a break-trough in this area.
3. FUTURE DEVELOPMENT AREAS Bottlenecks in air traffic management not only exist in airborne operations but also on the ground. Examples are the taxiing of aircraft, the allocation of resources on the ground for passenger handling and aircraft servicing, as well as the flow of passengers and cargo changing between the different transport systems of road, rail, and air. Capacity enhancements of operations on the ground can contribute significantly to the overall capacity of an airport. Moreover, support tools for capacity enhancements on the ground have a number of attractive characteristics when appropriately researched and designed:
Both development areas are needed to achieve the required air traffic capacity enhancements in the short and long run as the human operator and the human-
550
machine interface remain key elements of a successful application of automation and of overall system performance for years to come. This is particular true in the light of major operational changes like the introduction of more flexible air routes in Europe as decided by the European secretaries of transport in 1993 and implemented in April 2001.
sally -bus
a system that assists the operations manager to allocate passenger busses according to the current situation, that provides the current driving orders for bus drivers, and that takes into account the status reports of bus drivers.
4. CURRENT OPERATIONAL EXPERIENCES
sally -tow
a system that assists the operations manager to allocate towing vehicles according to the current situation.
sally -check-in
a configurable system for the flexible allocation of the check-in counters available at an airport.
The success of support tools is largely dependent on an approach described as human-centred automation. This approach attempts to increase the ability of the human operator to manage a complex operational situation and to be aware of the evolution of the situation by means of suitable tools. The responsibility for control and safety will, however, remain that of the human operator. Systems designed this way fmd acceptance by an increasing number of air traffic controllers and airport operations manager. The final proof, however, is their operational introduction and use for a prolonged period of time. Examples are: -
-
-
Much has been learned from the development and from the operation of COMPAS, FLOW MONITOR, and sally -stand in the fields of human-centred design and automation, machine-based support of air traffic and airport management, co-operation of human operators and machine-based support tools, and problem solving. The design philosophy to gain acceptance by the human operators continues to focus, therefore, on aspects that were presented some years ago in another context (McNeese, 1986) but which are fully applicable to the partnership of human operator and support tool:
Since its introduction into operational service in 1989 at the airport of Frankfurt/Main COMPAS (an aircraft arrival sequencing tool developed by DFS and DLR) was so well accepted by the air traffic controllers that it was maintained as one of the support tools also for the new air traffic controller work system of DFS that became operational in 2000 (Schenk, 1991). The FLOW MONITOR (a tool to monitor and to analyse the arriving and departing air traffic at an airport developed by DFS and DLR) was introduced into operational service in 1992 at the airport of Frankfurt/Main and serves as a major tool in the operations supervision and management (Schenk, 1994). sally -stand (a generic system for the planning of the optimal stand and gate allocation at an airport developed by delair Air Traffic Systems) was introduced into operational service in 2000 at the airport of Zurich! Switzerland.
-
Both partners must share overlapping knowledge and meaning.
-
Each partner must contribute insights into problem solution.
-
The processes that involve logic, rules or heuristics must be co-existent or co-explained in the 'mind' of each partner. There must be a shared language to communicate across one partner to another.
sally - resource allocation management systems - in particular represents a whole spectrum of products that efficiently help an operations manager to optimise the use of existing resources at an airport. Its generic system architecture and its control of activity scheduling by means of parameters allows a flexible adaptation to the requirements of an individual airport. Besides sally -stand the spectrum of products includes at current
-
In order to be efficient both partners must implicitly time manage information.
-
Some sense of authority or conflict resolution must exist when one partner disagrees with the other.
5. CHALLENGES AND OULOOK Without going into much detail, two of the most challenging areas that emerge from the current development of human-centred designs of air traffic
551
speech recognition technology and a context-sensitive syntax for phrases to be recognised, DLR in cooperation with DFS achieved remarkable results: the recognition error rate was reduced by 50% when the context-sensitive syntax was used instead of the usual static one. A recognition rate of 93% was achieved when the context-sensitive syntax and the ICAO standard phraseology were employed. A recognition rate of about 95% under true operational conditions seems to be within reach with some technical improvements of the subsystems used (Schaefer, 2001).
management support tools are intent recognition and speech recognition. Machines are currently unable to assess an air traffic situation in the terminal area of an airport in a way that their mental picture agrees acceptably with the mental picture of the air traffic controller. This will not change as long as it is not possible to submit to the machine past experiences as well as a situation dependent value system together with the momentary intentions of the human operator. Intent recognition could provide the planning, problem solving, and plan selecting machines with more timely information and enhance their acceptance by the human operator. This would prevent the machine to focus on problems that have changed or are overcome already by the human operator's momentary intentions. Air traffic controller intentions can change as rapidly as the air traffic situation changes. Even multi-processor machines often cannot catch-up in a timely manner with these changing demands of air traffic controllers to provide problem solutions in real-time.
Currently most support tools monitor a real air traffic situation for any changes compared to a planned air traffic situation. Changes are accommodated either by giving advisories to the aircraft/pilots to revert to the plan or by changing the plan. It is often the support tool time span between detecting a change and responding to the change that prevents it to be accepted by the human operator. If keyboard and mouse inputs as well as speech recognition would be employed to detect air traffic controller actions at the earliest instance of time, much could be gained regarding the timeliness of planning, problem solving, and plan selection by the support tool and thus its acceptance by the air traffic controllers. Both techniques - manual input sensing and speech recognition - are readily available. Combined with context-sensitive evaluation algorithms these techniques are considered an important step to take into account air traffic controller intentions or at least the influence of intentions on the machine-based planning, problem solving, and plan selection process at the earliest possible time.
Intent recognition must be performed in real-time and there are no techniques readily available to fulfil this task. For the time being a promising technique could be a machine-based, situation dependent, contextsensitive assessment of human operator intentions. In addition some form of co-operation between the human operator and the machine must exist to confIrm the human operator intentions assessed by the machine. This requires, however, a new form of logistic support and training of the air traffic controllers that does not exist today.
It is expected that non-intrusive techniques to collect human operator actions and responses will make future support tools for air traffic and operations management more acceptable to air traffic controllers and operations managers. These techniques will become even more important for the development and operational use of the next class of support - the assistant systems.
Experiences from tool development showed that attempts to ask air traffic controllers to use a keyboard to submit their intentions, to confmn or to deny intentions as assessed by the machine, or to hit at least a button if they felt that their mental picture of the air traffic situation and its evolution did not agree with the mental picture of the machine failed. The main reason was the fear that this form of cooperation with the machine would lead to additional and unacceptable duties, to more displays and controls, and to a disturbance of the current workflow that fmally would increase workload. The argument that workload would not be raised by the use of a tool that thinks and behaves like air traffic controllers and that could be more co-operative and more easily supervised than the current tools did not convince the test subjects at this time. As it was not possible to acquire the air traffic controller intentions directly, an attempt was made at least to record the outcomes of intentions at the earliest possible instance of time. Besides inputs from the mouse and keyboard, voice input appeared attractive in this context. With the help of existing
552
REFERENCES McNeese, M. D. (1986). Humane Intelligence: A Human Factors Perspective for Developing Intelligent Cockpits. NAECON, Dayton, Ohio, May 1986. Schaefer, D. (2001). Context-Sensitive Speech Recognition in the Air Traffic Control Simulation. EEC Note No. 02/2001. EUROCONTROL Experimental Centre. Schenk, H.-D. (1991). COMPAS-OP - Ein Planungssystem fUr den Flughafen Frankfurt. DLR-Nachrichten, February 1991 . Schenk, H.-D. (1994). Flow Monitor - Ein System zur Analyse des Anflugverkehrs am Flughafen Frankfurt. DLR-IB 112-94/03, DLR Braunschweig.
553
HMI ASPECTS OF SUPPORT TOOLS FOR AIR TRAFFIC MANAGEMENT
Dipl.-Ing. Ralf Beyer
delair Air Traffic Systems Lilienthalplatz 5 D-38J08 Braunschweig Federal Republic a/Germany
Abstract: Air traffic is growing but the resources of airspace and real estate for airports are rather limited. Therefore, a better utilisation of given resources is needed to achieve the necessary capacity enhancement. This in turns leads to more complex operational procedures and to the requirement of better support of the human operator in air traffic management by intelligent machines. Some examples of operational support tools are presented and future development areas for machine-based support in air traffic management are discussed with particular respect to the human-machine interface aspects involved. Copyright @200] IFAC Keywords: air traffic control, automation, continuous speech recognition, co-operation, decision support systems, ergonomics, human-centred design, human factors, manmachine interaction, man-machine systems.
Operations research has shown that operations in the terminal area of an airport can be regarded as a system of interacting processes that are often not optimised with respect to air traffic capacity and to the more general requirements of energy conservation, protection of the environment, and integration of air traffic with other modes of transport. Capacity gains can be expected, therefore, from a more efficient design, integration, and implementation of these interacting processes. This applies in particular to the control of the arriving, taxiing, and departing air traffic as well as to all types of operations on the ground. However, human operators will not be capable to achieve this process optimisation without the help of intelligent machines for situation monitoring, diagnosis, planning, plan selection, and plan execution.
1. INTRODUCTION Air traffic is growing and so are the delays in air traffic. A flight is said to be not on time if it is delayed by more than 15 minutes. In the United States, over 300,000 flights annually experience such delays. In Europe the situation is even worse because of the dense infrastructure, national regulations, and ecological constraints. Lufihansa, for instance, reported for the year 2000 that (only) SI% of its flights were on time and that the current goal is to increase this rate to 90%. While in 1997 about 7.5 million flights used the European airspace, S.6 million flights were counted in the year 2000, and about 12 million flights are expected by the year 2010. Germany with its central geographic position in Europe is particularly affected by this growth of air traffic resulting in about SOOO flights per day over Germany.
2. PAST EXPERIENCES WITH MACHINEBASED SUPPORT SYSTEMS
The bottlenecks of air traffic are still the airports and the surrounding terminal areas. However, the chance to extend existing airports in terms of real estate and thus larger infrastructures including more runways is rather limited. On the other hand capacity enhancements are needed in the light of the expected air traffic growth. Capacity enhancements must concentrate, therefore, on a better utilisation of given infrastructures and human resources.
To support human operators working in air traffic management, the concept of a machine-based system that manages the increasingly complex air traffic at large airports has been pursued for almost two decades. Although billions ofU.S. dollars were spent for research and development - the largest project being the Advanced Automation Suite (AAS) in the U.S. - no such comprehensive support system is in operation today. Major reasons are:
549
no need for national or regional agreements on their (local) introduction
sensory, algorithmic, and computational difficulties to compute and to predict aircraft trajectories with high accuracy in real-time, -
problems of conflict resolution in real-time,
-
operational difficulties to integrate a rather autonomous machine-based system for air traffic management into the overall system of airspace, airports, handling agents, airlines, and others in form of a collaborative decision making (CDM) process, and
-
lack of acceptance by the human operator.
The design, development, prototyping, and introduction of early sets of support tools less complex than the much needed assistant systems also required a significant effort. For support tools like the Computer Oriented Metering, Planning and Advisory System (COMPAS) developed by DLR and DFS in Germany or the Center-TRACON Automation System (CTAS) developed by NASA in the U.S. this cycle took up to 15 years. However, some of the support tools developed for air traffic controllers are operational today.
-
relatively short development cycle
-
non-intrusive to current airport operations
-
configurable to the particular needs of an individual airport
-
easy interaction among support tools for different operational areas
-
almost no safety risks
-
good expected/demonstrated acceptance by the human operator
Therefore and with the experiences of the past two major development areas for machine-based support and assistance of those working in air traffic and airport management exist today: 1. An increasing number of developments of support tools is foreseen that are needed for operations on the ground in the short run. Relevant products exist and more products will become available shortly because of low safety risks, because these tools are well accepted as responsibility remains with the human operator, and because an attractive return of investment can be expected from their introduction. With these tools significant capacity enhancements of airport operations on the ground can be achieved rather rapidly. These tools form the basis for the conception and the fUture development of human operator assistant systems that later may assume certain responsibilities extending from operational areas with low human operator interaction into areas which are currently the sole responsibility of the human operator.
COMPAS, for instance, estimates arrival times of aircraft, determines the required separation between aircraft of same or different weight classes, and suggests an optimum sequence of aircraft. It supports air traffic controllers in their task to produce a smooth flow of the arriving traffic into an airport while making best use of the existing airport capacity. The tool unburdens air traffic controllers from recurring tasks, leaves responsibility with the air traffic controllers, and does not involve safety risks: if the tool is turned-off air traffic controllers return to their previous operating practice at the expense of operational efficiency. COMPAS is ofa non-intrusive nature and has led to a smooth workflow in the management of the arriving air traffic at an airport. It is in operation since 1989 at the airport of FrarUkfUrtn\1ain.
2. On the other hand it becomes evident that support tools alone are inadequate to solve the bottlenecks in the departing, en-route, and arriving air traffic. Human operator assistant systems are required, therefore, which assume some of the responsibilities of the human operator. However, at current the chances are rather low that those working in air traffic management accept such systems and that a large-scale introduction needed to be efficient - can be agreed mid-term. Much more research on human factors, on the interaction of operational processes in air traffic, on safety related issues, and on human operator selection and training is required to achieve a break-trough in this area.
3. FUTURE DEVELOPMENT AREAS Bottlenecks in air traffic management not only exist in airborne operations but also on the ground. Examples are the taxiing of aircraft, the allocation of resources on the ground for passenger handling and aircraft servicing, as well as the flow of passengers and cargo changing between the different transport systems of road, rail, and air. Capacity enhancements of operations on the ground can contribute significantly to the overall capacity of an airport. Moreover, support tools for capacity enhancements on the ground have a number of attractive characteristics when appropriately researched and designed:
Both development areas are needed to achieve the required air traffic capacity enhancements in the short and long run as the human operator and the human-
550
machine interface remain key elements of a successful application of automation and of overall system performance for years to come. This is particular true in the light of major operational changes like the introduction of more flexible air routes in Europe as decided by the European secretaries of transport in 1993 and implemented in April 2001.
sally -bus
a system that assists the operations manager to allocate passenger busses according to the current situation, that provides the current driving orders for bus drivers, and that takes into account the status reports of bus drivers.
4. CURRENT OPERATIONAL EXPERIENCES
sally -tow
a system that assists the operations manager to allocate towing vehicles according to the current situation.
sally -check-in
a configurable system for the flexible allocation of the check-in counters available at an airport.
The success of support tools is largely dependent on an approach described as human-centred automation. This approach attempts to increase the ability of the human operator to manage a complex operational situation and to be aware of the evolution of the situation by means of suitable tools. The responsibility for control and safety will, however, remain that of the human operator. Systems designed this way fmd acceptance by an increasing number of air traffic controllers and airport operations manager. The final proof, however, is their operational introduction and use for a prolonged period of time. Examples are: -
-
-
Much has been learned from the development and from the operation of COMPAS, FLOW MONITOR, and sally -stand in the fields of human-centred design and automation, machine-based support of air traffic and airport management, co-operation of human operators and machine-based support tools, and problem solving. The design philosophy to gain acceptance by the human operators continues to focus, therefore, on aspects that were presented some years ago in another context (McNeese, 1986) but which are fully applicable to the partnership of human operator and support tool:
Since its introduction into operational service in 1989 at the airport of Frankfurt/Main COMPAS (an aircraft arrival sequencing tool developed by DFS and DLR) was so well accepted by the air traffic controllers that it was maintained as one of the support tools also for the new air traffic controller work system of DFS that became operational in 2000 (Schenk, 1991). The FLOW MONITOR (a tool to monitor and to analyse the arriving and departing air traffic at an airport developed by DFS and DLR) was introduced into operational service in 1992 at the airport of Frankfurt/Main and serves as a major tool in the operations supervision and management (Schenk, 1994). sally -stand (a generic system for the planning of the optimal stand and gate allocation at an airport developed by delair Air Traffic Systems) was introduced into operational service in 2000 at the airport of Zurich! Switzerland.
-
Both partners must share overlapping knowledge and meaning.
-
Each partner must contribute insights into problem solution.
-
The processes that involve logic, rules or heuristics must be co-existent or co-explained in the 'mind' of each partner. There must be a shared language to communicate across one partner to another.
sally - resource allocation management systems - in particular represents a whole spectrum of products that efficiently help an operations manager to optimise the use of existing resources at an airport. Its generic system architecture and its control of activity scheduling by means of parameters allows a flexible adaptation to the requirements of an individual airport. Besides sally -stand the spectrum of products includes at current
-
In order to be efficient both partners must implicitly time manage information.
-
Some sense of authority or conflict resolution must exist when one partner disagrees with the other.
5. CHALLENGES AND OULOOK Without going into much detail, two of the most challenging areas that emerge from the current development of human-centred designs of air traffic
551
speech recognition technology and a context-sensitive syntax for phrases to be recognised, DLR in cooperation with DFS achieved remarkable results: the recognition error rate was reduced by 50% when the context-sensitive syntax was used instead of the usual static one. A recognition rate of 93% was achieved when the context-sensitive syntax and the ICAO standard phraseology were employed. A recognition rate of about 95% under true operational conditions seems to be within reach with some technical improvements of the subsystems used (Schaefer, 2001).
management support tools are intent recognition and speech recognition. Machines are currently unable to assess an air traffic situation in the terminal area of an airport in a way that their mental picture agrees acceptably with the mental picture of the air traffic controller. This will not change as long as it is not possible to submit to the machine past experiences as well as a situation dependent value system together with the momentary intentions of the human operator. Intent recognition could provide the planning, problem solving, and plan selecting machines with more timely information and enhance their acceptance by the human operator. This would prevent the machine to focus on problems that have changed or are overcome already by the human operator's momentary intentions. Air traffic controller intentions can change as rapidly as the air traffic situation changes. Even multi-processor machines often cannot catch-up in a timely manner with these changing demands of air traffic controllers to provide problem solutions in real-time.
Currently most support tools monitor a real air traffic situation for any changes compared to a planned air traffic situation. Changes are accommodated either by giving advisories to the aircraft/pilots to revert to the plan or by changing the plan. It is often the support tool time span between detecting a change and responding to the change that prevents it to be accepted by the human operator. If keyboard and mouse inputs as well as speech recognition would be employed to detect air traffic controller actions at the earliest instance of time, much could be gained regarding the timeliness of planning, problem solving, and plan selection by the support tool and thus its acceptance by the air traffic controllers. Both techniques - manual input sensing and speech recognition - are readily available. Combined with context-sensitive evaluation algorithms these techniques are considered an important step to take into account air traffic controller intentions or at least the influence of intentions on the machine-based planning, problem solving, and plan selection process at the earliest possible time.
Intent recognition must be performed in real-time and there are no techniques readily available to fulfil this task. For the time being a promising technique could be a machine-based, situation dependent, contextsensitive assessment of human operator intentions. In addition some form of co-operation between the human operator and the machine must exist to confIrm the human operator intentions assessed by the machine. This requires, however, a new form of logistic support and training of the air traffic controllers that does not exist today.
It is expected that non-intrusive techniques to collect human operator actions and responses will make future support tools for air traffic and operations management more acceptable to air traffic controllers and operations managers. These techniques will become even more important for the development and operational use of the next class of support - the assistant systems.
Experiences from tool development showed that attempts to ask air traffic controllers to use a keyboard to submit their intentions, to confmn or to deny intentions as assessed by the machine, or to hit at least a button if they felt that their mental picture of the air traffic situation and its evolution did not agree with the mental picture of the machine failed. The main reason was the fear that this form of cooperation with the machine would lead to additional and unacceptable duties, to more displays and controls, and to a disturbance of the current workflow that fmally would increase workload. The argument that workload would not be raised by the use of a tool that thinks and behaves like air traffic controllers and that could be more co-operative and more easily supervised than the current tools did not convince the test subjects at this time. As it was not possible to acquire the air traffic controller intentions directly, an attempt was made at least to record the outcomes of intentions at the earliest possible instance of time. Besides inputs from the mouse and keyboard, voice input appeared attractive in this context. With the help of existing
552
REFERENCES McNeese, M. D. (1986). Humane Intelligence: A Human Factors Perspective for Developing Intelligent Cockpits. NAECON, Dayton, Ohio, May 1986. Schaefer, D. (2001). Context-Sensitive Speech Recognition in the Air Traffic Control Simulation. EEC Note No. 02/2001. EUROCONTROL Experimental Centre. Schenk, H.-D. (1991). COMPAS-OP - Ein Planungssystem fUr den Flughafen Frankfurt. DLR-Nachrichten, February 1991 . Schenk, H.-D. (1994). Flow Monitor - Ein System zur Analyse des Anflugverkehrs am Flughafen Frankfurt. DLR-IB 112-94/03, DLR Braunschweig.
553