WO2007115359A1

WO2007115359A1 - Display system for controlling aircraft traffic and method

Info

Publication number: WO2007115359A1
Application number: PCT/AU2007/000445
Authority: WO
Inventors: Andrew Louis Martin
Original assignee: Windbidco Pty Ltd
Priority date: 2006-04-10
Filing date: 2007-04-05
Publication date: 2007-10-18

Abstract

A display system is disclosed for use in controlling aircraft traffic. The display system includes means for displaying a representation of a first aircraft relative to a second aircraft. The display system also includes means for displaying a safety/risk zone in association with at least the representation of the first aircraft, wherein the safety/risk zone is adapted to move with the representation of the first aircraft to provide a dynamic indication of allowable spacing between the first and second aircraft. The safety/risk zone is updated at least periodically based on input data that contributes to the allowable spacing. The input data may include meteorological and wake vortex data in the vicinity of the first and second aircraft as well as aircraft and other relevant data.

Description

DISPLAY SYSTEM FOR CONTROLLING AIRCRAFT TRAFFIC AND METHOD

TECHNICAL FIELD The present invention relates to the field of display systems for use in controlling aircraft traffic and in particular to associated displays for use by aircraft traffic controllers and/or by cockpit crew of aircraft.

CROSS REFERENCE TO RELATED APPLICATIONS The present invention is related to the following international patent applications assigned to the present applicant, the disclosures of which are incorporated herein by cross reference.

PCT1 - AU01 /00247 entitled Acoustic Sounding PCT2 - AU02/01129 entitled Measurement of Air Characteristics in the lower atmosphere

PCT3 - AU2004/000242 entitled Improved Sodar Sounding of the lower atmosphere PCT4 - AU2004/001075 entitled Detection of Wake Vortices and the like in the lower atmosphere PCT5 - AU2006/000245 entitled Characterization of Aircraft Wake

Vortices

PCT6 - AU2006/000247 entitled Staged Sodar Sounding PCT7 - AU2006/000818 entitled Sodar Sounding of the Lower Atmosphere

BACKGROUND TO THE INVENTION

Many airports around the world are facing capacity constraints that are forecast to get much worse. The problem is well recognised as the cost in lost time and productivity has been estimated in billions of dollars. NASA/FAA and Eurocontrol have been looking for a means to relieve this problem for at least 20 years but, as far as applicant is aware, no simple practical solution has been proposed although many different schemes have been considered. One scheme that is showing promise in marginal weather is being tested by the Federal Aviation Administration (FAA) and NASA Ames SimLabs who are preparing wake vortex avoidance simulations for Simultaneous Offset Instrument Approach (SOIA) procedures (http://www.simlabs.arc.nasa.gov/newsletter/news.htmL Volume 6, Issue 1 , January 2006). SOIA procedures enable simultaneous instrument approaches to airports with parallel runways spaced less than 3000 feet apart. These procedures may allow improved airport efficiency and increased arrivals rates during marginal weather but are not suitable in poor weather conditions. A principal cause of capacity constraints around airports is poor weather and the associated restrictions that the presence of wake vortices place on spacing between aircraft in the vicinity of an airport.

Increasing congestion in airway traffic near major airports and an increasing disparity between aircraft types has a number of adverse consequences including: i) the task of aircraft traffic controllers becomes increasingly complex and onerous; ii) the task of aircrew using such airports also becomes increasingly complex and onerous; and iii) aircraft spacing, both along a flight path and across it in poor weather, is set by relatively conservative considerations relating to aircraft wake vortices so that permissible aircraft density near an airport in poor weather is limited more by wake vortex clearance requirements than by aircraft runway clearance time and is now a key limitation of airport usage.

The above limitations are more adverse to airport capacity where closely spaced runways are in use.

An object of the present invention is to provide an all weather safety/risk zone that may be maintained around an aircraft and displayed on an aircraft controller's display screen. The safety/risk zone may be depicted graphically and in a simple manner such that aircraft may be allowed to approach one another more closely without compromising safety while, at the same time, providing an aircraft controller with a relatively simple and intuitive visual indication of a traffic situation and with minimal change to the display or its normal modes of working.

The present invention is facilitated to a large extent by availability of techniques for accurately monitoring (i) wind and weather conditions in the vicinity of an airport up to an altitude of about 1000m and (ii) wake vortices shed by large aircraft on approach or take off as disclosed in the above identified international patent applications PCT1 - PCT7. The techniques disclosed in the international patent applications may be used to provide necessary data to an air traffic control system including data about wind shear and vortex persistence under prevailing conditions, which data may be used to determine the size and/or shape of the safety/risk zone surrounding each aircraft to be displayed on the controller's screen.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a display system for use in controlling aircraft traffic, said display system including means for displaying a representation of a first aircraft relative to a second aircraft, and means for displaying a safety/risk zone in association with at least said representation of said first aircraft, wherein said safety/risk zone is adapted to move with said representation of said first aircraft to provide a dynamic indication of allowable spacing between said first and second aircraft, and wherein said safety/risk zone is updated at least periodically based on input data that contributes to said allowable spacing.

The input data may include meteorological data in the vicinity of the first and second aircraft. The meteorological data may include one or more of wind strength, wind direction, atmospheric vertical profile data and visibility. The meteorological data may be applied to a regional meteorological predictor algorithm for predicting meteorological data up to 30 minutes ahead of real time. The input data may include wake vortex data in the vicinity of the first and second aircraft. The wake vortex data may include data obtained from a wake vortex sensor. The wake vortex data may be applied to a regional wake vortex predictor algorithm for predicting wake vortex data up to 30 minutes ahead of real time. The input data may include aircraft data. The input data may include security related data such as VIP status of passengers on board the aircraft.

The safety/risk zone may include a box rendered around the representation of the first aircraft wherein dimensions of the box are set by type of the first aircraft and/or wind direction. The second aircraft may be positioned laterally relative to the first aircraft. The safety/risk zone may include a box rendered around the representation of the first aircraft wherein the box includes a first dimension set by type and position of the second aircraft. A third aircraft may be positioned preceding the first aircraft. The box may include a second dimension set by type and position of the third aircraft. At least one dimension of the safety/risk zone may be determined dynamically via an automatic algorithm based on the input data. The algorithm may determine the at least one dimension based on one or more of wake vortex lifetime data, descent rate data, lateral drift rate data, leading aircraft type data, leading aircraft position data, adjacent aircraft type data and adjacent aircraft position data.

According to a further aspect of the present invention there is provided a method of displaying aircraft traffic including a representation of a first aircraft relative to a second aircraft, said method including displaying a safety/risk zone in association with at least said representation of said first aircraft, wherein said safety/risk zone is adapted to move with said representation of said first aircraft to provide a dynamic indication of allowable spacing between said first and second aircraft, and updating said safety/risk zone at least periodically based on input data that contributes to said allowable spacing.

The present invention may provide an air traffic display system in which a safety/risk zone associated with an aircraft is depicted visually and moves with a representation of the aircraft on a display. The representation may include a standard symbol that is used to represent an aircraft on a conventional air traffic control display system. The safety/risk zone may indicate a volume of space in the physical vicinity of the aircraft into which it is undesirable for other aircraft to enter for safety or security reasons. Preferably, the safety/risk zone may be depicted surrounding each aircraft in the display and may be shown moving with the representation of the associated aircraft on the display.

The safety/risk zone may be varied automatically and/or dynamically in size and geometry/orientation relative to the symbol of the aircraft according to at least one or more of the following data: i) known wake vortex characteristics data for the associated aircraft type; ii) minimum size data of other aircraft permitted to use the same airport or to join a landing or take-off train; iii) wind strength data in a vicinity of the associated aircraft; iv) wind direction data in a vicinity of the associated aircraft; v) weather conditions data such as visibility in the prevailing environment; and vi) security status data, that is, whether VIPs are aboard an associated aircraft and their number and/or rank.

In a simplified embodiment the safety/risk zone may include a basic sphere of fixed diameter centered on and traveling with the symbol of the associated aircraft. Allowing for theoretical contingencies that contribute to allowable spacing and a margin of error, the safety/risk zone may be significantly larger than that which could be established on the basis of actually available data. In the simple case, the safety/risk zone may not vary in size, even though available vortex and other weather-related data may suggest that it could be reduced in size and/or extent. In another embodiment, the safety/risk zone may be smaller than, and not coincident with, a zone established at a given time by vortex and weather related data. In the latter case there may be slight changes to boundaries of the associated safety/risk zone. It may be exceptional, but nevertheless not impossible, for an actual safety/risk zone to be much smaller than a safety/risk zone computed on the basis of available data. In the latter case, the safety/risk zone would be much the same as that computed for the aircraft without available data as in the case of the simplified embodiment.

While wake vortex characteristics and an associated safety/risk zone may be substantially determined by knowledge of aircraft type, it is desirable in accordance with an aspect of the present invention to modify the safety/risk zone according to available data such as wind speed, direction and/or short- term variability (related to gustiness or turbulence) in a dynamic fashion as the data becomes available from airport weather sensors. Scenarios envisaged may include: i) a steady cross wind may skew a Vortex zone' down-wind; ii) on a still day a vortex zone may extend directly behind the aircraft and above if the aircraft is in rapid decent; iii) the size of a vortex zone for various aircraft may be adjusted by regularly monitoring vortex lifetimes in landing and take off paths (the latter may be done by detecting and tracking vortices according to the teachings in applicant's international patent applications PCT 1 -7 identified herein; iv) the size and shape of a vortex zone for an aircraft of a given type may be adjusted according to wind conditions known to either extend vortex lifetime such as during relatively calm or steady wind conditions or to reduce vortex lifetime by causing its breakup or dissipation such as during gusty and turbulent conditions.

From another aspect, a safety/risk zone surrounding a symbol of the associated aircraft in an air traffic control display system may be rendered by reference to characteristics of a nearby aircraft, for example, an aircraft that is immediately ahead and, preferably also by reference to characteristics of the aircraft about which a safety/risk zone is rendered. The latter alternative may be preferable in situations involving relatively heavy traffic wherein many disparate aircraft may be involved. To illustrate a reason for this preference, a case wherein a large aircraft such as an Airbus 383 is approaching an airport may be considered in company with much smaller aircraft such as a Dash-8 and other large aircraft such as a Boeing 737. If a safety/risk zone is rendered around each aircraft based upon the type of that aircraft and the prevailing weather conditions (assumed to be common to all aircraft), the size of each safety/risk zone may be largely determined by aircraft type. The safety/risk zone may therefore trail the symbol representing the aircraft on the screen. Thus, the spacing of the or each other aircraft relative to the Airbus 383 may be the same, when the other aircraft is following the 383. Since vortices shed by the Airbus 383 may affect the Dash-8 much more severely than the Boeing 737, the size of the safety/risk zone associated with the Airbus 383 should be sufficient to safeguard the smallest aircraft permitted to use the same airport. However the safety/risk zone may be much larger than is necessary for a following Boeing 737. Therefore, permissible traffic density may be lower than optimum.

If a safety/risk zone is rendered around each aircraft based on both the type of that aircraft and as well as the type of aircraft that is closest ahead, the safety/risk zone around the following aircraft may vary to reflect a safe distance for the following aircraft.

The system of the present invention may be further elaborated by taking into account other aircraft that are above, below or to either side of the following aircraft. Data from all other aircraft may be added to create a three dimensional safety/risk zone or volume of space around the following aircraft that may determine how close it may approach the other aircraft as they approach a common airport together or fly through a major intersection of air routes.

In contrast to the first scenario in which a safety/risk zone around a given aircraft was determined by characteristics of the aircraft and prevailing weather conditions, the use of a safety/risk zone that is determined by characteristics of other nearby aircraft (as well as those of the given aircraft) may allow aircraft controllers to obtain greater aircraft density in heavy traffic conditions without compromising safety. The safety/risk zone around a given aircraft may extend in three dimensions to indicate a minimum safe distance that the given aircraft can approach others in the vicinity of a space that is being monitored by an aircraft traffic control system.

The display system of the present invention may not be restricted to controlling aircraft in the air. The principle of a safety/risk zone around an aircraft may be extended to controlling ground traffic at an airport including taxiing aircraft and its relationship to other aircraft, vehicles and personnel on the ground. In the case of controlling ground traffic the input data that contributes to allowable spacing may include positions of ground vehicles and other aircraft, personnel, jet blasts from aircraft, runway layouts, airport layouts including buildings, taxiways etc.

DESCRIPTION OF DRAWINGS

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings wherein:

Figure 1 , is a block diagram of an aircraft traffic control system according to one embodiment of the present invention;

Figure 2 is a block diagram of an aircraft traffic control system according to another embodiment of the present invention;

Figure 3 is a schematic diagram of a portion of a display on an aircraft controller's screen showing a first way in which a safety/risk zone associated with an aircraft in the air may be depicted;

Figure 4 is a schematic diagram of a portion of a display on an aircraft controller's screen showing a second way in which a safety/risk zone associated with an aircraft in the air may be depicted;

Figure 5 is a schematic diagram of a portion of a display on an aircraft controller's screen showing a way in which a safety/risk zone associated with an aircraft on the ground may be depicted; Figure 6 represents a portion of a conventional display screen of an aircraft traffic control system, without indicating use of the present invention;

Figure 7 shows a display screen similar to that in Figure 6 including markings around aircraft to indicate associated safety/risk zones ahead of the aircraft; and

Figure 8 shows a display similar to that in Figure 6 including markings around aircraft to indicate associated safety/risk zones behind the aircraft.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Figure 1 is a block diagram illustrating a system 10 depicting one way in which a safety/risk zone for an aircraft may be determined and dynamically updated. Two key input devices include a metrological vertical profiler 11 and an aircraft wake vortex sensor 12 which are located in the vicinity of a congested airport, perhaps with multiple sensors distributed along the approach and takeoff paths. Device 1 1 may include a sodar profiler as described in applicants international applications PCT1 , PCT2, PCT3, PCT6 and PCT7 referenced above. Device 12 may include a sodar wake vortex detector as described in applicants international applications PCT4 and PCT5 referenced above. The output of devices 1 1 and 12 are converted by processes 13, 14 and 15 into an index indicative of probability of persistent wake vortices. The index produced by process 15 is fed to process 16 together with data about aircraft types from register 17 using inputs 18 supplied by an existing traffic control system to generate a prediction of the size, duration and drift of wake vortices shed by an aircraft under prevailing conditions. The prediction generated by process 16 provides one input to process 19 by means of which a safety/risk zone represented by a box around a symbol of an aircraft is rendered on the screen.

Processes 13 and 14 may include a meteorology predictor as described in a paper entitled "Research towards a wake-vortex advisory system for optimal aircraft spacing", Comptes Rendus Physique, special issue on Aircraft trailing vortices/Tourbillons de sillages d'avion, Academie des Sciences, Paris, Vol. 6, No. 4-5, 2005, pp. 501 -523 (published by Elsevier) - T. Gerz, F. Holzapfel, W.

Bryant, F. Kόpp, M. Freeh, A. Tafferner and G. Winckelmans. This paper also shows how integration of the weather is done with a P2P model.

Processes 15 and 16 may include a wake vortex predictor as described in a paper entitled "Quantitative Estimation of Wake Vortx Safety Using The P2P Model" by Xie, Shortle and Choroba

(http://catsr.ite.qmu.edu/pubs/2005 ATM B.pdf). This paper sets out how to make estimations for a predictor.

Using inputs 18 supplied by an existing traffic control system, process 20 takes positional and type data for aircraft in view and determines which aircraft are close enough to one another to justify drawing of a safety/risk zone. Then, for each aircraft so identified, the type of the aircraft immediately ahead is considered to determine (i) size of vortices normally shed from the leading aircraft and (ii) sensitivity of the trailing aircraft to buffeting. Similar determinations may be undertaken for adjacent aircraft. These determinations are then output at 21 to box rendering process 19 to provide a dimension(s) for the box representing the safety/risk zone for the aircraft in question. An optional process 22 may generate a visual and/or audible alarm if any safety/risk zone is violated or breached. The visual alarm may be displayed on the aircraft controller's screen.

Figure 2 is a block diagram illustrating a system 23 for determining a safety/risk zone around an aircraft on the ground that should not be violated by other objects on the ground. Similar meteorological inputs 1 1 , 13 and 14 can be used as described with reference to Figure 1 as well as the described register 17, inputs 18 and processes 19, 20 and 22. Ground meteorological conditions are required 30 minutes ahead of real time to allow reconfiguration of the airport if conditions are predicted to change. The system 23 includes ground meteorological predictor 24 and a visibility monitor 25, the latter being a standard item in airports. An airport layout 26 is required as input data since aircraft may not be visible at all times due to topography or buildings etc. A set of spacing criteria are calculated for each aircraft type via process 27 and combined with airport layout data 26 to generate via process 19 safety/risk zones for each aircraft type and for each part of the airport. For aircraft requiring safety/risk zone determination, its position in the airport and status including speed, type, loaded/unloaded, stationary etc, may be used to generate an actual safety/risk zone for every aircraft on the ground. The safety/risk zone for the or each aircraft can then be drawn. The location of other objects including vehicles, personnel, buildings and other aircraft around the airport is generated via process 28 using common and readily location techniques such as a GPS. An alarm may be generated via process 22 if the safety/risk zone around any aircraft is violated.

Figures 3 and 4 illustrate alternative methods by which a safety/risk zone can be computed and depicted for a displayed aircraft in the air. The method shown in Figure 3 corresponds more closely with the system 10 shown in Figure 1 , while the method shown in Figure 4 is a variant which departs in some respects from the system of Figure 1. An important difference is that the safety/risk zone shown at 40 in Figure 4 is computed without regard to characteristics of nearby aircraft while safety/risk zone 30 in Figure 3 is computed with particular regard to type of nearby aircraft as well as type of aircraft about which the box is rendered.

Thus, in Figure 4, box 40 trails aircraft indicator 41 to indicate a volume of space in which wake disturbances from aircraft 41 can be expected. That is, box 40 depicts from the point of view of other aircraft, a potential safety/risk zone into which following aircraft should not enter. The area of box 40 depends on the propensity of aircraft 41 to shed vortices at the speed, direction, rate of climb or descent and the probable lifetime of vortices under current atmospheric conditions. The location of box 40 relative to aircraft 41 depends largely on prevailing wind direction.

In contrast, in Figure 3, box 30 is shown preceding aircraft 31 and represents from the point of view of aircraft 31 , the boundaries of a safety/risk zone that should not be 'pushed over or onto' any nearby aircraft because significant air disturbances from that nearby aircraft could then be encountered by aircraft 31. The area of safety/risk zone 30 thus indicates not only the probable lifetime of aircraft vortices under current atmospheric conditions but also a likelihood that aircraft 31 may be subjected to buffeting, which is dependent upon the type (including size) of aircraft 31 and the type (including size) of preceding aircraft and/or adjacent or laterally spaced aircraft.

An absence of a safety or safety/risk zone around an aircraft shown on the screen may indicate that the spacing of the aircraft is such that a potential risk such as a wake hazard is not present for that aircraft.

As wake vortex behavior may be highly weather dependent and may be influenced by position of an aircraft on an approach or departure path, as well as by other aircraft that are closest at a given time, the shape and dimensions of the safety/risk zone for each aircraft concerned may change. Dynamic up- dating of the safety/risk zone is therefore highly desirable. The system of Figure 1 , may update weather and probable vortex lifetimes at least every minute to provide a forecast that is 30 minutes ahead of real time. Data relating to aircraft that is closest at a given time may change more rapidly so that the safety/risk zones of those aircraft may need to be updated 'on demand' and possibly more rapidly than once every 30 minutes. Most conveniently they may need to be updated every minute. Indeed, the shape and volume of a safety/risk zone for a small aircraft may vary much more dramatically because a new aircraft may suddenly be closer to its safety/risk zone because of changing weather conditions. In operation, if one aircraft falls within the safety/risk zone of another then immediate action may be taken by an air traffic controller to increase spacing between the aircraft to avoid a potential risk such as a wake vortex hazard.

Another way in which a safety/risk zone 30 of an aircraft as shown in Figure 3 can change suddenly and significantly may be due to the presence of another aircraft alongside or above or below, as can easily happen during approaches to a busy airport with parallel runways in operation. Figure 5 shows a safety/risk zone 50 associated with an aircraft 51 on the ground. The dimensions of safety/risk zone 50 are determined via the system 23 shown in Figure 2 and are variable depending on meteorological conditions, aircraft type, aircraft status including speed, type, loaded/unloaded, stationary etc., airport layout data and the like. Safety/risk zone 50 denotes an area around aircraft 51 which all other objects should avoid to minimize risk to themselves and to aircraft 51.

Figure 6 shows a conventional display generated for use in air traffic control. Aircraft are identified by type gained from on-board transponder responses, with heading altitude and speed data also selectively available for display. The minimum spacing between aircraft at the same altitude or approach path near an airport is conventionally set by a number of 'rules of thumb' or conventions. In reasonably clear weather, termed Visual meteorological conditions' or VMC, closer spacing is permitted than in poor weather termed instrument meteorological conditions' or IMC. Under VMC, the closest allowable spacing between aircraft (both ahead and behind and side-to-side) is based on a somewhat arbitrary allowance for air disturbance that might be caused by the next aircraft ahead, assuming worst conditions and the largest aircraft flying while also allowing for a safety factor. This seriously limits airport capacity under VMC because it restricts the closeness (and therefore the number) of parallel runways as well as the maximum frequency of landing. Figure 4 shows no safety/risk zone around aircraft even though this varies under VMC or IMC. By providing a calculated safety/risk zone around an aircraft based on high quality weather information, the capacity of an airport may be improved in VMC conditions and greatly improved in IMC conditions by providing air traffic controllers and pilots with high quality, dynamic safety/risk zones.

Figure 7 shows a similar display as in Figure 6 except that five aircraft 73-77 in the lower left hand corner of the display are shown with surrounding rectangular box-like safety/risk zones 73a-77a respectively. Safety/risk zones 73a-77a are shown leading the symbols 73-77 signifying the associated aircraft. Safety/risk zones are not shown for other aircraft, eg. 78 because their spacing is determined by the system to be well in excess of a minimum that gives rise to potential risk and, therefore, do not present issues that needs to be flagged to the controller. Comments have been added in Figure 7 namely, 'wind direction', 'wake vortex clear area' and 'aircraft too close', which may not normally appear on the screen to avoid excessive screen clutter. Wind direction is shown because it influences disposition of the associated safety/risk zone for each aircraft depending on the type of aircraft that is closest upwind.

Figure 8 shows a similar display as in Figure 7 except that the box-like safety/risk zones 80a-83a are shown trailing the symbols 80-83 signifying the aircraft, rather than leading the aircraft as in Figure 7. The difference will be explained further below but it can be stated as follows.

A following aircraft eg. 73 in Figure 7 should not advance on an aircraft ahead eg. 74 to a point where the following aircraft's leading safety/risk zone 73a includes the safety/risk zone 74a of aircraft ahead.

A following aircraft eg. 80 in Figure 8 should not advance on an aircraft eg. 81 ahead to the point where the following aircraft 80 enters the trailing safety/risk zone 81 a of the aircraft 81 ahead.

The use of rectangular boxes 73a-77a and 80a-83a to denote safety/risk zones in figures 7 and 8 is a matter of illustrative convenience because the safety/risk zone will normally not be a simple rectangle but may be a more complex closed curve that may extend outwardly in any direction from the identifier for the aircraft in question depicted on the display. The size and shape of a box may be updated and modified dynamically according to weather inputs including wind speed and turbulence, declared VMC or IMC situations, the type (including essentially size) of adjacent aircraft and wake vortex dissipation rates under the prevailing conditions. The inputs for aircraft type, altitude, speed, heading and location are all available in a conventional manner from the radar system used in a conventional air traffic control system. Though there may be considerable computational complexity underlying the proportioning and depiction of the safety/risk zones, their interpretation should be relatively simple and intuitive to an experienced aircraft controller.

While examples of the invention have been described, it will be appreciated that many other examples are possible, and that many variations on the chosen example are possible, without departing from the scope of the invention as outlined above. For example the safety/risk zones may be depicted in many different ways including with different coloured areas, different types or colours of lines or circles, so long as an intuitive and informative display is created.

Claims

1. A display system for use in controlling aircraft traffic, said display system including means for displaying a representation of a first aircraft relative to a second aircraft, and means for displaying a safety/risk zone in association with at least said representation of said first aircraft, wherein said safety/risk zone is adapted to move with said representation of said first aircraft to provide a dynamic indication of allowable spacing between said first and second aircraft, and wherein said safety/risk zone is updated at least periodically based on input data that contributes to said allowable spacing.

2. A display system according to claim 1 wherein said input data includes meteorological data in the vicinity of said first and second aircraft.

3. A display system according to claim 2 wherein said meteorological data includes one or more of wind strength, wind direction, atmospheric vertical profile data and visibility.

4. A display system according to claim 2 or 3 wherein said meteorological data is applied to a regional meteorological predictor algorithm for predicting meteorological data up to 30 minutes ahead of real time.

5. A display system according to any one of the preceding claims wherein said input data includes wake vortex data in the vicinity of said first and second aircraft.

6. A display system according to claim 5 wherein said wake vortex data includes data obtained from a wake vortex sensor.

7. A display system according to claim 5 or 6 wherein said wake vortex data is applied to a regional wake vortex predictor algorithm for predicting wake vortex data up to 30 minutes ahead of real time.

8. A display system according to any one of the preceding claims wherein said input data includes aircraft data.

9. A display system according to any one of the preceding claims wherein said input data includes security related data such as VIP status of passengers on board said aircraft.

10. A display system according to any one of the preceding claims wherein said safety/risk zone includes a box rendered around said representation of said first aircraft wherein dimensions of said box are set by type of said first aircraft and/or wind direction.

1 1. A display system according to any one of claims 1 to 9 wherein said second aircraft is positioned adjacent said first aircraft and said safety/risk zone includes a box rendered around said representation of said first aircraft wherein said box includes a first dimension set by type and position of said second aircraft.

12. A display system according to claim 1 1 wherein a third aircraft is positioned preceding said first aircraft and said box includes a second dimension set by type and position of said third aircraft.

13. A display system according to any one of the preceding claims wherein at least one dimension of said safety/risk zone is determined dynamically via an automatic algorithm based on said input data.

14. A display system according to claim 13 wherein said algorithm determines said at least one dimension based on one or more of wake vortex lifetime data, descent rate data, lateral drift rate data, leading aircraft type data, leading aircraft position data, adjacent aircraft type data and adjacent aircraft position data.

15. A display system according to any one of the preceding claims including means for generating a visual and/or audible alarm when said safety/risk zone associated with said first aircraft is breached by another aircraft.

16. A display system according to any one of the preceding claims wherein said aircraft are in the air.

17. A method of displaying aircraft traffic including a representation of a first aircraft relative to a second aircraft, said method including displaying a safety/risk zone in association with at least said representation of said first aircraft, wherein said safety/risk zone is adapted to move with said representation of said first aircraft to provide a dynamic indication of allowable spacing between said first and second aircraft, and updating said safety/risk zone at least periodically based on input data that contributes to said allowable spacing.

18. A method according to claim 17 wherein said input data includes meteorological data in the vicinity of said first and second aircraft.

19. A method according to claim 18 wherein said meteorological data includes one or more of wind strength, wind direction, atmospheric vertical profile data and visibility.

20. A method according to claim 18 or 19 including applying said meteorological data to a regional meteorological predictor algorithm for predicting meteorological data up to 30 minutes ahead of real time.

21. A method according to any one of claims 17 to 20 wherein said input data includes wake vortex data in the vicinity of said first and second aircraft.

22. A method according to claim 21 wherein said wake vortex data includes data obtained from a wake vortex sensor.

23. A method according to claim 21 or 22 including applying said wake vortex data to a regional wake vortex predictor algorithm for predicting awake vortex data up to 30 minutes ahead of real time.

24. A method according to any one of claims 17 to 23 wherein said input data includes aircraft data.

25. A method according to any one of claims 17 to 24 wherein said input data includes security related data such as VIP status of passengers on board said aircraft.

26. A method according to any one of claims 17 to 25 wherein said safety/risk zone is denoted via a box and rendering said box around said representation of said first aircraft wherein dimensions of said box are set by type of said first aircraft and/or wind direction.

27. A method according to any one of claims 17 to 25 wherein said second aircraft is positioned laterally relative to said first aircraft and said safety/risk zone is denoted via a box and rendering said box around said representation of said first aircraft wherein said box includes a first dimension set by type and position of said second aircraft.

28. A method according to claim 27 wherein a third aircraft is positioned preceding said first aircraft and said box includes a second dimension set by type and position of said third aircraft.

29. A method according to any one of claims 17 to 28 including determining at least one dimension of said safety/risk zone dynamically via an automatic algorithm based on said input data.

30. A method according to claim 29 including using said algorithm to determine said at least one dimension based on one or more of wake vortex lifetime data, descent rate data, lateral drift rate data, leading aircraft type data, leading aircraft position data, adjacent aircraft type data and adjacent aircraft position data.

31. A method according to any one of claims 17 to 30 including generating a visual and/or audible alarm when said safety/risk zone associated with said first aircraft is breached by another aircraft.

32. A method according to any one of claims 17 to 31 wherein said aircraft are in the air.

33. A display system for use in controlling aircraft traffic control substantially as herein described with reference to the accompanying drawings.

34. A method of displaying aircraft traffic substantially as herein described with reference to the accompanying drawings.