Collison avoidance communication system and method

What is claimed is:

1. In a system having a plurality of equipped and unequipped aircraft at various locations and having a control station, each aircraft of said equipped set of nearby aircraft including an aircraft station comprising a controller, an input device and video display for allowing an aircraft crew member to interact with said controller, a location determination system coupled to said controller and a radio for communicating over a common communication channel, said radio coupled to said controller, a method of managing information useful for safely operating said aircraft, said method comprising steps of:

obtaining, at a first aircraft, first data describing locations of an equipped set of nearby aircraft, said first data being obtained from said equipped set of nearby aircraft;

obtaining, at said first aircraft, second data describing locations of an unequipped set of nearby aircraft, said second data being obtained from said control station; and

displaying, using different symbols for equipped and unequipped aircraft, said first and second location data on said video display at said first aircraft.

2. A method as claimed in claim 1 wherein said displaying step comprises a step of graphically indicating a location for said first aircraft relative to said locations for said equipped and unequipped sets of aircraft.

3. A method as claimed in claim 2 wherein said graphically indicating step controls a display to present icons corresponding to said first aircraft and to said equipped and unequipped aircraft, said icons being spaced apart on said video display in accordance with a non-linear scale so that geographic distance per unit of display distance is greater further away from said first aircraft.

4. A method as claimed in claim 1 wherein said obtaining first data step comprises steps of:

transmitting via said radio, from each aircraft in said equipped set of aircraft, a data communication, said data communications occurring over said common communication channel at diverse times; and

receiving via said radio said data communications at said first aircraft.

5. A method as claimed in claim 4 wherein said data communications transmitted from said equipped set of aircraft are first data communications, said method additionally comprising steps of:

transmitting via said radio a second data communication from said first aircraft, said second data communication conveying data describing a location for said first aircraft, and said second data communication occurring over said common communication channel; and

receiving said first and second data communications at said control station.

6. A method as claimed in claim 4 additionally comprising a step of selecting random points in time at which said data communications occur.

7. A method as claimed in claim 1 wherein:

said obtaining first data step comprises steps of:

transmitting via said radio, from each aircraft in said equipped set of aircraft, a first data communication, said first data communications occurring over said common communication channel at diverse times, and

receiving via said radio said first data communications at said first aircraft; and

said obtaining second data step comprises steps of:

transmitting, from said control station, a second data communication to convey said second data for one or more of said aircraft in said unequipped set of aircraft, said second data communication occurring over said common communication channel, and

receiving via said radio said second data communication at said first aircraft.

8. A method as claimed in claim 7 additionally comprising steps of:

operating a radar system to obtain said second data; and

communicating said second data from said radar system to said control station.

9. A method as claimed in claim 7 wherein said first and second data communications convey information at a maximum data rate, said method additionally comprising steps of:

spreading said first and second data communications over a frequency spectrum broader than said maximum data rate; and

correlating signals received at said first aircraft using a predetermined spreading code to detect said first and second data communications.

10. A method as claimed in claim 7 additionally comprising a step of repeating said obtaining first data and obtaining second data steps to keep information conveyed in said first and second data communications current at said first aircraft.

11. A method as claimed in claim 1 additionally comprising steps of:

obtaining, at said first aircraft, control data from said control station, said control data including data identifying a voice communication radio channel used in association with said control station; and

displaying said control data via said video display at said first aircraft.

12. A method as claimed in claim 1 additionally comprising steps of:

obtaining, at said first aircraft, control data from said control station, said control data including data describing weather conditions; and

displaying, via said video display, said control data at said first aircraft.

13. A method as claimed in claim 1 additionally comprising steps of:

obtaining, at said first aircraft, control data from said control station, said control data including data describing locations of geographic features; and

displaying, via said video display, said control data at said first aircraft.

14. A method as claimed in claim 1 additionally comprising steps of:

determining, at each aircraft in said equipped set of aircraft, a location for said each aircraft;

determining a location for said first aircraft at said first aircraft; and

transmitting via said radio, from said first aircraft, third data describing said location of said first aircraft.

15. A method as claimed in claim 14 wherein said transmitting third data step comprises a step of transmitting control data from said first aircraft via said radio, said control data identifying a radio channel to which a voice communication radio in said first aircraft is tuned.

16. A system for managing information useful in safely operating a population of aircraft including an equipped set of aircraft and an unequipped set of aircraft, each aircraft of said equipped set of nearby aircraft including an aircraft station comprising a controller, an input device and video display for allowing an aircraft crew member to interact with said controller, a location determination system coupled to said controller and a radio for communication over a common communication channel, said radio coupled to said controller, said system comprising:

a radar subsystem configured to determine locations for substantially all aircraft of said population of aircraft; and

a control station in data communication with said radar subsystem, said control station being configured to transmit, over a common channel, data describing locations for said unequipped set of aircraft wherein each aircraft station is configured to determine a location for its aircraft, to transmit data describing locations for its aircraft, to detect location data transmitted from other aircraft stations and said control station, and to display, using different symbols for equipped and unequipped aircraft said location data determined by said control station and said aircraft station.

17. A system for managing information as claimed in claim 16 wherein:

said control station is configured to transmit control data describing weather conditions over said common channel; and

each aircraft station is configured to display said control data.

18. A system for managing information as claimed in claim 16 wherein:

said control station is additionally configured to transmit control data identifying a radio channel being used for voice communications over said common channel; and

each aircraft station is additionally configured to display said control data.

19. A system for managing information as claimed in claim 16 wherein:

said control station is additionally configured to transmit, over said common channel, control data describing geographic features; and

each aircraft station is additionally configured to display said control data.

20. A system for managing information as claimed in claim 16 wherein each aircraft station is configured to transmit said data describing locations for its aircraft in a stream of data communications, wherein each of said data communications is delayed from a previous one of said data communications by a randomized interval.

21. A system for managing information as claimed in claim 16 wherein:

each aircraft station includes a spread spectrum radio for transmitting said data describing locations for its aircraft and for detecting said location data transmitted from other aircraft stations and said control station; and

said control station includes a spread spectrum radio for transmitting said data describing locations of said unequipped set of aircraft.

22. A system for managing information as claimed in claim 16 wherein:

said control station is further configured to detect said location data transmitted from a portion of said aircraft stations;

each aircraft station includes an aircraft radio and said control station includes a control radio; and

said aircraft and control radios are mutually configured so that communications between aircraft radios may be detected within a first range and so that communications between an aircraft and said control radio may be detected within a second range, said second range being greater than said first range.

23. A method for managing information useful in safely operating a population of aircraft which includes an equipped set of aircraft and an unequipped set of aircraft, each aircraft of said equipped set of nearby aircraft including an aircraft station comprising a controller, an input device and video display for allowing and aircraft crew member to interact with said controller, a location determination system coupled to said controller and a radio for communicating over a common communication channel, said radio coupled to said controller, said method comprising steps of:

operating a radar system to determine locations for substantially all aircraft of said population of aircraft;

transmitting, from a control station and in response to said operating step, data describing locations for said unequipped set of aircraft; and

at each aircraft from said equipped set of aircraft:

identifying a location for said equipped aircraft,

transmitting data describing said location determined in said identifying step,

detecting location data transmitted from other aircraft from said equipped set of aircraft and from said control station, and

displaying, using different symbols for equipped and unequipped aircraft said location data from said detecting step.

24. A method as claimed in claim 23 wherein said control station is a location data source and each of said aircraft from said equipped set of aircraft are location data sources and wherein data describing locations are transmitted from each location data source as a stream of data communications, wherein each of said data communications is delayed from a previous one of said data communications transmitted at the same location data source by a randomized interval.

25. A method as claimed in claim 23 additionally comprising steps of:

transmitting control data describing weather conditions from said control station; and

at each aircraft from said equipped set of aircraft:

detecting said control data, and

displaying said control data.

26. A method as claimed in claim 23 additionally comprising steps of:

transmitting control data identifying a radio channel being used for voice communications from said control station; and

at each aircraft from said equipped set of aircraft:

detecting said control data, and

displaying said control data.

27. A method as claimed in claim 23 additionally comprising steps of:

transmitting control data describing geographic features from said control station; and

at each aircraft from said equipped set of aircraft:

detecting said control data, and

displaying said control data.

28. A method as claimed in claim 23 additionally comprising a step of detecting, at said control station, location data transmitted by said aircraft from said equipped set of aircraft.

29. A method as claimed in claim 23 additionally comprising steps of:

at each aircraft from said equipped set of aircraft, transmitting control data identifying a voice channel being used at said aircraft; and

detecting said control data at said control station.

Description Submit all comments and votes

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to avionics. More specifically, the present invention relates to communication and other systems which function to facilitate aircraft collision avoidance, navigation and communications.

BACKGROUND OF THE INVENTION

Few pilots simply operate their aircraft. In addition to causing aircraft to operate as desired from instant to instant, pilots deal with numerous avionic systems. Through these systems pilots gain intelligence letting them know what to do to travel safely from point A to point B and to avoid collisions. Voice communication radios, navigation systems, compasses, altimeters and the like represent a few of such avionic systems.

In accordance with current practices, collision avoidance functions take place primarily over radios through voice communications with air traffic controllers. In a crowded airspace, a virtually continuous stream of conversations with air traffic controllers manages collision avoidance for the aircraft in the airspace. The air traffic controllers base their communications upon information generated by a massive infrastructure of collision avoidance systems. The collision avoidance infrastructure includes radar systems and a population of aircraft-mounted transponders.

The number and diversity of these aviation-related systems provides a complicated aircraft cockpit environment. Pilots digest vast amounts of visual and audible data, much of which is distracting and has little or no direct bearing upon pilots' immediate informational needs. Often times, verbal communications are misunderstood. At best, when verbal instructions are misunderstood from a radio they are repeated, which throws even more audible information at all pilots tuned to that frequency. In the worst cast, when verbal instructions are misunderstood pilots may err in following the instructions, leading to seriously unsafe conditions. The flood of verbal and visual information available to pilots and the complication of avionic systems leads to pilot fatigue, pilot error and generally unsafe aircraft operating conditions.

Industry experts have long recognized that additional or different types of aviation systems might improve airspace safety, and many alternate systems have been proposed. One desirable alternate solution to collision avoidance gives pilots visual information, such as on a video display terminal, describing the location of nearby aircraft. Pilots are ultimately responsible for the safe operation of their aircraft. This alternate collision avoidance system is desirable because it allows pilots to share with traffic controllers in making decisions regarding collision avoidance. Moreover, this solution lessens the workload and responsibilities placed on air traffic controllers.

While desirable in theory, the conventional proposals for this type of collision avoidance solution have two serious drawbacks. First, they typically place yet another avionic system in the cockpit to further burden pilots with data. Thus, these conventional proposals advocate the use of systems which typically complicate rather than simplify the cockpit. Second, these types of collision avoidance systems often require substantially all aircraft to be equipped with the system before a significant safety benefit may result. Often times, proposed alternate collision avoidance systems generate particularly unsafe conditions when nearby aircraft are not equipped with the alternate system.

This second problem is an extremely serious drawback. A massive infrastructure of radio systems, transponder systems, radar systems, navigation systems and the like currently exists in a vast number of aircraft, airports and other control facilities. Alternate avionic infrastructures cannot be brought instantly "on-line." In other words, the entire aviation industry cannot simply and instantly overcome the massive cost, installation, testing and troubleshooting problems posed by an alternate system's infrastructure. Consequently, alternate systems must co-exist with old systems, perhaps for a considerable period of time. When comparing existing and alternate systems, the existing systems are useful because the required infrastructure is already in place, and the results are still tolerable, albeit far less than desirable. The massive costs of an alternate infrastructure coupled with a lack of benefit, and even possible harm, until substantially all aircraft and facilities are equipped with the systems that link them in the alternate infrastructure and the additional cockpit complication imposed by an alternate system cause such alternate systems to be un-implementable for all practical purposes.

SUMMARY OF THE INVENTION

Accordingly, it is an advantage of the present invention that an improved collision avoidance and communication system is provided along with an improved method for communicating and for avoiding collisions.

Another advantage of the present invention is that an integrated system is provided which simplifies rather than complicates the cockpit and aircraft operations such as communication, navigation and collision avoidance.

Yet another advantage is that the present invention provides a collision avoidance system which gives pilots information regarding locations of nearby aircraft.

Yet another advantage is that the present invention provides a collision avoidance system which may be implemented gradually throughout the aviation industry.

Yet another advantage is that the present invention provides a collision avoidance system which instantly benefits "equipped" aircraft even though a substantial portion of the population of aircraft is not equipped.

The above and other advantages of the present invention are carried out in one form by a system having a plurality of aircraft at various locations and having a control station. The present invention may by carried out by a method of managing information useful for safely operating the aircraft. The method calls for obtaining, at a first aircraft, first data describing locations of an equipped set of nearby aircraft. The first data are obtained from the equipped set of nearby aircraft. Second data are obtained at the first aircraft. The second data describe locations of an unequipped set of nearby aircraft. The second data are obtained from the control station. The first and second location data are displayed at the first aircraft.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the Figures, wherein like reference characters refer to similar items throughout the Figures, and:

FIG. 1 shows a diagram of the environment in which the present invention operates;

FIG. 2 shows a block diagram of an exemplary control station used in connection with the present invention;

FIG. 3 shows a block diagram of an exemplary aircraft station used in connection with the present invention;

FIG. 4 shows a timing diagram that depicts transmissions from two sources of location data;

FIG. 5 shows a block diagram of an exemplary format used in conveying a first type of data communication;

FIG. 6 shows a block diagram of an exemplary format used in conveying a second type of data communication;

FIG. 7 is a block diagram of an exemplary format used in conveying a third type of data communication;

FIG. 8 is a flow chart of exemplary processes performed at a ground control station;

FIG. 9 is a flow chart of a transmit process;

FIG. 10 is a flow chart of a fill object list process;

FIG. 11 is a flow chart of a display process;

FIG. 12 is a flow chart of a maintain object list process;

FIG. 13 is a block diagram of an exemplary memory structure maintained at the ground control station;

FIG. 14 is a flow chart of exemplary processes performed at an aircraft station;

FIG. 15 is a flow chart of a transmit process;

FIG. 16 is a flow chart of a fill object process;

FIG. 17 is a flow chart of a display process;

FIG. 18 is a flow chart of a maintain object list process;

FIG. 19 depicts an example of a first display formed by the aircraft station; and

FIG. 20 depicts an example of a second display formed by the aircraft station.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of the environment in which the system and method of the present invention operate. As depicted in FIG. 1, airspace 10 includes a population of aircraft which includes equipped set of aircraft 12 and unequipped set of aircraft 14. The system and method of the present invention facilitate safe operation of aircraft 12, 14 within airspace 10, regardless of relative populations of equipped aircraft 12 and unequipped aircraft 14. Equipped aircraft 12 benefit from convenience in operating aircraft 12 and improved safety regardless of the number of unequipped aircraft 14 that may be present in airspace 10 at any given time. Unequipped aircraft 14 benefit because information concerning their locations is distributed to a number of pilots in addition to air traffic controllers.

Any number of airspaces 10 may exist with respect to a geographic area and airspaces 10 may overlap. Radar system 16 detects the presence of aircraft 12, 14 in airspace 10. Radar system 16 couples to ground control station 18. Data communications 20 are sent back and forth among equipped aircraft 12 and between equipped aircraft 12 and ground control station 18 over RF communication network 22.

Any number of equipped aircraft 12 may reside in any given airspace 10 at any instant in time. Equipped aircraft 12 differ from unequipped aircraft 14 because each equipped aircraft 12 carries aircraft station 24. Nothing prevents equipped aircraft 12 from also carrying other well known avionic equipment. In particular, equipped aircraft 12 may, but need not, carry conventional transponder 26. Any number of unequipped aircraft 14 may reside in the same airspace 10 where equipped aircraft 12 reside. Unequipped aircraft 14 do not carry functional aircraft stations 24. In other words, either aircraft station 24 has not been installed in unequipped aircraft 14 or a previously installed aircraft station 24 is not functioning properly. As is the current practice, a vast number of unequipped aircraft 14 include conventional transponders 26, but some of unequipped aircraft 14 do not even carry transponders 26.

For convenience, FIG. 1 illustrates equipped aircraft 12 as being grouped together and unequipped aircraft 14 as being grouped together. However, those skilled in the art will appreciate that no particular relative grouping, spacing or orientation is required or implied by the present invention. Rather, any one of aircraft 12, 14 may reside at any point and take any heading within airspace 10 for the purposes of the present invention.

Radar system 16 represents any of the conventional radar systems currently installed at numerous airports and other locations and currently used in connection with conventional air traffic control to achieve collision avoidance. Thus, radar system 16 includes primary radar system 28 coupled to secondary radar system 30. Primary system 28 desirably detects locations of aircraft 12, 14 through transponders 26. Location data obtained from primary radar 28 identify an aircraft's direction from primary radar 28 and an aircraft's distance from primary radar 28. Secondary radar system 30 employs skin tracking, assuming detected aircraft present a sufficient radar cross section to improve upon obtainable location data.

Secondary system 30 operates successfully regardless of particular radar cross sections presented to primary radar 28. In "mode A" operation, transponders 26 provide data identifying an aircraft's identification (ID) number. In "mode C" operation, transponders 26 provide altitude data. In "mode S" operation, transponders 26 provide even more sophisticated location data. Of course, aircraft 12, 14 must carry transponder 26 in order for transponder 26 to provide any data to secondary system 30. Different versions of transponders 26 may operate in different modes.

Although not shown in FIG. 1, radar system 16 also includes a sophisticated processing system that distinguishes aircraft 12, 14 from other objects and that merges primary and secondary radar system location data while distinguishing detected objects from one another. Radar system 16 further includes a display system (not shown) that graphically depicts the objects, such as aircraft 12, 14, detected through operation of radar system 16.

Communication network 22 operates over a common communication channel. In the preferred embodiment, network 22 operates by time multiplexing data communications 20 onto a single, common frequency band to which ground control station 18 and all aircraft stations 24 remain tuned. In other words, ground control stations 18 and aircraft stations 24 are nodes of network 22. Desirably, all airspaces 10 utilize the same frequency so that stations 24 do not require re-tuning as equipped aircraft 12 move from one airspace 10 to another airspace 10. As discussed below in more detail, interference over this common communication channel is limited because each data communication 20 is a short duration burst. In addition, antenna configuration, in combination with transmission power, limit the radio communication range of data communications 20 among equipped aircraft 12 to a few miles. On the other hand, more efficient antenna configurations allow a much greater radio communication range for data communications 20 sent between equipped aircraft 12 and ground control station 18.

The radio communication range of equipped aircraft 12 is desirably kept as small as possible to minimize the chances of interference between data communications 20 on network 22. And, this radio communication range may be small because aircraft collision avoidance related data, such as locations of nearby aircraft, describing far off objects are of little value to an individual aircraft. On the other hand, ground control station 18 requires a greater range because, among other functions, it provides collision avoidance services for all aircraft 12, 14 in airspace 10, whether near to or far from an antenna for ground control station 18. Since a much smaller number of ground control stations 18 are expected to operate on network 22 than the number of equipped aircraft 12, little increase in likelihood of interference between data communications 20 results from the relatively long communication range for ground control stations 18.

FIG. 2 is a block diagram of an exemplary ground control station 18 used in connection with the present invention. As shown in FIG. 2, ground control station 18 includes controller 32. Controller 32 includes one or more conventional computer systems. As is conventional for computer systems, controller 32 includes one or more processors, memory, timers, input devices, output devices and the like (not shown). The memory of controller 32 stores programs which, when executed, cause ground control station 18 to carry out processes (discussed infra, e.g., FIGS. 8-12). In addition, the memory includes variables, tables, databases and other memory structures that are manipulated due to the operation of ground control station 18. The timer (not shown) of controller 32 allows ground control station 18 to act in accordance with particular timing considerations that are discussed below.

Controller 32 has numerous inputs receiving data from, and outputs supplying data to, other devices. Radar system 16 couples to a data input for controller 32. Data received from radar system 16 preferably describes objects and data displayed on conventional air traffic control terminals. In other words, controller 32 receives location data from radar system 16. As a minimum, location data identify X-Y coordinates for a detected object, such as aircraft 12, 14. These X-Y data may correspond to data obtained only through primary radar 28. When location data refer to aircraft 12, 14 equipped with transponder(s) 26, they also include aircraft ID and possibly altitude data.

An optional input of controller 32 couples to voice communication radios 34 used at the facility where ground control station 18 is used, such as an airport or air traffic control facility. This input provides controller 32 with data identifying the voice channels being used by the facility for radio communication with aircraft 12, 14. When this input is omitted, data identifying radio voice communication channels may be entered using other conventional computer data entry techniques (e.g., manual entry via keyboard).

Another data input of controller 32 couples to a device or devices providing real time control data, such as an automated weather station 36. Control data represent any data, other than data describing aircraft locations, useful to control of equipped aircraft 12. Real time control data represent time varying control data. In particular, this real time control data may describe weather conditions, perhaps at an airport where ground control station 18 is installed. Weather conditions useful to aircraft operation include wind shear, wind speed, wind direction, temperature and barometer readings.

Real time control data may also include differential GPS data. As discussed in more detail below, equipped aircraft 14 include a location determination system, such as a Global Positioning System (GPS) receiver. As is well known to those skilled in the art, differential GPS data allows for improved accuracy over that otherwise obtainable through a GPS receiver. In accordance with the present invention, differential GPS data may, for example, provide correction data which help on-board GPS receivers accurately identify their locations as they approach a runway.

Another data input of controller 32 couples to a device, such as a memory device 38, which provides fixed control data inputs, i.e., data which do not significantly vary over time. Thus, such data may be loaded in memory device 38 using conventional data entry techniques and updated from time to time as needed. Those skilled in the art will appreciate that memory 38 may actually represent a portion of controller 32 rather than a separate device.

Fixed control data may, for example, describe particular nearby geographic features. Examples of geographic features include runways which have particular locations, altitudes and orientations, mountain peaks and antenna towers which have particular locations and altitudes and the like. In addition, fixed control data may include Notices to Airmen (NOTAMs) which are published from time to time to provide useful information to pilots operating aircraft in particular areas.

Another data input of controller 32 couples to a spread spectrum radio 40. Radio 40 allows ground control station 18 to communicate over network 22 (FIG. 1). This data input receives data communications 20 via antenna 54, which are broadcast by any source of location data, such as equipped aircraft 12 or possibly other ground control stations 18, on network 22. Controller 32 also couples to radio 40 via a serial output and a serial input.

Radio 40 includes spreader 42 which has an input coupled to the serial data output from controller 32. Spreader 42 has another data input which receives a spreading code from spreading code block 44. A correlator 46 also receives a spreading code from spreading code block 44, and correlator 46 provides a data output which couples to the serial data input of controller 32. An oscillator 48 couples to both a transmitter 50 and a receiver 52. Transmitter 50 receives a signal from an output of spreader 42 and modulates the signal for radiation from radio 40 through an antenna 54. Electromagnetic signals received at antenna 54 are passed to receiver 52. An output of receiver 52 couples to an input of correlator 46. Receiver 52 down-converts the signals received at antenna 54 to baseband, and passes the baseband signals to correlator 46.

Spreader 42 spreads data communication 20 received from controller 32 over a broad frequency spectrum relative to a maximum data rate at which data communication 20 is supplied to radio 40 from controller 32. By spreading the RF energy associated with data communication 20 over a relatively broad frequency spectrum, the data communication's immunity to multipath and other forms of interference improves. Correlator 46 performs a complementary function to spreader 42. Correlator 46 correlates a received signal using the spreading code to determine whether incoming data communication 20 has been detected by radio 40.

Spreader 42 usefully frequency spreads data communication 20 such that data communication 20 occupies a bandwidth of several to many times the bandwidth normally associated with the data rate. Spread spectrum communications may occupy bandwidths of 25% or more of the nominal carrier frequency at which radio 40 transmits and receives data. Smaller bandwidths (e.g., 1%, 2% . . . 5%, 10% . . . 20% or more or less) are also desirably employed in many applications.

Another output of controller 32 couples to video display terminal 56. Video display terminal 56 may resemble a conventional video terminal of the type used in aircraft traffic control or any other type of video display terminal known to those skilled in the art. Controller 32 displays location data for aircraft 12, 14 and other data on video display terminal 56. Controller 32 controls the images shown or otherwise displayed on video terminal 56 in a conventional manner.

FIG. 3 shows a block diagram of exemplary aircraft station 24 (FIG. 1) used in connection with the present invention. Preferably, all equipped aircraft 12 include aircraft stations 24 compatible with that shown in FIG. 3. However, nothing prevents various aircraft stations 24 from including fewer features than those described below for aircraft station 24.

As shown in FIG. 3, aircraft station 24 includes a controller 58. Controller 58 includes one or more conventional computer systems. As is conventional for computer systems, controller 58 includes one or more processors, timers, input devices, output devices and the like. The timer (not shown) of controller 58 allows aircraft station 24 to act in accordance with particular timing considerations discussed infra (e.g., FIG. 4 and associated text).

Memory 60 couples to controller 58 and stores programs which, when executed, cause aircraft station 24 to carry out processes that are discussed below. In addition, memory 60 includes variables, tables, databases and other memory structures that are manipulated due to the operation of aircraft station 24. Memory 60 also stores data controlling images viewed on video display terminal 62 (coupled to a data output of controller 58).

Controller 58 has other inputs receiving data from other devices and outputs supplying data to other devices. For example, location determination system 64 couples to one of the data inputs. The above-discussed GPS receiver preferably serves as location determination system 64 in the preferred embodiment of the present invention, but other location systems known to those skilled in the art may be adapted for use in connection with the present invention. Location determination system 64 provides data to controller 58 which describe a current location for an equipped aircraft 12 within which station 24 resides.

Another input of controller 58 couples to a voice communication radio 66 which is also located in equipped aircraft 12. Voice communication radio 66 represents a conventional radio of the type used by pilots in verbally communicating with airport control towers, air traffic control facilities, and the like. This input provides controller 58 with data identifying the voice channels currently being used by radio 66.

Another data port, which supports both input and output data, of controller 58 couples to a spread spectrum radio 68. Spread spectrum radio 68 resides in equipped aircraft 12 and is desirably configured approximately as described above in connection with spread spectrum radio 40 (FIG. 2). In fact, spread spectrum radio 68 for each equipped aircraft 12 is desirably compatible with radios 40 located in ground control stations 18 (FIGS. 1-2). In other words, data communications 20 transmitted from any spread spectrum radio 40 or 68 may be detected by any other spread spectrum radio 40 or 68 within range.

Another data input of controller 58 couples to input device 70, usefully a switch or a pointing device of the type conventionally used in connection with video display terminals. Input device 70 allows a pilot of equipped aircraft 12 to issue instructions to aircraft station 24. Such instructions may, for example, instruct aircraft station 24 to display a particular one of several different types of screen images at video display terminal 62.

Generally speaking, a