GB2379035A

GB2379035A - Aircraft control system for avoiding predetermined geographical boundaries

Info

Publication number: GB2379035A
Application number: GB0215426A
Authority: GB
Inventors: Matthew Emmerson Allen; Keith Raymond Tart
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-09-20
Filing date: 2002-07-04
Publication date: 2003-02-26
Anticipated expiration: 2022-07-04
Also published as: GB0122678D0; GB0215426D0; GB2379035B

Abstract

A flight control system for an aircraft has means such as GPS for determining the geographical position of an aircraft, and means for comparing the position with stored geographical locations 50. The control system automatically alters the course or height of the aircraft, irrespective of any pilot commands, to avoid the stored locations. The control system may transmit a signal to warn aircraft in the vicinity that it is no longer under pilot control, and may automatically land the aircraft at a secure airport, having dumped excess fuel on the way.

Description

Aircraft Control System This invention relates to a vehicle control system, especially such a system for an aircraft.

It is widely appreciated that aircraft (particularly civil passenger aircraft) are at risk of being commandeered by unauthorised people. Recent events have shown that aircraft pilots can be overpowered and unauthorised people can fly aircraft such as passenger airliners into buildings with great loss of life.

A system is known wherein a flight control system compares the position of an aircraft as determined by a Global Positioning Satellite (GPS) system or the like with a map of the terrain over which the aircraft is expected to fly, detailing geographical and man-made structures. With this information the system can alert a pilot if the aircraft appears to be on a collision course. Such a system would be theoretically suitable for reducing the risk of a ground collision. However, this type of system has the disadvantage of requiring a very large database detailing all topographical data proximal the flight-path, much of which is irrelevant. In addition, use of such a system is impractical when an aircraft legitimately needs to fly near buildings and the like; for example, during landing at an airport, as implementation of such a system could prevent the routine landings along such a flight-path.

During flight, passenger airliners frequently fly on autopilot. While it is possible for such autopilot systems to be password protected to avoid unauthorised access such security has its limitations. Threats can persuade pilots to unlock such systems, and ultimately the aircraft normally returns to manual control, if it is to land before running out of fuel.

'1 ere is also an urgent need to protect designated ground sites that are thought likely to be attractive targets for pilots who wish to deliberately crash an aircraft. For example, such sites may be buildings in which thousands of people work or sites of national and international importance, such as military and governmental installations, and key economic and historic buildings. Such sites can be protected by air to ground projectile systems but such systems present great potential danger, especially to passengers of the aircraft. Furthermore, stationing them at all of the locations is costly and impractical and, indeed, represents a potential additional security threat.

An aim of the present invention is to provide an aircraft control system that offers increased security against the aircraft being flown in an unauthorised manner. Another

aim is to provide an aircraft : control system that prevents flight of an aircraft into 'Lit t excluded airspace.

According to a first aspect of the invention there is provided a flight control system for an aircraft, comprising means for determining the geographical position of the aircraft and means for comparing it with pre-determined geographical boundaries and control means designed to override a normal control system accessible to a pilot to alter the course of the aircraft irrespective of any pilot commands.

According to a second aspect of the invention there is provided a flight control system for an aircraft comprising an on board global positioning system that continually determines the geographical location of the aircraft and compares it with pre-determined excluded geographical locations that represent excluded zones and as necessary activates control means within the aircraft to prevent the aircraft being piloted within said excluded zones.

se control system can take control of an aircraft in the event of it being commandeered, and can prevent the aircraft entering pre-determined geographical boundaries, (which may take the form of excluded zone (s) ). An excluded zone may typically be defined to protect densely populated areas, important buildings etc..

This geographical boundary may be an open border or closed zone. A closed border (zone), (or indeed its airspace) may extend upwardly from a pre-determined ground area by a specified distance and thereby define an excluded volume of airspace. Many excluded zones may be pre-determined for key potential targets in a wide variety of international locations. The location of pre-determined zones may be stored using software, preferably appropriate hardware, most preferably in encrypted format.

Embodiments of the invention will now be described by example only and with reference to the following schematic diagrams in which; Figure 1 shows the major aspects for a preferred embodiment of the invention, and Figure 2 shows an aircraft fitted with the invention avoiding an excluded zone, and the use of polar co-ordinates to determine excluded air space.

Since aircraft flight control systems, such as auto-pilots, are many and well known they shall not be described here to maintain conciseness. The applicant refers the reader to many applications for patents in the name of Boeing RIM, BAE RIM and others.

Referring to Figure 1, an aircraft 8 such as a passenger aircraft has a global positioning system 12 (or the like), control system 10, and auto-pilot 24. The control system 10 comprises means for storing 14 excluded zone data, a comparator 16, revised flight path calculator 18, verifier 20, and an interface facility 22. Optionally, there is provided a two way transceiver 28 that allows communication between ground control 34 and verifier 20 via interface means 26. Also a warning beacon 32 is

optionally activated by verifier 20 via second interface means 30. Optionally, control system 10 may receive data from an altimeter (not shown).

In use, the global positioning system 12 continually sends geographical position data to comparator means 16. Comparator 16 has access to data defining excluded zones 14. Optionally, data from an altimeter may also be provided to the comparator. From real time position data, the comparator 16 calculates ground speed and flight direction and on the assumption that the aircraft will continue on its present course triggers an intervention signal when it is within a predetermined distance or (minimum) time from (reaching a boundary or) entering an excluded zone. At (roughly or) precisely the same time a flight path that will avert the excluded zone is calculated. These data are stored, for example in the comparator 18 or the verifier 20. Verifier 20 switches control of the aircraft from on board pilots to the system of the invention. Verifier 20 also prevents control of the aircraft being taken from on board pilots unless specified verification check (s) have been made. This will typically comprise confirmation that one or more parallel systems have also been triggered. For example, the aircraft may have several systems according to the invention working in parallel in order to avoid false interventions. Furthermore, the aircraft may be fitted with a"dummy"system to prevent tampering by saboteurs or others. Interface 22 allows the flight path that averts the excluded zone to be communicated to an auto-pilot 24 or similar device that controls the flight speed/path of the aircraft. Such an auto-pilot 24 would be provided with means to prevent on board pilot control in the event of an intervention signal being verified. Optionally, once so triggered the system would use warning beacon 32 to transmit a signal to (the ground and/or) other aircraft in its vicinity so that pilots of such aircraft were aware the aircraft was no longer under pilot control. Optionally, the system would also include a two way transmitter and receiver 28 that allows secure encrypted communication with a government or security agency or ground control.

This option would allow this ground facility 34 to transmit an encrypted signal to the aircraft 28 that would pass to verifier 20 via interface 26 and thereby either return control to on board pilots or alternatively allow the ground facility to directly control

L. set the auto-pilot 24 such that the aircraft was partly or fully under the control of ground based authorities.

A boundary such as an excluded zone 50 may be defined around buildings 52 (see Figure 2). Excluded zone 50 can be defined in a way that is independent of the height of the aircraft above ground level. This can offer the advantage of preventing bypassing of the system of the invention by tampering with altimeters or associated equipment that determines the height of the aircraft above ground level. In this case, excluded zones 50 may comprise a boundary such as a"wall"53 which will correspond to a matrix of geographical grid co-ordinates (XI, YI ; X2, Y2; X3, Y3; X4, Y4........... Xn, Yn) that define an excluded area of land (or sea) at ground level and thereby prevent flight in all of the airspace vertically above this excluded area. It will be appreciated that the boundary does not have to be closed. It could be in the form of a border line.

Additionally and/or alternatively, the excluded zones may also be defined to allow the aircraft entering airspace a pre-determined height above sea level, by defining a"roof 54 to the excluded zone 50. This may correspond the airspace extending a pre-specified height above an excluded area of land. That allows non dangerous aircraft to continue flying on a non dangerous path without changing course.

The excluded zone may also be defined by a matrix of three dimensional; co-ordinates that define a non planar boundary between permitted and excluded air space. This boundary may be defined at least in part by polar co-ordinates combined with fixed reference points, for example, points on buildings or at fixed distances above buildings (see Figure 2). This more complex definition of excluded air space may allow the aircraft flight control system to avoid entry within the excluded zone with less drastic flight manoeuvre.

i.. one embodiment the control system of the invention takes averting action to avoid an excluded zone based on air ground speed and flight direction data measured by standard aircraft systems. Thus, by continually monitoring ground speed and direction data and comparing this with any excluded zone falling in the near term flight path of the aircraft the system overrides pilot commands and takes action to avoid the excluded zone well before entering the proximity of an excluded zone. This may allow the aircraft to gradually change course, which is preferable to a sudden change in course and also offers the possible advantage of not being immediately detected by an unauthorised pilot. Of course, in certain situations, maximum aircraft movement may be required; for example, where the legitimate flight path of the aircraft closely approaches an excluded zone.

In a further embodiment of the invention, following control action to avoid an excluded zone the plane would continue to be flown by auto-pilot to a pre-determined location. The location may be a"safe"airport ; for example, a nearby military airport (which is better equipped to deal with saboteurs). In such circumstances the control system of the invention may also activate systems within the aircraft to dump excess fuel prior to landing, again without any option for the pilot to override this action.

In another embodiment of the invention a facility is provided for a ground based government or security agency to transmit an encrypted signal that unlocks the control system of the invention and returns control to a pilot on board the aircraft.

The invention is particularly suited for use in aircraft having fly-by-wire control systems wherein most or all aircraft functions are under computer control.

According to another aspect of the invention there is provided a control system for an aircraft, comprising means for detecting imminent crash situation, and means for releasing fuel from fuel supply and from aircraft in response. Predetermined zones such as green field sites are programmed as safe to eject fuel in a foreseeable yet

unavoidable aircraft failure situation. Fuel ejection can reduce the severity of a crash induced explosion or eliminate explosion altogether. Fuel may be treated (say chemically) prior to being ejected from aircraft. Aircraft may have means to bum fuel as it leaves aircraft. In that way, no liquid fuel reaches ground and persons below and /or other aircraft in the vicinity have a warning of a possible imminent crash and its approximate location. Fuel ejection may be dependent on aircraft height, in that above a certain height fuel will almost completely disperse before hitting ground/building level.

The control system may have means to monitor orientation of aircraft and act where orientation is excessive and/or suspicious (e. g. a very steep dive). Control system may have means for preventing aircraft entering a dive of more than a certain angle e. g. 45 degrees at certain area above or adjacent to an excluded zone. This may be only be practical where the excluded zone is small to allow successful alteration of course of aircraft if it does try to approach an excluded zone, whereas larger excluded zones would not be avoidable if aircraft dived (almost vertically) into the middle of an excluded zone.

Civilian passenger aircraft often stick closely to known routes between two locations such as cities. In a further aspect of the invention the control system may have a pre-programmed flight path between certain locations, and the flight path has a border around it (to allow for some deviation during flight e. g. emergency landing) and means for preventing aircraft leaving border zone.

A warning to other aircraft and/or ground may be given by a known warning device to proclaim that the aircraft is approaching/has approached border zone.

According to another aspect of the invention, the aircraft control system has detection means which detects at which longitude aircraft flies through a certain latitude, and is

L signed to apply correcting means to alter the flight path if the said latitude approaches (allowable) boundary longitude (s).

According to another aspect of the invention, the aircraft control system has detection means which detects at which latitude aircraft flies through a certain longitude, and is designed to apply correcting means to alter the flight path if the said longitude approaches (allowable) boundary latitude (s).

The control system may define an excluded zone extending substantially vertically to a height h2 equal to height of tallest building structure or the like hi (in Figure 2), in the excluded zone, plus a height h3 ; where h3 may be the maximum vertical distance attainable in a maximum angle controlled dive towards the zone.

The size of the excluded zone may be determined by calculating a boundary for the excluded zone that is dependent upon the approach speed of the aircraft; eg the boundary of an excluded zone may be larger (eg the roof may be higher) if an aircraft approaches it at a high dive speed and relatively smaller (eg the roof may be lower) if an aircraft approaches it at a low speed.

The distance between excluded zone boundary and a protected building etc. may be such as to allow avoidance if an aircraft enters the zone and is auto lifted/swerved at maximum capability.

This invention may be applicable to other kinds of craft such as sea crafts and land vehicles.

Claims

CLAIMS A flight control system for an aircraft comprising means for determining the geographical position of the aircraft and means for comparing it with pre-determined geographical location (s) and control means designed to override a normal control system accessible to a pilot to alter the course of the aircraft irrespective of any pilot commands.
2. A flight control system for an aircraft comprising an on board global positioning system that continually determines the geographical location of the aircraft and compares it with pre-determined excluded geographical locations that represent excluded zones and as necessary activates control means within the aircraft to prevent the aircraft being piloted within said excluded zones.
3. A flight control system according to any preceding claim wherein the geographical position of the aircraft is determined by a global positioning satellite (GPS) system.
4. An aircraft control system wherein the pre-determined geographical locations correspond to the location of on ground structures that are considered prime targets of saboteurs.
5. An aircraft control system according to any preceding claim wherein the control means comprise a fly-by-wire system for controlling the flight path of the aircraft.
6. A flight control system according to any preceding claim comprising means for ensuring that the aircraft lands at the nearest of a pre-selected secure airport using autopilot facilities following activation of the system to avoid an excluded zone.
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A flight control system according to Claim 6 wherein the aircraft automatically dumps excess fuel during part of its journey to a secure airport.
8. A flight control system according to any preceding claim that following activation to of the system to avoid an excluded zone propagates a warning system to alert other aircraft in its vicinity that it is no longer under pilot control.
9. A flight control system according to any preceding claim that may be re-set to allow pilot control following receipt an encrypted command transmitted by a government agency.
10. A flight control system according to Claim 9 wherein the encrypted signal is transmitted or relayed by a satellite.
11 A flight control system according to any preceding claim wherein the control means takes averting action to avoid the excluded zone based on flight direction and ground velocity data measured by aircraft equipment.
12. A flight control system according to Claim 11 wherein the control system takes averting action that corresponds to changes in flight direction experienced during normal flight navigation.
13. A flight control system according to any preceding claim wherein following averting action to avoid an excluded zone the aircraft ascends or descends to a pre-determined height.
14. A flight control system according to any preceding claim wherein following averting action to avoid an excluded zone all vital aircraft functions are controlled by commands transmitted from the ground by a government agency.

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15. A flight control system according to Claim 1, wherein the control system has a deep store which stores all excluded zone (subject to updating) locations.
16. A flight control system according to Claim 15, comprising another store which stores one or more locations for a designated geographical area.
17. A flight control system according to Claim 16, comprising a range made from the sum of approximately the range of the aircraft considering fuel load and/or weather and/or altitude) plus a reasonable safety factor.
18. A flight control system according to any preceding claim, wherein the aircraft control system has detection means which detects at which longitude aircraft flies through a certain latitude, and is designed to apply correcting means to override the pilot and alter the flight path if aircraft flies through latitudes at points approaching (allowable) boundary longitude (s).
19. A flight control system according to any preceding claim, wherein the aircraft control system has detection means which detects at which latitude aircraft flies through a certain longitude, and applies correcting means to override the pilot and alter the flight path if aircraft flies through longitudes at points approaching (allowable) boundary latitude (s).