U.S. patent application number 12/487844 was filed with the patent office on 2010-01-07 for method and system for resolving traffic conflicts in take-off and landing.
This patent application is currently assigned to University of Malta. Invention is credited to Andrew Sammut, Brian Zammit, David Zammit-Mangion.
Application Number | 20100004800 12/487844 |
Document ID | / |
Family ID | 40940988 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100004800 |
Kind Code |
A1 |
Zammit-Mangion; David ; et
al. |
January 7, 2010 |
Method and system for resolving traffic conflicts in take-off and
landing
Abstract
A method and system for resolving existing and potential traffic
conflicts that may occur during take-off and landing in aviation
that includes means of monitoring movements on the runway, its
approaches and environs to determine whether a conflict or
potential conflict exists, means to resolve a conflict and to
generate an output pertaining to this resolution.
Inventors: |
Zammit-Mangion; David;
(Mellieha, MT) ; Sammut; Andrew; (L-Iklin, MT)
; Zammit; Brian; (Mosta, MT) |
Correspondence
Address: |
Department of Electronic SYstems Engineering;University of Malta
--
Msida
MSD 2080
omitted
|
Assignee: |
University of Malta
Msida
MT
|
Family ID: |
40940988 |
Appl. No.: |
12/487844 |
Filed: |
June 19, 2009 |
Current U.S.
Class: |
701/3 |
Current CPC
Class: |
G08G 5/065 20130101;
G08G 5/045 20130101; G08G 5/0065 20130101; G08G 5/025 20130101 |
Class at
Publication: |
701/3 |
International
Class: |
G05D 1/00 20060101
G05D001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 20, 2008 |
MT |
4225 |
Claims
1. A method of detecting or monitoring the presence of traffic or
obstacles in the vicinity of an aircraft or its intended path
during the approach to a runway, landing or take-off, that
determines whether a conflict or potential conflict exists, that
determines a manoeuvre that will successfully resolve the conflict
and generates an output pertaining to the determined manoeuvre.
2. The method of claim 1, wherein the conflict geometry and
dynamics are used to determine the manoeuvre to resolve the
conflict or potential conflict.
3. The method of claim 1, wherein the performance of the aircraft
is used to determine the manoeuvre to resolve the conflict or
potential conflict.
4. The method of claim 3, wherein scheduled performance data is
used to determine the manoeuvre to resolve the conflict or
potential conflict.
5. The method of claim 1, wherein a directive aural alert or
instruction is generated.
6. The method of claim 5, wherein the alert directs the pilot to
perform a go-around during landing, to stop during take-off, or to
stop during taxi as the aircraft approaches a runway.
7. The method of claim 1, wherein the aircraft is triggered to
automatically execute the intended manoeuvre.
8. The method of claim 1, further including the generation of aural
alerts pertaining to the distance to the conflict.
9. The method of claim 1, further including the generation of an
aural alert advising the pilot that the conflict is resolved when
the conflict is resolved.
10. The method of claim 1, further including the storage and
retrieval of runway and airport survey data.
11. The method of claim 1, further including the graphical display
of the aircraft's position with respect to the runway or other
geographical points on the airfield.
12. The method of claim 11, further including the graphical display
of other traffic in relation to geographic points on the airfield
and in relation to the aircraft.
13. The method of claim 1, further including communication means
with other aircraft, vehicles or entities to enable the
coordination of a conflict resolution manoeuvre.
14. The method of claim 13, wherein information pertaining to the
detected conflict is transmitted.
15. The method of claim 1, wherein a conflict is resolved in
coordination with the conflict traffic or entity.
16. A system for detecting or monitoring the presence of traffic or
obstacles in the vicinity of an aircraft or its intended path
during the approach to a runway, landing or take-off, that
determines whether a conflict or potential conflict exists, that
determines a manoeuvre that will successfully resolve the conflict
and generates an output pertaining to the determined manoeuvre, the
system including data acquisition means, a data processing device
and an output device to generate an output pertaining to the
determined manoeuvre.
17. The system of claim 16, wherein the output device includes an
audio device.
18. The system of claim 16, wherein the output device includes a
display device.
19. The system of claim 16, wherein the output device is
electrically connected to the aircraft's guidance system.
20. The system of claim 16, including a data storage device for
storing and retrieving runway and airport survey data.
21. The system of claim 16, including a wireless datalink device
for communicating with other aircraft, vehicles or entities.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method and system for
resolving traffic or other physical conflicts that may occur during
take-off and landing.
BACKGROUND OF THE INVENTION
[0002] Aircraft are constantly operating in close proximity of
other aircraft and, on the ground, also in close proximity of other
vehicles and obstacles. Separation from such hazards, therefore, is
of prime importance in assuring the safe continuation of a flight.
In flights operating under Visual Flying Rules (VFR), the
responsibility of separation lies with the pilot. Separation is
normally ensured through good situational awareness of traffic in
the vicinity of the ownship. This is traditionally achieved by
keeping a good look-out and through radio communication, which
allows the crew to build a mental picture of the traffic movements
in the vicinity. Under Instrument Flying Rules (IFR), separation is
the responsibility of air traffic control (ATC), where the air
traffic control officer (ATCO) directs traffic in such a way to
ensure safe separation between all entities.
[0003] In controlled airfields, the ATCO is responsible for the
control of traffic in and around the airfield and it is the ATCO
who provides clearances for aircraft to enter a runway, take-off or
land. It is therefore the ATCO who ensures that any movements are
well clear of the particular aircraft in take-off or landing. In
essence, the ATCO reserves the runway (or a portion of it) for the
exclusive use of this aircraft and procedures are rigorously
followed to ensure safe separation from other aircraft.
Nevertheless, it is good airmanship for pilots to independently
ensure that they are cleared to enter a runway, land on it or
take-off, that the approaches of a runway are indeed clear before
entering it and, before taking off or landing, that the runway
itself is clear. Such actions are, of course, more effective in
situations of good visibility and in reduced visibility and bad
weather, pilots and ATCOs are more careful to ensure that
separation is indeed maintained. In fact, reduced visibility
operations are subject to more stringent separation rules, where
separation between aircraft is intentionally increased and certain
manoeuvres are not allowed.
[0004] Therefore, whereas the procedure dictates that the ATCO is
responsible for traffic separation, the pilot also plays an active
role in ensuring that the required separation is indeed preserved.
The pilot also plays a critical role in restoring this separation
when it is lost and this role is essential for the mitigation of
the risk of collision.
[0005] Positional and traffic situational awareness are fundamental
in maintaining safe separation between aircraft and this is
generally achieved through good communication on voice radio, which
allows the relevant parties to build a mental picture of all
movements in the vicinity.
[0006] However, notwithstanding rigorous procedure, training and
good practice, the current procedural method of maintaining
separation is prone to failure. This repeatedly results in aircraft
(and vehicles) coming in conflict with one another on the runway.
Indeed, in the US alone, during the period 2003 to 2006, 1306
runway incursions have been reported [FAA Runway Safety Report,
September 2007, Federal Aviation Administration]. The FAA then
defined runway incursion as any occurrence in the airport runway
environment involving an aircraft, vehicle, person or object on the
ground that creates a collision hazard or results in a loss of
required separation with an aircraft taking off, intending to take
off, landing or intending to land. In October 2007, the FAA adopted
the ICAO definition, which defines a runway incursion as any
occurrence at an aerodrome involving the incorrect presence of an
aircraft, vehicle, or person on the protected area of a surface
designated for the landing and take-off of an aircraft.
[0007] Current procedure, therefore, can be considered
unsatisfactory and needs to be complemented by a means that
monitors traffic in the vicinity and warns the pilot accordingly.
In a way, a sort of `electronic-supervisor` is required in order to
complement the pilot (or ATCO) and to provide appropriate advice
when he or she fails to see or detect the conflict.
PRIOR ART
[0008] A number of solutions have been proposed in an attempt to
mitigate the risk of runway collision. These can conceptually be
divided into two categories, namely ground-based systems that are
installed in an airport, and airborne solutions that are installed
on board aircraft (and are therefore not airport specific).
[0009] Ground-based systems generally depend on sensors and other
equipment installed at various locations on the airfield. One such
system is Northrop Grumman's Nova 9000 Runway Incursion Monitoring
and Conflict Alert System (RIMCAS) that provides an alert of a
conflict to the ATCO, who is then expected to take positive action
to resolve the conflict. Another method and system that also
provides situational awareness to the ATCO is described in U.S.
Pat. No. 5,629,691 (Jain). A third example that proposes the
monitoring of aircraft and vehicles on the ground to alert flight
controllers is disclosed in U.S. Pat. No. 6,486,825 (Smithey). Yet
another ground-based system, disclosed in U.S. Pat. No. 6,920,390
(Mallet et al.), uses sensors to locate aircraft position and
displays route guidance information to vehicles and aircraft via
boards installed at various positions on the airfield. This system
is primarily aimed at reducing inadvertent entry into a runway
whilst taxying, usually the result of lost or disoriented pilots.
It therefore targets taxying aircraft and not aircraft in take-off
or landing. Another proposal, described in U.S. Pat. No. 7,117,089
(Khatwa et al.) describes a Ground Runway Awareness and Advisory
System (GRAAS) intended to provide aural situational awareness to
vehicle operators and pedestrians, optionally supplemented with a
video display. The equipment would either be hand held or installed
in the ground vehicle.
[0010] Although ground-based systems have been shown to be
effective at reducing runway incursions, the above methods only
provide a partial solution to the problem of runway traffic
conflicts. This is because, in the prior art, the aircraft in
take-off or in landing (one of the parties usually involved in the
runway conflict) is either not advised at all by the system (eg.
GRAAS) or is advised indirectly, through ATCO voice communication.
Whilst the former does not provide protection to the aircraft in
take-off or landing, the latter will incur a delay between system
alert and pilot reaction. This is inadequate, since reaction time
may be critical for the safe avoidance of the collision threat. A
further limitation is that such ground-based systems depend on the
ATCO transmitting the correct instruction in a timely, efficient
and unambiguous manner over the radio. In critical situations, this
may be demanding and indeed may even not be managed adequately, as
exemplified by a number of known transcripts of runway incursion
incidents. Such limitations clearly jeopardise the effectiveness of
the alerting system in critical situations. Furthermore,
ground-based systems depend on the installation of the equipment by
the airport and/or air traffic service provider of the airport.
Consequently, protection will only be available at airports where
such systems are installed. This is a significant limitation,
particularly considering that today, still only a small number of
airports are equipped with runway incursion alerting systems.
[0011] Airborne solutions mitigate the said shortcomings by being
independent of airport equipment and by providing primary
information directly to the crew of the aircraft in take-off or
landing. One example of an airborne system is described in U.S.
Pat. No. 6,606,563 (Corcoran, III). This system is designed to
mitigate the risk of runway incursion by providing alerts to the
pilot that he or she is approaching or has entered a `zone of
awareness` such as a particular runway. The system, however,
operates independently of other traffic and specifically does not
identify or alert runway conflicts. The patent was continued in
other patents by the assignee (Honeywell International Inc.),
including U.S. Pat. No. 7,117,089 (Khatwa) described earlier and
U.S. Pat. No. 7,206,698 (Conner et al.). The latter discloses a
display device to display airport survey data (such as runways) and
the plotting of third party aircraft data (such as position)
received from RF broadcasts. The system also provides means of
determining potential conflicts with such traffic and to generate
advisories accordingly. A portion of the described system is the
Aircraft Position Situational Awareness System (APSAS). APSAS
determines the position of the aircraft relative to the airport,
receives broadcasts from other aircraft and determines whether
potential conflicts in the occupation of runways exists. The system
graphically displays the ownship and other aircraft position in
relation to the runway and annunciates potential conflicts. The
aural alert indicates that a runway being approached or entered is
occupied, being vacated or being approached by another vehicle. In
a further extension of this system, U.S. Pat. No. 7,363,145 (Conner
et al.) discloses a method for annunciating imminent landing
situational advisories, but these are not related to runway
conflicts.
[0012] Another system that identifies runway conflicts is described
in U.S. Pat. No. 6,850,185 (Woodell). The document describes a
system based on airborne radar intended to identify any obstacle on
the runway and to alert the crew of the presence of the
obstacle.
[0013] The alerting of a conflict directly on the aircraft in
take-off or landing is an improvement over the current operational
standard. Indeed, recent prior art proposing ground-based systems
have also incorporated the alerting of a conflict directly to the
crew on the aircraft, as disclosed in U.S. Pat. No. 7,385,527
(Clavier) and U.S. Pat. No. 7,535,404 (Corrigan). However, these
systems generate only advisory alerts, that is, alerts relating to
the existence or the potential existence of a conflict. This again
provides only partial protection, since alerts that are generated
simply on the basis of the existence of a conflict (that is,
without taking into account the conflict dynamics and aircraft
performance) cannot reliably relate to how a conflict should be
resolved. As a result, alerts generated by prior art such as that
referred to above, still require the crew to take the following
steps to successfully resolve the conflict following its
annunciation: [0014] 1) identify the conflict (conflict aircraft
and its position in relation to the ownship), typically via the
graphical display [0015] 2) determinate a manoeuvre that will
successfully resolve the conflict [0016] 3) decide to execute the
manoeuvre [0017] 4) execute the manoeuvre.
[0018] Steps 1 to 3 increase crew workload in critical moments
during take-off and landing and can take several seconds to
complete under normal working conditions. It is immediately
appreciated by those knowledgeable in the art, however, that the
take-off and landing phases of flight impose high workload and
operational pressures to the pilot, particularly in bad weather
conditions. An additional complication is that during these phases
of flight, situations that may be hazardous to the safe
continuation of the flight may develop very quickly and with very
little warning. It is also well known that human decision-making
capabilities and reaction times are compromised when workloads are
high and when threatening situations are announced without prior
warning. As a result, in such circumstances, the risk of the pilot
erring in any of the above steps, thereby breaking the path to
successful mitigation of the conflict, is significant. Indeed, in
the operational environment, the mental processing and subsequent
decision taking relating to runway conflicts can be demanding, is
subject to hesitation and even erroneous conclusions. Another
consideration is that, during take-off, it may not be possible for
the crew to identify very quickly from a graphical display
(particularly in critical circumstances) whether it is better to
abort the run and to stop before the conflict, or to continue the
take-off and overfly it safely.
[0019] Consequently, the method of providing an aural alert that
only advises the crew of the existence or potential existence of a
conflict will require the pilot to carry out all the four named
steps and therefore provides only a partial solution to runway
conflicts due to the described limitations.
[0020] Honeywell International Inc. discloses a method and system
of avoiding runway collisions in U.S. Pat. No. 7,479,925. The
method described is based on identifying three restricted zones
associated with a runway and its environs and generating an aural
advisory message and signals according to the presence of aircraft
within these restricted zones. For example, an audible warning may
include `Traffic on Runway` or `Traffic on Approach`. The system
depends on aircraft communicating via a wireless communication
system that is programmed to receive messages from other aircraft
if positioned off an active runway on the ground, and to transmit
and receive messages if it is on the runway or airborne on
approach. In this way, an aircraft on approach or on the runway can
indicate their presence, whilst other aircraft can receive such
messages.
[0021] As this method also generates alerts based only on the
presence of a conflict, it too cannot provide reliable means of
generating an output relating to the resolution of a conflict and
therefore likewise can only provide partial protection against
runway collisions.
[0022] In order to provide a fast, reliable and repeatable response
to a conflict in a cockpit, it is advantageous to at least
eliminate or automate at least the first two steps above. This can
be done by a system that also determines an escape manoeuvre and
then generates an output pertaining to that escape manoeuvre. It is
immediately appreciated by those knowledgeable in the art that the
reliable calculation of a feasible escape manoeuvre requires the
consideration of the dynamics of the conflict and the performance
of the aircraft that is expected to execute the escape
manoeuvre.
SUMMARY OF THE PRESENT INVENTION
[0023] There exists a need, therefore, for a system that monitors
the traffic movements in the vicinity of the ownship and its
intended path, that determines whether a conflict or potential
conflict exists and determines an escape manoeuvre that will
successfully resolve the conflict.
[0024] The present invention provides a method and system that
facilitate the successful mitigation of traffic conflicts by
overcoming at least some of the limitations of prior art.
[0025] According to the present invention, there is provided a
method that detects or monitors the presence of traffic or
obstacles in the vicinity of the ownship or its intended path, that
determines whether a conflict or potential conflict exists, that
determines an escape manoeuvre that will successfully resolve the
conflict and generates an output pertaining to the determined
manoeuvre.
[0026] By detecting or monitoring the presence of traffic or
obstacles in the vicinity of the ownship and its intended path, the
method is capable of identifying whether the target presents a
threat by coming or potentially coming in conflict with the
ownship.
[0027] Advantageously, the detection or monitoring process may
refer to a database containing runway and airport survey data to
determine the position of traffic in relation to particular areas,
zones or locations in an airfield such as a runway or its
threshold.
[0028] Advantageously, the determination of the existence or
potential existence of a conflict is based on the position and
state of the ownship in relation to the position or geometry of the
airfield and in relation to the position and state of the target
traffic or obstacle.
[0029] By determining an escape manoeuvre that will successfully
resolve the conflict, the method is capable of relieving the crew
of the decision of how to mitigate the conflict, thus providing a
better method of mitigating the threat of collision.
[0030] Advantageously, the determination of the escape manoeuvre
takes into account the position and state of the ownship in
relation to the position and geometry of the airfield and in
relation to the position and states of the conflict traffic or
obstacle.
[0031] Advantageously, the determination of the escape manoeuvre
takes into account the performance of the ownship to ensure that
the said manoeuvre can be successfully executed.
[0032] Advantageously, the method provides an output that relates
to the manoeuvre to be executed. The output may be, but is not
restricted to, an aural alert or message, a visual alert, an
electrical or electronic signal, or a combination thereof. The
electrical or electronic signal may stimulate or direct means of
controlling the aircraft such as the flight guidance computer on
board the ownship.
[0033] According to another aspect of the present invention, a
plurality of escape manoeuvres may be determined and one is
selected on the basis of pre-defined criteria.
[0034] According to another aspect of the present invention, the
method may include steps for providing graphical means of
displaying the position of the ownship in relation to the position
and layout of the airfield and in relation to the position and
states of the conflict traffic or obstacle. In addition, other
traffic or obstacles that may not be in conflict with the ownship
may also be displayed.
[0035] By displaying the airfield traffic and obstacles, the method
provides enhanced situational awareness in relation to traffic
conflicts and their mitigation.
[0036] According to yet another aspect of the present invention,
the method may include steps for communicating with other traffic.
Advantageously, by communicating with other traffic, the escape
manoeuvres of the ownship and the other traffic with which it is in
conflict can be coordinated.
[0037] Preferably, through coordination, the escape manoeuvre is
determined collaboratively with the conflict traffic.
Advantageously, by determining the escape manoeuvre
collaboratively, the conflict can be resolved with minimal
disruption to operations whilst maintaining the necessary levels of
safety in the circumstances.
[0038] According to another aspect of the present invention, the
method may include steps for communicating with air traffic
control. Advantageously, by communicating with air traffic control,
the air traffic control officer can be warned of the conflict and
advised of the escape manoeuvre made by the aircraft.
[0039] According to a further aspect of the invention, there is
provided a system, including data acquisition means, a data
processing device and output means, the system being constructed
and arranged to operate in according to a method as defined by the
present invention.
[0040] According to the present invention, there is provided a
system that detects or monitors the presence of traffic or
obstacles in the vicinity of the ownship and its intended path,
that determines whether a conflict or potential conflict exists,
that determines an escape manoeuvre that will successfully resolve
the conflict and generates an output pertaining to the determined
manoeuvre.
[0041] According to a further aspect of the invention, the output
means may include an aural alerting system, a graphic display,
means for electrically or electronically transmitting the output,
or combinations thereof.
[0042] According to a further aspect of the invention, the system
may include a wireless datalink to support the electronic
communication between the ownship and other aircraft for the
coordination and cooperative resolution of the conflict.
[0043] According to a further aspect of the invention, the wireless
datalink may communicate with air traffic control to provide an
alert pertaining to the conflict and information pertaining to the
action taken to resolve the conflict.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0044] An embodiment of the invention will now be described with
reference to the accompanying drawings, in which:
[0045] FIG. 1 illustrates the block diagram of one embodiment of
the disclosed system;
[0046] FIG. 2 presents an example of a runway incursion, with an
aircraft approaching a runway to land and another aircraft entering
the runway;
[0047] FIGS. 3 and 4 are flow diagrams illustrating the main steps
of the conflict alerting method for take-off and landing in a
preferred embodiment of the disclosed system;
[0048] FIG. 5 illustrates schematically the preferred conflict
state logic;
[0049] FIG. 6 is a flow diagram illustrating the main steps of a
collaborative decision making process.
[0050] In the preferred embodiment, conflict detection is based on
the definition of a `protected zone` around a runway. As a runway
is essentially reserved for an aircraft conducting a take-off or
landing, the `protected zone` defines the area that is effectively
reserved exclusively to the said aircraft during the manoeuvre. The
extent of the `protected zone` depends, amongst other factors, on
the runway geometry and ownship manoeuvre. If another aircraft,
vehicle or obstacle enters the `protected zone` it may come in
conflict with the ownship. The scenario depicted in FIG. 2 only
illustrates a typical conflict situation and it is understood that
many different situations can exist, for both take-off and landing.
In this example, the aircraft equipped with the system, referred to
as the `ownship` (50), is approaching the runway (52) to land. The
`protected zone` (54) includes the runway, its approaches and the
immediate environs. Other aircraft (56, 58) are manoeuvring in the
vicinity of the runway. In the example depicted in FIG. 2, one
aircraft (56) is just outside the `protected zone` and therefore
does not come in conflict with the ownship, whilst another (58) is
within the `protected zone` and therefore comes in potential
conflict with the ownship. An aircraft within the `protected zone`
is referred to as an `intruder`.
[0051] The main steps of the alerting process carried out during
landing in a preferred embodiment of the disclosed system are shown
in FIG. 3. In this process, initialisation is done automatically as
the ownship approaches the runway to land (100). The correct runway
on which the landing will be carried out is identified
automatically and the system retrieves geographical information
pertaining to the runway and its environs from a database. On
initialisation, it will initiate surveillance (102) and will
monitor movements (including other traffic and vehicles) ahead of
the aircraft and in the vicinity of the runway and the aircraft's
intended path. Such a surveillance function may be obtained through
new technologies such as ADS-B, other sensors such as radar, or a
combination of such systems through the employment of sensor fusion
techniques. The landing surveillance terminates (120) when the
landing manoeuvre is complete, typically either when the aircraft
slows down to taxi speed or will have initiated a go-around. It is
understood that the surveillance function is not necessarily
dedicated to the embodiment of the disclosed method and system, but
may, for example, be part of an overall surveillance function on
board the ownship. In such embodiments, the surveillance function
may not terminate when the landing is complete and continue to
provide surveillance during other phases of flight.
[0052] The surveillance function uses vector notation to represent
positional and kinematic information of targets and the ownship as
well as airfield geometry and geometry of the `protected zone`.
Depending on the type of data acquisition system, transformations
are carried out to translate the information into a 2-dimensional,
flat earth plot. For example, ADS-B derived data provides
positional information in the form of latitude and longitude. This
is translated first to Cartesian coordinates referenced to
earth-centred, earth-fixed (ECEF) axes and then to axes referenced
to the runway threshold.
[0053] As the aircraft approaches the runway, the surveillance
function assigns the runway (or a portion of it) to the ownship and
creates a `protected zone` around it. Nominally, the `protected
zone` is assigned to the ownship 30 seconds before it flies over
the runway threshold. This length of time, however, may be assigned
a different value. Preferably, a conflict is detected (104) in
accordance to the logic presented in FIG. 5. The Conflict State
(68) is set to True when a target enters the `protected zone` (60),
the separation between the ownship and the target is decreasing
(62) and logic rules associated with separation minima and the
flight phase (manoeuvre) of the ownship and conflict entity are
satisfied (64, 66, 67). It is understood that this logic is only
one example of the embodiment of the method disclosed and different
logic functions can be applied within the scope of the
invention.
[0054] On the identification of a conflict, according to FIG. 3, a
conflict resolution computer determines whether either option of
continuing the landing and aborting it (performing a go-around) are
feasible to mitigate the threat of collision and determines the
preferred option (106). This calculation includes ownship
performance calculations. In the event the continuation of the
landing is preferred, the alert is suppressed. If, on the other
hand, a go-around is warranted, a directive alert, advising the
pilot to go-around, such as `Go-Around . . . . Traffic` is
generated (108). Such an alert, which may be preceded by a unique
sound (often referred to as a gong or bell), would direct the pilot
to immediately initiate the manoeuvre whilst giving a reason for
the instruction. The particular tone and the nature and specific
wording of the alert may differ, depending on precise flight deck
aural alerting philosophy of the particular aircraft. The alert may
be repeated, nominally every 4 seconds until the conflict is
resolved or the directive alert is followed (109). When the
conflict is resolved, a `conflict clear` alert is generated (114).
In the event the aircraft has landed, the steps followed will be
identical to those of an aborted take-off (116, 188).
[0055] In the case of take-off (FIG. 4), the function provides
similar surveillance (150) and conflict detection (152). The
conflict resolution computer determines whether it is safer to
continue the take-off manoeuvre or to abort the run (154) and will
suppress any alert in the former case (156). A `Stop . . . Traffic`
alert is generated (158) to direct the crew to abort the run if the
run is to be aborted. The exact wording and nature of the alert may
vary and the alert may be likewise preceded by a bell or gong. As
in the case for landing, the alert may be repeated, nominally every
4 seconds, until the conflict is resolved (not shown in FIG. 4),
the aircraft will have passed a critical speed (typically, but not
limited to, V.sub.1) or an abort initiated (160).
[0056] If a take-off is aborted, distance call-outs to the intruder
are generated (162), nominally every 200 m above 1000 m and every
100 m for smaller separations until the closure rate falls below a
threshold, nominally set at 20 kts. It is understood that the exact
wording, thresholds and other cues can vary and any appropriate
wording or values can be used.
[0057] Distance call-outs are also generated during landing in the
event the ownship continues the landing manoeuvre, as shown in FIG.
3 (116, 118).
[0058] A variety of performance equations known to those
knowledgeable in the art can be used by the performance calculator
to determine whether a potential ownship manoeuvre can resolve a
conflict. A preferred method uses scheduled aircraft performance
data that is modified to take into account the actual progress of
the ownship in the manoeuvre.
[0059] The method and system of the present invention can also
provide surveillance and resolve traffic conflicts that may occur
whilst the ownship is taxying on the runway or in its environs. For
example, in a preferred embodiment, whilst taxying towards or on
the runway, the surveillance computer monitors the runway and its
approaches to determine whether any aircraft is taking off or
landing. If the conflict detection computer detects a conflict or
potential conflict, it determines an escape manoeuvre, typically by
estimating whether the ownship can stop before entering the runway
or vacate the runway safely to resolve the conflict. It then
generates alerts pertaining to the preferred manoeuvre. Preferably,
an aural alert such as `Stop--Runway Incursion` and `Vacate
Runway--Traffic` are generated.
[0060] Advisory alerts may also be generated. For example, if an
aircraft is detected on approach to a runway and the ownship is
taxying towards its extended path, a `Traffic on Approach` alert
may be generated.
[0061] Preferably, the steps calculating the escape manoeuvre (106,
154) include steps that can support cooperative conflict resolution
with the intruder aircraft. If the intruder aircraft is also
equipped with this capability, this would allow conflict resolution
to be achieved with minimal disruption or risk of accident. For
example, if the ownship is advanced in the take-off run and an
aircraft enters the `protected zone` (thus becoming a `intruder`),
it may be advantageous to resolve the conflict by stopping the
intruder before it crosses the projected path of the ownship,
whilst allowing the ownship to continue the take-off. Without
cooperative resolution, the ownship cannot take into account any
escape manoeuvre conducted by the intruder and may have to abort
the run to avoid a collision. The cooperative conflict resolution
capability thus allows, in this example, the conflict to be
resolved without the ownship having to carry out a high speed
abort. Such a manoeuvre always introduces a risk of disruption to
operations, damage and injury and is normally avoided unless the
risks associated with continuing the take-off are higher. It is
evident, therefore, that cooperative conflict resolution can offer
better solutions to a conflict on the runway.
[0062] A variety of methods for cooperative conflict resolution can
be employed. The steps of one method are shown in FIG. 6, which is
simplified for clarity. In this method, as the system on board the
aircraft performing the take-off or landing detects a conflict with
an intruder in the `protected zone` (180), it determines whether
the intruder can stop before physically entering the runway (181).
If this is not the case, as, for example, when the intruder is
already on the runway, the ownship broadcasts the conflict
situation (184) and continues to resolve the conflict independently
of the intruder (192). If, however, the intruder is capable of
stopping, the ownship will broadcast an instruction for the
intruder to stop (182). This may take the format, for example, of a
repeated radio transmission of a digital message that also contains
other information pertaining to the conflict (such as, but not
limited to, aircraft and runway identification information). The
system then waits for a predetermined period, such as, but not
limited to, 0.3 seconds, for acknowledgement (or agreement) from
the intruder. If no acknowledgement is received, the system
continues to resolve the conflict independently of the intruder
(192). If the intruder transmits the acknowledgement, the system
continues to monitor the intruder to verify that it has indeed
stopped short of the runway, allowing the ownship to proceed with
its manoeuvre (190) which may be either to continue with the
original intentions prior to the conflict or to abort (go-around in
the case of a landing, stop in the case of a take-off).
Furthermore, in this method, if the system on board the aircraft
taxying on the runway or its environs detects a conflict with an
intruder in the `protected zone`, it determines whether the ownship
can stop prior to entering the runway or vacate it in time and then
broadcasts a message pertaining to the conflict. It may also
transmit a message pertaining to the escape manoeuvre being
executed. If the taxying aircraft receives a message instructing it
to stop from an intruder that is taking off or landing, the
conflict resolution computer determines whether the ownship can
indeed resolve the conflict by stopping and transmits a reply
pertaining to the conflict resolution computer's output. In this
way, the taxying aircraft will be acknowledging or otherwise the
instruction transmitted by the other aircraft in take-off or
landing.
[0063] When both the ownship and the intruder are equipped with a
system according to the invention, both are independently capable
of detecting the conflict. Consequently, it is possible for both
entities to simultaneously attempt to broadcast the conflict
situation. Accordingly, the present invention includes means for
message separation. These means can use, for example, but are not
limited to, known frequency multiplexing or time division
multiplexing techniques to allow simultaneous transmissions of
messages.
[0064] It is understood that many variations of the above steps can
be made without departing from the spirit and scope of the
invention. Variations may be due to, but are not limited to, the
capabilities and equipment installed on the ownship. For example,
the result of the steps calculating the escape manoeuvre (106, 154)
can be used to control the automatic guidance system such as the
autopilot on board the aircraft. In this case, the aural alerts
generated may be different and be informative rather than directive
in nature.
[0065] The main components of one embodiment of the system
disclosed are shown schematically in FIG. 1. The Data Acquisition
Unit (10) consolidates data from a plurality of sources (12) such
as, but not limited to, ADS-B, Radar, the Flight Management System,
Air Data Computer, navigation computer, etc. Preferably, one of the
sources also includes a database containing airfield survey
data.
[0066] The output from the Data Acquisition Unit (10) is
transmitted to the Surveillance Computer (14), which carries out
the surveillance function. The Surveillance function identifies the
`protected zone` around the runway and monitors movements (bodies,
vehicles or aircraft) to determine whether these are within this
`protected zone` or otherwise. The Conflict Detection Computer (18)
determines whether aircraft within the `protected zone` constitute
a threat or risk of conflict with the ownship, using state
information from the ownship and the target aircraft. The Conflict
Resolution Computer (22) uses performance data of the ownship
sourced from the Performance Computer (24) to compute an escape
manoeuvre to allow the ownship to avoid a collision with the
intruder. If the ownship and intruder aircraft are equipped with
cooperative conflict resolution capability, the Conflict Resolution
Computer communicates with its counterpart on the intruder aircraft
via a wireless Data Link (20). The output of the Conflict
Resolution Computer is transmitted to the Alert Generator (26). The
Alert Generator, which may include alert prioritisation algorithms,
will generate alerts via the audio system (28) and, optionally,
graphically via a Display Device (16). The Display Device may
typically involve existing equipment on the aircraft such as the
Primary Flight Display, Navigation Display or a Cockpit Display of
Traffic Information (CDTI). In addition, the surveillance computer
may optionally generate outputs on the Display Device (16),
including outputs pertaining to the relative positions of the
ownship and targets with respect to the geographic position and
orientation of the airfield or runway.
[0067] In one embodiment of the system, the output of the Conflict
Resolution Computer is transmitted to the automatic guidance device
of the ownship (32).
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