Patent Grant
7116266
Conventionally, avionics, engineers and certification bodies are improving and providing pilots and flight crews with information necessary to identify in-flight traffic. An approach has been to provide the flight crew with information on the location of other aircraft in the area. One exemplary system which is capable of providing this information, is known as a traffic alert and collision avoidance system (TCAS). The systems are required for all airliners flying the United States air space today. TCAS devices have been designed to interrogate transponders of other aircrafts, sometimes referred to as intruder aircraft. The TCAS system evaluates the threat of collision with other aircraft and coordinates an avoidance maneuver for the aircraft.
Recently, the aviation industry has worked to define a new standard of performance for Mode S transponders which are the communication devices used in most TCAS systems. The extension of the function of Mode S transponders is to provide more information about the state and plans of aircraft which are under surveillance. This extended information may collectively be called “enhanced surveillance”. The feature is designed to provide ground-based aircraft control and additional information to enable improved management of air traffic. Although this information is provided from Mode S transponders to ground-based air traffic control, it may be desirable and useful for a first aircraft to be able to interrogate a Mode S transponder and receive enhanced surveillance information from a Mode S transponder on a second aircraft.
Accordingly, there is a need for a system and method in which the first aircraft may request and receive enhanced surveillance information from other airborne Mode S transponders. Further, there is a need for a system and method in which the first aircraft may request and receive enhanced surveillance information from a second aircraft Mode S transponder and provide integrity checking of the position of the aircraft. Further still, there is a need for a airborne system onboard a first aircraft which may interrogate a second aircraft's Mode S transponder at a variable rate, the rate dependent upon the determined dynamics of particular requested data.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.
What is provided is a traffic alert and collision and avoidance system (TCAS). The TCAS comprises a first interrogator associated with a first aircraft, the first transponder sending an interrogation request. The TCAS system also comprises a second transponder associated with a second aircraft, the second transponder responding to the interrogation request. The response comprises enhanced surveillance data that was asked for in the request.
What is also provided is a method of providing air traffic information from a first aircraft to a second aircraft. The method comprises receiving an interrogation request from a first aircraft. The request includes a request for enhanced surveillance data. The method also comprises responding by a second aircraft transponder a message comprising enhanced surveillance data that was asked for in the request.
Further, what is provided is a method of integrity checking the position of a second aircraft. The method comprises interrogating an aircraft transponder including a request for enhanced surveillance data including the position of the second aircraft. The method also comprises receiving a reply to the interrogation request by the first aircraft. Further, the method comprises calculating the position of the second aircraft based on the message response time and its bearing. Further still the method comprises comparing the calculated position with the received position. Yet further still, the method comprises determining the integrity of the received position.
Further still, what is provided is a method of interrogating the traffic alert and collision avoidance system transponder. The method comprises interrogating an aircraft transponder including a request for enhanced surveillance data. The method also comprises determining based on the enhanced surveillance data received, whether the rate of interrogation should be changed. Further, the method comprises changing the rate of interrogation if it is determined that the rate should be changed.
Alternative examples and other exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims.
The invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like elements, in which:
Before describing in detail the particular improved system and method, it should be observed that the invention includes, but is not limited to a novel structural combination of conventional data/signal processing elements and communication circuits, and not in the particular detailed configurations thereof. Accordingly, the structure, methods, functions, control and arrangement of conventional components and circuits have, for the most part, been illustrated in the drawings by readily understandable block representations and schematic diagrams, in order not to obscure the disclosure with the structural details which will be readily apparent to those skilled in the art, having the benefit of the description herein. Further, the invention is not limited to the particular embodiments depicted in the exemplary diagrams, but should be construed in accordance with the language in the claims.
Referring now to
Table 1 is an exemplary embodiment of the registers identified in a Mode S transponder and the register parameter contents that may be extracted from the transponder by an interrogator according to the ground-initiated COMM-B protocol (GICB). The information shown corresponds with enhanced surveillance data.
Referring to
As an example, an operational enhancement that may occur using enhanced surveillance data is an opportunity to avoid collisions and/or reduce the number of false alarms by utilizing information of the intended trajectory of a second aircraft. In past applications of TCAS, the inability to obtain the intended trajectory information has been a significant limitation to TCAS applications.
TCAS must provide decisions to avoid collisions with enough warning to allow the pilot of the aircraft to react. The period is typically 30 to 45 seconds. Without intent information, TCAS may only be used to project the trajectory of the intruder based on the past behavior of that aircraft. If the intruder does not intend to continue “doing what it's been doing”, this projection may be in error. This may result in unnecessary alarms or alarms that come without comfortable warning. In the case that enhanced surveillance information is available to the aircraft and the intended trajectory is known, alarms can be deferred without the potential for a collision. One such situation, for example, is called a “bump up.” This occurs when a first aircraft is level at a given altitude and an intruder aircraft is climbing to level off at an altitude 1,000 feet below the first aircraft. In today's TCAS systems, TCAS does not know that the intruder intends to level off and issues an alarm, advising the pilot of the first aircraft to climb to avoid the intruder. However, the alarm, in this case, is unnecessary and could be avoided if TCAS had known that the intruder was going to level off.
The implementation of the system utilizes existing hardware on aircraft. TCAS interrogates Mode S transponders for the purpose of obtaining range and altitude. Enhanced surveillance transponders have the capability to respond to an interrogation requesting the enhanced information discussed above. The Mode S transponder responds with the enhanced surveillance information requested by an interrogator by processing the content of the interrogation. TCAS needs only to change the data content of its existing interrogation to request the data information in this way. Only minor changes to the content of the TCAS interrogation and no changes to the enhanced surveillance Mode S transponder are necessary to make the new information available for use by TCAS. The airborne interrogator may use the ground-initiated comm-B protocol (GICB) to extract the information from other aircraft. The protocol has already been standardized internationally in the Mode S minimum operational performance standard (ICAO annex 10).
Referring now to
As a result of the use of an interrogation to obtain enhanced surveillance information from an intruder aircraft, a further benefit may be obtained. If the information requested is the other aircraft's position based on its on-board navigation system (such as a GPS system or other on-board navigation systems), the result may be verified by comparing it to its own aircraft's position. The difference in position should agree within some tolerance level with the range and bearing measured directly as a result of the interrogation. This check provides a level of integrity to the position information that cannot be achieved by a system where the position of the other aircraft is merely broadcast.
An exemplary process in which integrity of another aircraft's position is checked by a first aircraft is depicted by process 400 of
Additionally, a system where interrogation is used to obtain enhanced surveillance data from another aircraft provides benefits in that the interrogator may vary its rate of interrogation to satisfy the needs of a dynamic situation. For example, if the data is changing fast and the situation demands attention, the interrogator can increase the rate of interrogation, allowing the data to closely follow the situation of the other aircraft. If the situation is changing slowly and does not demand close attention, the interrogator can reduce its interrogation rate to minimize channel loading. A further benefit of the interrogation system may be that if the data is not received the first time, a retry can occur to insure the information is obtained.
Having the enhanced surveillance data available to an aircraft may allow an aircraft to maintain spacing with another aircraft very precisely in addition to all of the other benefits described above with regards to the communication of enhanced surveillance data.
While the detailed drawings, specific examples, and particular formulations given describe preferred and exemplary embodiments, they serve the purpose of illustration only. The inventions disclosed are not limited to the specific forms shown. For example, the methods may be performed in any of a variety of sequence of steps. The hardware and software configurations shown and described may differ depending on the chosen performance characteristics and physical characteristics of the computing and communication devices. For example, the type of computing and communications devices, communications bus, or processor used may differ. The systems and methods depicted and described are not limited to the precise details and conditions disclosed. Furthermore, other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the invention as expressed in the appended claims.
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