Data processing: vehicles – navigation – and relative location – Relative location – Collision avoidance
Reexamination Certificate
2002-02-11
2003-04-08
Black, Thomas G. (Department: 3663)
Data processing: vehicles, navigation, and relative location
Relative location
Collision avoidance
C701S007000, C701S302000, C301S064600, C342S029000, C342S455000
Reexamination Certificate
active
06546338
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the management of the risks of in-flight collision between aircraft.
2. Discussion of the Background
Risks of collision between aircraft have been taken into consideration very early in the history of air transport owing to the fact that concentrations of aircraft occur naturally in the vicinity of airports. To avert such collisions, according to the first solution devised, aircraft were required to follow strictly demarcated air corridors in which their progress was monitored from the ground by air traffic controllers belonging to air traffic control (ATC) organizations. Air traffic controllers are responsible for a territory in which they organize the circulation of aircraft in authorized air corridors. For the regulation of air traffic, the controllers on the ground have information available on the movement of aircraft above their territory. This information comes from the flight plans of aircraft communicated in advance, real-time measurements by their surveillance radars dispersed over their territory and sound and data exchanges with the crew and navigation equipment of the aircraft. The risks of collision between aircraft are detected on the ground by the air traffic controllers using data in their possession and also in flight by the crews of aircraft who keep a visual watch. However, except in cases of extreme emergency, the initiative for avoidance maneuvers comes under the sole responsibility of air traffic controllers.
Traffic density is constantly increasing in the vicinity of certain airports, and the risks of collision are becoming increasingly a matter of concern. This is why the United States Federal Aviation Administration (FAA) launched a program in the 1960s to create equipment for the automatic detection of in-flight collision risks designed initially for passenger aircraft. This program led to the devising of several successive generations of a system known as the Traffic Collision Avoidance System (TCAS) specializing in the detection of very short-term in-flight collision risks (i.e. risks of collision within less than one minute)
A set of TCAS instruments establishes co-operation between aircraft travelling in the same neighborhood by means of another piece of onboard equipment, the transponder, whose use in the meantime, has become widespread on board aircraft for the transmission, to the ground, of information on the aircraft so as to improve their localization by the air traffic controllers.
A first generation of TCAS instruments that was available towards the 1980s, the TCAS 1 system, worked together with Mode-C transponders originally designed to respond to an interrogation by a special radar placed on the ground, known as an “secondary radar” to give a piece of information on the identity and altitude of the aircraft that carried it and also enable a measurement of the distance between said aircraft and the secondary radar and a measurement of the speed of said aircraft, these measurements being based on the propagation time of the radio-electrical signals and the variation of this propagation time from one interrogation to another. When placed on board an aircraft, a TCAS 1 instrument periodically sends interrogation signals to the mode-C transponders of the aircraft moving in the vicinity. It picks up their responses, processes these responses, and deduces their positions in terms of distance and heading, the speeds and the altitude levels of the different aircraft moving in the vicinity of the aircraft into which the instrument is integrated. It places this information at the disposal of the crew by means of a special screen and generates alarms known as Traffic Advisories (TA) when it is detected that aircraft could come close within far too small a distance. The crew of an aircraft equipped with the TCAS 1 is informed of the risk of collision but receives no advice on the nature of the evasive maneuver to be performed. This evasive maneuver cannot be done without reference to the air traffic controller, and only in the vertical plane and within a limit of 300 feet.
A second generation of TCAS instruments which is more efficient, namely the TCAS II generation, is currently available. The TCAS II co-operates with mode-C transponders or mode-S transponders and, in addition to the TA alarms, gives Resolution Advisories (“RA”) consisting of instructions to climb or descend at 2,500 feet per minute in order to avoid another aircraft, often with an indication of the descent or climb gradient to be adopted to eliminate the risk of collision. Furthermore, when two aircraft involved in a collision risk are both equipped with TCAS II instruments, their TCAS II instruments work together to prevent any conflict and not give the two aircraft simultaneous and contradictory advice on maneuvers that would not eliminate the risks of collision.
A third generation of TCAS instruments, namely the TCAS III generation, is not being envisaged. This is a generation with higher precision in the assessment of heading positions, paths and speeds of other aircraft obtained by means of a specific directional antenna and improved mode-S transponders which, in their response signals, give the GPS (global positioning system) position and the speed vector of the carrier of the transponder. These TCAS III instruments would furnish advice on RA maneuvers including lateral evasion instructions in the horizontal plane, made possible by the improved precision that is being anticipated.
The congestion of air traffic routes over certain territories, for example in Europe, and the improvement of the precision of the navigation means available to the aircraft following the deployment of the GPS satellite navigation systems such as the American GNSS (Global Navigation Satellite System) or the Russian GLONASS (GLObal Navigation Satellite System) are today leading air-traffic control authorities to consider abandoning the requirement, on certain routes, for aircraft to follow preset air corridors and to consider the granting to aircraft, of a certain degree of liberty in the choice of their route outside airports approach zones and outside certain flight levels. This is the navigation technique known as “Free Flight.” In addition to a reduced concentration of aircraft in the sky outside airport approach zones and, hence, a reduction in the risks of collision between aircraft, this technique of Free Flight navigation is likely to enable the following of the great circles track between points of the globe that are not directly linked by a predefined air corridor and for which the following of predefined air corridors necessitates more or less great detours.
The Free Flight navigation technique requires not only that aircraft should be equipped with precise navigation means but also that they should be capable, on their own, of resolving conflicts of traffic with other aircraft giving rise to medium-term collision risks, namely risks of collision within about five to ten minutes, whereas this conflict resolution is the task of air traffic controllers during traffic within predefined air corridors. It can be envisaged that the function of medium-term air collision protection will be fulfilled up board aircraft using the Free Flight navigation technique by means of the latest generations of TCAS instruments by augmenting their sensitivity so as to obtain sufficiently early anti-collision warnings, especially as the main problem encountered with TCAS instruments, namely that of false alarms, does not arise beyond a certain distance from airports.
Although a TCAS instrument with increased sensitivity is able to warn an aircraft carrying using the Free Flight technique of a risk of medium-term collision, namely a risk of collision within five to ten minutes, and warn this instrument that it is up to itself to carry out an avoidance maneuver, it cannot propose the most appropriate modification of the aircraft route and, at most, gives a suggestion of an avoidance maneuver by the top, the bottom, right or left
Sainthuile Gerard
Solans Christophe
Black Thomas G.
Mancho Ronnie
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Thales
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