Abstract: The present invention is concerned with a system in which when the altitude of a subject aircraft becomes lower than a predetermined altitude, a warning limit value is reduced or made equal to zero on the minimum altitude side whereby a useless alarm based on response signals delivered from other aircraft staying in or taxiing in the airport are suppressed.

Abstract: A device of suppressing incorrect alarms to be issued from an airplane collision avoidance system installed in a first airplane, wherein when it is found that a product obtained by multiplying a relative distance of the first airplane relative to a second airplane by a sine of a relative horizontal angle is constant or when it is found that results derived from a comparison between a relative speed of the first airplane relative to the second airplane and a speed vector in the direction toward the second airplane obtained from a relative horizontal angle of the first airplane relative to the second airplane and a speed of the first airplane in the direction of extension of a nose is substantially zero, it is determined that the second airplane is held in an immovable state, i.e., it stays in a waiting state.

Abstract: The present invention is concerned with a system in which when the altitude of a subject aircraft becomes lower than a predetermined altitude, a warning limit value is reduced or made equal to zero on the minimum altitude side whereby a useless alarm based on response signals delivered from other aircraft staying in or taxiing in the airport are suppressed.

Abstract: The present invention relates to a indicating system for warning airspace or threatening aircraft in aircraft collision avoidance system which provides simply and inexpensively information required for safe cruising of aircraft with respect to range of warning airspace of aircraft, positions of other aircraft involving threatening of collision, and flight courses of proximate said other aircraft involving threatening of collision.

Abstract: A collision avoidance system using on-board B-CAS equipment having an object to minimize interference with the ground SSR stations and to effect precise tracking or distance-altitude measurement when necessary. Normally passive surveillance is made to detect the presence of other aircraft in the B-CAS range. Active surveillance is added when required. In the active surveillance mode, initiated on locating an intruder aircraft, the power and interrogation signal are varied when the intruder aircraft becomes a threat aircraft to minimize interference with the ground SSR stations and aircraft outside the threat zone while maintaining accuracy of detection and tracking of the threat aircraft at a high level.

Abstract: A collision avoidance system for aircraft using an on-board beacon interrogator. If altitude information is not included in a response signal from a transponder of an other aircraft or the response signal is garbled because a plurality of other aircraft are responding to the same interrogation signal, the system automatically switches to a beacon based proximity warning system and indicates the distance or other indication to the detected aircraft.

Abstract: A collision avoidance system for aircraft in which one aircraft is equipped ith an interrogation station having a secondary surveillance radar. Coarse distance measurement is effected either by passive or active distance measurement or by both of them. If the detected distance lies within a certain limit, the output power and/or period of the interrogation signal of the secondary surveillance radar of the subject aircraft is altered so as to effect fine distance measurement. This system can be applied without increasing interference against the existing secondary surveillance radar system by keeping the output power and period of interrogation signal in a minimum required extent. By the same reason the system can keep the interference at a small extent between proximate aircraft, each mounting this collision avoidance system.

Abstract: A collision avoidance system for aircraft in which one aircraft is equipped with an interrogation station having a secondary surveillance radar. .[.Coarse.]. .Iadd.A .Iaddend.distance measurement is effected either by passive or active distance measurement or by both of them. If the detected distance lies within a certain limit, the output power and/or period of the interrogation signal of the secondary surveillance radar of the subject aircraft is altered .[.so as to effect fine distance measurement.].. This system can be applied without increasing interference against the existing secondary surveillance radar system by keeping the output power and period of interrogation signal in a minimum required extent. By the same reason the system can keep the interference at a small extent between proximate aircraft, each mounting this collision avoidance system.