Abstract: An airborne collision avoidance system includes a receiver stage constructed and arranged to detect (a) at a first radio frequency, first interrogation signals, and first collision resolution advisory (RA) signals transmitted from other nearby aircraft, and (b) at a second radio frequency, first acquisition signals including position information with respect to the nearby aircraft, and first reply signals from the nearby aircraft. A transmitter stage is constructed to produce (a) at the first radio frequency, second interrogation signals and second collision RA signals, and (b) at the second radio frequency, second acquisition signals including position information with respect to the given aircraft, and second reply signals from the given aircraft in response to the first interrogation signals. Tracking and collision avoidance information derived by a system processor from the detected first acquisition and first RA signals is shown on a cockpit display.

Abstract: An airborne collision avoidance system includes a receiver stage constructed and arranged to detect (a) at a first radio frequency, first interrogation signals, and first collision resolution advisory (RA) signals transmitted from other nearby aircraft, and (b) at a second radio frequency, first acquisition signals including position information with respect to the nearby aircraft, and first reply signals from the nearby aircraft. A transmitter stage is constructed to produce (a) at the first radio frequency, second interrogation signals and second collision RA signals, and (b) at the second radio frequency, second acquisition signals including position information with respect to the given aircraft, and second reply signals from the given aircraft in response to the first interrogation signals. Tracking and collision avoidance information derived by a system processor from the detected first acquisition and first RA signals is shown on a cockpit display.

Abstract: Collision avoidance systems are provided for groups of aircraft operating in close proximity, as during formation flights or cooperative missions. Fixed and rotary airfoil aircraft with separations of 30 feet to 5 miles, for example, participate in a local radio sub-net. An aircraft receiving CAS sub-net signals derives signal transit time values representing differences between send and receive times and which are used to derive data on inter-aircraft range and closing rate. With synchronized clocks, highly-accurate one-way ranging uses assigned time slots with predetermined sub-net time-of-day timing of transmissions. Round-trip ranging operates with less accurate time synchronization, and systems may operatively select between one-way and round-trip ranging. By exchange of range and closing rate data among aircraft, 3-D data for current three-dimensional location of aircraft enables evasive action determination.