Horizontal miss distance filter system for suppressing false resolution alerts

A horizontal miss distance filter system is provided for inhibiting resolution alert messages from an air traffic alert and collision avoidance system to a pilot's display. The horizontal miss distance filter employs a parabolic range tracker to derive a range acceleration estimate utilized to discriminate intruder aircraft having non-zero horizontal miss distances. The horizontal miss distance calculated from the range data provided by the parabolic range tracker is compared with a bearing based horizontal miss distance provided by a bearing based tracker. The smaller of the two calculated horizontal miss distances defines a projected horizontal miss distance which is compared with a threshold value. Any resolution alert for intruder aircraft whose projected horizontal miss distance is greater than the threshold will be inhibited unless it is determined that the encounter involves a maneuver of one of the aircraft. As many as five maneuver detectors may be employed to assess whether the encounter involves a maneuver. If any of the maneuver detectors establish the occurrence of a maneuver, then a resolution alert provided from the TCAS system will not be inhibited.

Patent #: 5566074 Issue Date: October 15, 1996