Active Beacon Collision Avoidance Logic Evaluation. volume I. Mode C Equipped (ATCRBS) Threat Phase.

Abstract : The purpose of this project was to evaluate and refine the April 1979 version of the Beacon Collision Avoidance System (BCAS) logic prior to Active BCAS prototype flight testing. The April 1979 version of the BCAS logic added changes to support multiple aircraft resolution, conflict indicator register interfacing, and new surveillance function interfacing. The first phase of the evaluation was conducted from April 1979 to September 1979. This phase evaluated logic performance against mode C equipped (ATCRBS) threats. The evaluation identified modifications which could improve logic performance. Interim improvements have been made to the vertical tracker. The modifications improve command sense choice logic performance for ATCRBS threats (by using greater dependence on current relative vertical position), resolution performance (by modifying ATCRBS-threat sense choice logic), and vertical speed limit (VSL) alarm performance. Generally, good protection was provided by the BCAS logic against abrupt horizontal maneuvers by ATCRBS threats. VSL alarms generated sufficient vertical separation when the BCAS aircraft's vertical rate was above 1,000 feet per minute. Below 1,000 feet per minute, tracker noise often resulted in a transition from VSL alarms to positive or negative BCAS maneuver advisories. Before proceeding to subsequent phases of the evaluation, large portions of the logic modifications that were identified in this report became permanent algorithm changes. (Author)