THE CONFLICT DETECTION LOGIC OF THE COLLISION-AVOIDANCE SYSTEM ACAS-II

The development of systems to decrease the risk of collision within the civil aviation started in the early sixties. For the first time ever, the FAA's system proposal TCAS II obtained maturity for series production and after several serious ''near-miss encounters'' within the U.S. airspace, a public law mandated the gradual installation of TCAS II avionics by December 30, 1990. Therefore, an increasing number of TCAS II equipped aircraft will be found outside the U.S. National Airspace System (NAS). Whenever TCAS II declares an nearby aircraft to be a threat, it can issue an Resolution Advisory (RA) and therefore interfere with normal Air Traffic Control (ATC). Starting from this problem, the main issues of a conflict detection logic for an airborne collision avoidance system will be discussed in this paper.