Effects of revised ACAS II algorithm version 7 based on RA report

Abstract

ACAS, Airborne Collision Avoidance System, is known as a system to reduce the risk of midair collisions between aircraft. The ICAO SARPs, Standards and Recommended Practices, for ACAS II were issued on 9 November 1995 with waiting for its implementation. TCAS, Traffic Alert and Collision Avoidance System, units had already been produced and installed in many aircraft as the ACAS implementation with interim SARPs for operational evaluations before its approval as first SARPs with some revision.

In Japan, the ACAS units and their operational procedure have been evaluated since 1990. The operational evaluation for all ACAS equipped aircraft in Japanese airspace has been carried out based on the ICAO guideline since 1992. The collision avoidance logic for TCAS II has been upgraded from 6.04A to 7 during the evaluation activities. The upgrade began since 2000. All TCAS II units for Japanese registered aircraft have upgraded to version 7 by January 2003.

Since it is important to observe the operational situation of ACAS II, flight crews are encouraged to report RAs as ever. The RA report is submitted by flight crews on their experienced RA after the flight. This report includes the information on RA and conditions of encounter with it. About 3000 RA reports have been collected and analyzed by ENRI for this paper.

This paper reports on the statistics on ACAS II aircraft and the monitoring results based on the RA reports. The results of analysis on the relationship among element on the RA reports are summarized in this paper.