Honeywell TCASII/ACAS II Collision Avoidance System User’s Manual

This manual applies to systems which are compliant to RTCA DO185A MOPS Change 7.0 and RTCA “DO185” MOPS Change 6.04a. These systems are referred to as TCAS II (Traffic Alert and Collision Avoidance System) in the United States and ACAS II (Airborne Collision Avoidance System) internationally.

The terminology is used interchangeably and, for the purpose of discussion, TCAS II will be the terminology used in this manual. TCAS II is a system used for detecting and tracking aircraft in the vicinity of your own aircraft.By interrogating their transponders it analyzes the replies to determine range,bearing,and if reporting altitude,the relative altitude of the intruder.

Should the TCAS II processor determine that a possible collision hazard exists,it issues visual and audio advisories to the crew for appropriate vertical avoidance maneuvers. TCAS is unable to detect any intruding aircraft without an operating transponder. There are two types of cockpit displays for TCAS II, the Resolution Advisory (RA) display and the Traffic Advisory (TA) display.The RA display is incorporated into the vertical speed indicator (VSI).By illuminating red and green areas around the dial it displays the required rate,or limitation of climb or descent,to avoid a possible collision.

The TA display shows the intruding aircraft’s relative position and altitude with a trend arrow to indicate if it is climbing or descending at greater than 500 feet per minute.This TA display may be provided on the weather radar indicator, on a dedicated TCAS display or a TA/VSI display. The TA display identifies the relative threat of each intruder by using various symbols and colors.