Description And Operation; General; Purpose Of Equipment - Honeywell CAS-100 Maintenance Manual

Collision avoidance system

Table of Contents

1. General

This section contains data for the function and the operation of the Honeywell CAS-100 Collision

Avoidance System, hereafter referred as the CAS-100, TCAS, or by its full nomenclature. The

CAS-100 components are shown in Figure 1.

A. Purpose of Equipment

CAS-100 is an airborne traffic alert and collision avoidance advisory system that operates

without the support from Air Traffic Control (ATC) ground stations. The system senses nearby

intruder aircraft equipped with transponders that reply to the Air Traffic Control Radar Beacon

System (ATCRBS), Mode C, or Mode S interrogations. The danger potential of intruder

aircraft to own aircraft is continuously monitored and analyzed by the Traffic Alert and Collision

Avoidance System (TCAS). The nearby transponder-equipped aircraft are shown on a traffic

advisory display. The TCAS system gives traffic advisory alerts and vertical maneuvering

resolution advisories during danger conditions to prevent airborne collisions.

NOTE: The vertical maneuvering resolution advisories given by TCAS are calculated and

given against the intruder aircraft that report altitude data in their transponder

messages. Traffic advisories are given for nonaltitude reporting (NAR) aircraft only.

A traffic advisory display warns the flight crew to the position of nearby aircraft threats and

possible threats. This warning improves the ability of the flight crew to see the intruder aircraft

before answering the resolution advisory. The resolution advisories are shown around the

edge of a Traffic Advisory/Vertical Speed Indicator.

A Resolution Advisory/Vertical Speed Indicator displays only resolution advisories around its

edge. The indicator can be used if the traffic advisories are shown on another display unit.

Detection and tracking of intruder aircraft is performed by transmission and receptions from a

top-mounted TCAS directional antenna. This function can also be performed with a

bottom-mounted TCAS omnidirectional or bottom-mounted TCAS directional antenna.

TCAS finds the aircraft that uses a Mode S transponder by listening for the Mode S squitter

transmissions. Mode S transponders tell their presence by transmitting a squitter message

one time for each second. TCAS also finds the aircraft equipped with transponders that do

not reply to Mode S interrogations, but do reply to Mode C interrogations. TCAS must search

for Mode C equipped intruder aircraft, because Mode C transponders do not transmit squitter

messages. When the presence of a Mode S or Mode C intruder is made sure, TCAS starts to

track the intruder. TCAS can track a total of 30 Mode S and Mode C intruders.

Use or disclosure of information on this page is subject to the restrictions in the proprietary notice of this document.

MAINTENANCE MANUAL

CAS-100 COLLISION AVOIDANCE SYSTEM