chapter  21
5 Automatic dependent surveillance-broadcast
Pages 2

The development of Mode S has led onto two

related systems: traffic alert and collision

avoidance systems (TCAS) and automatic

dependent surveillance-broadcast (ADS-B). Both

systems can exchange data directly between

aircraft. TCAS is a surveillance system that

provides warnings directly to the crew when other

navigation systems (including ATC) have failed

to maintain safe separation of aircraft. ADS-B is

an emerging technology for air traffic

management (ATM) that is intended to replace

conventional secondary surveillance radar. TCAS

is addressed in the Chapter 22; ADS-B is

described below.