Page 159 - Planning and Design of Airports

Air Traf fic Management 127

Global Navigation
Satellite
System

ADS-B
Collision
ADS-B Avoidance
ADS-B

Surveillance
Radar Air Traffic ADS
Modes Management Receiver

FIGURE 3-20 Rendering of ADS-B system (Atcmonitor.com).

(ADS-B) systems broadcast information to all equipped aircraft and air
traffic management facilities, identifying their locations to other traffic
in the system, providing the added ability to safety avoid collisions
even in poor visibility conditions. Originally tested in Alaska between
2000 and 2003, ADS-B is quickly becoming a standard component of air
traffic navigation systems in the United States. A rendering of the
ADS-B system is Fig. 3-20.

The Modernization of Air Traffic Management
Despite the proliferation of GPS-based navigation since the beginning of
the twenty-first century, the principal aids for the control of air traffic by
air traffic management personnel are still voice communication and
radar. Air traffic controllers monitor the spacing between aircraft on the
radarscope and instruct pilots by means of voice communication.
Radar returns appear on the radarscope as small blips. These are
reflections from the aircraft body. Primary radar requires the installation
of rotating antennas on the ground and the range of the primary radar is
a function of its frequency. Secondary radar consists of a radar receiver
and transmitter on the ground that transmits a coded signal to an aircraft
if that aircraft has a transponder. A transponder is an airborne receiver
and transmitter which receives the signal from the ground and responds
by returning a coded reply to the interrogator on the ground. The coded
reply normally contains information on aircraft identity and altitude.
Information from primary and secondary radar returns are pro-
vided to air traffic controllers via an alphanumeric display on their
radar “scopes,” as illustrated in Fig. 3-21. The first line shows the