ADS -B
What you need to know
BY 2020, AIRCRAFT OWNERS flying in airspace requiring a Mode-C
transponder will need to equip their aircraft with ADS-B Out.
Having just bought a plane recently—more on that in a future column—I started checking out alternate approaches for complying
with the mandate.
ADS-B stands for automatic dependent surveillance-broadcast. It
is automatic because, unlike a transponder, it broadcasts continuously, not just when interrogated by radar or a traffic collision
avoidance system (TCAS). It is dependent, since it relies on GPS
information. It provides the same surveillance function as radar, but
GPS Satellite
GPS
GPS
GPS
109OES
Traffic
(jets)
109OES
Traffic
978 UAT
Tra ffi c / W eather
Traffic / Weather
M ode-C
does so by broadcasting its position.
There are two ADS-B capabilities. ADS-B
Out, the only one mandated by the new rule,
refers to an aircraft broadcasting its position
and other information. Unfortunately,
equipping aircraft with ADS-B Out will cost
thousands but not yield any new benefits.
Owners can elect to also equip with ADS-B
In, which allows an aircraft to receive traffic
information from other ADS-B-equipped
GPS
Traffic
978 UAT
No ADS-B
ADS-B Ground Station
(relay between 109OES and 978 UAT)
ATC Radar
ATC Controller
ADS-B Out equipped aircraft determine their position using GPS (red arrows) and broadcast position data (yellow lines) to similarly equipped ADS-B aircraft and to
ADS-B ground stations. ADS-B ground stations uplink traffic threats (yellow lines) to aircraft equipped with both ADS-B In and Out and traffic and weather data to
aircraft that use 978 UAT for ADS-B.
