AEA Pilot's Guide 2021-2022 - 38

ADS (MORE THAN) B
Continued from page 37
spending money on new equipment,
the FAA offered ADS-B In. This is
a system that provides users of
ADS-B Out data, which prior to the
rule change was only available by
subscribing to a service provider.
Both 1090ES transponders and 978
UATs are able to receive ADS-B In,
which consists of traffic information
called TIS-B, and flight information
called FIS-B. Pilots using moving
map displays can see TIS-B data
on their screens, which gives them
greater awareness of nearby traffic.
FIS-B provides pilots with weather
information, notices to airmen, pilot
reports of turbulence or weather, and
information about temporary flight
restrictions or special use airspace.
You may be wondering about the
other ADS. What most people know
generally as ADS-B In is officially
Automatic Dependent SurveillanceRebroadcast,
or ADS-R. All the data
collected from the various sources
mentioned previously gets broadcast
out to the 1090ES transponders and the
978 UATs. The only operators left out of
this data are those without ADS-B, who
in one sense are flying blind.
Everything described so far works
between aircraft and ground stations
or in aircraft equipped with collision
avoidance systems, aircraft to aircraft.
For aircraft far from air traffic control
sites such as over the ocean, there
is another ADS called ADS-C. The
" C " in ADS-C stands for contract.
A contract is the link between the
ADS system in the aircraft through a
satellite communication system to the
air traffic controller.
Not only did we all need to learn
about the proper setting of the unique
identifier code for ADS-B equipment,
but we also need to learn some (new
to many of us) terms about navigation
quality. The link between the 1090ES
or the 978 UAT must be accurate
and reliable. To define accuracy and
reliability, there are four parameters
that must be monitored. Each quality
indicator uses a numbered scale
to represent reliability or accuracy.
Technicians will need to learn about:
*
Navigation integrity category,
which reports a number that
indicates the radius to which
position errors are contained.
For example, an NIC of 11
tells us errors are contained
to be within a 7.5 meter circle.
In contrast, an NIC of 0 tells
us the errors could be more
than 20 nautical miles.
*
There are two types of
NIC, one for position and
one for velocity. NICP for
position must be a level
10 for ADS-B and 11 for
precision approaches. NICV,
for velocity ranges from 0
for unknown speed to 4 for
speed accuracy of less than
0.3 meters per second.
*
System design assurance
indicates the probability an
undetected fault will cause false
information to be transmitted.
The numbers range from 3,
which is less than 1 per 10
million flight hours, down to 0,
which is unknown.
*
Like SDA, system integrity
level also calculates odds. In
this case, SIL is calculating
the chances of exceeding the
NIC radius and has the same
number scale as SDA.
Traffic Information Services-Broadcast is part of ADS-R for both 978 UAT and
1090 ES equipped aircraft.
A few years ago, an engineer
shared his pessimistic view that a
large portion of ADS systems were
not installed correctly. I'm not sure
the situation was as bad as he
thought, but I should note the FAA
began cracking down on improperly
configured ADS-B address codes
in 2018. This could be due, in part,
to the learning curve experienced
by everyone involved in the
implementation of the new system. q
- 38 -
AEA Pilot's Guide 2021-2022

Table of Contents for the Digital Edition of AEA Pilot's Guide 2021-2022
