AIM
11/3/22
2.
One of the data elements transmitted by
ADS
−
B is the aircraft’s Flight Identification
(FLT ID). The FLT ID is comprised of a maximum of
seven alphanumeric characters and must correspond
to the aircraft identification filed in the flight plan.
For airline and commuter aircraft, the FLT ID is
usually the company name and flight number (for
example, AAL3432), and is typically entered into the
avionics by the flight crew during preflight. For
general aviation (GA), if aircraft avionics allow
dynamic modification of the FLT ID, the pilot can
enter it prior to flight. However, some ADS
−
B
avionics require the FLT ID to be set to the aircraft
registration number (for example, N1234Q) by the
installer and cannot be changed by the pilot from the
cockpit. In both cases, the FLT ID must correspond to
the aircraft identification filed in its flight plan.
ATC automation systems use the transmitted ADS
−
B
FLT ID to uniquely identify each aircraft within a
given airspace, and to correlate it to its filed flight
plan for the purpose of providing surveillance and
separation services. If the FLT ID and the filed
aircraft identification are not identical, a Call Sign
Mis
−
Match (CSMM) is generated and ATC automa-
tion systems may not associate the aircraft with its
filed flight plan. In this case, air traffic services may
be delayed or unavailable until the CSMM is
corrected. Consequently, it is imperative that flight
crews and GA pilots ensure the FLT ID entry
correctly matches the aircraft identification filed in
their flight plan.
3.
Each ADS
−
B aircraft is assigned a unique
ICAO address (also known as a 24
−
bit address) that
is broadcast by the ADS
−
B transmitter. This ICAO
address is programmed at installation. Should
multiple aircraft broadcast the same ICAO address
while transiting the same ADS
−
B Only Service
Volume, the ADS
−
B network may be unable to track
the targets correctly. If radar reinforcement is
available, tracking will continue. If radar is
unavailable, the controller may lose target tracking
entirely on one or both targets. Consequently, it is
imperative that the ICAO address entry is correct.
4.
Aircraft that are equipped with ADS
−
B
avionics on the UAT datalink have a feature that
allows them to broadcast an anonymous 24
−
bit ICAO
address. In this mode, the UAT system creates a
randomized address that does not match the actual
ICAO address assigned to the aircraft. The UAT
anonymous 24
−
bit address feature may only be used
when the operator has not filed an IFR flight plan and
is not requesting ATC services. In the anonymity
mode, the aircraft’s beacon code must be set to 1200
and, depending on the manufacturer’s implementa-
tion, the aircraft FLT ID might not be transmitted.
Pilots should be aware that while in UAT anonymity
mode, they will not be eligible to receive ATC
separation and flight following services, and may not
benefit from enhanced ADS
−
B search and rescue
capabilities.
5.
ADS
−
B systems integrated with the
transponder will automatically set the applicable
emergency status when 7500, 7600, or 7700 are
entered into the transponder. ADS
−
B systems not
integrated with the transponder, or systems with
optional emergency codes, will require that the
appropriate emergency code is entered through a pilot
interface. ADS
−
B is intended for inflight and airport
surface use. Unless otherwise directed by ATC,
transponder/ADS
−
B systems should be turned “on”
and remain “on” whenever operating in the air or on
the airport surface movement area.
d. ATC Surveillance Services using ADS
−
B
−
Procedures and Recommended Phraseology
Radar procedures, with the exceptions found in this
paragraph, are identical to those procedures pre-
scribed for radar in AIM Chapter 4 and Chapter 5.
1.
Preflight:
If ATC services are anticipated when either a VFR or
IFR flight plan is filed, the aircraft identification (as
entered in the flight plan) must be entered as the
FLT ID in the ADS
−
B avionics.
2.
Inflight:
When requesting surveillance services while air-
borne, pilots must disable the anonymous feature, if
so equipped, prior to contacting ATC. Pilots must also
ensure that their transmitted ADS
−
B FLT ID matches
the aircraft identification as entered in their flight
plan.
3.
Aircraft with an Inoperative/Malfunctioning
ADS
−
B Transmitter:
(a)
ATC will inform the flight crew when the
aircraft’s ADS
−
B transmitter appears to be inopera-
tive or malfunctioning:
4
−
5
−
18
Surveillance Systems