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AIM

10/12/17

4−5−17

Surveillance Systems

2. An aircraft’s Flight Identification (FLT ID),

also known as registration number or airline flight

number, is transmitted by the ADS-B Out avionics.

The FLT ID is comprised of a maximum of seven

alphanumeric characters and also corresponds to the

aircraft identification annotated on the ATC flight

plan. The FLT ID for airline and commuter aircraft is

associated with the company name and flight number

(for example, AAL3342). The FLT ID is typically

entered by the flightcrew during preflight through

either a Flight Management System (FMS) interface

(Control Display Unit/CDU) or transponder control

panel. The FLT ID for General Aviation (GA) aircraft

is associated with the aircraft’s registration number.

The aircraft owner can preset the FLT ID to the

aircraft’s registration number (for example,

N235RA), since it is a fixed value, or the pilot can

enter it into the ADS-B Out system prior to flight.

ATC systems use transmitted FLT IDs to uniquely

identify each aircraft within a given airspace and

correlate them to a filed flight plan for the provision

of surveillance and separation services. If the FLT ID

is not entered correctly, ATC automation systems

may not associate surveillance tracks for the aircraft

to its filed flight plan. Therefore, Air Traffic services

may be delayed or unavailable until this is corrected.

Consequently, it is imperative that flightcrews and

GA pilots ensure the FLT ID entry correctly matches

the aircraft identification annotated in the filed ATC

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. The ICAO

address is programmable 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.

Aircraft that is equipped with ADS−B avionics on the

UAT datalink have a feature that allows it 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. After January 1, 2020, and in the airspace

identified in § 91.225, the UAT anonymous 24−bit

address feature may only be used when the operator

has not filed a flight plan and is not requesting ATC

services. In the anonymity mode, the aircraft’s

beacon code must set to 1200, and depending on the

manufacturer’s implementation, the aircraft’s call

sign might not be transmitted. Operators should be

aware that in UAT anonymous mode they will not be

eligible to receive ATC separation and flight

following services, and will likely not benefit from

enhanced ADS−B search and rescue capabilities.

4. 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 in−flight and

airport surface use. ADS−B systems should be

turned “on” −− and remain “on” −− whenever

operating in the air and moving on the airport

surface. Civil and military Mode A/C transpon-

ders and ADS−B systems should be adjusted to the

“on” or normal operating position as soon as

practical, unless the change to “standby” has been

accomplished previously at the request of ATC.

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 a request for ATC services is predicated on ADS−B

and such services are anticipated when either a VFR

or IFR flight plan is filed, the aircraft’s FLT ID as

entered in Item 7 of the ICAO flight plan (Block 2 of

FAA domestic flight plan) must be entered in the

ADS−B avionics.

2. Inflight:

When requesting ADS−B services while airborne,

pilots should ensure that their ADS−B equipment is

transmitting their aircraft’s registration number or

the approved FAA/ICAO company or organizational

designator, prior to contacting ATC. Aircraft

equipped with a “VFR” or anonymous feature, will

not broadcast the appropriate aircraft identification

information and should disable the anonymous

feature before contacting ATC.