AIM
11/3/22
with the transponder in the altitude reporting mode
(consult the aircraft’s flight manual to determine the
specific transponder position to enable altitude
reporting) and ADS
−
B Out transmissions enabled at
all airports, any time the aircraft is positioned on any
portion of the airport movement area. This includes
all defined taxiways and runways. Pilots must pay
particular attention to ATIS and airport diagram
notations, General Notes (included on airport charts),
and comply with directions pertaining to transponder
and ADS-B usage. Generally, these directions are:
(a) Departures.
Select the transponder mode
which allows altitude reporting and enable ADS-B
during pushback or taxi-out from parking spot. Select
TA or TA/RA (if equipped with TCAS) when taking
the active runway.
(b) Arrivals.
If TCAS equipped, deselect TA
or TA/RA upon leaving the active runway, but
continue transponder and ADS
−
B transmissions in
the altitude reporting mode. Select STBY or OFF for
transponder and ADS
−
B upon arriving at the
aircraft’s parking spot or gate.
4. Transponder and ADS-B Operations
While Airborne.
(a)
Unless otherwise requested by ATC,
aircraft equipped with an ATC transponder main-
tained in accordance with 14 CFR Section 91.413
MUST operate with this equipment on the
appropriate Mode 3/A code, or other code as assigned
by ATC, and with altitude reporting enabled
whenever in controlled airspace. If practicable,
aircraft SHOULD operate with the transponder
enabled in uncontrolled airspace.
(b)
Aircraft equipped with ADS
−
B Out
MUST operate with this equipment in the transmit
mode at all times, unless otherwise requested by
ATC.
(c)
When participating in a VFR formation
flight that is not receiving ATC services, only the lead
aircraft should operate their transponder and ADS
−
B
Out. All other aircraft should disable transponder and
ADS
−
B transmissions once established within the
formation.
NOTE
−
If the formation flight is receiving ATC services, pilots can
expect ATC to direct all non
−
lead aircraft to STOP
SQUAWK, and should not do so until instructed.
5.
A pilot on an IFR flight who elects to cancel
the IFR flight plan prior to reaching their destination,
should adjust the transponder/ADS
−
B according to
VFR operations.
6.
If entering a U.S. OFFSHORE AIRSPACE
AREA from outside the U.S., the pilot should advise
on first radio contact with a U.S. radar ATC facility
that such equipment is available by adding
“transponder” or “ADS
−
B” (if equipped) to the
aircraft identification.
7.
It should be noted by all users of ATC
transponders and ADS
−
B Out systems that the
surveillance coverage they can expect is limited to
“line of sight” with ground radar and ADS
−
B radio
sites. Low altitude or aircraft antenna shielding by the
aircraft itself may result in reduced range or loss of
aircraft contact. Though ADS
−
B often provides
superior reception at low altitudes, poor coverage
from any surveillance system can be improved by
climbing to a higher altitude.
NOTE
−
Pilots should refer to AIM, Paragraph 4
−
5
−
7, Automatic
Dependent Surveillance
−
Broadcast (ADS
−
B) Services,
for a complete description of operating limitations and
procedures.
b. Transponder/ADS
−
B Code Designation
1.
For ATC to utilize one of the 4096 discrete
codes, a four
−
digit code designation will be used; for
example, code 2102 will be expressed as “TWO ONE
ZERO TWO.”
NOTE
−
Circumstances may occasionally require ATC to assign a
non
−
discrete code; i.e., a code ending in “00.”
REFERENCE
−
FAA Order JO 7110.66, National Beacon Code Allocation Plan.
c. Automatic Altitude Reporting
1.
Most transponders (Modes C and S) and all
ADS
−
B Out systems are capable of automatic
altitude reporting. This system converts aircraft
altitude in 100
−
foot increments to coded digital
information that is transmitted to the appropriate
surveillance facility as well as to ADS
−
B In and
TCAS systems.
2.
Adjust the transponder/ADS
−
B to reply on
the Mode 3/A code specified by ATC and with
altitude reporting enabled, unless otherwise directed
by ATC or unless the altitude reporting equipment has
not been tested and calibrated as required by 14 CFR
Section 91.217. If deactivation is required by ATC,
Services Available to Pilots
4
−
1
−
16