AIM

8/15/19

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Radio Communications Phraseology

2.

At times, a controller/specialist may be

working a sector with multiple frequency assign-
ments. In order to eliminate unnecessary verbiage
and to free the controller/specialist for higher priority
transmissions, the controller/specialist may request
the pilot “(Identification), change to my frequency
123.4.” This phrase should alert the pilot that the
controller/specialist is only changing frequencies, not
controller/specialist, and that initial callup phraseolo-
gy may be abbreviated.

EXAMPLE

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“United Two Twenty

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Two on one two three point four” or

“one two three point four, United Two Twenty

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Two.”

e. Compliance with Frequency Changes.

When instructed by ATC to change frequencies,
select the new frequency as soon as possible unless
instructed to make the change at a specific time, fix,
or altitude. A delay in making the change could result
in an untimely receipt of important information. If
you are instructed to make the frequency change at a
specific time, fix, or altitude, monitor the frequency
you are on until reaching the specified time, fix, or
altitudes unless instructed otherwise by ATC.

REFERENCE

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AIM, Paragraph 5

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1 , ARTCC Communications

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4. Aircraft Call Signs

a. Precautions in the Use of Call Signs.

1.

Improper use of call signs can result in pilots

executing a clearance intended for another aircraft.
Call signs should 

never be abbreviated on an initial

contact or at any time when other aircraft call signs
have similar numbers/sounds or identical letters/
number;

 e.g., Cessna 6132F, Cessna 1622F,

Baron 123F, Cherokee 7732F, etc.

EXAMPLE

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Assume that a controller issues an approach clearance to
an aircraft at the bottom of a holding stack and an aircraft
with a similar call sign (at the top of the stack)
acknowledges the clearance with the last two or three
numbers of the aircraft’s call sign. If the aircraft at the
bottom of the stack did not hear the clearance and
intervene, flight safety would be affected, and there would
be no reason for either the controller or pilot to suspect that
anything is wrong. This kind of “human factors” error can
strike swiftly and is extremely difficult to rectify.

2.

Pilots, therefore, must be certain that aircraft

identification is complete and clearly identified

before taking action on an ATC clearance. ATC
specialists will not abbreviate call signs of air carrier
or other civil aircraft having authorized call signs.
ATC specialists may initiate abbreviated call signs of
other aircraft by using the 

prefix and the last three

digits/letters

 of the aircraft identification after

communications are established. The pilot may use
the abbreviated call sign in subsequent contacts with
the ATC specialist. When aware of similar/identical
call signs, ATC specialists will take action to
minimize errors by emphasizing certain numbers/let-
ters, by repeating the entire call sign, by repeating the
prefix, or by asking pilots to use a different call sign
temporarily. Pilots should use the phrase “VERIFY
CLEARANCE FOR (your complete call sign)” if
doubt exists concerning proper identity.

3.

Civil aircraft pilots should state the aircraft

type, model or manufacturer’s name, followed by the
digits/letters of the registration number. When the
aircraft manufacturer’s name or model is stated, the
prefix “N” is dropped; e.g., Aztec Two Four Six Four
Alpha.

EXAMPLE

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1.

Bonanza Six Five Five Golf.

2.

Breezy Six One Three Romeo Experimental (omit

“Experimental” after initial contact).

4.

Air Taxi or other commercial operators 

not

having FAA authorized call signs should prefix their
normal identification with the phonetic word
“Tango.”

EXAMPLE

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Tango Aztec Two Four Six Four Alpha.

5.

Air carriers and commuter air carriers having

FAA authorized call signs should identify themselves
by stating the complete call sign (using group form
for the numbers) and the word “super” or “heavy” if
appropriate.

EXAMPLE

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1.

United Twenty

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Five Heavy.

2.

Midwest Commuter Seven Eleven.

6.

Military aircraft use a variety of systems

including serial numbers, word call signs, and
combinations of letters/numbers. Examples include
Army Copter 48931; Air Force 61782; REACH
31792; Pat 157; Air Evac 17652; Navy Golf Alfa
Kilo 21; Marine 4 Charlie 36, etc.