How to make a radio call: structure, call signs and standard words

Every radio call has the same shape

Whether you are asking for taxi, calling the tower inbound or checking in with a new controller, a radio call follows one skeleton: who you are calling, who you are, and what you want. Get that order right and the rest is filling in the blanks with the phraseology for each phase of flight.

In the United States the reference is the FAA Aeronautical Information Manual (AIM), chapter 4, section 2. Outside the US the rules come from ICAO, which Europe applies through SERA section 14 and the UK explains in CAP 413, the CAA radiotelephony manual. The structure is the same everywhere; this article points out where the US and ICAO wording differ.

Before you press the button

AIM 4-2-2 and CAP 413 (paragraph 2.8) give nearly the same advice:

• Listen before you transmit. If someone else is talking, keying your mic just blocks both of you. After a frequency change, pause and listen first
• Think before you key. Know what you are going to say; write down anything long
• Speak in a normal, conversational tone, with the mic close to your lips and at a steady distance
• CAP 413 adds: keep an even pace of no more than 100 words per minute, pause slightly before and after numbers, and avoid "er" and chatty courtesies
• After you release the button, give the controller a few seconds before calling again

The initial call: who and who

AIM 4-2-3 defines the format for the initial contact, meaning the first call to a facility or to a new controller:

1. Name of the facility you are calling
2. Your full aircraft identification
3. Your position, when you are on the airport surface
4. The type of message to follow, or your request if it is short
5. "Over", only if required

ICAO says the same in a stricter way. SERA.14055 requires the full call signs of both stations when establishing contact, the station called first and the station calling second. The ground station answers with your call sign, then its own, which is the invitation to go ahead. CAP 413 (2.25) shows it as "pass your message". If you are sure the station will hear you, you can include the message in the first call without waiting for that reply.

The FAA encourages this too: AIM 4-2-3 says that when reception is reasonably assured, putting your request, position or altitude and the ATIS code in the first call reduces frequency congestion, as long as you don't overload the controller.

These are AIM examples of good initial calls:

And this is the ICAO style exchange from CAP 413, where the pilot calls, waits, and then gives the message:

What goes in the first call

Under ICAO rules as written in SERA.14065, the minimum content depends on who you are calling:

Heavy aircraft add HEAVY (or SUPER), and you report your level rounded to the nearest 100 ft of what your altimeter shows. In the US, AIM 4-2-3 asks you to acknowledge every frequency change before switching, so the controller knows you got it.

When ATC moves you to another frequency on the same sector ("change to my frequency 134.5"), AIM 4-2-3 says the check-in can be abbreviated, for example "United Two Twenty-Two on one three four point five".

Call signs: full and abbreviated

This is one of the clearer FAA vs ICAO differences.

FAA (AIM 4-2-4). Civil pilots say the aircraft type, model or manufacturer followed by the registration digits and letters. When you use the name, you drop the N: "Bonanza Six Five Five Golf". Once communication is established, ATC may abbreviate using the prefix and the last three characters, and from then on you can use that abbreviation too. Never abbreviate on initial contact or when similar call signs are on frequency.

ICAO / SERA.14050. There are three types of full call sign: (a) the registration, (b) the operator's telephony designator plus the last four characters of the registration, and (c) the telephony designator plus the flight number. Type (a) shortens to the first character and at least the last two; type (c) is never abbreviated. You may only use the short form after the ground station has used it first.

Both systems agree on the important part: your call sign goes with every readback of a clearance, and if you have any doubt that a clearance is yours, ask. AIM 4-2-4 gives the phrase "VERIFY CLEARANCE FOR (your complete call sign)". More on that in ATC clearance readbacks.

Words with fixed meanings

ICAO standard words have one meaning each. CAP 413 lists them in chapter 2 and SERA.14045 has the same list. The ones a pilot uses most:

Two US notes. AIM 4-2-3 lists "Affirmative" among the acknowledgement words, while ICAO uses AFFIRM. And CAP 413 marks OVER and OUT as not normally used on VHF; the AIM likewise says "over" only "if required".

Tip: ROGER only means you heard the transmission. It is not a readback and it does not mean you will comply. Clearances and instructions get read back.

Fixing mistakes and asking for repeats

SERA.14075 sets the ICAO method:

• Made an error? Say CORRECTION, repeat the last correct group, then the correct version
• If it is clearer to start over: CORRECTION, I SAY AGAIN and the whole message
• Missed something? SAY AGAIN, or for part of it SAY AGAIN ALL BEFORE..., SAY AGAIN ALL AFTER... or SAY AGAIN (word) TO (word)
• If your readback was wrong, the controller replies NEGATIVE, I SAY AGAIN and the correct items

Radio check and the readability scale

The ICAO radio check (SERA.14070, CAP 413 2.93 to 2.94) is: station called, your call sign, RADIO CHECK, and the frequency. The reply gives your call sign, theirs, and a readability number:

Ending the contact

AIM 4-2-3 says to acknowledge with your call sign, at the start or the end, plus Wilco, Roger, Affirmative, Negative or another fitting word, for example "PIPER TWO ONE FOUR LIMA, ROGER". If you are receiving a service such as VFR traffic advisories and you leave the area or the frequency, tell ATC and end the contact. If you cannot raise anyone, AIM gives "ANY RADIO (tower) (station), GIVE (call sign) A CALL ON (frequency)".

Common mistakes

1. Starting with your own call sign instead of the station you are calling
2. Abbreviating your call sign before ATC has done it
3. Answering ROGER to something that needs a readback
4. Leaving out your position to tower, or your altitude when checking in
5. Composing the message while talking, with pauses and "ums" that tie up the frequency
6. Keying without listening and stepping on someone else

Quick reference

How to practice

• Write out your usual first calls (ground, tower, departure, approach) in the order station, call sign, position or altitude, request, and say them out loud
• Practice the listening side: pick out your call sign fast and pull out the instruction
• Record yourself and cut the filler words

If you want to practice calls with a controller that talks back, you can do it in English or Spanish with KoAir.

Related: the ICAO phonetic alphabet, ATC clearance readbacks and how to say numbers on the radio.