How to Select and Use the Correct Common Traffic Advisory Frequency – ATC Communication (2023)

A pilot named Michael recently wrote to me with this question about the use of a Common Traffic Advisory Frequency (CTAF).

“I have a question regarding Unicom’s vs CTAF’s. I’m an Alaska pilot and I also have some time in Eastern Washington, Oregon and Western Idaho. When I was getting my lessons in that region we were warned about the transition from Unicom’s to CTAF’s — essentially that many Unicom frequencies are not manned continuously or at all. A call to the Unicom might be helpful to learn the active runway or if there was some activity which might be of concern to you – should someone answer the frequency, but we were told that all traffic in the vicinity of an uncontrolled airport with a designated CTAF should make all their self announcements on that CTAF rather than on the Unicom frequency.”

This was my reply: “Should pilots make position reports on the CTAF? The answer is yes. The confusion arises because Unicom may be a CTAF.

Here’s the definition from the AIM: “The CTAF may be a UNICOM, MULTICOM, FSS, or tower frequency and is identified in appropriate aeronautical publications.”

How to Select and Use the Correct Common Traffic Advisory Frequency – ATC Communication (1)

Take this Frequency and Use It

There are general rules in the AIM for selecting the appropriate CTAF frequency. You’ll find those rules in Table 4-1-1, which is kind of hard to find in the AIM. Look for the table just below Section 4-1-9 which is titled Traffic Advisory Practices at Airports Without Operating Control Towers.

If you look in the left column of this table, you will see the column heading “Facility at Airport”. The choices in that column talk about whether the airport uses Unicom, a dedicated Flight Service Station frequency, or the frequency of a tower that is closed.

There is also one listing covering the oddball airport with no facility of any kind. In that case, you are expected to self-announce on the Multicom frequency of 122.9.

CTAF in Real Life

Let’s look at 2 of the most typical radio arrangements at uncontrolled airports. We’ll check the AIM’s table, and proceed from there.

Let’s say today we are going to fly into the Socorro Municipal Airport near Socorro, New Mexico. We look at our Albuquerque sectional chart and find Socorro centered on the left third of the chart. The data next to the airport includes an AWOS-3 frequency of 118.325 and a Unicom frequency of 122.8. Notice next to the Unicom frequency there is a letter C inside a filled-in magenta circle. That letter C stands for CTAF. It means Unicom frequency 122.8 is the CTAF.

How to Select and Use the Correct Common Traffic Advisory Frequency – ATC Communication (2)

Just to double-check, because that’s what the AIM tells us to do, we go into the Airport/Facility Directory’s listing for Socorro. Sure enough, under the heading Communications, the Directory shows Socorro’s Unicom frequency as 122.8. It also says 122.8 is the CTAF.

How to Select and Use the Correct Common Traffic Advisory Frequency – ATC Communication (3)

Let’s Fly and Talk

Armed with this information, here’s how we’ll proceed. As we are flying inbound, some distance from Socorro, we’ll dial up the AWOS-3 frequency and get the automated weather report for the airport.

Soccoro Municipal Airport automated weather observation, 1755 Zulu. Sky clear, visibility 10 miles, wind 300 at 10 knots. Temperature 4, dewpoint minus 4, altimeter 30.08. Remark AO2 Sea Level Pressure 17371040. Check density altitude.

Next, about 10 miles from the airport, we’ll make this radio call on Unicom, “Socorro Unicom, Cessna 9130 Delta 10 miles west of the airport, inbound for landing with the numbers, request an airport advisory.”

Adding the remark “with the numbers” means you have listened to the weather report on AWOS. This tells the person manning Unicom you don’t need him to say the wind direction or altimeter setting at the airport. If you don’t say “with the numbers” the person at the other end of the radio should give you this basic information.

You make your request, and hopefully, the person manning the Unicom station will answer with something that sounds like this.

“Aircraft calling Socorro, Socorro is using Runway 33, left traffic. There are 2 aircraft in the pattern.”

What if No One Answers?

But, let’s say you make that radio call requesting an airport advisory and you don’t get a reply. You know you have the correct frequency dialed in and your radio is working. You hear other aircraft reporting their position at Socorro.

Not to worry. Going back to the AIM’s table 4-1-1 we look at the row next to the heading “UNICOM (No Tower or FSS)”. In the column labeled “Frequency Use”, it says “Communicate with UNICOM station on published CTAF frequency (122.7; 122.8; 122.725; 122.975; or 123.0). If unable to contact UNICOM station, use self-announce procedures on CTAF.”

Wait a minute. What does that last sentence mean, “If unable to contact UNICOM station, use self-announce procedures on CTAF”? If you don’t read carefully, you might interpret that to mean Unicom and CTAF are two separate frequencies.

That’s not what it means. Focus on the word “station” in that sentence and it makes more sense. Read it like this: If unable to reach the person manning the Unicom base station to get an airport advisory, begin self-announcing on CTAF, which may be the same frequency used by the base station.

I should also add, and these are my words, not the AIM’s: Continue to listen on the Unicom frequency to get a sense of who is in the traffic pattern and determine what runway they are using.

Of course, if no one is talking on the frequency, pilots or Unicom station operator, then it’s a good idea to survey the airport pattern before entering. Your flight instructor can advise you how to do this and add his or her own techniques.

Self-Announce on CTAF

Table 4-1-1 of the AIM says make your first position report 10 miles from the airport. Then, report entering downwind, entering base leg, and entering final approach. If making a full stop, report clear of the runway.

That’s all there is to radio work when approaching an airport that uses a dedicated Unicom frequency for CTAF.

Sorry Folks, Tower’s Closed. Moose Out Front Should’ve Told You.*

New day, new airport.

This evening, you are flying towards your destination of Redding Municipal Airport near Redding, California. The local time is 21:40 and Redding’s part-time tower is closed.

How to Select and Use the Correct Common Traffic Advisory Frequency – ATC Communication (4)

A check of the Klamath Falls sectional chart shows a Unicom frequency at the airport of 122.95, but the circled C symbol is next to the control tower frequency of 119.8. This means the tower’s frequency is the CTAF when the tower is closed. A check of Redding’s listing in the Airport Facility Directory confirms this information.

Next, let’s go into Table 4-1-1 in the AIM and look at the row with the heading, “Tower or Flight Service Station Not in Operation”. The listed procedure is to self-announce on the CTAF frequency. We’ll use 119.8 for self-announce at Redding.

What about the listed Unicom frequency? Should you use that to get an airport advisory? It’s unlikely anyone will answer you on Unicom because the Airport Facility Directory says the airport is attended only from dawn till dusk. So why is there even a Unicom frequency listed for this airport? Likely it’s there as a backup frequency in case the primary CTAF is NOTAM-ed out of service.

In this situation, how are you going to get a weather update for the airport? The answer is to call Flight Service. Flight service will be able to give you the current weather, but don’t expect a full airport advisory because Flight Service does not play an airport advisory role at Redding.

Let’s Fly and Talk at Redding

So in actual practice, here’s how I’d handle my arrival at Redding. Some distance from the airport, I’d contact the nearest Flight Service Station for a weather update. In this area, Rancho Murieta Radio handles that request.

Next, I’d dial up the CTAF (119.8) and report inbound when 10 miles from the airport.

“Redding Traffic, Cessna 9130 Delta, 10 miles northwest of the airport, inbound for landing, Redding.”

As I proceed inbound, I’d listen carefully for any reports from other aircraft. If I don’t hear anything, I would not, I repeat would not make this radio transmission. “Traffic in the area, please advise.” Why wouldn’t I make this call? Because the AIM is very specific when it says, “‘Traffic in the area, please advise’ is not a recognized Self−Announce Position and/or Intention phrase and should not be used under any condition.” In a manual that is supposed to be a collection of best practices, it’s rare for the FAA to say something with such as strong foot stomp.

After my 10-mile report, I would make my standard reports entering downwind, entering base, entering final, and clearing the runway.

The Takeaways on CTAF

To summarize, CTAF is a common traffic advisory frequency that may be a Unicom frequency, a Tower frequency, or a Flight Service Station frequency. Check your sectional chart and the Airport Facility Directory to see which one applies for your airport. Use Table 4-1-1 in the AIM to determine the correct procedures for the frequency in use as CTAF. If there is no dedicated frequency of any kind for the airport, self-announce your position on the Multicom frequency of 122.9.

Questions? Comments? Write what’s on your mind in the comments section below. I monitor and reply to all incoming comments. Or, if you would like to write to me directly, you can reach me at I also hang out in the Twitterverse at

This article was Part 2 in a series of 3 that will be combined into a single Radar Contact Show at a later date.

Coming up in Part 3: It’s what you don’t hear on a CTAF that can sneak up and get you.

*A twist on John Candy’s line in the movie “National Lampoon’s Vacation”.

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