A Common Traffic Advisory Frequency (also known as CTAF) is a radio frequency used in general aviation in the United States, Canada and Australia. Many smaller airports do not have control towers managing their operations, as they are too small and/or infrequently trafficked to warrant the expense of a tower and trained controllers. In addition, many airports which do have control towers close them during quiet hours for the same reasons. However, multiple aircraft will often be using these airports at the same time, and there must be a standard means for these aircraft to communicate. Even if there is no traffic, an aircraft that approaches such an airport with the intent of landing or an aircraft preparing to depart such an airport must have a means of announcing their intentions just in case there is someone out there.

The CTAF is how pilots do just that. Such airports have a designated CTAF, which is listed in references such as the US FAA's Airport/Facility Directory. Whenever an aircraft approaches or prepares to depart such an airport, the pilot is required to monitor this frequency and announce all significant aircraft moves (departure, entering the traffic pattern, landing, clearing the runway) over the same. This way, even if there is no staffed facility at an airport, you can be relatively confident that there is a way for airport operations to 'self coordinate.' Generally, if you are flying within ten miles of such an airport and are below 3000 or 5000 feet, it's a good idea to listen in on the CTAF to see what folks around you are doing. If you plan on landing at the airport, it's procedure to announce your presence ten miles out and state your intentions.

In the case of airports which only have a UNICOM or MULTICOM frequency assigned, this frequency is generally used as the CTAF for that airport. Airports with control towers which close will generally use the tower's assigned frequency for CTAF during the hours of closure. On a sectional chart (in the U.S, at least) the CTAF will be listed for each airport which does not have a tower. NOTE: if an airport has a control tower which is closed, be careful! Do not assume that the airport has reverted to the 'standard' UNICOM or MULTICOM frequency! The CTAF is likely the control tower's assigned frequency; if you monitor/broadcast on UNICOM/MULTICOM at these airports, it is likely no-one else will be on your push!

Since there are relatively few frequencies assigned for CTAF use, it is common for airports which share a CTAF to be within radio range of each other. For this reason, and to reduce confusion in general, there are some simple procedures for using CTAF. Whenever announcing, the pilot should always include the following information:

  • The airport he or she is addressing
  • Their own aircraft registration number or identification
  • Their intentions
  • Their destination or departure runway if any
  • The airport he or she is addressing

Nope, you didn't misread, the airport is in there twice. This is so that those listening in have two chances to identify the airport to which the message applies; perhaps their radio automatic squelch cut off the initial words, or perhaps they just started paying attention on hearing a voice - the repeat at the end makes things safer. So a CTAF advisory might sound like the following: "Northampton traffic, Bonanza Six Three Seven Zero Bravo is ten miles south of the field inbound for a full stop and will enter a left crosswind for runway One Four Northampton."

Some final notes - it's preferable to use the airport name, even if it's a local colloquial name, rather than an alphanumeric airport facility code - many smaller airports in the U.S. have three-digit alphanumerics which are great unique identifiers for informational purposes but which don't grab the attention of pilots on the radio the way familiar name does. Also, the use of the word 'traffic' following the airport name indicates that you intend this transmission for general reception, and that you're not talking to a FBO base station (UNICOM) but are coordinating with traffic in the area.

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