AIM ¶ 4-1-5 — IFR Release at Non-Towered Airports
AIM 4-1-5 explains when IFR pilots landing at airports without an operating control tower should switch to the CTAF/airport advisory frequency.
In Plain English
When you're flying IFR into an airport without an operating control tower, ATC will tell you to switch to the airport advisory frequency (CTAF) once direct communication with them is no longer needed. This matters because:
- ATC and centers don't have local traffic information — they don't know which runway is in use or what VFR traffic is operating in the pattern.
- The instrument approach you're flying may not align with the runway actually in use at that field.
- Other pilots in the pattern are self-announcing on CTAF, not talking to ATC.
As a pilot, you should switch to the airport advisory frequency expeditiously once authorized so you can:
- Hear position reports from VFR and IFR traffic in the pattern.
- Determine the runway in use and wind conditions.
- Self-announce your position on the approach.
This is recommended guidance, not a regulatory mandate, but it's a critical safety practice on every IFR arrival to a non-towered field. Get the airport advisory information early — ideally before you're established on the approach.
AIM Source Text
FAA AIM ¶ 4-1-54-1-5. 4-1-5. Communications Release of IFR Aircraft Landing at an Airport Without an Operating Control Tower
Aircraft operating on an IFR flight plan, landing at an airport without an operating control tower will be advised to change to the airport advisory frequency when direct communications with ATC are no longer required. Towers and centers do not have nontower airport traffic and runway in use information. The instrument approach may not be aligned with the runway in use; therefore, if the information has not already been obtained, pilots should make an expeditious change to the airport advisory frequency when authorized. REFERENCE- AIM, Para 5-4-4 , Advance Information on Instrument Approach.
Oral Exam Questions a DPE Might Ask
Q1When operating IFR into an airport without an operating control tower, when should you switch to the airport advisory frequency?
Per AIM 4-1-5, ATC will advise you to change to the airport advisory frequency when direct communications with ATC are no longer required, and you should make an expeditious change once authorized.
Q2Why is it important to monitor the airport advisory frequency (CTAF) when conducting an IFR approach to a non-towered airport?
Per AIM 4-1-5, towers and centers do not have nontower airport traffic or runway-in-use information, and the instrument approach may not be aligned with the runway in use, so the CTAF is the only source for that local traffic and runway information.
Q3Does ATC know what runway is in use at a non-towered airport you're flying an instrument approach into?
No. Per AIM 4-1-5, towers and centers do not have nontower airport traffic and runway in use information, which is why pilots must obtain it on the airport advisory frequency.
Related Paragraphs in AIM Chapter 4