PA.III.A.K1FAA-S-ACS-6C · Nov 2023Knowledge
How to obtain appropriate radio frequencies.
How to obtain appropriate radio frequencies.
Bottom line
At an airport without an operating control tower, the key to communicating is selecting the correct common frequency, the Common Traffic Advisory Frequency (CTAF). A CTAF is a frequency designated for carrying out airport advisory practices while operating to or from an airport without an operating control tower. The CTAF may be a UNICOM, MULTICOM, Flight Service Station (FSS), or tower frequency, and it is identified in appropriate aeronautical publications.
Key numbers
| Number | What it means |
|---|---|
| more than 30 minutes flying time or 100 NM from nearest shore | Overwater radio |
| no more than a 30-minute gap | VHF gap |
FAA references
- PHAK ch. 14 (p. 14-2) — FAA-H-8083-25C (2023)
- 14 CFR 91.511 (Communication and navigation equipment for overwater operations.) — eCFR current as of 2026-03-05
- AFH Glossary (p. G-4) — FAA-H-8083-3C
- 14 CFR 91.131 (Operations in Class B airspace.) — eCFR current as of 2026-03-05
- RMH ch. 8 (p. 8-4) — FAA-H-8083-2A
- AFH ch. 13 (p. 13-15) — FAA-H-8083-3C
- PHAK ch. 14 (p. 14-23) — FAA-H-8083-25C (2023)
- AIM 6-3-2 (Obtaining Emergency Assistance) — AIM Basic 2/20/25 w/ Change 1 (8/7/25) & Change 2 (1/22/26)
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