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CA.III.A.K2FAA-S-ACS-7B · Nov 2023Knowledge

Proper radio communication procedures and air traffic control (ATC) phraseology.

ACS element text (the applicant demonstrates understanding of)

Proper radio communication procedures and air traffic control (ATC) phraseology.

Bottom line

At a nontowered airport, two-way radio communications are not required, but transmitting intentions on the specified frequency is a good operating practice. ICAO has adopted a phonetic alphabet that should be used in radio communications, and pilots should use it to identify their aircraft when communicating with ATC.

Key numbers

Key numbers for Proper radio communication procedures and air traffic control (ATC) phraseology.
NumberWhat it means
121.5 MHzGuard freq
7700EAL squawk
within 12 miles and at or below 12,000 feet MSLEAL broadcast

FAA references

  1. PHAK ch. 14 (p. 14-2) — FAA-H-8083-25C (2023)
  2. PHAK ch. 14 (p. 14-23) — FAA-H-8083-25C (2023)
  3. AFH ch. 18 (p. 18-22) — FAA-H-8083-3C
  4. RMH ch. 6 (p. 6-4) — FAA-H-8083-2A
  5. RMH ch. 3 (p. 3-4) — FAA-H-8083-2A
  6. AFH ch. 1 (p. 1-12) — FAA-H-8083-3C
  7. AIM 11-8-2 (UAS Operations and Air Traffic Control (ATC)) — AIM Basic 2/20/25 w/ Change 1 (8/7/25) & Change 2 (1/22/26)
  8. 14 CFR 91.129 (Operations in Class D airspace.) — eCFR current as of 2026-03-05
  9. AIM 4-3-13 (Traffic Control Light Signals) — AIM Basic 2/20/25 w/ Change 1 (8/7/25) & Change 2 (1/22/26)
  10. AFH ch. 13 (p. 13-15) — FAA-H-8083-3C
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