AIM 4-1, AIM 4-2 and ACS Operations Task A

Aviation radio and the phonetic alphabet

The Part 107 test expects you to understand how manned pilots talk. Here are CTAF, MULTICOM, ATIS, the phonetic alphabet and time, straight from the AIM.

Part 107, explained › Operations · Last reviewed October 25, 2026 against the eCFR and faa.gov. UAV Campus is not affiliated with the FAA.

How should a drone pilot use the aviation radio and phonetic alphabet?

The FAA tests radio knowledge so you can follow manned aircraft: a CTAF is the frequency for airport advisories where there is no operating tower, ATIS is a continuous recorded broadcast of noncontrol information, and the ICAO phonetic alphabet (Alfa, Bravo, Charlie) spells out letters that might otherwise be misheard. Pilots say times in UTC, called Zulu.

Airports without an operating tower: a CTAF may be a UNICOM, MULTICOM, FSS or tower frequency, shown in aeronautical publications (AIM 4-1). Where there is no tower, FSS or UNICOM, pilots self-announce on MULTICOM 122.9. Self-announcing is how manned pilots broadcast position or intentions, and the ACS asks you to know how a CTAF is used to monitor manned aircraft communications (ACS Operations Task A). The AIM also says the phrase "Traffic in the area, please advise" is not a recognized self-announce phrase.

ATIS information includes the airport name, a phonetic letter code, the time of the latest weather in UTC, wind, visibility and the runway in use. A missing sky condition and visibility means ceiling 5,000 feet or above and visibility 5 miles or more. Pilots tell controllers they have the broadcast by repeating the code word, as in "Information Sierra received," and the phrase "have numbers" never means the ATIS was received (AIM 4-1-13).

The phonetic alphabet is used by FAA personnel when conditions make information hard to receive, and pilots should use it when identifying their aircraft on initial contact with ATC (AIM 4-2-7). FAA uses UTC for all operations, and "local" or the time zone must be stated when local time is given (AIM 4-2-12).

Sources: AIM 4-1, Airport Operations and ATIS · AIM 4-2, Radio Communications Phraseology and Techniques · ACS, Operations, Task A. Radio Communications Procedures

What the FAA says

AIM 4-1, CTAF

A CTAF is a frequency designated for the purpose of carrying out airport advisory practices while operating to or from an airport without an operating control tower.

AIM 4-1-13, ATIS

ATIS is the continuous broadcast of recorded noncontrol information in selected high activity terminal areas.

AIM 4-2-7, Phonetic Alphabet

The International Civil Aviation Organization (ICAO) phonetic alphabet is used by FAA personnel when communications conditions are such that the information cannot be readily received without their use.

AIM 4-2-12, Time

The term “Zulu” may be used to denote UTC.

Sources: AIM 4-1, CTAF · AIM 4-1-13, ATIS · AIM 4-2-7, Phonetic Alphabet · AIM 4-2-12, Time

Exam traps

  • The absence of a sky condition or ceiling and/or visibility on ATIS indicates a ceiling of 5,000 feet or above and visibility of 5 miles or more.
  • The phrase "have numbers" does not indicate receipt of the ATIS broadcast and should never be used for that purpose.
  • Where there is no tower, FSS or UNICOM, self-announce on MULTICOM frequency 122.9.
  • ATIS is noncontrol information: it is a recorded broadcast, not a controller talking to you.

Quick quiz: 3 questions

Similar to the FAA test, not the actual test questions. Each answer shows its FAA source.

Question 1 of 3

Automatic Terminal Information Service (ATIS) is the continuous broadcast of recorded information concerning

  1. A nonessential information to reduce frequency congestion.
  2. B pilots of radar-identified aircraft whose aircraft is in dangerous proximity to terrain or to an obstruction.
  3. C non control information in selected high-activity terminal areas.
Show the answer
Answer: C. non control information in selected high-activity terminal areas.

FAA source: FAA-H-8083-25C Glossary, Automatic terminal information service (ATIS)

Question 2 of 3

Absence of the sky condition and visibility on an ATIS broadcast indicates that

  1. A the ceiling is at least 5,000 feet and visibility is 5 miles or more.
  2. B weather conditions are at or above VFR minimums.
  3. C the sky condition is clear and visibility is unrestricted.
Show the answer
Answer: A. the ceiling is at least 5,000 feet and visibility is 5 miles or more.

(This is a rote memory item.)

FAA source: AIM 4-1-13, Automatic Terminal Information Service

Question 3 of 3

If Dallas Executive Tower is not in operation, which frequency should be used as a Common Traffic Advisory Frequency (CTAF) to monitor airport traffic? (Area 3)

FAA testing supplement figure for quiz question 3
Tap the figure to open it full size.
  1. A 126.35 MHz.
  2. B 127.25 MHz.
  3. C 122.95 MHz.
Show the answer
Answer: B. 127.25 MHz.

(As seen in this figure, the control tower frequency is 127.25, which also means that when the tower is closed, traffic will be announced on this frequency.)

FAA sources: FAA-H-8083-25C ch. 14, Nontowered Airport · FAA-H-8083-25C ch. 14, Recommended communication procedures (Figure 14-1)

What does "Information Sierra" mean on the radio?

Sierra is the phonetic letter code of the current ATIS broadcast. Pilots repeat the code word on initial contact to show they have received it.

Source: AIM 4-1-13, ATIS

What time standard do pilots use on the radio?

FAA uses Coordinated Universal Time (UTC) for all operations, and the word Zulu may be used to denote UTC.

Source: AIM 4-2-12, Time

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More on this topic: Part 107 operations and decision-making.