Sarah Nilsson JD, PhD, MAS
Sarah NilssonJD, PhD, MAS

UA.V.A.K1 - Airport operations with and without an operating control tower


Air Safety Institute Interactive module: Runway Safety


Remote pilot sUAS study guide


Radio communications are an important aspect for the safe operation of aircraft in the NAS. It is through radio communications that pilots give and receive information before, during and at the conclusion of a flight. This information aids in the flow of aircraft in highly complex airspace areas as well as in less populated areas. Pilots can also send and receive important safety of flight issues such as unexpected weather conditions, and inflight emergencies. Although small UA pilots are not expected to communicate over radio frequencies, it is important for the UA pilot to understand “aviation language” and the different conversations they will encounter if the UA pilot is using a radio to aid them in situational awareness when operating in the NAS. Although much of the information provided here is geared toward crewed aircraft pilots, the UA pilot needs to understand the unique way information is exchanged in the NAS. 


If you want to listen to Air Traffic Control recordings click HERE


AIM 4−1−2

Control Towers

Towers have been established to provide for a safe, orderly and expeditious flow of traffic on and in the vicinity of an airport. When the responsibility has been so delegated, towers also provide for the separation of IFR aircraft in the terminal areas.


AIM 4−2−6

Ground Station Call Signs

Pilots, when calling a ground station, should begin with the name of the facility being called followed by the type of the facility being called as indicated in TBL 4−2−1.

AIM 4-1-9

a. Airport Operations Without Operating Control Tower

1. There is no substitute for alertness while in the vicinity of an airport. It is essential that pilots be alert and look for other traffic and exchange traffic information when approaching or departing an airport without an operating control tower. This is of particular importance since other aircraft may not have communication capability or, in some cases, pilots may not communicate their presence or intentions when operating into or out of such airports.

To achieve the greatest degree of safety, it is essential that all radio-equipped aircraft transmit/receive on a common frequency identified for the purpose of airport advisories.


2. An airport may have a full or part-time tower or FSS located on the airport, a full or part-time UNICOM station or no aeronautical station at all. There are three ways for pilots to communicate their intention and obtain airport/traffic information when operating at an airport that does not have an operating tower: by communicating with an FSS, a UNICOM operator, or by making a self-announce broadcast.

NOTE− FSS airport advisories are available only in Alaska.


3. Many airports are now providing completely automated weather, radio check capability and airport advisory information on an automated UNICOM system. These systems offer a variety of features, typically selectable by microphone clicks, on the UNICOM frequency. Availability of the automated UNICOM will be published in the Chart Supplement U.S. and approach charts.


UA.V.A.K2 - Description and use of a Common Traffic Advisory Frequency (CTAF) to monitor crewed aircraft communications

AIM 4-1-9

b. Communicating on a Common Frequency

1. The key to communicating at an airport without an operating control tower is selection of the correct common frequency. The acronym CTAF which stands for Common Traffic Advisory Frequency, is synonymous with this program. 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. The CTAF may be a UNICOM, MULTICOM, FSS, or tower frequency and is identified in appropriate aeronautical publications.

NOTE− FSS frequencies are available only in Alaska.


2. CTAF (Alaska Only). In Alaska, a CTAF may also be designated for the purpose of carrying out advisory practices while operating in designated areas with a high volume of VFR traffic.


3. The CTAF frequency for a particular airport or area is contained in the Chart Supplement U.S., Chart Supplement Alaska, Alaska Terminal Publication, Instrument Approach Procedure Charts, and Instrument Departure Procedure (DP) Charts. Also, the CTAF frequency can be obtained by contacting any FSS. Use of the appropriate CTAF, combined with a visual alertness and application of the following recommended good operating practices, will enhance safety of flight into and out of all uncontrolled airports.

UA.V.A.K3 -  Recommended traffic advisory procedures used by crewed aircraft pilots, such as self-announcing of position and intentions 

AIM 4-1-9

c. Recommended Traffic Advisory Practices

1. Pilots of inbound traffic should monitor and communicate as appropriate on the designated CTAF from 10 miles to landing. Pilots of departing aircraft should monitor/communicate on the appropriate frequency from start-up, during taxi, and until 10 miles from the airport unless the CFRs or local procedures require otherwise.


2. Pilots of aircraft conducting other than arriving or departing operations at altitudes normally used by arriving and departing aircraft should monitor/communicate on the appropriate frequency while within 10 miles of the airport unless required to do otherwise by the CFRs or local procedures. Such operations include parachute jumping/dropping, en route, practicing maneuvers, etc.


3. In Alaska, pilots of aircraft conducting other than arriving or departing operations in designated CTAF areas should monitor/communicate on the appropriate frequency while within the designated area, unless required to do otherwise by CFRs or local procedures. Such operations include parachute jumping/dropping, en route, practicing maneuvers, etc.


g. Self-Announce Position and/or Intentions

1. General. Self-announce is a procedure whereby pilots broadcast their position or intended flight activity or ground operation on the designated CTAF. This procedure is used primarily at airports which do not have an FSS on the airport. The self-announce procedure should also be used if a pilot is unable to communicate with the FSS on the designated CTAF. Pilots stating, “Traffic in the area, please advise” is not a recognized Self−Announce Position and/or Intention phrase and should not be used under any condition.


2. If an airport has a tower and it is temporarily closed, or operated on a part-time basis and there is no FSS on the airport or the FSS is closed, use the CTAF to self-announce your position or intentions.


3. Where there is no tower, FSS, or UNICOM station on the airport, use MULTICOM frequency 122.9 for self-announce procedures. Such airports will be identified in appropriate aeronautical information publications.


4. Practice Approaches. Pilots conducting practice instrument approaches should be particularly alert for other aircraft that may be departing in the opposite direction. When conducting any practice approach, regardless of its direction relative to other airport operations, pilots should make announcements on the CTAF as follows:

(a) Departing the final approach fix, inbound (nonprecision approach) or departing the outer marker or fix used in lieu of the outer marker, inbound (precision approach);

(b) Established on the final approach segment or immediately upon being released by ATC;

(c) Upon completion or termination of the approach; and

(d) Upon executing the missed approach procedure.


5. Departing aircraft should always be alert for arrival aircraft coming from the opposite direction.


6. Recommended self-announce phraseologies:

It should be noted that aircraft operating to or from another nearby airport may be making self-announce broadcasts on the same UNICOM or MULTICOM frequency. To help identify one airport from another, the airport name should be spoken at the beginning and end of each self-announce transmission.

(a) Inbound


Strawn traffic, Apache Two Two Five Zulu, (position), (altitude), (descending) or entering downwind/base/final (as appropriate) runway one seven full stop, touch−and−go, Strawn.

Strawn traffic Apache Two Two Five Zulu clear of runway one seven Strawn.

(b) Outbound


 Strawn traffic, Queen Air Seven One Five Five Bravo (location on airport) taxiing to runway two six Strawn.

Strawn traffic, Queen Air Seven One Five Five Bravo departing runway two six. Departing the pattern to the (direction), climbing to (altitude) Strawn.

(c) Practice Instrument Approach


 Strawn traffic, Cessna Two One Four Three Quebec (position from airport) inbound descending through (altitude) practice (name of approach) approach runway three five Strawn.

Strawn traffic, Cessna Two One Four Three Quebec practice (type) approach completed or terminated runway three five Strawn.



(Refer to FAA-CT-8080-2H, Figure 26, area 2.)

While monitoring the Cooperstown CTAF you hear an aircraft announce that they are midfield left downwind to RWY 13. Where would the aircraft be relative to the runway?

  1. The aircraft is East
  2. The aircraft is South
  3. The aircraft is West

UA.V.A.K4 - Aeronautical advisory communication station (UNICOM) and associated communication procedures used by crewed aircraft pilots

AIM 4-1-9

e. Information Provided by Aeronautical Advisory Stations (UNICOM)

1. UNICOM is a nongovernment air/ground radio communication station which may provide airport information at public use airports where there is no tower or FSS.


2. On pilot request, UNICOM stations may provide pilots with weather information, wind direction, the recommended runway, or other necessary information. If the UNICOM frequency is designated as the CTAF, it will be identified in appropriate aeronautical publications.


f. Unavailability of Information from FSS or UNICOM

Should LAA by an FSS or Aeronautical Advisory Station UNICOM be unavailable, wind and weather information may be obtainable from nearby controlled airports via Automatic Terminal Information

Service (ATIS) or Automated Weather Observing System (AWOS) frequency.


h. UNICOM Communications Procedures

1. In communicating with a UNICOM station, the following practices will help reduce frequency congestion, facilitate a better understanding of pilot intentions, help identify the location of aircraft in the traffic pattern, and enhance safety of flight:

(a) Select the correct UNICOM frequency.

(b) State the identification of the UNICOM station you are calling in each transmission.

(c) Speak slowly and distinctly.

(d) Report approximately 10 miles from the airport, reporting altitude, and state your aircraft type, aircraft identification, location relative to the airport, state whether landing or overflight, and request wind information and runway in use.

(e) Report on downwind, base, and final approach.

(f) Report leaving the runway.


2. Recommended UNICOM phraseologies:

(a) Inbound







(b) Outbound





AIM 4−1−12

Use of UNICOM for ATC Purposes

UNICOM service may be used for ATC purposes, only under the following circumstances:

a. Revision to proposed departure time.

b. Takeoff, arrival, or flight plan cancellation time.

c. ATC clearance, provided arrangements are made between the ATC facility and the UNICOM licensee to handle such messages.


Remote pilot sUAS study guide

Communication/Broadcast Procedures

A MULTICOM frequency of 122.9 will be used at an airport that is non-towered and does not have a FSS or UNICOM.


Recommended Traffic Advisory Practices

Although a remote pilot-in-command is not required to communicate with crewed aircraft when in the vicinity of a non-towered airport, safety in the National Airspace System requires that remote pilots are familiar with traffic patterns, radio procedures, and radio phraseology.

When a remote pilot plans to operate close to a non-towered airport, the first step in radio procedures is to identify the appropriate frequencies. Most non-towered airports will have a UNICOM frequency, which is usually 122.8; however, you should always check the Cart Supplements U.S. or sectional chart for the correct frequency. This frequency can vary when there are a large number of non-towered airports in the area. For non-towered airports that do not have a UNICOM or any other frequency listed, the MULTICOM frequency of 122.9 will be used. These frequencies can be found on a sectional chart by the airport or in the Chart Supplements publication from the FAA.

When a crewed aircraft is inbound to a non-towered airport, the standard operating practice is for the pilot to “broadcast in the blind” when 10 miles from the airport. This initial radio call will also include the position the aircraft is in relation to north, south, east or west from the airport. For example:

Town and Country traffic, Cessna 123 Bravo Foxtrot is 10 miles south inbound for landing, Town and Country traffic. 

When a crewed aircraft is broadcasting at a non-towed airport, the aircraft should use the name of the airport of intended landing at the beginning of the broadcast, and again at the end of the broadcast. The reason for stating the name twice is to allow others who are on the frequency to confirm where the aircraft is going. The next broadcast that the crewed aircraft should make is:

Town and Country traffic, Cessna 123 Bravo Foxtrot, is entering the pattern, mid-field left down-wind for runway 18, Town and Country traffic.

The aircraft is now entering the traffic pattern. In this example, the aircraft is making a standard 45 degree entry to the downwind leg of the pattern for runway 18. Or, the aircraft could land straight- in without entering the typical rectangular traffic pattern. Usually aircraft that are executing an instrument approach will use this method. Examples of a radio broadcast from aircraft that are using this technique are:

For an aircraft that is executing an instrument approach:

Town and Country traffic, Cessna 123 Bravo Foxtrot, is one mile north of the airport, GPS runway 18, full stop landing, Town and Country traffic.

As the aircraft flies the traffic pattern for a landing, the following radio broadcasts should be made:

Town and Country traffic, Cessna 123 Bravo Foxtrot, left base, runway 18, Town and Country traffic.

Town and Country traffic, Cessna 123 Bravo Foxtrot, final, runway 18, Town and Country traffic.

After the aircraft has landed and is clear of the runway, the following broadcast should be made:

Town and Country traffic, Cessna 123 Bravo Foxtrot, is clear of runway 18, taxing to park, Town and Country traffic.

When an aircraft is departing a non-towered airport, the same procedures apply. For example, when the aircraft is ready for takeoff, the aircraft should make the following broadcast:

Town and Country traffic, Cessna 123 Bravo Foxtrot, departing runway 18, Town and Country traffic.

For safety reasons, a remote pilot must always scan the area where they are operating a small UA. This is especially important around an airport. While it is good operating procedures for crewed aircraft to make radio broadcasts in the vicinity of a non-towered airport, by regulation, it is not mandatory. For this reason, a remote pilot must always look for other aircraft in the area, and use a radio for an extra layer of situational awareness. 

UA.V.A.K5 - Automatic Terminal Information Service (ATIS)

Remote pilot sUAS study guide

Automated Terminal Information Service (ATIS)

The Automated Terminal Information Service (ATIS) is a recording of the local weather conditions and other pertinent non-control information broadcast on a local frequency in a looped format. It is normally updated once per hour but is updated more often when changing local conditions warrant. Important information is broadcast on ATIS including weather, runways in use, specific ATC procedures, and any airport construction activity that could affect taxi planning.

When the ATIS is recorded, it is given a code. This code is changed with every ATIS update. For example, ATIS Alpha is replaced by ATIS Bravo. The next hour, ATIS Charlie is recorded, followed by ATIS Delta and progresses down the alphabet. 

AIM 4−1−13

Automatic Terminal Information Service (ATIS)

a. ATIS is the continuous broadcast of recorded noncontrol information in selected high activity terminal areas. Its purpose is to improve controller effectiveness and to relieve frequency congestion by automating the repetitive transmission of essential but routine information. The information is continuously broadcast over a discrete VHF radio frequency or the voice portion of a local NAVAID. Arrival ATIS transmissions on a discrete VHF radio frequency are engineered according to the individual facility requirements, which would normally be a protected service volume of 20 NM to 60 NM from the ATIS site and a maximum altitude of 25,000 feet AGL. In the case of a departure ATIS, the protected service volume cannot exceed 5 NM and 100 feet AGL. At most locations, ATIS signals may be received on the surface of the airport, but local conditions may limit the maximum ATIS reception distance and/or altitude. Pilots are urged to cooperate in the ATIS program as it relieves frequency congestion on approach control, ground control, and local control frequencies. The Chart Supplement U.S. indicates airports for which ATIS is provided.


b. ATIS information includes the time of the latest weather sequence, ceiling, visibility, obstructions to visibility, temperature, dew point (if available), wind direction (magnetic), and velocity, altimeter, other pertinent remarks, instrument approach and runway in use. The ceiling/sky condition, visibility, and obstructions to vision may be omitted from the ATIS broadcast if the ceiling is above 5,000 feet and the visibility is more than 5 miles. The departure runway will only be given if different from the landing runway except at locations having a separate ATIS for departure. The broadcast may include the appropriate frequency and instructions for VFR arrivals to make initial contact with approach control. Pilots of aircraft arriving or departing the terminal area can receive the continuous ATIS broadcast at times when cockpit duties are least pressing and listen to as many repeats as desired. ATIS broadcast must be updated upon the receipt of any official hourly and special weather. A new recording will also be made when there is a change in other pertinent data such as runway change, instrument approach in use, etc.



Dulles International information Sierra. 1300 zulu weather. Measured ceiling three thousand overcast. Visibility three, smoke. Temperature six eight. Wind three five zero at eight. Altimeter two niner niner two. ILS runway one right approach in use. Landing runway one right and left. Departure runway three zero. Armel VORTAC out of service. Advise you have Sierra.


c. Pilots should listen to ATIS broadcasts whenever ATIS is in operation.


d. Pilots should notify controllers on initial contact that they have received the ATIS broadcast by repeating the alphabetical code word appended to the broadcast.


“Information Sierra received.”


e. When a pilot acknowledges receipt of the ATIS broadcast, controllers may omit those items contained in the broadcast if they are current. Rapidly changing conditions will be issued by ATC and the ATIS will contain words as follows:


“Latest ceiling/visibility/altimeter/wind/(other conditions) will be issued by approach control/tower.”

 NOTE − The absence of a sky condition or ceiling and/or visibility on ATIS indicates a sky condition or ceiling of 5,000 feet or above and visibility of 5 miles or more. A remark may be made on the broadcast, “the weather is better than 5000 and 5,” or the existing weather may be broadcast.


f. Controllers will issue pertinent information to pilots who do not acknowledge receipt of a broadcast or who acknowledge receipt of a broadcast which is not current.


g. To serve frequency limited aircraft, FSSs are equipped to transmit on the omnirange frequency at most en route VORs used as ATIS voice outlets. Such communication interrupts the ATIS broadcast. Pilots of aircraft equipped to receive on other FSS frequencies are encouraged to do so in order that these override transmissions may be kept to an absolute minimum.


h. While it is a good operating practice for pilots to make use of the ATIS broadcast where it is available, some pilots use the phrase “have numbers” in communications with the control tower. Use of this phrase means that the pilot has received wind, runway, and altimeter information ONLY and the tower does not have to repeat this information. It does not indicate receipt of the ATIS broadcast and should never be used for this purpose.


UA.V.A.K6 - Aircraft call signs and registration numbers

Remote pilot sUAS study guide

Aircraft Call Signs

When operating in the vicinity of any airport, either towered or non-towered, it is important for a remote pilot to understand radio communications of crewed aircraft in the area. Although 14 CFR part 107 only requires the remote pilot to receive authorization to operate in certain airport areas, it can be a good operating practice to have a radio that will allow the remote pilot to monitor the appropriate frequencies in the area. The remote pilot should refrain from transmitting over any active aviation frequency unless there is an emergency situation. 

Aviation has unique communication procedures that will be foreign to a remote pilot who has not been exposed to “aviation language” previously. One of those is aircraft call signs. All aircraft that are registered in the United States will have a unique registration number, or “N” number. For example, N123AB, which would be pronounced in aviation terms by use of the phonetic alphabet as, “November One-Two-Three-Alpha-Bravo.” In most cases, “November” will be replaced with either the aircraft manufacturer’s name (make) and in some cases, the type of aircraft (model). Usually, when the aircraft is a light general aviation (GA) aircraft, the manufacturer’s name will be used. In this case, if N123AB is a Cessna 172, the call sign would be “Cessna, One-Two-Three-Alpha-Bravo.” If the aircraft is a heavier GA aircraft, such as a turbo-prop, or turbo-jet, the aircraft’s model will be used in the call sign. If N123AB is a Cessna Citation, the call sign would be stated as, “Citation, One- Two-Three-Alpha-Bravo.” Typically, airliners will use the name of their companies and their flight number in their call signs. For example, Southwest Airlines flight 711, would be said as, “Southwest- Seven-One-One.” There are a few airlines such as British Airways who will not use the company name in their call sign. For example, British Airways uses “Speedbird.”

To close, a remote pilot is not expected to communicate with other aircraft in the vicinity of an airport, and should not do so unless there is an emergency situation. However, in the interest of safety in the NAS, it is important that a remote pilot understands the aviation language and the types of aircraft that can be operating in the same area as a small UA. 


AIM 4−2−4

Aircraft Call Signs

a. Precautions in the Use of Call Signs.

1. Improper use of call signs can result in pilots executing a clearance intended for another aircraft.

Call signs should never be abbreviated on an initial contact or at any time when other aircraft call signs have similar numbers/sounds or identical letters/number; e.g., Cessna 6132F, Cessna 1622F, Baron 123F, Cherokee 7732F, etc.


Assume that a controller issues an approach clearance to an aircraft at the bottom of a holding stack and an aircraft with a similar call sign (at the top of the stack) acknowledges the clearance with the last two or three numbers of the aircraft’s call sign. If the aircraft at the bottom of the stack did not hear the clearance and intervene, flight safety would be affected, and there would be no reason for either the controller or pilot to suspect that anything is wrong. This kind of “human factors” error can strike swiftly and is extremely difficult to rectify.


2. Pilots, therefore, must be certain that aircraft identification is complete and clearly identified before taking action on an ATC clearance. ATC specialists will not abbreviate call signs of air carrier or other civil aircraft having authorized call signs. ATC specialists may initiate abbreviated call signs of other aircraft by using the prefix and the last three digits/letters of the aircraft identification after communications are established. The pilot may use the abbreviated call sign in subsequent contacts with the ATC specialist. When aware of similar/identical call signs, ATC specialists will take action to minimize errors by emphasizing certain numbers/letters, by repeating the entire call sign, by repeating the prefix, or by asking pilots to use a different call sign temporarily. Pilots should use the phrase “VERIFY CLEARANCE FOR (your complete call sign)” if doubt exists concerning proper identity.


3. Civil aircraft pilots should state the aircraft type, model or manufacturer’s name, followed by the digits/letters of the registration number. When the aircraft manufacturer’s name or model is stated, the prefix “N” is dropped; e.g., Aztec Two Four Six Four Alpha.


1. Bonanza Six Five Five Golf.

2. Breezy Six One Three Romeo Experimental (omit “Experimental” after initial contact).


4. Air Taxi or other commercial operators not having FAA authorized call signs should prefix their normal identification with the phonetic word “Tango.”


Tango Aztec Two Four Six Four Alpha.


5. Air carriers and commuter air carriers having FAA authorized call signs should identify themselves by stating the complete call sign (using group form for the numbers) and the word “super” or “heavy” if appropriate.


1. United Twenty−Five Heavy.

2. Midwest Commuter Seven Eleven.


6. Military aircraft use a variety of systems including serial numbers, word call signs, and combinations of letters/numbers. Examples include Army Copter 48931; Air Force 61782; REACH

31792; Pat 157; Air Evac 17652; Navy Golf Alfa Kilo 21; Marine 4 Charlie 36, etc.


UA.V.A.K7 - Phonetic alphabet

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. ATC facilities may also request pilots to use phonetic letter equivalents when aircraft with similar sounding identifications are receiving communications on the same frequency. Pilots should use the phonetic alphabet when identifying their aircraft during initial contact with air traffic control facilities. Additionally, use the phonetic equivalents for single letters and to spell out groups of letters or difficult words during adverse communications conditions. (See TBL 4−2−2.)


UA.V.A.K8 - Phraseology: altitudes, directions, speed, and time

AIM 4−2−8


a. Figures indicating hundreds and thousands in round number, as for ceiling heights, and upper wind levels up to 9,900 must be spoken in accordance with the following.


1. 500 . . . . . . . . five hundred

2. 4,500 . . . . . . four thousand five hundred


b. Numbers above 9,900 must be spoken by separating the digits preceding the word “thousand.”


1. 10,000 . . . . . one zero thousand

2. 13,500 . . . . . one three thousand five hundred


c. Transmit airway or jet route numbers as follows.


1. V12 . . . . . . . Victor Twelve

2. J533 . . . . . . . J Five Thirty−Three


d. All other numbers must be transmitted by pronouncing each digit.


10 . . . . . . . . . . . one zero

e. When a radio frequency contains a decimal point, the decimal point is spoken as “POINT.”


122.1 . . . . . . . . . one two two point one

NOTE − ICAO procedures require the decimal point be spoken as “DECIMAL.” The FAA will honor such usage by military aircraft and all other aircraft required to use ICAO procedures.


AIM 4−2−9

Altitudes and Flight Levels

a. Up to but not including 18,000 feet MSL, state the separate digits of the thousands plus the hundreds if appropriate.


1.  12,000 . . . . . one two thousand

2.  12,500 . . . . . one two thousand five hundred


b. At and above 18,000 feet MSL (FL 180), state the words “flight level” followed by the separate digits of the flight level.


1. 190 . . . . . . . . Flight Level One Niner Zero

2. 275 . . . . . . . . Flight Level Two Seven Five




The three digits of bearing, course, heading, or wind direction should always be magnetic. The word “true” must be added when it applies.


1. (Magnetic course) 005 . . . . . . zero zero five

2. (True course) 050 . . . . . . . . . . zero five zero true

3. (Magnetic bearing) 360 . . . . . three six zero

4. (Magnetic heading) 100 . . . . . heading one zero zero

5. (Wind direction) 220 . . . . . . . . wind two two zero


AIM 4−2−11


The separate digits of the speed followed by the word “KNOTS.” Except, controllers may omit the word “KNOTS” when using speed adjustment procedures; e.g., “REDUCE/INCREASE SPEED TO TWO FIVE ZERO.”


(Speed) 250 . . . . . . . . . . . . . . . . . two five zero knots

(Speed) 190 . . . . . . . . . . . . . . . . . one niner zero knots

The separate digits of the Mach Number preceded by “Mach.”


(Mach number) 1.5 . . . . . . . . . . . . Mach one point five

(Mach number) 0.64 . . . . . . . . . . . Mach point six four

(Mach number) 0.7 . . . . . . . . . . . . Mach point seven


AIM 4−2−12


a. FAA uses Coordinated Universal Time (UTC) for all operations. The word “local” or the time zone equivalent must be used to denote local when local time is given during radio and telephone communications. The term “Zulu” may be used to denote UTC.


0920 UTC . . . . . zero niner two zero, zero one two zero pacific or local, or one twenty AM

b. To convert from Standard Time to Coordinated Universal Time:

c. A reference may be made to local daylight or standard time utilizing the 24−hour clock system. The hour is indicated by the first two figures and the minutes by the last two figures.


0000 . . . . . . . . . . . . . . . . . . . . . . . zero zero zero zero

0920 . . . . . . . . . . . . . . . . . . . . . . . zero niner two zero


d. Time may be stated in minutes only (two figures) in radiotelephone communications when no misunderstanding is likely to occur.


e. Current time in use at a station is stated in the nearest quarter minute in order that pilots may use this information for time checks. Fractions of a quarter minute less than 8 seconds are stated as the preceding quarter minute; fractions of a quarter minute of 8 seconds or more are stated as the succeeding quarter minute.


0929:05 . . . . . . time, zero niner two niner

0929:10 . . . . . . time, zero niner two niner and one−quarter

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