Aviation Learning Center Document Radio Communications Phraseology and Techniques - P-8740-47
Author: Federal Aviation Administration Date: revised April 2006
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Introduction
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Note: Information in this document was adapted from FAA pamphlet P-8740-47.

Radio communications are a critical link in the ATC system. The link can be a strong bond between pilot and controller or it can be broken with surprising speed and disastrous results. This pamphlet provides basic procedures for new pilots, and highlights safe operating concepts for all pilots.

The single most important concept in pilot-controller communications is understanding. It is essential, therefore, that pilots acknowledge each radio communication with ATC by using the appropriate aircraft call sign. Brevity is important, and transmissions should be as concise as possible while still ensuring that the controller understands what you want to do. Moreover, you, the pilot, must understand exactly what ATC wants you to do.

Pilots will find the Aeronautical Information Manual's Pilot/Controller Glossary very helpful in learning what certain words or phrases mean. Good phraseology enhances safety, and is the mark of a professional pilot. Jargon, chatter, and "CB" slang have no place in ATC communications. The Pilot/Controller Glossary is the same glossary used in the ATC controller's handbook. Pilots should study and review this document from time to time to sharpen communication skills.

Calls to air traffic control (ATC) facilities (ARTCCs, approach control facilities, towers, FSSs) over radio and ATC operational telephone lines (lines used for operational purposes such as controller instructions, briefings, opening and closing flight plans, issuance of IFR clearances and amendments, etc.) may be monitored and recorded for operational uses such accident investigations, accident prevention, search and rescue purposes, specialist training and evaluation, and technical evaluation and repair of control and communications systems.

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Radio Technique - Overview
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Here are some general tips for good aviation radio technique:

Listen before you transmit. Many times can get the information you want through ATIS or by monitoring the frequency. Except for a few situations where some frequency overlap occurs, if you hear someone else talking, attempting to transmit will be futile. You will probably jam ("step on") someone else's attempt to transmit, causing a need to repeat the call. If you have just changed frequencies, first pause and listen to make sure the frequency is clear.

Think before keying your transmitter. Know what you want to say and, if it is lengthy, (e.g., a flight plan or IFR position report), jot it down so you do not waste transmission time trying to remember what you need to say.

Position the microphone very close to your lips. After pressing the mike button, a slight pause may be necessary to be sure that the first word is transmitted. Speak in a normal conversational tone.

Be patient. When you release the transmit button, wait a few seconds before calling again. The controller or FSS specialist may be jotting down your number, looking for your flight plan, transmitting on a different frequency, or selecting the transmitter to your frequency.

Be alert to the sounds, or lack of sounds, in your receiver. Check your volume, recheck your frequency, and make sure your microphone is not stuck in the transmit position. Frequency blockage can occur for extended periods of time due to unintentional transmitter operation. This type of interference is commonly referred to as "stuck mike," and controllers may refer it in this manner when attempting to assign an alternate frequency. If the assigned frequency is completely blocked by this type of interference, use the procedures described for en route IFR radio frequency outage (see below) to establish or reestablish communications with ATC.

Be sure that you are within the performance range of your radio equipment, and also the ground station equipment. Remote radio sites do not always transmit and receive on all of a facility's available frequencies, particularly with regard to VOR sites where you may hear but not reach a ground station's receiver. Remember that higher altitude increases the range of VHF "line of sight" communications.

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Contact Procedures - Overview
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Initial Contact

The term "initial contact" or "initial callup" means the first radio call you make to a given facility, or the first call to a different controller or FSS specialist within a facility. Use the following format:

  • Who - Part 1 - State the name of facility you are calling (e.g., "Miami Center").
  • Who - Part 2 - State your full aircraft identification (as filed in the flight plan) (e.g., "Skylane 54321")
  • Where - State your position (e.g., "Over XYZ VOR").
  • What - State your request (e.g., "Request clearance into Class B airspace.")

Putting it all together:

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used for alignment Who-Part 1  Who-Part 2  Where You Are  What You Want used for alignment
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used for alignment Miami Center  Skylane 54321  Over XYZ VOR  Request clearance into Class B used for alignment
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If radio reception is reasonably assured, including your request, your position or altitude, or brief reports such as the phrase "with Information Charlie" (for ATIS) in the initial contact helps decrease radio frequency congestion. Use discretion, though, and do not overload the controller with information he does not need. If you do not get a response from the ground station, recheck your radios or use another transmitter, but keep the next contact short.

Initial Contact When Transmitting and Receiving Frequencies Differ

If you are attempting to establish contact with a ground station and you are receiving on a different frequency than that transmitted, be sure to indicate the VOR name or the frequency on which you expect a reply. Most FSSs and control facilities can transmit on several VOR stations in the area. Use the appropriate FSS name as indicated on charts. New York FSS transmits on the Kennedy, Hampton and Calverton VORTACs. If you are in the Calverton area, your initial call would be:

"New York Radio, Cessna three one six zero foxtrot, listening Calverton VOR."

If the chart indicates FSS frequencies above the VORTAC or in FSS communications boxes, transmit or receive on those frequencies nearest your location.

If you are unable to establish contact and you need to call any ground station, your call might be:

"Any (radio) (tower) (station), call Cessna three one six zero foxtrot on (frequency) or (VOR)."

If an emergency exists or you need assistance, say so immediately!

Subsequent Contacts and Responses to Callup from a Ground Facility

Use the same format as used for initial contact, except that if possible, you should state your message or request in the initial call. The ground station name may be omitted if the message requires an obvious reply and there is no possibility for misunderstanding. You should acknowledge all calls or clearances unless the controller or FSS specialist advises otherwise.

There are some occasions when the controller must issue time-critical instructions to other aircraft, and may be in a position to observe your response, either visually or on radar. If the situation demands your response, take appropriate action or immediately advise the facility of any problem. Acknowledge with one of the following words:

  • Wilco,,which means "I will comply."
  • Roger, which means "I have received and understood your last transmission."
  • Affirmative, which means "Yes"
  • Negative, which means "No" or
  • Other appropriate remark

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Working with ATC
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Overview

Air Route Traffic Control Centers (ARTCCs), known to pilots as "Centers," are capable of direct communications with IFR air traffic on certain frequencies. Maximum communications coverage is possible through the use of Remote Center Air/Ground (RCAG) sites comprised of both VHF and UHF transmitters and receivers. These sites are located throughout the US. Although they may be several hundred miles away from the ARTCC, they are remoted to the various ARTCCs by land lines or microwave links.

Since IFR operations are expedited through the use of direct communications, pilots are requested to use these frequencies strictly for communications pertinent to the control of IFR aircraft. Flight plan filing, en route weather, weather forecasts and similar data should be requested through FSSs, company radio, or appropriate military facilities capable of performing these services.

ATC Frequency Change Procedures

An ARTCC is divided into sectors. Each sector is handled by one controller or, in some cases, a team of controllers and has its own discrete sector frequency. As a flight progresses from one sector to another, ATC will ask the pilot to change to the appropriate sector frequency. ATC will use the following phraseology to instruct the pilot to make a frequency change:

(Aircraft Identification), contact (facility name or location name and terminal function) on (frequency) at (time, fix or altitude).

When advised by ATC to change frequencies, first acknowledge the instruction. If you select the new frequency without an acknowledgment, the controller's work load is increased because he or she has no way of knowing whether you received the instruction or have had radio communications failure.

If you are instructed to make the frequency change at a specific time, fix, or altitude, continue to monitor the frequency you are on until reaching the point specified for the frequency change. ATC will omit frequency change restrictions whenever pilot compliance is expected upon receipt. If there are no frequency change restrictions, therefore, you should select the new frequency as soon as possible after acknowledging the instruction. A delay in making the change could cause you to miss important information.

When you make the frequency change, change, you should first listen on the new frequency. If you hear someone else talking, attempting to transmit will "step on" (jam) someone else's attempt to transmit, causing a need to repeat the call and wasting time for everyone. Make sure the frequency is clear before you attempt to transmit.

Your initial call after being handed off to a new controller can be very brief. Examples:

With VFR Flight Following:Salt Lake Center, Skylane 54321, four thousand, five hundred, VFR.

On IFR Flight Plan:Jacksonville Center, Skylane 54321, five thousand, assigned heading two three zero.

Position Reports

To make an IFR position report, use the following phraseology:

(Name) CENTER, (aircraft identification), (position), (time), (time to next fix), (time to following fix). For example:

(Name) Center, (aircraft identification), estimating (reporting point and time) at (altitude or flight level) climbing (or descending) to (altitude or flight level).

Note that exact altitude or flight level means to the nearest 100 foot increment. Exact altitude or flight level reports on initial contact provide ATC with information required prior to using MODE C altitude information for separation purposes. At times, controllers will ask pilots to verify that altitude. The phraseology used will be:

"Verify at (altitude)."

In climbing or descending situations, controllers may ask pilots to "Verify assigned altitude as (altitude)." Pilots should confirm that they are at the altitude stated by the controller or that the assigned altitude is correct as stated. If this is not the case, they should inform the controller of the actual altitude being maintained or the different assigned altitude. Important: Pilots should not take action to change actual altitude or different assigned altitude to the altitude stated in the controller's verification request, unless the controller specifically authorizes a change.

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Call Signs
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Aircraft Call Signs

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).

It is very important to ensure use of correct call signs. Aircraft with similar call signs may be on the same frequency, and improper use of call signs can result in one pilot executing a clearance intended for another aircraft. To avoid this problem, never abbreviate your call sign on an initial contact, or at any time when other aircraft call signs you hear on the frequency have similar numbers/sounds or identical letters/numbers to those of your own aircraft (e.g., Cessna 6132F, Cessna 1622F, Baron 123F, Cherokee 7732F, etc.).

For example, 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 his 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.

Pilots must therefore be certain that aircraft identification is complete and correct before taking action on an ATC clearance. ATC will not abbreviate call signs of an air carrier or other civil aircraft having authorized call signs. ATC may initiate abbreviated call signs of other aircraft by using the prefix and the last three digits/letters of the aircraft identification after two-way communications have been established. The pilot may use the abbreviated call sign in subsequent contact with ATC.

When aware of similar/identical call signs, ATC will take action to minimize errors by emphasizing certain numbers/letters, repeating the entire call sign, repeating the prefix, or by asking pilots to use a different call sign temporarily. If you have any doubt as to whether a control instruction is intended for you, do not hesitate to make sure. Use the phrase, "Verify clearance for (your call sign) " to request clarification.

Ground Station Call Signs

When calling a ground station, begin with the name of the facility being called, followed by the type of the facility being called. The correct terms are as follows:

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Student Pilot Radio Identification

To help the student pilot acquire sufficient practical experience in the environment in which he or she will be required to operate, special procedures exist for student pilots who wish to receive additional assistance while operating in areas of concentrated air traffic. If you are a student pilot, you should identify yourself as such during the initial call to an FAA facility. For example:

"Dayton Tower, Fleetwing 1234, Student Pilot."

This special identification will alert ATC to provide the student pilot with any extra assistance and consideration needed. Though highly recommended, this procedure is not mandatory.

Air Ambulance Flights

Civilian air ambulance flights responding to medical emergencies (carrying patients, organ donors, organs, or other urgently needed lifesaving medical material) will be expedited by ATC when necessary. When expeditious handling is required, add the word "Lifeguard" in the remarks of the flight plan. In radio communication, these flights use the call sign "Lifeguard" followed by the aircraft type and registration letters/numbers. When requested by the pilot, ATC provides necessary notification to expedite ground handling of patients; when possible, however, this information should be passed in advance through non-ATC communications systems.

Extreme discretion is necessary in using the term "Lifeguard." It is intended only for those missions of an urgent medical nature and for use only for that portion of the flight requiring expedited handling. Similar provisions have been made for the use of "Air Evac" and "Med Evac" by military air ambulance flights, except that these military flights will receive priority handling only when specifically requested.

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Radio Malfunction Procedures
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Aircraft Radio Malfunctions

Inoperative Receiver. If you are approaching a towered airport and have reason to believe your transmitter works but your receiver is inoperative, remain outside or above the airport traffic area until you determine the direction and flow of traffic. Then you should advise the tower of your type aircraft, position, altitude, intention to land, and request that you be controlled with light signals (see below). When you are approximately 3 to 5 miles from the airport, advise the tower of your position and join the airport traffic pattern. From this point on, watch the tower for light signals. Thereafter, if a complete pattern is made, transmit your position downwind and/or turning base leg.

Inoperative Transmitter. If you are approaching a towered airport and have reason to believe your receiver works but your transmitter is inoperative, remain outside or above the airport traffic area until you can determine the direction and flow of traffic, then join the airport traffic pattern. Monitor the primary local control frequency as depicted on Sectional Charts for landing or traffic information, and look for a light signal addressed to your aircraft. During daylight hours, acknowledge tower transmissions or light signals be rocking your wings. At night, acknowledge by blinking the landing or navigation lights.

Inoperative Transmitter and Receiver. If you are approaching a towered airport and have reason to believe that your transmitter and receiver are both inoperative, remain outside or above the airport traffic area until you can determine the direction and flow of traffic. Then join the airport traffic pattern and maintain visual contact with the tower to receive light signals. During daylight hours, acknowledge tower transmissions or light signals by moving the ailerons or rudder. At night, acknowledge by blinking the landing or navigation lights.

If you experience radio failure prior to leaving the aircraft parking area, make every effort to have the equipment repaired. If you are unable to have the malfunction repaired, it is possible in some areas to call the tower by telephone and request authorization to depart without two-way radio communications. (Note: This procedure would not be authorized in areas such as the Washington DC Air Defense Identification Zone, or ADIZ, where two-way communications are required at all times. If the tower grants your request, you will receive departure information and instructed to monitor the tower frequency or watch for light signals, as appropriate. During daylight hours, acknowledge tower transmissions or light signals by moving the ailerons or rudder. At night, acknowledge by blinking the landing or navigation lights.

If radio malfunction occurs after departing the aircraft parking area (i.e., on the taxiway), watch the tower for light signals or monitor tower frequency. Note: Refer to 14 CFR 91.87 and 14 CFR 91.77 for additional information..

Light Gun Signals

An airport control tower uses the following procedures to issue control instructions to aircraft not equipped with radio, or those with inoperative radios. ATC personnel use a directive traffic control signal which emits an intense narrow light beam of a selected color (either red, white, or green) when controlling traffic by light signals.

Although the traffic signal light offers the advantage that some control may be exercised over nonradio ("NORDO") aircraft, pilots should be aware of the following disadvantages.

  • The pilot may not be looking at the control tower at the time a signal is directed toward him.
  • The directions transmitted by a light signal are very limited, since only approval or disapproval of a pilot's anticipated actions may be transmitted. No supplement or explanatory information may be transmitted except by the use of the "General Warning Signal," which advises the pilot to be on the alert.

Between sunset and sunrise, a "NORDO" pilot on the ground seeking to attract the attention of the control tower should turn on a landing light and taxi the aircraft into a position clear of the active runway. so that the landing light is visible to the tower. The landing light should remain on until appropriate signals are received from the tower.

During daylight hours, acknowledge tower transmissions or light signals by moving the ailerons or rudder. At night, acknowledge by blinking the landing or navigation lights. If a radio malfunction occurs after departing the parking area, watch the tower for light signals or monitor tower frequency.

The following table summarizes light gun signals.

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used for alignment Steady  Green  Cleared for Takeoff  Cleared to Land used for alignment
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used for alignment Alternating  Red/Green  Use Extreme Caution  Use Extreme Caution used for alignment
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ATC Radio Outages

ARTCCs normally have at least one back up radio receiver and transmitter system for each frequency which can usually be placed into service quickly with little or no disruption of ATC service. Occasionally, technical problems may cause a delay but switchover seldom takes more than 60 seconds. When it appears that the outage will not be quickly remedied, the ARTCC will usually request a nearby aircraft, if there is one, to switch to the affected frequency to broadcast communications instructions. It is important, therefore. that the pilot wait at least one minute before deciding that the ARTCC has actually experienced a radio frequency failure. When such an outage does occur. the pilot should, if workload and equipment capability permit, maintain a listening watch on the affected frequency while attempting to comply with the following recommended communications procedures.

  • If two-way communications cannot be established with the ARTCC after changing frequencies, a pilot should attempt to recontact the transferring controller for the assignment of an alternative frequency or other instructions.
  • When an ARTCC radio frequency failure occurs after two-way communications have been established, the pilot should attempt to reestablish contact with the center on any other known ARTCC frequency, preferably that of the next responsible sector when practicable, and ask for instructions. When the next normal frequency change along the route is known to involve another ATC facility, the pilot should contact that facility, if feasible, for instructions. If communications cannot be reestablished by either method, the pilot is expected to request communications instructions from the FSS appropriate to the route of flight.

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Emergency Locator Transmitter (ELT)
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General

Emergency Locator Transmitters (ELTs) are required for most general aviation airplanes (14 CFR 91.52). ELTs of various types have been developed as a means of locating downed aircraft. These electronic, battery-operated transmitters emit a distinctive downward sweep audio tone on 121.5 MHz and 243.0 MHz. If "armed" and subjected to crash forces, they are designed to automatically activate and continuously emit these signals. The transmitters will operate continuously for at least 48 hours over a wide temperature range. A properly installed and maintained ELT can expedite search and rescue operations and save lives.

Testing

ELTs should be tested in accordance with the manufacturer's instructions, preferably in a shielded or screened room to prevent the broadcast of signals which could trigger a false alert. When this kind of testing cannot be done, aircraft operational testing is authorized on 121.5 MHz and 243.0 MHz as follows.

  • Tests should be conducted only during the first five minutes after any hour. If operational tests must be made outside of this timeframe, they should be coordinated with the nearest FAA Control Tower or FSS.
  • Tests should be no longer than three audible sweeps.
  • If the antenna is removable, a dummy load should be substituted during test procedures.
  • Airborne tests of the ELT are not authorized.

False Alarms

Use caution should to prevent the inadvertent activation of your ELT in the air or while it is handled on the ground. Accidental or unauthorized activation will generate an emergency signal that cannot be distinguished from the real thing, which could lead to expensive and frustrating searches. A false ELT signal could also interfere with genuine emergency transmissions and hinder or prevent the timely location of crash sites. Frequent false alarms could also result in complacency and decrease the vigorous reaction that must be attached to all ELT signals.

Numerous cases of inadvertent activation have occurred as a result of aerobatics, hard landings, movement by ground crews, and aircraft maintenance. These false alarms can be minimized by monitoring 121.5 MHz and/or 243.0 MHz as follows.

  • Prior to engine shut down at the end of each flight.
  • When the ELT is handled during installation or maintenance.
  • When maintenance is being performed in the vicinity of the ELT.
  • When the aircraft is moved by a ground crew.

If you hear an ELT signal, turn off the ELT to determine if it is transmitting. If it has been activated, maintenance might be required before the unit is returned to the "ARMED" position.

Inflight Monitoring

While you are flying, you might want to use your second radio (if installed) to monitor 121.5 MHz and/or 243.0 MHz to assist in identifying possible emergency ELT transmissions. If you hear an ELT signal, report the following information to the nearest air traffic facility.

  • Your position at the time the signal was first heard.
  • Your position at the time the signal was last heard.
  • Your position at maximum signal strength.
  • Your flight altitudes and frequency on which the emergency signal was heard - 121.5 MHz or 243.0 MHz.

If possible, give these positions relative to a navigation aid. If the aircraft has homing equipment, provide the bearing to the emergency signal with each reported position.

Search and Rescue Satellite (SARSAT)

Search and rescue is a lifesaving service provided through the combined efforts of the federal agencies signatory to the national search and rescue plan, and the agencies responsible for search and rescue in each state. Operational resources are provided by the US Coast Guard, Department of Defense components, the Civil Air Patrol, the Coast Guard Auxiliary, state, county, and local law enforcement and other public safety agencies.

The introduction of the SARSAT system enhances the effectiveness of search and rescue. SARSAT also amplifies the importance of ensuring that your ELT remains silent, except for authorized testing or in an actual emergency. Search and rescue missions launched because of a false ELT signal are costly and unnecessary. Search and rescue services include search for missing aircraft, survival aid, rescue, and emergency medical help for the occupants after an accident site is located.

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Radio Communication References
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Phonetic Alphabet

The International Civil Aviation Organization (ICAO) phonetic alphabet is used in aviation communications to ensure clear understanding of critical information, such as call signs. Use the phonetic alphabet when identifying your 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 sounds during adverse communications conditions.

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used for alignment L  o - o o  Lima  LEE-MAH used for alignment
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used for alignment M  - -  Mike  MIKE used for alignment
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used for alignment N  - o  November  NO-VEM-BER used for alignment
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used for alignment O  - - -  Oscar  OSS-CAH used for alignment
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used for alignment P  o - - o  Papa  PAH-PAH used for alignment
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used for alignment R  o - o  Romeo  ROW-ME-OH used for alignment
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used for alignment S  o o o  Sierra  SEE-AIR-RAH used for alignment
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used for alignment T  -  Tango  TANG-GO used for alignment
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used for alignment U  o o -  Uniform  YOU-NEE-FORM used for alignment
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used for alignment V  o o o -  Victor  VIK-TAH used for alignment
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used for alignment W  o - -   Whiskey  WISS-KEY used for alignment
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used for alignment X  - o o -  Xray  ECKS-RAY used for alignment
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used for alignment Y  - o - -  Yankee  YANG-KEY used for alignment
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used for alignment Z  - - o o  Zulu  ZOO-LOO used for alignment
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used for alignment 1  o - - - -  One  WUN used for alignment
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used for alignment 2  o o - - -  Two  TOO used for alignment
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used for alignment 3  o o o - -  Three  TREE used for alignment
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used for alignment 4  o o o o -  Four  FOW-ER used for alignment
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used for alignment 5  o o o o o  Five  FIFE used for alignment
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used for alignment 6  - o o o o  Six  SIX used for alignment
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used for alignment 7  - - o o o  Seven  SEV-EN used for alignment
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used for alignment 8  - - - o o  Eight  AIT used for alignment
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used for alignment 9  - - - - o  Nine  NIN-ER used for alignment
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used for alignment 0  - - - - -  Zero  ZEE-RO used for alignment
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Figures (Numbers)

Aviation communications for figures, or numbers, uses hundreds and thousands in round numbers for ceiling heights. Upper wind levels up to 9900 are expressed as follows.

  • 500 - "five hundred"
  • 4500 - "four thousand five hundred"
  • 10,000 - "one zero thousand"
  • 13,500 - "one three thousand five hundred"
  • V12 - "Victor twelve"
  • J533 - "J five thirty-three"
  • 10 - "one zero"
  • 122.1 - "one two two point one"

Note: ICAO procedures require the decimal point be spoken as "decimal," and the FAA will honor such usage by military aircraft and all other aircraft required to use ICAO Procedures.

Altitudes and Flight Levels

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

  • 12,000 - "one two thousand"
  • 12,500 - "one two thousand five hundred"

At and above 18,000 feet MSL (FL 180) say the words, "flight level" followed by the separate digits of the flight level. For example:

  • 190 - " flight level one niner zero"

Directions

The three digits of bearing, course, heading or wind direction should always be magnetic. The word "true" must be added when it applies. For example:

  • (magnetic course) 005 - "zero zero five"
  • (true course) 050 - "zero five zero true"
  • (magnetic bearing) 360 - "three six zero"
  • (magnetic heading) 100 - "one zero zero"
  • (wind direction) 220 - "two two zero"

Speeds

The separate digits of the speed followed by the word "KNOTS." Controllers may omit the word "KNOTS" when using speed adjustment procedures, e.g., " reduce/increase speed to two five zero" For example:

  • (speed) 250 - "two five zero knots"
  • (speed) 190 - "one niner zero knots"
  • (mach number) 1.5 - "mach one point five"
  • (mach number).64 - "mach point six four"

Time

Aviation uses Greenwich Mean Time (GMT), now called Universal Coordinated Time (UTC) or "Zulu," (Z) for all operations. To convert from Standard Time to Zulu:

--Eastern Standard Time - Add 5 hours

--Central Standard Time - Add 6 hours

--Mountain Standard Time - Add 7 hours

--Pacific Standard Time - Add 8 hours

For Daylight Savings Time, subtract one hour from each of the conversion factors listed above.

Aviation also uses the 24-hour clock system in radio communications. The hour is indicated by the first two figures and the minutes by the last two figures of the time description. For example:

  • 0000 - zero zero zero zero
  • 0920 - zero niner two zero

Time may be stated in minutes only (two figures) in radio communications when no misunderstanding is likely to occur. 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 eight seconds are stated as the preceding quarter minute; fractions of a quarter minute of eight seconds or more are stated as the succeeding quarter minute. For example:

0929:05 - time zero niner two niner

0929:10 - time zero niner two niner and one-quarter

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About This Series
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The purpose of this series of Federal Aviation Administration (FAA) Aviation Safety Program publications is to provide the aviation community with safety information that is informative, handy, and easy to review. Many of the publications in this series summarize material published in various FAA advisory circulars, handbooks, other publications, and various audiovisual products developed by the FAA and used in its Aviation Safety Program.

Some of the ideas an materials in this series were developed by the aviation industry. The FAA acknowledges the support of the aviation industry and its various trade and membership groups in the production of this series.

Comments regarding these publications should be directed to the National Aviation Safety Program Manager, Federal Aviation Administration, Flight Standards Service.

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