Air Traffic Control Communication Procedures

• The safety of air traffic control relies on effective pilot and air traffic controller communication.
• Miscommunication can lead to aircraft accidents, so pilots and controllers must follow proper communication procedures.
• Accidents and incidents in the last 50 years resulted from communication errors.
• Pilots and controllers must thoroughly understand communication procedures and phraseology.
• English is the international language for ATC communications per the International Civil Aviation Organization (ICAO).
• Controllers should use standard language given foreign pilots may not fully grasp English.
• Phraseology and slang not approved by ICAO or the FAA should never be used with any pilot.
• Standard procedures reduce miscommunication risks.

Radio Communication History

• Radio has been the main way pilots and controllers in the U.S. communicate since 1936, when it was installed in Cleveland.
• The basics of radio communication are still the same, even though equipment changed.

Simplex vs. Duplex

• One-way communication existed in the early air traffic control system.
• Controllers communicated with pilots with simplex systems but not vice versa.
• Airlines hesitated to install transmitters because of bulky, heavy radio equipment, so planes only had receivers.
• Ground-based navaids started allowing controllers to transmit using navigation aid frequencies.
• Controllers could transmit using the navaid but advancements allowed pilots to still use it for navigation.
• Aircraft operators added transmitting equipment when radio benefits became clear.
• This equipment operated on different frequencies to prevent interference with ground-based navaids which increased aircraft weight and control tower costs.
• Aircraft without transceivers could not communicate with control towers during the transition from navaid communication.
• As an interim solution; Control towers got receivers, planes got transmitters and ground-based navaids handled tower-to-aircraft communication and radios handled aircraft-to-tower.
• Aircraft transmitters used different frequencies than ground-based navaids to stop interference, this is called duplex communications.
• Duplex systems are still used, especially at FAA flight service stations that receive on one frequency and transmit to aircraft on a local VORTAC.

Simplex Communication

• Pilots can communicate with controllers using one discrete frequency.
• This system is now used in ATC, known as simplex.
• Every ATC facility in the U.S. mainly uses simplex communication.

Frequency Assignments

• International agreements allocate radio frequency bands, mainly in the high (HF), very high (VHF), and ultra-high (UHF) spectrums.
• High frequencies are used for long-range communication because they aren't restricted to line of sight, only a few ATC facilities such as ARTCCs use them.
• Most U.S. ATC facilities use both VHF and UHF for air-to-ground communication.
• Military airplanes use UHF radio equipment, while VHF is used by both military and civilian aircraft.
• The Federal Communications Commission (FCC) assigns ATC frequencies with FAA help.
• The FCC often assigns the same frequency to two or more ATC facilities due to the limited number of frequencies.
• The FCC must carefully check for potential interference before assigning frequencies because radio transmissions from high-altitude aircraft go further than lower ones.

Radio Operation

• Most air traffic controllers use radio gear for their jobs.
• Equipment complexity ranges with the facility's capabilities.
• Each controller gets radio frequencies for pilot communication and telephone access to communicate with nearby controllers.
• Sophisticated voice switching systems are installed in ATC facilities to allow easy communication.
• Most controllers have boom mikes and headsets, others use standard microphones, speakers, or telephone handsets (TELCO).
• Each controller selects a channel to talk to other controllers or pilots, messages route through an overhead speaker.
• Most facilities are set up so any controller can use any assigned frequency.

Standard Phraseology for Verbal Communications

• Controllers must use standard phraseology and procedures from ICAO and the FAA to avoid confusion.
• Controllers should use this format when talking to pilots or each other;
  • Aircraft/controller identification
  • Caller identification
  • Message content according to FAA standards
  • Termination with controller initials
• Terminating with initials simplifies controller identification if there is a subsequent investigation.
• ICAO and FAA have approved standard pronunciations of letters and numbers due to the risk of misunderstandings with spoken words.
• Controllers should use these pronunciations when communicating with pilots or other controllers.
• Air traffic controllers must use standardized phraseology.
• Numbers must be spoken separately unless a group pronunciation is required.

Standard Number/Letter Pronunciation

• 0 is pronounced "Zee-ro"
• 1 is pronounced "Wun"
• 2 is pronounced "Too"
• 3 is pronounced "Tree"
• 4 is pronounced "Fow-er"
• 5 is pronounced "Fife"
• 6 is pronounced "Six"
• 7 is pronounced "Sev-en"
• 8 is pronounced "Ait"
• 9 is pronounced "Nin-er"
• A is pronounced "Al-fah"
• B is pronounced "Brah-voh"
• C is pronounced "Char-lee"
• D is pronounced "Del-ta"
• E is pronounced "Eck-oh"
• F is pronounced "Foks-trot"
• G is pronounced "Golf"
• H is pronounced "Hoh-tell"
• I is pronounced "In-dee-ah"
• J is pronounced "Jewlee-ett"
• K is pronounced "Key-loh"
• L is pronounced "Lee-mah"
• M is pronounced "Mike"
• N is pronounced "Nov-em-ber"
• O is pronounced "Oss-cah"
• P is pronounced "Pah-pah"
• Q is pronounced "Key-beck"
• R is pronounced "Row-me-oh"
• S is pronounced "See-air-ah"
• T is pronounced "Tang-go"
• U is pronounced "You-nee-form"
• V is pronounced "Vik-tah"
• W is pronounced "Wiss-key"
• X is pronounced "Ecks-ray"
• Y is pronounced "Yang-key"
• Z is pronounced "Zoo-loo"

Pronouncing Number Groups

• 15, Separate: "One five" Group: "Fifteen"
• 132, Separate: "One three two" Group: "One thirty-two"
• 569, Separate: "Five six niner" Group: "Five sixty-nine"
• Enunciate each digit separately for serial numbers.

Altitudes, Flight Levels, Descents, Decision Heights & Time

• Altitudes are measured above mean sea level (MSL), except for cloud ceilings (above ground level/AGL).
• Tell pilots that the altitude is above ground level when giving them an AGL reading.
• Altitudes are separated by thousands and hundreds; pronounce digits separately for thousands, group for hundreds:
• 3,900 Three thousand niner hundred
• 12,500 One two thousand five hundred
• 17,000 One seven thousand
• Flight levels are preceded by "flight level" and each number should be said separately:
• Flight level 180 Flight level one eight zero
• Flight level 390 Flight level three niner zero
• Minimum descent or decision height altitudes on approach charts are prefixed with the type of altitude, and each number is said separately:
• MDA 1,950 Minimum descent altitude one niner five zero
• DH 620 Decision height six two zero
• A common time system is needed for ATC.
• The FAA and ICAO have agreed all ATC facilities must use coordinated universal time (UTC), previously known as Greenwich mean time (GMT).
• The use of UTC worldwide avoids time zone questions and eliminates "a.m."/"p.m." with a 24-hour clock, and avoid "o'clock."
• A number with fewer than four digits should be prefixed with a zero.
• A.M. times stay the same, P.M. times have twelve added to them.
• 6:20 a.m. 0620
• 6:20 p.m. 1820
• Local time is converted to UTC by adding or subtracting the time difference.

UTC Conversions

• Eastern standard time (EST) Conversion: +5 hours
• Eastern daylight time (EDT) Conversion: +4 hours
• Central standard time (CST) Conversion: +6 hours
• Central daylight time (CDT) Conversion: +5 hours
• Mountain standard time (MST) Conversion: +7 hours
• Mountain daylight time (MDT) Conversion: +6 hours
• Pacific standard time (PST) Conversion: +8 hours
• Pacific daylight time (PDT) Conversion: +7 hours
• Alaskan standard time (AST) Conversion: +9 hours
• Alaskan daylight time (ADT) Conversion: +8 hours
• Convert local time to a 24-hour clock, and add the required time difference to convert it to UTC.
• Subtract the appropriate time difference, and convert from a 24-hour to a 12-hour format to convert from UTC to local time.
• Append "zulu" to UTC time, or "local" to local time to prevent confusion.
• Give time by saying each digit separately:
• 6:20 a.m. gives Time zero six two zero zulu
• 1:35 p.m. gives Time one three three five zulu

Altimeter Settings

• Pilots need barometric pressure for accurate altitude reading.
• Announce the altimeter reading by saying each digit and precede with the word "altimeter":
• 29.92 gives Altimeter two niner niner two
• 20.16 Altimeter two zero one six
• When giving altimeter settings to foreign pilots, be aware pilots from countries that use the metric system measure pressure in millibars and it's their responsibility to do the conversions or ask for the metric readings.

Wind Direction, Velocity, Navigation and Frequencies

• Wind direction is measured relative to magnetic north, rounded to the nearest 10°.
• A 360° wind comes north to south, and a 90° wind comes from the east.
• International wind velocity is measured in knots, where 1 knot equals 1.15 miles per hour.
• Wind data is always preceded by the word "wind," and each number's digits are read separately:
• Wind from the north at 15 knots, will be Wind three six zero at one five
• Wind from the east at 10 knots with gusts to 25 knots, will be Wind zero niner zero at one zero gusts to two five
• If equipment is not working, wind uses "estimated" and if it's changing, "variable" is used for direction and "gusts" for peak speed:
• Wind one five zero variable at one two gusts to three five
• Headings are measured in reference to magnetic north, must have three digits to do this a zero is added if required, use the word "heading":
• 005° Heading zero zero five
• 090° Heading zero niner zero
• 255° Heading two five five
• Runway numbers correspond to the runway's magnetic heading, rounded to the nearest 10°.
• The remaining digit is dropped, for example, a heading of 360° makes runway 36 where the opposite direction on that heading is 18.
• Each runway number is said individually and preceded by "runway," suffixes like "L," "R," or "C" are added for parallel runways:
• Runway Heading 090° Runway Number 9 Runway niner
• Runway Heading 261° Runway Number 26 Runway two six
• Runway Heading 138° Runway Number 14R Runway one four right
• Los Angeles International Airport has 4 parallel runways designated; 25L, 25R, 24L, and 24R.
• Say radio frequencies separately, and VHF uses 25 kHz spacing.
• The next usable number above 119.600 is 119.625 that's followed by 119.650, 119.675, and 119.700.
• The first number after the decimal is read, next number not if it is zero, never read the third since it can only be a zero or five.
• Low Frequency/Medium Frequency used by nondirectional beacons are always whole numbers, VHF and UHF use "point" for the decimal.
• "Kilohertz" suffixes L/MF frequencies:
• 119.600 mHz is One one niner point six
• 343.000 mHz is Three four three point zero
• 123.050 mHz is One two three point zero five
• The FAA and ICAO has differing standards for comms; ICAO uses "decimal" instead of "point, 123.050 would be One two three decimal zero five.
• MLS and TACAN channels use channel numbers are are said separately and they are not given explicitly:
• MLS channel 530 is M-L-S channel five three zero
• TACAN channel 90 is TACAN channel niner zero

Speeds, Facilities and Routes

• Aircraft speeds, like wind speeds, use knots, and pilots must be aware that requested speeds are in knots.
• 100 knots is about 115 miles per hour.
• To express speeds, each digit is said separately, and followed by the word "knots":
• Speed 250 is Two five zero knots
• Speed 95 is Niner five knots
• ATC facilities are named by city and facility type:
• Facility Type Local control is Tower
• Facility Type Ground control is Ground
• Facility Type Clearance delivery is Clearance
• The names of nearby cities are used in centers and approach controls.
• Navy airports are marked with "navy."
• Airways are named using the route ID in group form:
• Route V12 is Victor twelve
• Route J97 is Jay ninety-seven
• VOR radials are prefixed with the VOR name, and numbers must be said separately:
• Three five five bearing from the Pully radio beacon
• Intersections located along an airway use a five-letter intersection name, or VOR radial and DME from that VOR:
• Staks intersection
• Flite waypoint
• Communications procedures for air traffic controllers are in the Air Traffic Control Handbook.
• Sticking to procedures cuts confusion and issues.

Clearances

• Airplanes must be cleared (C) before joining.
• A clearance allows a pilot to go to a point or do something specific.
• When giving a clearance or teaching a control, the controller must find the aircraft and give the command to land or take off.:
• Phraseology United seven twelve runway two four cleared for takeoff translates to Authorizes pilot to take off using runway 24.
• Phraseology Beech eight delta mike, after departure, turn left and proceed direct to the Boiler VOR, runway one zero cleared for takeoff. translates to Clearance directs pilot to turn left and proceed to Boiler VOR.
• Examples of other phraseology are; Delta one ninety-one, after departure turn right heading one two zero, runway three five cleared for takeoff, American nine twenty-one cleared to land runway niner, Aztec seven eight one cleared for touch and go runway two three, Mooney three six charlie cleared for stop and go runway five and Sport zero two romeo cleared for low approach runway three two.