Airport Air Traffic Control Communications PDF

Airport Air Traffic Control Communications / 191 The safe operation of the nation’s air traffic control system ultimately depends on reliable and accurate communication between pilots and air traffic control- lers. Virtually every instruction, procedure, or cleara...

Airport Air Traffic Control Communications / 191 The safe operation of the nation’s air traffic control system ultimately depends on reliable and accurate communication between pilots and air traffic control- lers. Virtually every instruction, procedure, or clearance used to separate or assist aircraft relies on written or verbal communication. Any miscommunica- tion between participants in the air traffic control system might contribute to or even be the direct cause of an aircraft accident with a subsequent loss of life. For this reason, proper and correct communications procedures must be observed by both pilots and controllers. Many of the accidents and incidents that have occurred over the last fifty years can be attributed to improper or misunderstood communications. Although many improvements to the air traffic control communications system have made it less reliant on verbal or written communication, pilots and con- trollers will continue to rely on human communication well into the twenty-first century. Thus, controllers must possess a proper understanding of communica- tions procedures and phraseology. American pilots and controllers are fortunate that the International Civil Aviation Organization (ICAO) has designated English as the international lan- guage for ATC communications worldwide. This standard reduces the number of words and communications procedures that American controllers need to learn. However, air traffic controllers should realize that although foreign pilots are able to communicate using English, they probably do not have full com- mand of the language. Thus, phraseology and slang not approved by ICAO or the FAA should never be used when communicating with foreign pilots. It is also recommended that standard phraseology be used when communicating with American pilots or controllers. Using standard procedures will help reduce the risk of miscommunication. Radio Communication Ever since radio communications equipment was installed in the Cleveland, Ohio control tower in 1936, radio has become the primary means of pilot– controller communication in the U.S. air traffic control system. Although the type of radio equipment has since changed, the basic principles of radio com- munication remain the same today. Simplex The earliest type of radio communication used in the air traffic control system versus was one way. Controllers could communicate with pilots, but not vice versa. Duplex Since the required radio equipment in those early years was quite bulky and heavy, airlines were reluctant to install both a navigation receiver and a com- munications transmitter on each aircraft. Thus, most aircraft were equipped only with a navigation receiver. Ground-based navaids were eventually modified to permit controllers to transmit instructions using the navigation aid frequencies. At first, this com- munication rendered the navaid useless while the controller was transmitting, 192 / CHAPTER 4 but later advances permitted the controller to transmit using the navaid while still allowing the pilot to use the ground station for navigation. As the benefits of radio communication became increasingly evident, aircraft operators chose to add transmitting equipment to their planes. The equipment operated on a different set of frequencies to eliminate any possible interference with the ground-based navaids. This development created its own set of problems, however. The addition of a separate transmitter and receiver markedly increased the weight of the aircraft, and adding separate transmitters and receivers in each control tower required an additional expenditure. Fur- thermore, during the transition from the navaid-based communication system, aircraft not equipped with transceivers would be unable to communicate with the control towers. An interim solution was to install receiving equipment in the control towers and transmitting equipment in the aircraft. This system still used the ground-based navaids for tower-to-aircraft communication but used the newly installed radios for aircraft-to-tower communication. To eliminate navaid interference, the aircraft transmitters used a different frequency from that used by the ground-based navaids. This two-frequency system is known as duplex communications (see Figure 4–1). Duplex was used in the air traffic control system for many years and is still used in some parts of the United States. In particular, FAA flight service stations are usually equipped to receive on one frequency while transmitting to the aircraft over a local VORTAC. The duplex system has disadvantages, how- ever, that spurred the development of a radio system that would permit pilots Separate frequency Transmitter Receiver Figure 4–1. Duplex transmission principles.  Airport Air Traffic Control Communications / 193 Same frequency Transmitter/receiver Figure 4–2. Simplex transmission principles. to communicate with controllers using one discrete frequency. This system was finally implemented within the ATC system and is known as simplex commu- nications (see Figure 4–2). For the most part, every ATC facility in the United States relies primarily on simplex communications. Frequency Various international agreements allocate certain radio frequency bands for use Assignments in aeronautical communications. These frequency bands exist primarily in the high (HF), very high (VHF), and ultra-high (UHF) spectrums. High frequencies are primarily used for long-range communication, since these frequencies are not line of sight and can follow the curvature of the Earth. Only a few ATC facilities, such as ARTCCs with oceanic responsibility, find a need to use these frequencies. Most U.S. ATC facilities use both VHF and UHF for routine air-to-ground communication. UHF radio equipment is primarily used by military aircraft, whereas VHF is used by both military and civilian aircraft. The frequencies used in ATC communications are assigned by the Federal Communications Commission (FCC) in cooperation with the FAA. Since there is not a sufficient number of available frequencies in either the VHF or UHF spectrum to permit every ATC facility to operate using a separate frequency, the FCC often assigns the same frequency to two or more ATC facilities. Because the radio trans- missions from high-altitude aircraft travel farther than those from low-flying aircraft, the FCC must carefully determine any potential interference problems before assigning these frequencies. 194 / CHAPTER 4 To simplify the task of assigning frequencies, the FCC has assigned these blocks of VHF bands for the following uses: Frequencies Use 108.000–117.950 Navigation aids 118.000–121.400 Air traffic control 121.500 Emergency search and rescue 121.600–121.925 Airport utility and ELT test 121.950 Aviation instructional and support 121.975 FSS private aircraft advisory 122.000–122.050 En route flight advisory service (EFAS) 122.075–122.675 FSS private aircraft advisory 122.700–122.725 UNICOM 122.750 Aircraft air-to-air 122.775 Aviation instruction and support 122.800 UNICOM 122.825 Domestic VHF 122.850 Multicom 122.875 Domestic VHF 122.900 Multicom 122.925 Multicom 122.950 Unicom 122.975–123.000 Unicom 123.050–123.075 Unicom 123.100 Aeronautical search and rescue 123.125–123.275 Flight test stations 123.300 Aviation support 123.325–123.475 Flight test stations 123.500 Aviation support 123.525–123.575 Flight test stations 123.600–123.650 FSS air carrier advisory 123.675–128.800 Air traffic control 126.200 Air traffic control (military common) 128.825–132.000 Domestic VHF (operational control) 132.025–136.975 Air traffic control Radio Most air traffic controllers use radio equipment to perform their ATC duties. Operation This equipment may be either fairly simple or very complex, depending on the capabilities of the facility. In general, each controller is assigned one or more radio frequencies for communications with pilots and has access to telephone equipment that permits communication with other controllers in the same  Airport Air Traffic Control Communications / 195 facility or in adjacent facilities. The design of the voice switching system installed in most ATC facilities is sophisticated enough to permit such communication effortlessly. Most controllers are outfitted with a boom mike and headset assembly that permits them to move freely around the facility while still remaining in contact with the pilots. Other controllers may use standard microphones and speakers or telephone handsets provided by the local telephone company (which is known throughout the FAA by the generic term TELCO). Each controller has a switching panel to choose whether to communicate with other controllers or to the pilot over the radio. The system is designed so that when the controller is communicating on one particular channel, any message sent to him or her on either the radio or another landline is routed through an overhead speaker. Most facilities are equipped such that every frequency assigned to that facility can be used by any controller there. Standard To ensure that miscommunication is kept to a minimum, it is imperative that Phraseology controllers use the standard phraseology and procedures that have been recom- for Verbal mended by ICAO and the FAA. When communicating with pilots or other Communica- controllers, a controller should always use the following message format: tions 1. Identification of the aircraft or controller being contacted. This serves to alert the intended receiver of the upcoming transmission. 2. Identification of the calling controller. This serves to identify who is initiating the communication. 3. The contents of the message. The message format should conform to standards approved by the FAA. 4. Termination. In communications with another ATC facility, the message should be terminated with the controller’s assigned operating initials. This procedure simplifies identification of the controller if a subsequent investigation is necessary. Certain letters and numbers may sound similar to each other when spoken over low-fidelity radio or telephone equipment. In addition, accents and dialects may make it difficult to discern and identify the exact content of a message. To alleviate this problem, a standard for pronunciation of letters and numbers has been approved by ICAO and adopted by the FAA. This standard is presented in Table 4–1. The standardized pronunciations should be used by controllers whenever communicating with pilots or other controllers. Air traffic control- lers should also use the following standardized phraseology when passing along control instructions or various information to pilots or to other controllers. Numbers Each number should be enunciated individually unless group form pronunciation is stipulated. For example: Group Form Individual Number Pronunciation Pronunciation 1 One One 10 Ten One zero 196 / CHAPTER 4 Table 4–1. Standard Phraseology for Numbers and Letters Character Word Pronunciation 0 Zero Zee-ro 1 One Wun 2 Two Too 3 Three Tree 4 Four Fow-er 5 Five Fife 6 Six Six 7 Seven Sev-en 8 Eight Ait 9 Nine Nin-er A Alpha Al-fah B Bravo Brah-voh C Charlie Char-lee D Delta Del-ta E Echo Eck-oh F Foxtrot Foks-trot G Golf Golf H Hotel Hoh-tell I India In-dee-ah J Juliett Jewlee-ett K Kilo Key-loh L Lima Lee-mah M Mike Mike N November Nov-em-ber O Oscar Oss-cah P Papa Pah-pah Q Quebec Key-beck R Romeo Row-me-oh S Sierra See-air-ah T Tango Tang-go U Uniform You-nee-form V Victor Vik-tah W Whiskey Wiss-key X X-ray Ecks-ray Y Yankee Yang-key Z Zulu Zoo-loo  Airport Air Traffic Control Communications / 197 Group Form Separate Number Pronunciation Pronunciation 15 Fifteen One five 132 One thirty-two One three two 569 Five sixty-nine Five six niner Unless otherwise specified, when serial numbers are pronounced, each digit should be enunciated individually. Altitudes Unless otherwise specified, every altitude used in the ATC system is measured above mean sea level (MSL). The only routine exception is cloud ceilings, which are measured above ground level (AGL). A controller who must issue an AGL altitude to a pilot should advise the pilot that the altitude is above ground level. Altitudes should be separated into thousands and hundreds, and the thousands should be pronounced separate from the hundreds. Each digit of the thousands number should be enunciated individually, whereas the hundreds should be pronounced in group form: Altitude Pronunciation 3,900 Three thousand niner hundred 12,500 One two thousand five hundred 17,000 One seven thousand Flight Levels Flight levels should be preceded by the words “flight level,” and each number should be enunciated individually: Flight Level Pronunciation 180 Flight level one eight zero 390 Flight level three niner zero Minimum Descent or Decision Height Altitudes Minimum descent or decision height altitudes published on instrument approach procedure charts should be prefixed with the type of altitude, and each number in the altitude should be enunciated individually: Altitude Pronunciation MDA 1,950 Minimum descent altitude one niner five zero DH 620 Decision height six two zero Time Since numerous ATC procedures require the use of time, a common sys- tem of time measurement is essential to the safe operation of the ATC system. The FAA and ICAO have agreed that local time is not to be used within the ATC system. Instead, every ATC facility around the world must use the same 198 / CHAPTER 4 GMT – 8 GMT – 7 GMT – 6 GMT – 5 hours hours hours hours 9:00 A.M. 10:00 A.M. 11:00 A.M. 12:00 P.M. Pacific Mountain Central standard standard Eastern standard standard time time time time Pacific standard Mountain standard Central standard Eastern standard time meridian time meridian time meridian time meridian 120° 105° 90° 75° Figure 4–3. Time zones across the United States. time standard, known as coordinated universal time (UTC). UTC is the same as local time in Greenwich, England, which is located on the 0° line of longitude, also known as the prime meridian. UTC was previously known as Greenwich mean time (GMT). The use of UTC around the world eliminates the question of which time zone a facility or aircraft is located in (see Figure 4–3). In addition, UTC eliminates the need for “a.m.” and “p.m.” by using a 24-hour clock system. UTC is always issued as a four-digit number, and the word “o’clock” is never pronounced. The conversion from a 12-hour clock to a 24-hour clock is fairly simple: Any time that has fewer than four digits should be prefixed with a zero. Any time between midnight and noon (a.m.) is not converted to a 24-hour clock. Any time between noon and midnight (p.m.) always has twelve hours added to it to differentiate it from a.m. time. For example, 6:20 a.m. becomes 0620, and 6:20 p.m. becomes 1820. Local time is converted to UTC by either adding or subtracting the number of hours indicated in the following chart:  Airport Air Traffic Control Communications / 199 Time Zone Difference Eastern standard time (EST) 5 hours Eastern daylight time (EDT) 4 hours Central standard time (CST) 6 hours Central daylight time (CDT) 5 hours Mountain standard time (MST) 7 hours Mountain daylight time (MDT) 6 hours Pacific standard time (PST) 8 hours Pacific daylight time (PDT) 7 hours Alaskan standard time (AST) 9 hours Alaskan daylight time (ADT) 8 hours To convert from local time to UTC, convert the local time to a 24-hour clock, and then add the required time difference. To convert from UTC to local time, subtract the difference and convert from a 24-hour to a 12-hour format. For example: 4:35 a.m. (EST) is 0435 (EST), which is 0935 (UTC) 9:13 p.m. (PDT) is 2113 (PDT), which is 0413 (UTC) 1125 (UTC) is 0425 (MST), which is 4:25 a.m. (MST) To prevent any confusion when issuing time to the pilot, the controller should suffix any UTC time with the word “zulu” and any local time with the word “local.” Any issuance of time should also be preceded by the word “time.” When issuing time, the controller should enunciate each digit individually: Time (12-hour clock) Time (24-hour clock) Pronunciation 6:20 a.m. 0620 Time zero six two zero zulu 1:35 p.m. 1335 Time one three three five zulu Altimeter Settings The pilot must be issued the proper barometric pressure so that the aircraft’s altimeter can be properly adjusted to indicate altitude above mean sea level. The controller should issue these altimeter settings by individually enunciating every digit without pronouncing the decimal point; the altimeter setting should be preceded by the word “altimeter”: Altimeter Setting Pronunciation 29.92 Altimeter two niner niner two 20.16 Altimeter two zero one six Care should be taken when issuing altimeter settings to foreign pilots. Pilots from countries that have converted to the metric system no longer measure barometric pressure in inches of mercury but in millibars. It is the foreign pilot’s responsibility to convert the issued altimeter setting to millibars or to request a metric altimeter setting from the controller.  200 / CHAPTER 4 Qualimetrics, Inc. Figure 4–4. A digital wind direction and velocity Figure 4–5. An analog wind direction and velocity indicator. indicator. Wind Direction and Velocity Wind direction at airports is always determined in reference to magnetic north and indicates the direction that the wind is blowing from. The direction is always rounded off to the nearest 10°. Thus, a wind blowing from north to south is a 360° wind; a wind from the east is a 90° wind. The international standard for measuring wind velocity requires that wind speeds be measured in knots; 1 knot equals approximately 1.15 miles per hour. Wind direction and velocity information is always preceded by the word “wind,” with each digit of the wind direction enunciated individually. The wind direction is then followed by the word “at” and the wind velocity in knots, with each digit enunciated individually. If the wind measurement devices (see Figures 4–4 and 4–5) are inoperative, the wind speed and direction are preceded by the word “estimated.” If the wind direction is constantly changing, the word “vari- able” is suffixed to the average wind direction. If the wind velocity is constantly changing, the word “gusts” and the peak speed are suffixed to the wind speed. Here are some examples: Wind Direction Wind Speed Pronunciation From the north 15 knots Wind three six zero at one five From the east 10 knots with Wind zero niner zero at one occasional gusts zero gusts to two five to 25 knots Variable from 12 knots with Wind one five zero variable at the southeast occasional gusts one two gusts to three five to 35 knots  Airport Air Traffic Control Communications / 201 Wind Direction Wind Speed Pronunciation Estimated from Estimated at Estimated wind two three the southwest 15 knots zero at one five Headings Aircraft headings are also measured in reference to magnetic north. If the heading contains fewer than three digits, it should be preceded by a sufficient number of zeros to make a three-digit number. Aircraft headings should always be preceded by the word “heading,” with each of the three digits enunciated individually. Here are some examples: Heading Pronunciation 005° Heading zero zero five 090° Heading zero niner zero 255° Heading two five five Runway Numbers Runways are also numbered in reference to their magnetic heading. The runway’s number is its magnetic heading rounded to the nearest 10° with leading and trailing zeros removed. For example, a runway head- ing north would have a magnetic heading of 360°. Dropping the trailing zero makes this runway number 36. Since the other end of the runway heads the opposite direction (south, which is a heading of 180°), it is runway 18. Each digit of a runway number is enunciated individually. Runway designations are always prefixed with the word “runway,” followed by the runway number and a suffix, if necessary. For example: Runway Heading Runway Number Pronunciation 090° 9 Runway niner 261° 26 Runway two six 138° 14R Runway one four right 14C Runway one four center 14L Runway one four left If two or three runways are constructed parallel to each other, the suffixes L for “left,” R for “right,” and C for “center” are used to differentiate the runways from one another (see Figure 4–6). If there are four or more parallel runways, some may be given a new number fairly close to their magnetic heading such as the Los Angeles International Airport, which has four parallel runways num- bered 25L, 25R, 24L, and 24R. Radio Frequencies When issuing radio frequencies, the controller should enunciate each digit individually. Current VHF communications radios use 25 kHz spacing between assigned frequencies. For instance, the next usable frequency above 119.600 is 119.625, followed by 119.650, 119.675, and 119.700. The first number after the decimal is always pronounced, whether or 202 / CHAPTER 4 N 23 27R 9L 093° 273° 8° 22 27C 9C 092° 272° 27L 9R 089° 269° ° 48 5 Figure 4–6. Runway numbering. not it is a zero. But if the second number after the decimal is a zero, it is not pronounced. The third number after the decimal is never pronounced, since it is always either a zero or a five and can be assumed. Low Frequency/Medium Frequency used by nondirectional beacons are always pronounced as whole numbers. VHF and UHF communication and navigation frequencies always use the decimal point. The decimal should be pronounced as “point.” For L/MF frequencies, the number should be suffixed with the word “kilohertz.” Here are some examples: Frequency Pronunciation 119.600 mHz One one niner point six 343.000 mHz Three four three point zero 123.050 mHz One two three point zero five 131.725 mHz One three one point seven two 401 kHz Four zero one kilohertz The FAA communications standard differs somewhat from that recommended by ICAO. Most ICAO member nations use the word “decimal” instead of “point.” For example, using ICAO procedures, 123.050 would be pronounced as “One two three decimal zero five.” MLS or TACAN Channels Microwave landing system and TACAN station frequencies are not issued explicitly. Channel numbers are used instead. MLS and TACAN channels are issued as two- or three-digit numbers, with each digit being enunciated individually. For example:  Airport Air Traffic Control Communications / 203 Channel Pronunciation MLS channel 530 M-L-S channel five three zero TACAN channel 90 TACAN channel niner zero Speeds Aircraft speeds, like wind speeds, are always measured in knots. This occasionally causes some confusion with older general aviation aircraft equipped with airspeed indicators that indicate in miles per hour. Care should be taken when issuing speeds to small aircraft to ensure that the pilots realize that the requested airspeed is measured in knots. A rule of thumb is that an airspeed in miles per hour is about fifteen percent higher than the equivalent airspeed in knots. Thus, 100 knots is about 115 miles per hour. Airspeeds are always expressed with each digit being enunciated individually and suffixed with the word “knots,” as in the following examples: Speed Pronunciation 250 Two five zero knots 95 Niner five knots Air Traffic Control Facilities ATC facilities are identified by name, using the name of the city where the facility is located followed by the type of facility or the operating position being communicated with: Facility Type Pronunciation Local control Tower Ground control Ground Clearance delivery Clearance Air route traffic control center Center Flight service station Radio Approach control Approach Departure control Departure Flight watch Flight watch If a particular city has two or more airports, the airport name is used instead of the city name. Approach controls and centers are always named after the larg- est nearby city. Navy airports are always prefixed with “navy” to differentiate them from civilian facilities. Here are some examples: Lafayette Tower Chicago approach Indianapolis center Navy Glenview tower Terre Haute radio 204 / CHAPTER 4 Route and Navigation Aid Descriptions Airways are always described with the route identification pronounced in group form. The route number is prefixed with “victor” if it is a low-altitude airway or “jay” if it is a jet route. For example: Route Pronunciation V12 Victor twelve J97 Jay ninety-seven Radials that emanate from a VOR should be pronounced as a three-digit num- ber with each digit being enunciated individually (similar to the way aircraft headings are pronounced). The radial number is prefixed with the VOR name and is always suffixed with the word “radial” (the word “degree” is never used when describing radials): Boiler one four three radial Indianapolis three six zero radial Champaign zero zero six radial Bearings from nondirectional beacons (NDBs) are expressed as magnetic bear- ings from the station and are suffixed with the station’s identifying name and the words “radio beacon” or “outer compass locator” as appropriate: Three five five bearing from the Pully radio beacon Two seven eight bearing from the Earle outer compass locator Intersections located along an airway are described using either (1) the five- letter approved intersection name (found in FAA order 7350.5, “Location Identifiers”), or (2) the VOR radial and DME distance from the VOR. Here are some examples: Staks intersection Flite waypoint Boiler zero niner zero radial one two mile fix ATC Communications Procedures The communications procedures that should be used by air traffic controllers are detailed in the Air Traffic Control Handbook. Although individual circum- stances may require modification of these procedures, adhering to them will help eliminate confusion and potential problems.  Airport Air Traffic Control Communications / 205 The remainder of this chapter describes the most common phrases used by air traffic controllers, including how and when to use each phrase and some examples of proper phraseology. The terms may be used when communicat- ing in writing as well as orally. To increase efficiency and conserve space when writing these phrases, standard operating procedure requires that controllers abbreviate them. The approved abbreviation appears in parentheses after each phrase. Clearance Any IFR or participating VFR aircraft operating within controlled airspace must be cleared (C) prior to participating in the ATC system. A clearance autho- rizes a pilot to proceed to a certain point or to perform a specific maneuver. When issuing a clearance or a control instruction, the controller must identify the aircraft, identify the ATC facility, and then issue the clearance or instruc- tion. This instruction could be a clearance to take off or land, to perform an instrument approach procedure, or to proceed to an airport or navigational fix, as in the following examples: Phraseology Explanation United seven twelve runway two This authorizes the pilot to take off four cleared for takeoff. using runway 24. Beech eight delta mike, after This clearance directs the pilot to departure, turn left and proceed turn left after takeoff from runway direct to the Boiler VOR, runway 10 and proceed to the Boiler VOR. one zero cleared for takeoff. Delta one ninety-one, after After departing runway 35, the departure turn right heading pilot will turn right to a heading one two zero, runway three of 120°. five cleared for takeoff. American nine twenty-one cleared This authorizes the pilot to make to land runway niner. a full-stop landing on runway 9. Aztec seven eight one cleared for A touch and go clearance permits touch and go runway two three. the aircraft to land on the runway but take off again before actually coming to a stop. This maneuver is usually used by students practicing takeoffs and landings. Mooney three six charlie cleared A stop and go clearance is similar for stop and go runway five. to a touch and go except that the aircraft comes to a full stop on the runway prior to beginning its takeoff run. Sport zero two romeo cleared for In a low approach, the pilot low approach runway three two. approaches to land on the runway but does not actually make contact with the surface. Upon reaching the desired altitude, the pilot begins a climb and departs.