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General Introduction

• Air Traffic Control Services (ATC) ensure safe, orderly, and efficient air traffic.
• ATC aims to expedite and maintain orderly air traffic flow and prevent collisions.
• ATC prevents collisions between aircraft in the air and on the aerodrome maneuvering area.
• ATC also prevents collisions between aircraft and vehicles, as well as aircraft and obstructions in the aerodrome maneuvering area.
• ATC services include Aerodrome Control Service (TWR), Approach Control Service (APP), and Area Control Service (ACC).
• Air traffic control officers (ATCO) manage aircraft throughout all phases of flight.
• ATCOs use communication, navigation, and surveillance to give information, instructions, and clearances to pilots.
• Air traffic control services provide controlled flights in a controlled airspace (Control Area - CTA).
• All planes subject to separation must be separated by at least 5 NM (9.26 km) horizontally and 1000 FT (300 m) vertically.
• Typically, two ATCOs work together: one handling incoming flights, and one working the radar.
• ATCOs rotate positions every one to two hours to reduce fatigue.
• All air traffic controllers function as a team.
• An ATCO can control about 40 aircraft in their sector per hour.
• During peak periods, ACC can control up to 170 GAT IFR operations per hour given that there is a maximum of 12 sectors simultaneously open.

Roles and Responsibilities in Zagreb ACC

• Flow management position (FMP) is responsible for monitoring, planning, and coordinating Air Traffic Flow Management (ATFM) measures.
• ATFM provides a safe, orderly, and efficient flow of air traffic with maximum ATC capacities.
• ATFM ensures compatibility between traffic demand (TD) and the declared capacity of relevant ATC units.
• The air traffic flow management is provided by the Eurocontrol's Network Manager Operations Centre (NMOC).
• Flow management controllers cooperate with the NMOC at the tactical level.
• The aim is to provide aircraft operators an relevant alternative, such as adjusting departure time, changing routes or flight profile, to minimize traffic delays.
• Flight Data Officer (FDO) is responsible for collecting, maintaining, and providing data on all flight operations and air navigation infrastructure.
• FDO ensures the admission of flight plans and related messages, checks flight plan accuracy, and enters military flight data.
• Flight Information Centre (Zagreb FIC) is a special sector within Zagreb ACC.
• Zagreb FIC helps activate flight plans, forwards data to sectors, provides weather reports, and offers navigation assistance for VFR flights.
• Pilots intending to fly in controlled airspace up to 1000 FT shall contact FIC Zagreb.
• ACC supervisor (SUP) acts as the focal point for inquiries regarding the performance of the watch.
• Duties of the ACC supervisor include: managing staff, coordinating ATFM measures with FMP, and opening/closing sectors.
• Supervisor's deputy works with the Airspace Management Cell (AMC) and manages emergencies like loss of communication or illegal activities.

Importance of Communication

• The primary purpose of the ATC system is to prevent aircraft collisions and to provide a safe, orderly, and expeditious flow of traffic.
• Safe operation of the air traffic control system depends on reliable and accurate communication between pilots and air traffic controllers.
• Instructions, procedures, and clearances rely on written or verbal communication.
• Miscommunication might contribute to aircraft accidents.
• Proper communication procedures must be observed by both pilots and controllers.

Radio Communications

• Air traffic controllers use radio equipment to perform ATC duties.
• Controllers are assigned radio frequencies for communications with pilots.
• Controllers have access to telephone equipment for communication with other controllers.
• Controllers use standard microphones and speakers or telephone handsets.
• Each controller has a switching panel to communicate with other controllers or pilots via radio.
• The system routes messages to an overhead speaker when communicating on a channel.
• The message format is as follows: Identification of the aircraft or controller being contacted, Identification of the calling controller, and Contents of the message.

Termination and Standardized Communication

• Messages with another ATC facility should be terminated with the controller's operating initials.
• Termination simplifies identification of the controller when a subsequent investigation is necessary.
• Pronunciation standards alleviate the issue of similar sounds between certain letters and numbers.
• Air traffic controllers should use standardized phraseology when communicating.
• The International Civil Aviation Organization (ICAO) designated English as the international language for ATC communications worldwide.

Numbers

• Each number should be enunciated individually unless group form pronunciation is stipulated.

Altitudes and Flight levels

• Altitudes used in the ATC system are 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.
• Each digit of the thousands number should be enunciated individually, whereas the hundreds should be pronounced in group form.
• Flight levels should be preceded by the words “flight level,” and each number should be enunciated individually:

Time

• Every ATC facility uses coordinated universal time (UTC) the same as local time in Greenwich, England, which is located on the 0° line of longitude, also known as the prime meridian.
• UTC eliminates the question of which time zone a facility or aircraft is located in.
• 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.
• 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.
• When issuing time, the controller should enunciate each digit individually.
• To prevent any confusion when issuing time to the pilot, the controller should suffix with the word "zulu" (UTC) and any local time with the word "local.”

Aircraft Identification

• Aircraft are identified by using standard procedures that help eliminate confusion and misdirected instructions.
• Control information directed to one aircraft must be received by the pilots of that aircraft.
• It is also important that the controller be certain with which aircraft he or she is communicating.
• An aircraft call sign is a group of alphanumeric characters used to identify an aircraft in air-ground communications.
• Type (a) includes characters corresponding to the registration marking of the aircraft.
• Type (b) includes the telephony designator of the aircraft operating agency with the last four characters of the registration marking.
• Type (c) includes the telephony designator of the aircraft operating agency, followed by the flight identification.

Call Signs and Transponders

• The full call sign must be used when establishing communications.
• Abbreviated call signs may be used after satisfactory communication has been established.
• Most authorized airline names are easily recognizable.
• Every airline has a three letter designator to be used in written communications.
• The transponder is the airborne portion of the secondary surveillance radar system.
• Aircraft have transponders to assist in identifying them on air traffic control radar.
• Transponder transmissions are used as a means of detecting aircraft at risk of colliding with each other.
• Air traffic control units say "squawk" when assigning an aircraft a transponder code.
• A transponder code consists of four numbers from 0 to 7, making 4,096 possible codes.
• Code 7500 is used to indicate hi-jack, Code 7600 indicates loss of communication, and Code 7700 indicates general emergency.