3.1 Radio Communication the Basics [S]
Communication is essential for air traffic control. Both text and radio can be used (even if voice is preferred) in order to exchange information and are equally important. Sending in a flight plan is a form of communication, as are the instructions transmitted over radio between pilot and controller. Messages between two or more controllers, in order to coordinate traffic, are also communication. In short, there is a lot of communication required in order to control the traffic in the air.
With this amount of messages being sent, there is an obvious risk for misunderstanding. There is also a need to keep transmissions short in order to save valuable time. These are the main reasons why a special format and syntax of radio communication has been created. In order to give proficient and safe ATC, you will need to learn this radio communication language.
Fictive callsigns will be used in the examples below:
XXX123 = Exair 123
Let’s start with the basics – there are some basic rules that you need to adhere to or there will be chaos:
Listen before you talk It's impossible for two radio stations to transmit on the same frequency at the same time. If this is done, the radio signal will be blocked and this will result in a nasty noise on the frequency. Therefore it's important that every station monitors the frequency for about 5 seconds before transmitting, to make sure there’s no ongoing radio traffic. If you hear an ongoing conversation, wait until the conversation is over before you begin to transmit. Don’t start your communication if there is a read-back expected on the last transmission even if there is a short pause.
Think before you talk The radio traffic flow should be as smooth as possible. To achieve this it's vital to "think first" before transmitting so that a clear, concise and uninterrupted message can be sent.
Use standard phraseology and syntax (As far as possible)
To prevent misunderstandings and to maintain the radio traffic as effective as possible, stick to standardized phraseology and skip slang and of course private messages.
Speak out Long messages shall be cut into shorter phrases with a little pause in between. Normal speaking speed is about 100 words / min but when reading out long messages such as weather reports and complicated route clearances, decrease the speed to about 60 words / min. When transmitting, talk with normal voice tone and keep the microphone at a constant distance from your mouth.
3.1.2. Language [S]
English is the primary language for communication in aviation. Local language is allowed in most European countries, i.e. French in France, German in Germany, but in most countries English is prevailing at international airports. Local language may be common at smaller airports where there is lots of general aviation and/or VFR traffic.
There are several advantages to using English, the most obvious being that everybody on the radio channel understands everybody. English is the international language of aviation and will be used as the default language. If the piolt and ATC controller are able to speak a common language other than English, this language may be used in order to ease communication.
Due to the fact that it is impossible to see the one you are talking to when using a radio, it is vital that all stations at all time knows who is transmitting and to whom the message is sent to. Hence all users of the radio shall have a specific and unique callsign.
(NOTE: the system prevents you to log on using a callsign already in use).
If you for example are flying DLH123, your callsign will be DLH123 (Read Lufthansa one-two-three). If you are talking to for example Stockholm Control then Stockholm Control will use "ESOS_CTR" as his/her callsign.
When establishing contact with a station you must first state what station you are addressing your call to, and then state your own callsign. When the receiving station calls you back, he/she must first state your callsign and then his/her own callsign. An example of establishing contact:
XXX123: "Somewhere Control, Exair one-two-three, good evening"
When contact is established, the controller may leave out his/her own callsign when answering or contacting aircraft with which he/she has already established contact.. The controller may also use abbreviated callsigns if contact is established and there is no risk of misunderstanding a callsign. Once contact is established, aircraft also may leave out the controllers’ callsign when transmitting a request. An example of a descent clearance once contact is established:
Control: "Exair one-two-three, Descend to flight level one-two- zero."
XXX123: “Descend to flight level one-two-zero, Exair one-two- three"
Callsigns used by airline flights usually consist of the airline's callsign followed by the flight number (SAS123 being "Scandinavian 123"). General aviation flights, however, normally use the aircraft's registration as callsign. Example: SE-IBG (Sierra-Echo-India-Bravo-Golf)
When checking in to a new controller you have to state your full callsign, (all five letters).
As long as the controller calls the pilot using the full callsign, the pilot should use it as well. However, the controller often reduces the callsign to the first letter, followed by the two or three last letters, for example S-BG. If aircraft with similar callsigns, such as SE-IBG and SE-EBG are on the same frequency, ATC must not reduce the callsign so that confusion may occur. In this case the correct abbreviation would be S-IBG and S-EBG. When ATC has contacted the pilot using the abbreviated callsign, the pilot may use it as well.
When a station takes the initiative to call another station, regardless of whether the stations have established contact or not, it is mandatory to begin the transmission saying the station callsign so all others in the frequency know who is transmitting. This does not apply to the controller since all stations recognize the controller and it will be pretty obvious who is directing the traffic. An example where XXX123 takes the initiative and requests descent:
XXX123: "Exair one-two-three, request descent"
CTR: "Exair one-two-three, descend to flight level one-two-zero"
XXX123 “Descend to flight level one-two-zero, Exair one-two-three”
Below is another example, where the controller takes the initiative and issues a clearance for XXX123 to turn left direct TROSA VOR. Note that the controller leaves out his/her callsign:
Control: "Exair one-two-three turn left direct TROSA"
XXX123: "Left direct TROSA, Exair one-two-three"
3.1.4 Readback [S]
When a controller (or aircraft) transmits a message to a station it is very important that the receiving station acknowledge the message and reads back any required parts.. If the receiving station does not acknowledge, the transmitted message is considered as a lost transmission and the sender should resend the message or check if the receiving station got the message.
Note: that when a pilot reads back a message, the pilot should end the transmission by stating his/her callsign.
3.1.5. Readability [S]
When calling another radio station, it is some times good to perform a radio-check to test the transmission and reception quality. For this purpose a readability scale has been developed:
2 Readable now and then
3 Readable, but with difficulty
5 Perfectly readable (loud and clear)
XXX123: "Somewhere Tower, Exair 123 - radio check"
Note: 5 by 5 does not mean 5 out of 5. The First value indicates the signal strength, the second value is the signal clarity.
3.1.6. Priority [S+]
To obtain a smooth traffic flow and to avoid any situation where less important messages block the frequency and obscure more vital messages to be sent, a message priority and classification list has been developed. This list shows that some messages have a higher priority as follows:
To a friend, you can tell a story in a number of different ways. To a pilot, you should give instructions in a very strict and specified way. This is to minimize the risk of misunderstandings and keep the message as short as possible. Some words, which you normally think of as synonyms, can not be exchanged in aviation, since they mean different things. It is hence important to learn the phraseology used in aviation.
It is a bit like learning a new language and this can only be done by practice. Many persons are afraid of talking on the radio. It can be hard to get all words right in the beginning, but you should remember that it is often better to say something, even though it isn’t perfectly correct, than saying nothing at all. Practice and studying radio phraseology will give you experience.
You can find various phraseology links under References sub menu on the left side of the screen.
3.3 Radio Communication - specific
When the aircraft is airborne it is essential for ATC to verify that the transponder is working properly and that a good radar image is shown on the scope with a correct information tag. This is why pilots should report their current altitude and the one they are climbing or descending to when they check in to a new controller. They should also report which intersection/heading or (in certain FIR's) the SID they are over or following. When the controller has verified that the tag on the radarscope matches the information given by the pilot, he can reply with “radar contact or “identified"
TWR: “Exair 131, contact somewhere Control on 118.4”
XXX131: “Somewhere Control on 118.4, Exair 131”
XXX131: “Somewhere Control, Exair 131, passing 3000 ft, climbing to 5000 ft”
CTR: “Exair 131 good evening, Somewhere Control radar contact, Climb to FL 320”
XXX131: “Climb to FL 320, Exair 131”
Pilots appreciate if they can receive a continuous climb from take off to cruise altitude. The controllers should therefore try to re-clear the aircraft for a higher flight level well before it reaches the current cleared level.
TWR: “Exair 131, when airborne contact departure on 126.65. Runway 19 Right, cleared for take off, winds 170 at 21 knots.”
Below are some other examples of take off clearance that can be used.
TWR: “Exair 131, when airborne fly runway heading and climb to 5000 ft. Runway 21, winds 190 at 15 knots, cleared for take off.”
“Right turn out” must always be specified if a right turn is to be performed after take-off, because left turn is standard procedure. This is not required, however, if the aircraft is on a SID which begins with a right turn, since the right turn is implied in the clearance for the SID.
In the cruise the most common phraseology is the frequency changes between different controllers.
During the cruise phase of flight, the pilots should check the ATIS broadcast for their destination airport if it is available. By doing this they will get such information as current weather and runway in use so they can start planning for their arrival. Pilots should report the current ATIS designation to the controller handling the arrival traffic.
If no ATIS is available this kind of information can be forward to the pilots from the controller directly.
CTR: “Exair 131, are you ready to copy MET REPORT for Somewhere airport?”
XXX131: “Affirmative go ahead, Exair 131”
CTR: “Met report for Somewhere, Winds 210 degrees at 9 knots, visibility 5 kilometers in light rain, scattered clouds at 2000 ft and overcast at 4000 ft, Temperatures 15, dewpoint 14, QNH 998. Expect ILS approach for runway 17”
XXX131: “QNH 998, transition level 55, runway 17, Exair 131”
Note the mandatory data in the read back of this example: altimeter setting, Transition Level and runway in use.
Most major airports have pre-defined arrival routes (STAR), which are used to reduce workload for the controller handling the final stage of the flight by channelling arriving IFR traffic.
CTR: “Exair 131, descend to flight level 100”
XXX131: “Descend to flight level 100, Exair 131"
If there is no conflicting aircraft in the way, the ATC on duty can issue the following descend clearance to an aircraft before the pilot has requested descent:
CTR: “Exair 131, when ready, descend to flight level 100”
XXX131: “When ready descend to flight level 100, Exair 131”
This means that the pilot can maintain the current altitude and start the descent whenever he wants.
Now an example when the aircraft is cleared below the transition Level (TL) for the first time. QNH should always be read out when this is done:
APP: “Exair 131, descend to 2500 ft on QNH 998, Transition level 55”
XXX131: “Descend to 2500 ft on QNH 998, Transition level 55”, Exair 131”
The TL is omitted where ATIS is available, because TL is included in the ATIS
APP: “Exair 1465, descend to 4000 ft on QNH 998”
XXX1465: “Descend to 4000 ft on QNH 998, Exair 1465”
There are many different ways to make an approach to an airport. An aircraft can:
Let us now see some examples of the instructions given by ATC for these 5 different approaches:
(1) An aircraft (XXX950) is approaching an airport without ATIS and STARs. The pilot has received inbound clearance from ACC "via LAPSI runway 19"
(3) An aircraft (XXX131) is approaching airport Somewhere on XYZ 3 ECHO arrival. The airport has ATIS and the STARs will guide the aircraft all the way in to final approach course. So if the traffic situation is light and no ATC vectors are needed for separation it can expect to follow the arrival route all the way in to the localizer.
Exair131: "somewhere control, ExAir131 flight level 100"
APP: "ExAir131, radar contact. Descent to 2500 ft on QNH998, cleared ILS approach runway 17"
ExAir131 "Descent to 2500 ft on QNH998, cleared ILS approach runway 17, Exair 131"
(5) A visual approach is basically a pilot's request approach. This means that the pilot will take the shortest and most convenient way to the runway. A visual approach is permitted (ATC approval is required) whenever there is visual contact to the destination airport
X4321 Is inbound ABC VOR with runway 07 in use at “somewhere” Airport
X4321 “Exair4321:”Somewhere Approach, ExAir4321 request visual approach runway 07
APP: “Exair4321 roger, report runway in sight"
X4321: “Wilco, Exair4321”
X4321: “Exair 4321 runway in sight”
APP: “Exair 4321, cleared visual approach runway 07, final”
X4321: “Cleared visual approach runway 07 wilco, Exair 4321”
3.3.4. Holds [S+]
XXX4321: “ExAir 4321 request detailed holding instructions”
APP: “ExAir 4321 hold at DEF, inbound track 272, left hand pattern, expected approach time 21”
XXX4321: “Hold at DEF, inbound track 272, left hand pattern, ExAir 4321.”
APP: “ExAir 4321 make a right 360 for spacing”
XXX4321: “Make a right 360, ExAir 4321.”
APP: “ExAir 4321 orbit left until further advised”
XXX4321: “Orbit left, ExAir 4321
Some examples of phraseology to use when putting aircrafts back on course after holdings:
APP: “ExAir 4321, exit DEF holding on course and descend to FL 090 ”
X4321: “Exit DEF holding on course and descend to FL 090, ExAir4321”
- - - -
APP: “ExAir 112, leave DEF on heading 170”
X112: “Leaving DEF on heading 170, ExAir 112”
3.3.5. Missed Approach [S]
A missed approach can be initiated both from the pilot or the controller to prevent a dangerous situation from occurring.
If the runway is occupied or if the arriving aircraft is too high or to fast on the approach, the controller can instruct the pilot to carry out a missed approach.
Every runway has a missed approach procedure that the pilot is expected to follow unless otherwise instructed by ATC. Often ATC revises the missed approach procedure due to traffic or to shorten the aircraft’s route. Missed approach initiated by the pilot
X4321: “ExAir 4321, going around”
TWR: “ExAir 4321, roger, climb to 4000 feet and turn right heading 300. Radar vectors for a new approach”
X4321: “Climb to 4000 feet and right heading 300, ExAir 4321”
TWR: “ExAir 4321 contact somewhere Approach on 126.650”
Missed approach initiated by ATC:
TWR: “ExAir 4321 go around (I say again, go around).”
X4321: “Going around, ExAir 4321”
TWR: “ExAir 4321, climb to 4000 ft and turn right heading 300, vectoring for new approach.”
3.4. Correcting Mistakes [S]
Useful words here to use: Correction, Say again and Negative.
The example below shows a situation where the pilot in XXX123 does not copy the name of the VOR (SCHIPHOL, SPL) that he is cleared to and ATC thereofore spells out the identification code of the (VOR