|
3. Communications
3.1 Communication the basics
3.1.1 Radio Technique
3.1.2 Language
3.1.3 Callsign
3.1.4 Readback
To
download this chapter... right-click and select "Save
destination as ..."
3.1 Radio Comminication 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
Control= Somewhere
Back
to Top
3.1.1. Radio Technique [S]
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.
Back
to Top
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. It is the pilot who
chooses which
language is used, and ATC should respond in the same language. However,
ATC may suggest changing language is it is belived that it will ease
communication.
Back to
Top
3.1.3. Callsign [S]
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"
Control: "Exair one-two-three, Somewhere Control, 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 firts 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"
Back to
Top
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.
Items that must always be read back in full are all clearances
(including altitudes, heaings, speeds, radials etc), runway in use,
altimeter setting (QNH or QFE) and transition level, and all
frequencies. For a controller, this is extremely important to remember,
since if a pilot's readback is incorrect, the controller has to ask for
confirmation, i.e a new readback. There are also items that should not
be read back to reduce unnesessary radio transmissions. In short, this
includes everything not mentioned above, but a few examples are: wind,
temperature and other weather information (except altimeter settings)
and traffic information in detail. Here are a few examples of how
to acknowledge transmissions:
Arrival:
"Exair one-two-three, turn left heading
three-six-zero, descend to altitude two-thousand-five-hundred feet on
QNH niner-niner-eight"
XXX123:
"left three-six-zero, descend to
two-thousand-five-hundred feet, QNH niner-niner-eight, Exair
one-two-three"
Tower:
"Exair one-two-three, wind
two-six-zero degrees at one-two knots, runway two-six, cleared to land"
XXX123: "runway two-six, cleared to land, Exair one-two-three"
Note:
that when a pilot reads back a message, the pilot should end the
transmission by stating his/her callsign.
Remark: “Roger”
means “I have received and understood your message”, and thus is only used to
acknowledge messages, or parts of messages, which do not require a read back.
“Roger” does NOT mean either “yes” or “no”. When a positive or negative reply
is required, the phrases “affirm” and “negative” should be used..
Back to Top
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:
Scale Definition
1 Unreadable
2 Readable now and then
3 Readable, but with difficulty
4 Readable
5 Perfectly readable (loud and clear)
XXX123: "Somewhere Tower, Exair 123 - radio check"
Tower: "Exair 123, somewhere Tower, Read you five"
XXX123: "Roger, read you five as well, Exair123"
XXX020: "Somewhere Tower, Exair 020, radio check"
Tower: "Exair 020, Somewhere Tower, read you five by five - go ahead"
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.
Back to Top
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:
1
Emergency messages Begin the
transmission with: "MAYDAY, MAYDAY, MAYDAY"
Use
this transmission only when an emergency is stated.
2 Urgency messages Begin the transmission
with: "PAN PAN, PAN PAN, PAN PAN ”
Use this
transmission only on situations that might develop to an emergency
3 Messages related to direction finding helping
disoriented aircraft to obtain their position
4 Flight safety messages Clearances, position reports and vital
weather information as SIGMET.
5 Other weather information METAR etc.
6 Airline messages, for the airlines flight office, service of
aircraft etc
Back to Top
3.2 Phraseology [S]
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 on the VATEUD TD site www.vateud-td.org/handbooks/reference.asp
Back to Top
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”
Back to Top
3.3.1. Take Off [S]
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.
If this means that the aircraft must be handed over to a new controller it is important to make this handover well in advance.
One example is the handover from TWR to DEP. One method of preventing
“level offs” because of long hand over times is to issue
the following clearance before departure:
TWR:
“Exair 131, when airborne contact departure on 126.65. Runway 19
Right, cleare 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.
TWR: “Exair 131, Runway 08, right turn out, cleared for take off. ”
Back to Top
3.3.2. Cruise [S+]
In the cruise the most common phraseology is the frequency changes between different controllers.
CTR_1: “Exair 131, contact Another Control on 124.40 ”
XXX131: “Another Control on 124.40, Exair 131”
XXX131: “Another Control, Exair 131, flight level 360”
CTR_2: “Exair 131, Another Control, radar contact”
or
CTR_2: "Exair 131, Another Control, identified"
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”
CTR: “Exair131”
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.
The
clearance to fly these routes should be given well before the aircraft
reaches the first waypoint of the STAR. The inbound clearance is
normally given by the lass ACC controller before the flight is
transferred to the APP controller. However, thisvaries between
different countries and airports.
CTR:
“Exair 131, cleared to Somewhere via
Rasmu 3 Echo arrival runway 17”
XXX131: “Rasmu 3 Echo runway 17, Exair 131”
When it is time to leave cruise altitude and start descent it is important to remember the following.
It is the pilot’s responsibility to request descend in order to
meet aircraft performances and any altitude restriction on the STAR or
approach
XXX131: “Exair 131, request descent”
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:
| 
