Study Guide:Radio Telephony

About this Document

This document ist part of the VACC Austria Study Guide, intended to assist VACC controllers in learning their "hob" (actually: their hobby). This page is an addition to the Study Guide:OBS and covers the rules and procedures on how to speak on the radio. We assume that you have read and understood the Study Guide:OBS before. The information is based on the [CAP413 Radio Telephony Manual] of the British CAA, which is a very thorough (260pages!) document. This page is more like a tutorial: step-by-step, and only covers the basics.

Basic principles

Talking on the air is (sometimes) stressy. Voice quality may be bad or broken, but yet: it is the only link between ATC and aircraft, and therefore: highly security sensitive. You want to make sure that...

• Communication is short
• Communication is unambiguous ("what did he mean?")
• Communication is fail-proof

To achieve this, there are some rules which you should follow.

Talking on the air is (sometimes) stressy. Voice quality may be bad or broken, but yet: it is the only link between ATC and aircraft, and therefore: highly security sensitive. If it does not work, [this] could happen again. You want to make sure that...

• Communication is short
• Communication is unambiguous ("what did he mean?")
• Communication is fail-proof (lost and misunderstood messages are detected and corrected).

To achieve this, people have invented something, called phraseology. Almost 99% of all radio communication is standard messages. If all the standard messages are predefined, then both sides instantly know, what they are talking about, and the non-standard communication (in "normal words") is down to an absolute minimum. Therefore, we learn this phraseology.

Basic Rules

In order to achieve the goals set above the following rules important:

Listen before you talk

If two people talk on the radio at the same time, they don't hear each other, and all others only hear a nasty squeak. 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.

Standard phraseology looks like this - in a dotted box (no, this is not standard phraseology, this is just how it looks like in this wiki!)

Letters and numbers are spelled

On the Radio, it is impossible to distinguish a "B" from a "D". Therefore, letter combinations (like callsigns, see below) are spelled. In the air, we use the NATO alphabet: Buchstabiertabelle. Same is with numbers. It is difficult to distinguish "60" from "16", so numbers are read out as single digits: "six-zero" and "one-six", where "9" is "niner" to distinguish it from "five", decimal reads "decimal", and for "00" you should say "hundred" and "000" you say "thousand". There are very few exceptions for abbreviations which are used frequently, like VOR, NDB, ILS or VMC. An example:

ATC: Alpha Hotel Bravo Uniform, Radar identified at five thousand feet. Climb and maintain flight level one two zero. 
ATC: Alpha Hotel Bravo Uniform, direct Lima November Zulu NDB, contact Wien Radar one three four decimal three five, bye!

Stations have callsigns

You want to make sure everyone is well identified. Therefore, every participant on the network has his own Callsign. Controller Positions are identified by their location and their Function (e.g. Wien Radar, Graz Tower), Aircraft either by their Registration (e.g. OE-ALB) or an Airline Callsign followed by a combination of numbers and letters (e.g. AUA25LM, SWR387). The airline is called by its real name (i.e. "Austrian" for AUA).

Callsigns are vital, because you have to say them every time you transmit something to make sure, it is from and for the right guy.

Readback

When a controller (or aircraft) transmits a message to a station it is crucial that the receiving station acknowledge the message. But saying "roger" is only in movies - what are you "roger"ing? The called station understood something, but what? The solution is simple: The called station reads back the information in relevant parts. If the receiving station does not read back, the transmitting station must transmit again.

• Items that must always be read back in full are all clearances (including altitudes, headings, speeds, radials etc), runway in use, altimeter setting (QNH or QFE) and transition level, and all frequencies.

• 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.

LOWW_APP: AUA251, turn left heading 290, descend Altitude 5000 feet, QNH 1019.
AUA251: Turn left heading 290, descending altitude 5000 feet QNH 1019, AUA251 

LOWW_TWR: AUA251, traffic information: Cessna on rwy 16 downwind, report in sight.
AUA251: Traffic in sight, AUA251.

LOWW_GND: OE-DLT, taxi to Holding Point Runway 29 via Exit 12, M and A1, QNH 1019, give way
to Speedbird Airbus A320 crossing you right to left on M.
OE-DLT: Taxiing to H/P Rwy 29 via Exit 12, M and A1, giving way on M, QNH 1019, OE-DLT.

Contact - messages - handover

All conversation follows the following pattern:

1. Contact
2. ... messages (there may be pauses, and other messages to other stations)
3. handoff/handover.

Contact

Radio communication is like talking to each other in a dark room: You have to say hello, who you are, and that you are here now. Like this, an aircraft arrives in an airspace and needs to tell "Hi, I'm here!" (it's pilots' jobs to contact - in real life, ATC does not know if they listen or not). To initiate the contact between two stations an initial call has to be made. Example - Austrian 251 is calling Wien Tower:

AUA251: Wien Delivery, Austrian 251, [servus], Radiocheck 
LOWW_DEL: Austrian 251, Wien Delivery, [servus,] read you 5 by 5

Contact has standard phraseology depending on the circumstances - see the sections of the controller positions.

Messages

Once contact is established, you stay in contact, even if you don't talk to each other. This means: You know that the other station listens and will pick up conversation any time. Contact is not one-to-one: ATC has contact with all aircraft in his area, whether he talks to them or not.

In ongoing conversation, three rules apply:

• Pilots who address ATC, say their callsign first, then the message (ATC knows: if a callsign comes up, he is meant and he knows, by whom.)

AUA251: Austrian251 requesting descent.

• ATC always addresses the called station first, and then the message (ATC only talks to pilots, so whenever an aircraft's callsign comes up, there is only one guy who could be meant).

ATC: Austrian 251, descend FL 120.

• Pilots who read back an ATC instruction, put their callsign at the end. This makes sure that the right person has understood the instruction (Imagine the wrong plane descends!)

AUA251: Descending FL 120, Astrian 251.

Now one Example for normal Clearence. You will learn in detail in the next section. Situation: Austrian 251 is Requesting clearance to München, Gate C34, Fokker 70, Info C on board.

AUA251: Good Day Wien Delivery, Austrian 251 Info C on board, Gate C34, requesting clearence to München.
LOWW_DEL Austrian 251, cleared to München via SITNI4C, initial climb 5000 ft, Squawk 4612, info C correct.
AUA251: Cleared to München, Sitni4C, Squawk 4612, AUA251.

Handover/Handoff: At some point, it's time to say good bye - that is handoff or handover. It is vital that no aircraft disappears from the radio. Handover is transfer to another station. Handoff is dropping contact into uncontrolled airspace (like UNICOM).

LOWW_DEL Austrian 251, readback correct, for push and start contact Wien Ground (LOWW_GND) 119.4, Bye Bye.
AUA251: Contacting Ground 119,4, bye!

1. Standard Syntax

1) Syntax

A call has the following structure:

Called station, calling station, Message
Example: LHA123: Wien Radar, Leipzig Air 123 with you, FL240

4) Reserved words

Some words are reserved and should only be used, if they are meant:

• mayday and Pan-pan: Only use it, when you declare it.
• takeoff and landing: Only use it, when you clear (or read back) for takeoff or to land. If you report ready for t... no: you report ready for departure.
• Affirm(ative) means "yes". Negative means "no". Unable means that the pilot can't do what the ATC just instructed.

---