Message Format and Content

Feature Desk, Aviation Gurukul, GOLN

3 years ago

Message Format and Content

Description

The purpose of all RTF messages is to convey information or instructions unambiguously to a specific recipient or recipient. The use of standard format and content will help to achieve this purpose.

Use of non-standard message format and/or content may result in one or more of the following undesirable outcomes:

The message is not received by the intended recipient;

The message is acted on by an unintended recipient (Call-sign Confusion);

The message has to be repeated, resulting in a delay in response and frequency congestion;

All or part of the message is misunderstood;

Parts of the message may be confused and incorrectly acted on.

Composition of Messages

The following provisions are abridged from ICAO Annex 10 Volume II, Chapter 5, Section 5.2.1. are designed to achieve the above objectives:

Messages … shall comprise the following parts in the order stated:

a) call sign indicating the addressee and the originator;

b) text.

Note.— The following examples illustrate the application of this procedure:

(call-sign) BRUSSELS CONTROL SPEEDBIRD 1234

(text) REQUEST RADIO CHECK

(call-sign) LUFTHANSA ABCD LONDON CONTROL

(text) CONTACT AMSTERDAM RADAR ON ONE TWO THREE DECIMAL SEVEN

When the text of a message to be transmitted … to an aircraft in flight contains approved ICAO abbreviations, these abbreviations should normally be converted during the transmission of the message into the unabbreviated words or phrases that the abbreviations represent in the language used, except for those which, owing to frequent or common practice, are generally understood by aeronautical personnel.

Establishment of radiotelephony communications

Full radiotelephony call signs shall always be used when establishing communication.

The calling procedure of an aircraft establishing communication shall follow the following format:

Call-sign of the station called, followed by the call sign of station calls.

e.g. BRUSSELS CONTROL SPEED BIRD 1234.

The reply to the above calls shall follow the following format:

Call-sign of the station calling followed by call-sign of the answering station. This shall be considered the invitation to proceed with transmission by the station calling.

e.g. LUFTHANSA ABCD LONDON CONTROL.

Subsequent radiotelephony communications

Abbreviated radiotelephony call signs, shall be used only after satisfactory communication has been established and provided that no confusion is likely to arise.

An aircraft station shall use its abbreviated call sign only after it has been addressed in this manner by the aeronautical station.

To avoid any possible confusion, when issuing ATC clearances and reading back such clearances, controllers and pilots shall always add the call sign of the aircraft to which the clearance applies.

Communications shall be concise and unambiguous, using standard phraseology whenever available.

The receiving operator shall make certain that the message has been received correctly before acknowledging receipt.

When transmitted by an aircraft station, the acknowledgment of receipt of a message shall comprise the call sign of that aircraft.

An aircraft station should acknowledge receipt of important air traffic control messages or parts thereof by reading them back and terminating the readback by its radio call sign.

Note: Air traffic control clearances, instructions, and information requiring readback are specified in PANS-ATM (ICAO Doc 4444).

If the receiving operator is in doubt as to the correctness of the message received, he shall request repetition either in full or in part.

If in checking the correctness of a readback, an operator notices incorrect items, he shall transmit the words “NEGATIVE I SAY AGAIN” after the readback followed by the correct version of the items concerned.

Non-regulatory advice

The following advice will enhance readability and reduce the chance of misunderstanding:

Limit the number of elements in a message to two to reduce the chance of an element being missed or misheard.

The elements of an RTF frequency are treated by a pilot as individual digits; therefore, a frequency change should not be combined with another instruction. This also prevents situations where the crew makes incorrect readback of the instruction and leaves the frequency.

Avoid combining numerical elements which may easily be confused in the same message, for example, flight level and heading.

Preface any nonstandard instructions with the phrase ‘nonstandard’ e.g. “descend now nonstandard level 75”, to ensure the pilot notes the differences from standard.