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Speed and Timeliness of Communication

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Category: Air Ground Communication Air Ground Communication
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The speed and timeliness of transmissions make important contributions to the communications process:

  • If the transmission is too fast, the recipient may be unable to copy it correctly;
  • If a transmission is received at a time of high workload, it may be incorrectly copied or misunderstood.


Unless a message is copied correctly, its content may be misunderstood or not correctly acted upon.

A message which is received at a time of high pilot workload disrupts the train of actions being followed (e.g. a check-list) and items may be missed.

The necessity to repeat an incompletely copied or understood message wastes time.


Transmissions must be conducted concisely in a normal conversational tone; full use must be made of standard phraseologies wherever these are prescribed in relevant ICAO documents or procedures.

Speech transmitting technique should be such that the highest possible intelligibility is incorporated in each transmission. Fulfilment of this aim requires that air crew and ground personnel should:

a) enunciate each word clearly and distinctly;
b) maintain an even rate of speech not exceeding 100 words per minute. When a message is transmitted to an aircraft and its contents need to be recorded the speaking rate should be at a slower rate to allow for the writing process. A slight pause preceding and following numerals makes them easier to understand;
c) maintain the speaking volume at a constant level;
d) be familiar with the microphone operating techniques particularly in relation to the maintenance of a constant distance from the microphone if a modulator with a constant level is not used;
e) suspend speech temporarily if it becomes necessary to turn the head away from the microphone.

Speech transmitting technique should be adapted to the prevailing communications conditions. (ICAO Annex 10, Volume II, Chapter 5 Para 5.2.1.)

Timeliness of communication

Deviation from an ATC clearance may be required for operational reasons (e.g. a heading deviation or altitude deviation for weather avoidance, or an inability to meet a restriction). Both the pilot and the controller need time to accommodate this deviation; therefore ATC should be notified as early as possible.

Pilot workload varies according to conditions and phase of flight. Periods of very high workload include:

  • Descent, approach and landing;
  • Unusual situations such as equipment malfunction or extreme weather; and,

Contributory Factors

Frequency Congestion;



Radio interference;

Expectation of clearance.


Control the speed of transmission to reduce the chances of pilot error.

ATCOs may not be able to avoid passing or revising clearances during periods of high workload; however, by understanding when these occur, by passing on clearances as early as possible and by carefully monitoring read-back, they can reduce the possibility of error. Further improvements may be possible by taking account of likely flight-deck work-load when designing or revising procedures.

Avoid multiple frequency changes during high workload periods following take-off and during the departure.

Further Reading

AGC Safety Letters:

  • Safety Letter 1;
  • Safety Letter 2;
  • Safety Letter 3.

EUROCONTROL Action Plan for Air-Ground Communications Safety, including:

  • Briefing Note AGC5 – Radio Discipline;

EUROCONTROL Level Bust Toolkit:

  • Briefing Note GEN2: Pilot-Controller Communications;
  • Briefing Note ATM1: Understanding the Causes of Level Busts.