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EHM-1997 Alexander:
Automatic Terminal Information Service

Written by Ricardo Plácido  
Thursday, 06 November 2008 23:28
Source: IVAO Academy

Before departing from or arriving at an airport, pilots want to have the latest operational airport information (runway-in-use, closed taxiways,...) and the newest weather update (wind direction and speed, cloudbase,...). To avoid that the ATC frequency would become congested by pilots who request this information, it is made available via the Automatic Terminal Information Service.

In real-life, at the airports where it is installed, the ATIS is continuously broadcasted over a separate VHF radio frequency or on the voice portion of a local NAVIGATION AID such as a VOR. Area Control Centers, Upper Area Control centers and Military controlled airfields have no ATIS.

What does ATIS tell us?

ATIS information generally includes:

* Name of aerodrome;
* Arrival and/or departure indicator;
* Designator;
* Time of observation, if appropriate;
* Surface wind direction and speed, including significant variations;
* Visibility and, when applicable, RVR;*
* Present weather;*
* Cloud below 1 500 m (5 000 ft) or below the highest minimum sector altitude (MSA), whichever is greater; cumulonimbus (Cb); if the sky is obscured, vertical visibility when available;*
* Air temperature;
* Dew point temperature;
* Altimeter setting(s);
* Any available information on significant meteorological phenomena in the approach and climb-out areas including wind shear, and information on recent weather of operational significance;
* Trend forecast, when available;
* Type of approach(es) to be expected;
* The runway(s) in use;
* Significant runway surface conditions and, if appropriate, braking action;
* Holding delay, if appropriate;
* Transition level, if applicable;
* Other essential operational information;
* Specific ATIS instructions.
* These elements are replaced by the term “CAVOK” when:


* the visibility is 10 km or more;
* no significant weather;
* no clouds below 1.500 m (5000 ft) or below the highest minimum sector altitude (MSA), whichever is greater;
* no cumulonimbus (Cb);
Example:

"Lisbon Approach information DELTA recorded at 0915z
LPPT 070900Z 28005KT 9999 FEW030 BKN039 09/03 Q1021 NOSIG
ARR RWY 21 / DEP RWY 21 / TRL FL050 / TA 4000FT
ILS21 109.50/Crs 208
CONFIRM ATIS INFO DELTA on initial contact".

Pilots can receive the continuous ATIS broadcast at times when cockpit duties are least pressing and listen to as many repeats as desired.

ATIS broadcasts shall be updated each time a new routine weather report or special weather report is issued and also when there is a change in other important data such as runway change, instrument approach in use, etc.

How to make sure the lastest information is received?
Pilots should obtain the ATIS information, whenever ATIS is in operation.
The current ATIS message is identified by a letter and is valid until a significant change has to be made (new runway in use, weather deterioration or improvement, facility failure).
The first ATIS of the day is usually identified as "Information Alpha" (see "Letters Codes" for details about letters codification).
The second ATIS message will be "Information Bravo".
Then Information Charlie,Delta etc... when reaching Zulu, the next will be Alpha again.
On initial contact , pilots should inform controllers that they received the latest ATIS information by repeating the letter of the alphabet of the ATIS, like "Information Sierra".
Controllers will pass important information to pilots who do not acknowledge the letter of the ATIS or received ATIS information that is no longer correct.

What information is contained in a real ATIS?
There is one single ATIS message for one airfield; an ATIS is not established for several airfields. This message is usually recorded by the ground controller or automated system and broadcasted continuously on a specific frequency which can be found on approach charts.

The message contains:


* Aerodrome name, identification letter and time (UTC);
* Approach procedure in use;
* Runway in use and runway conditions (flooded, braking action action poor medium or good...);
* Transition level;
* Any relevant information (bird warning, navaid unserviceable...);
* Weather conditions, including wind, visibility, ceiling and cloudiness, temperature, dew point and altimeter setting (QNH);
* Significant weather (rain shower, snow...);
* Specific instructions (like speed restrictions); usually an ATIS also ends by "Advise controller you have information x at initial contact". This enable the controller to know you got the current details about the airfield.
Example:

   
This is Paris-Charles de Gaulle information Mike recorded at 1800z.
Landing runway 27, departure runways 26R/26L.
Transition level 60.
Locator CGO unserviceable.
Wind 300°/9kt, visibility 10 km or more, ceiling scattered at 12000 ft, temperature 24, dew point 11, QNH 1018.
Advise controller on initial contact you have information Mike.

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