By Andy Alexander
ATIS (Automatic Terminal Information Service) is a recording that some airports broadcast in order to reduce frequency congestion. Current weather information, active runway information, NOTAMs, and other useful pieces of information are included in the ATIS. The ATIS is usually updated every hour or when there is a sudden weather change at the airport. ATIS is how pilots get the latest information about an airport over the radio and this is simulated in VATSIM.
Elements of the ATIS
Location: The airport that is broadcasting the ATIS
Identifier: Each ATIS is given a letter to identify it. This letter is spoken as all letters are in aviation, using the phonetic alphabet.
Time of Issue: This is the time that the recording was made, given in Zulu time, which is explained here: Coordinated Universal Time∞
Winds: Current wind information. If winds are 6 knots or less and varying in direction, they're considered Variable (VRB). If the winds are less than 3 knots the winds are listed as Calm. A variation of 10 knots or more is considered a Gust (Example: 120/21G33. 'Winds from one two zero at two one knots gusting to three three knots'.) .
Visibility: The current visibility at the airport. Less than 3 miles is IFR. Three miles or greater is VFR.
Weather Phenomenon: Rain, Mist, Snow, Thunderstorm, etc.
Sky Condition: This will give the altitude of the bottom (base) of the clouds relative to ground level (AGL) as well as the amount of cloud cover. A Ceiling is defined as cloud coverage of Broken or higher. This will become important when determining whether conditions are VFR or IFR. A ceiling of less than 1000ft or lower is considered IFR.
- Few (FEW): 2/8 or less of the sky area is covered with clouds.
- Scattered (SCT): 2/8-4/8 of the sky is covered with clouds.
- Broken (BKN): 4/8-6/8 of the sky is covered with clouds.
- Overcast (OVC): 6/8 or more of the sky is covered with clouds.
Temperature/Dewpoint: The current temperature and dewpoint at the airport.
Altimeter: The current barometric pressure of the airport, given in inches of mercury in the US and Canada, and millibars (or hectopascals) every where else.
Approaches and Runways in Use: The current approaches and runways being used for takeoff and landing.
Remarks/Notams: Other information such as bird activity, unlit towers in the area, inoperative airport lighting or systems, etc. are listed in this section.
Closing Remark: Each ATIS will close with "Advise controller on initial contact, you have (current ATIS letter: Alpha/Bravo/Charlie/etc..)". The first call to any ATC at the airport should include the ATIS identifier. This tells ATC that the pilot has listened to and understands the current ATIS information.
Gleim's Aviation Weather & Weather Services Fourth Edition, 2005 (ISBN 158194258-3).