Automatic Terminal Information Service
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Automatic Terminal Information Service, or ATIS, is a continuous broadcast of recorded noncontrol information in busier terminal (i.e. airport) areas. ATIS broadcasts contain essential information, such as weather information, which runways are active, available approaches, and any other information required by the pilots, such as important NOTAMs. Pilots usually listen to an available ATIS broadcast before contacting the local control unit, in order to reduce the controllers' workload and relieve frequency congestion.
The recording is updated when there is a significant change in the information, like a change in the active runway. It is given a letter designation (e.g. bravo), from the Phonetic Alphabet. The letter progresses down the alphabet with every update and starts at Alpha each day. When contacting the control tower or ground station, a pilot will indicate he/she has "information" and the ATIS identification letter to let the controller know that the pilot is up to date with all current information.
Contents |
[edit] Sample message - audio
| Message | Explanation |
|---|---|
| This is Schiphol arrival information Kilo | Indicates the broadcast is for aircraft inbound to Schiphol, and the bulletin's identification letter. |
| Main landing runway 18 Right | Main runway used for landing is 18R |
| Transition level 50 | Lowest usable flight level is 50. See Transition altitude. |
| 200 degrees, 11 knots | Wind direction from azimuth 200 degrees (south-southwest), average 11 knots |
| Visibility 10 kilometres | General visibility 10 kilometers or more |
| Few 1300 feet, scattered 1800 feet, broken 2200 feet | Cloud layers at the indicated altitude above the airport |
| Temperature 15, dewpoint 13 | Temperature and dewpoint in degrees Celsius. |
| QNH 995 hectopascal | QNH 995 hectopascal. |
| No significant change | No significant change in weather expected. |
| Contact Approach and Arrival callsign only | When instructed to contact the Approach and Arrival controller, check in with callsign only (for the sake of brevity) |
| End of information Kilo | End of bulletin, and the bulletin's identification letter again. |
See METAR for a more in-depth explanation of aviation weather messages and terminology.
[edit] Sample message - text
On tuning to an ATIS frequency, a pilot might hear:
- Vancouver International information Bravo, weather at one three five five Zulu. Wind three zero zero at eight, visibility five. Five hundred scattered, one thousand two hundred few, ceiling three thousand overcast, temperature one five, dew-point eight. Altimeter two niner eight seven. IFR approach is ILS or visual, runway two six left and runway two six right. Simultaneous parallel ILS approaches in use. Departures, runway two six left. GPS approaches available. VFR aircraft say direction of flight. All aircraft read back all hold short instructions. Advise controller on initial contact that you have Bravo.
This translates to:
- Vancouver International Airport, the information Bravo is issued at 13:55 UTC. The winds are from 300 (~northwest) at 8 Knots. Five statute miles visibility. At 500 feet there are scattered clouds, at 1,200 there are few clouds, at 3,000 feet there is an overcast flight ceiling. The temperature is 15°C (some airports don't include this due to variability). The dew point is 8°C. The altimeter setting is 29.87 inches of mercury (however this could also be expressed in millibars or hectopascals.) Visual and simultaneous ILS landings available using runways 26L and 26R, while departures may use runway 26L. You can conduct an approach via a GPS system. When you first contact air traffic control, inform them your direction of flight if you are using Visual Flight Rules, and that you have information Bravo. Any "hold short" instructions the controller gives you need to be read back to the controller to confirm you have received them properly.
[edit] System operation
In its simplest form, the ATIS is a continuously playing recording of a person reading the message aloud. Because the message needs to be re-recorded at every update (which is several times per hour at least), this is quite cumbersome. Nowadays, most airports use a more automated system using a speech synthesizer, also known as TTS (Text To Speech) Software, where a computer voice speaks the message. Most systems use a female voice, because female voices are often easier to understand when radio reception is less than optimal. Furthermore, certain features of today's speech synthesis technology, which make the resulting voice sound more natural, are often disabled to enhance readability under suboptimal conditions. In the ATIS sound sample above, the numbers are spoken in a non-fluid manner to help prevent misunderstandings.
Data for the ATIS system may be entered by hand, coming from a METAR, or be taken directly from sensors on the Airport. During normal operation, most modern ATIS systems are fully automated and do not require a controller to intervene. This is only necessary in case of sensor failures or other unusual activities, provided that the weather data processing on that airport is automated.
Some airports have separate ATIS broadcasts for arriving and departing aircraft, each on its own frequency. This keeps the message brief. It is also possible to have other information interesting to pilots in the ATIS broadcast, most often within the so-called remarks.
ATIS broadcasts are most often spoken in the English language. However, many countries alternatively offer native-language ATIS broadcasts. For example, the ATIS system of Toluca Airport transmits ATIS in English and Spanish, alternating languages on the same radio frequency.
[edit] Technical background
ATIS systems can be classified as Solid-State and PC-based. Solid-State ATIS systems are microcontroller-powered devices that incorporate speech synthesis and data processing in a single piece of proprietary equipment, while PC-ATIS systems are based on COTS-Hardware, like normal rack-mounted PCs with multiple high-performance soundcards.
Many high-capacity airports employ the use of Digital ATIS (or dATIS). dATIS is a transcribed, digitally transmitted version of the ATIS audio broadcast, usually accessed from a digital display such as an EFB or an FMS. dATIS may be incorporated into the core ATIS system, or be realized as a separate system with a data interface between voice ATIS and dATIS.
