Automatic terminal information service, or ATIS, is a continuous broadcast of recorded noncontrol aeronautical 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.
Contents
The recording is updated in fixed intervals or when there is a significant change in the information, e.g. a change in the active runway. It is given a letter designation (e.g. bravo) from the ICAO spelling alphabet. The letter progresses through the alphabet with every update and starts at alpha after a break in service of 12 hours or more. When contacting the local control unit, a pilot will indicate he/she has "information <letter>", where <letter> is the ATIS identification letter of the ATIS transmission the pilot received. This allows the ATC controller to verify whether the pilot has all the current information.
International Airport Example 1
See METAR for a more in-depth explanation of aviation weather messages and terminology.
Example 2
On tuning to an ATIS frequency, a pilot might hear:
Vancouver International information Bravo one three five five Zulu weather. Wind three zero zero at eight, visibility five. Five hundred few, one thousand two hundred scattered, 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 few clouds, at 1,200 there are scattered clouds, at 3,000 feet there is an overcast cloud 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 Instrument Flight Rules, 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. Any "hold short" instructions the controller gives you need to be read back to the controller to confirm you have received them properly. Finally, inform the controller that you have information Bravo (i.e. this information) when you first talk to him or her.Example 3
This example was recorded on 11 July 2016 at London Stansted Airport during which time there were ongoing maintenance works taking place on the taxiway surface in a part of the airport near the cargo terminal; the ATIS broadcast reflects this.
System operation
The ATIS at an airport is usually given by an automated voice, this allows a busy air traffic controller to quickly type a new ATIS message (or for a computer system reading weather instruments to generate parts of the message dynamically) instead of making a time-consuming voice recording, although at some smaller, less busy airports with a control tower, it may be made by a controller and not a computer. Most airports in a certain country will often have the same ATIS format or layout with the same automated voice. For example, all ATIS information at major airports in the United Kingdom such as Heathrow, Gatwick, Manchester, Birmingham, Edinburgh and even smaller ones, such as East Midlands and Newcastle, have a similar format or layout and are all given by the same automated voice.
Shown below are samples of the same ATIS information formatted according to the formats used at two of the UK airports, both of which have the same automated voice as nearly all other UK airports. It shows that some airports give information that others do not even within the same country.
Luton information Oscar, time 1250. Runway in use 26. Expect an ILS approach. Surface wind 230 8 knots. Visibility 10 kilometers or more. Scattered 2,800 feet. Temperature +18. Dewpoint +10. QNH 1016. Threshold QFE 997 hectopascal. Transition level flight level 60. Departing aircraft should make initial contact with Luton ground on 121.750. Acknowledge receipt of information Oscar and advise aircraft type on first contact.
Stansted information Oscar, time 1250. Runway in use 22. Expect an ILS approach. Ground is open. Delivery is closed. Surface wind 230 8 knots. Visibility 10 kilometers or more. Scattered 2,800 feet. Temperature +18. Dewpoint +10. QNH 1016. Transition level flight level 60. Acknowledge receipt of information Oscar and advise aircraft type on first contact.
As Heathrow and Manchester airports both have two runways and both airports use one for arrivals and the other for departures, they have two ATIS frequencies, one for arrivals and one for departures. Manchester only uses its second runway part-time however both ATIS frequencies still remain active when only one runway is active, both ATIS services will have a recorded message saying "single runway operations" after it gives the runway in use when this is the case.
Technical background
ATIS systems can be classified into 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 airports also employ the use of Digital ATIS (D-ATIS). D-ATIS is a text-based, digitally transmitted version of the ATIS audio broadcast. It is accessed via a data link service such as the ACARS and displayed on an electronic display in the aircraft. D-ATIS is incorporated on the aircraft as part of its electronic system, such as an EFB or an FMS. D-ATIS may be incorporated into the core ATIS system, or be realized as a separate system with a data interface between voice ATIS and D-ATIS.