ATIS - Automated Terminal Information Service

The Automated Terminal Information Service or ATIS (pronounced AY-tis) is a recorded message that provides pilots with current airfield and weather information. These recordings provide information such as the present winds, altimeter settings, active runways, airfield hazards or any other pertinent airfield information relative to the safety of flight. Each recording is normally updated hourly, however, at times of rapidly changing weather conditions the recording may be updated as often as necessary. Each recording is identified by a phonetic letter which changes with each updated broadcast. ATIS broadcasts are often also simulcast on the local VOR, VOT, or VHF Omnidirectional Range test transmitter.

Pilots are required to check the current ATIS prior to their initial contact with ATC. This initial call may sound something like,

"Clearance it's Air Canada 856, gate 22 with information Delta".

This serves as notice to the controller that the pilot has received the latest ATIS information and is aware of current conditions. With technology such as ACARS, equipped aircraft often receive the current ATIS information automatically via datalink. Another standard with ATIS recordings is the use of TVGS or Text to Voice Generating System. This system compiles data for the ATIS broadcast and automatically generates a synthesized voice recording of the information. The following is an example of an ATIS broadcast as monitored on 120.825 MHz from Pearson International Airport:

"This is Toronto Int'l Airport information ALPHA, Toronto weather at 2100 Zulu, 5,000 scattered, visibility 25, temperature 24, dewpoint 12, wind 280 degrees at 6 knots, altimeter 3020. The IFR approach is ILS runway 24 right, tower frequency 118.35 and ILS runway 23 tower frequency 118.7. Departure runways are 24 right and 23. Inform Toronto ATC on initial contact that you have received information ALPHA".

Clearance Delivery

All IFR flights require a "flight plan" which is filed, accepted, and entered into the ATC system computers. Controllers working the clearance delivery position are responsible for conveying and/or verifying the filed flight plan with the pilot in order to confirm the routing. The route must allow for enough room between cruising aircraft to avoid conflicts. If a conflict is detected a routing amendment is issued which may alter the original flight plan. Sometimes, in lieu of an amendment, a flight may be held at the gate to allow the original flight plan to remain active. This is more commonly known as a "gate hold". By way of an example, if any one of the enroute centers are experiencing traffic congestion, aircraft destined for airports within these areas may be required to delay their departure.

Center Stored Routes

A system known as "Center Stored Routes" was developed to allow controllers to issue a flight plan clearance without having to read the entire flight plan, which in some cases can be rather lengthy. A center stored route is kept on file and activated prior to a flights departure. Because of the airways structure, scheduled flights often use the same route between city pairs. When a pilot contacts clearance delivery the controller now only has to use the term "center stored route" to describe the flight plan route. By reading the following two examples it is easy to see the time saved with this procedure.

(Complete flight plan clearance)

"Air Canada 430 is cleared to the Dorval Airport via the Pearson 1 Departure, Toronto 078 degree radial, J-594 Massena, Victor 203 Franx, Franx 5 arrival, depart runway 23, squawk 2022".

(Center stored clearance)

"Air Canada 430 is cleared to the Dorval Airport via the Pearson 1 Departure, "center stored route", depart runway 23, Squawk 2022".

Once the controller has read the routing clearance over the air, the pilot is expected to read it back to confirm that all the details have been heard correctly. This is very critical in case there has been an amendment to the original flight plan.

PDC - Pre Departure Clearance

The "Pre-Departure Clearance" is yet another time saving system becoming more widely used by airlines and ATC for flight plan verification. This system uses the ACARS datalink network to uplink the filed flight plan to the cockpit printer. Each PDC request is assigned a corresponding numerical identifier (see example below) which the pilot can then refer to when contacting Clearance Delivery. The PDC request is initiated by the pilot, within a short period of time the aircrew will then receive a printed copy of the filed flight plan. Examples of this are as follows;

C-FMWP BOEING 767-333ER
ATC P3
Using Ground Station 2
Message Type 4P
64 YYZOWAC 03JAN/0208 YYZ C-FMWP/ /0862
TIMESTAMP 03JAN00 02:08
*PRE-DEPARTURE CLEARANCE*
610
FLT ACA0862/02 CYYZ
H/B763/W P0235 BQ330
XPRD 0516 EDCT 2135
USE SID PEAR 8
DEPARTURE RUNWAY 23
DEST EGLL

C-FMWP BOEING 767-333ER
Using Ground Station 2
Message Type 4P
CONTACT 121.3 WITHIN 10 MIN OF PUSH
WITH SID, RWY AND IDENTIFIER 275U
YYZ079 J594 MSS J586 YJN
46N070W MIILS N113B DOTTY
NATU 54N015W NATU //

Tower - Airport Control

The Control Tower is often considered the heart of an airport, and rightfully so. Constructed in all shapes and sizes, control towers are usually located in an area which give the controllers the best vantage point over the entire field. No aircraft may land or depart without permission from the control tower. Aircraft operating within an area referred to as the "Airport Control Zone" also receive their instructions from the tower. Aircraft movements both on the ground and within the airport control zone fall under two separate categories of control. Control between the terminal buildings and the runways is the responsibility of ground controllers. Aircraft engaging in takeoff or landing procedures are handled by Airport Controllers. Depending on the size of the airport there may be more than one controller assigned to either position.

Airport Control Zone

Airport Control Zones have been designated at certain airports to keep IFR flights within controlled airspace during approaches and to facilitate the control of VFR and IFR traffic. These zones normally have a radius of 7 nautical miles and are capped at 3,000 feet above aerodrome elevation. Aircraft within this area are required to report to the control tower on the assigned frequency. Military control zones usually have a 10 nautical mile radius and are capped at 6,000 feet above aerodrome elevation.

Two examples of tower transmissions to aircraft:

"Air Canada 792, taxi Delta, cross runway 33, enter the ramp at Delta Papa"

"Air Canada 856, clear for takeoff runway 23, winds 230 at 6, contact departure 128.8 airborne"

Ground Control

All communications heard on the ground control frequencies are directed to aircraft or emergency and airport service vehicles transiting the taxiways or apron areas. The main responsibility of ground controllers is to direct aircraft safely to and from their gates or parking stands. Ground controllers take up a position in the control tower to better coordinate aircraft movements with "Airport Controllers" who issue landing and takeoff clearances. A base map of your local airport will enable you to follow an aircraft's progress to and from the runway. Pilots are required to contact ground control for taxi instructions once clear of the active runway or prior to pushback from their gate or parking stand. Aircraft that are being towed to and from airport hangars also receive their instructions from ground controllers. The tow operator is responsible for obtaining this clearance. All airport service and emergency vehicles are required to contact ground control with their intentions prior to entering a taxiway or runway.

A typical instruction from a ground controller would be;

"Air Canada 791, taxi via Bravo to Hotel, right turn on Hotel and hold short of runway 23, contact tower on 118.7 in the holding bay".

Apron Control

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