OTHER FEATURES

Up to this point we have only been discussing primary radar returns (actual reflections from a target), but a controller sees a lot more than raw radar returns on his/her radar display. The total presentation is made up of a combination of real-time information, video map overlays, and processed information that includes some or all of the following items:

• Passive radar reflections or what we have been referring to as primary radar returns. This type of target is only found on surveillance radar systems and is not associated with digital radar equipment. With digital radar, all of the processed information on the radar display would be displayed in a symbolic and graphic format.

• An interchangeable video map overlay which usually depicts obstructions, airports, airspace boundaries, airways and/or navigational aids, and instrument approach courses. A controller has the ability to select from the several maps, including an emergency map which shows highway markings and an exploded view of airports and emergency landing areas.

• Secondary, or active radar returns, which are electronic signals from a transponder and are referred to as beacon replies. The target associated with this signal overlies the primary target return from those aircraft that are equipped with and using a transponder. The resultant target is called a beacon control slash and looks like a longer, slightly fat-in-the-middle, primary return. (This is a good place to mention a very important aspect of active radar returns. In order for this type of target to be displayed, both radar and transponder have to be working together. If the transponder is not broadcasting an identifiable reply, it might as well be turned off. This is one reason that we sometimes cannot find an aircraft that is receiving an interrogation signal on its transponder, and it is the most important reason to keep that thing calibrated.) When this beacon control slash is displayed on a radar scope using selected beacon code enhancement features, the target has two slashes. The second of these targets is always in a direct line between the radar antenna and the aircraft and positioned beyond the real target. The space between these slashes will fill in when the controller asks a pilot to ident. This type of system is normally only used when a facility is not equipped with or is not using a numeric or alphanumeric tracking system.

• Numeric or alphanumeric characters which provide information about the aircraft's call sign, speed, and altitude.

There are several other enhancements associated with this system so let's talk a little more about this system.

Most ATC facilities are now equipped with some type of numeric or alphanumeric tracking system that is associated with the transponder or beacon reply, and some even have systems that will track primary targets. In the terminal environment, there is a wide range of equipment sophistication in use depending on the complexity level and needs of the facility and the type of equipment that was in use at the time it was installed. This equipment is constantly being upgraded as technology improves, as FAA funds permit, and as the needs of the facility dictate.

TPX-42

One of the earlier, older systems, called TPX-42, uses a numeric readout on the radar scope and will only depict transponder codes and, in those cases where the transponder has Mode C capability, the altitude of a target. Another, slightly more sophisticated system, called direct altitude and identity readout (DAIR), is essentially an enhanced TPX-42 system capable of tracking a target and using alphanumeric characters to depict call sign, altitude, ground speed, and some additional information associated with that flight. This system is used primarily within the military and will interface with some of the systems in use at ARTCCs.

ARTS

The most commonly used types of alphanumeric tracking systems in use in the terminal environment are called ARTS. There are several different generations of ARTS, suffixed 1, 2, 3, and 3A, depending on the generation being used. All of these systems have a wide range of services available to the controller and, indirectly, the pilot. As an example, ARTS-3A has the capability of tracking a target while displaying, through the use of a data block which follows the target, the following information:

• the target's call sign

• type of aircraft

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