PRECISION APPROACH RADAR

While ASR provides pilots with horizontal guidance for instrument approaches via a ground-based radar, Precision Approach Radar (PAR) provides both horizontal and vertical guidance for a ground controlled approach (GCA). In the U.S., PAR is mostly used by the military. Radar equipment in some ATC facilities operated by the FAA and/or the military services at joint-use locations and military installations are used to detect and display azimuth, elevation, and range of aircraft on the final approach course to a runway. This equipment may be used to monitor certain nonradar approaches, but it is primarily used to conduct a precision instrument approach.

BRIGHT RADAR INDICATOR TERMINAL EQUIPMENT

Bright Radar Indicator Terminal Equipment (BRITE) provides radar capabilities to towers, a system with tremendous benefits for both pilots and controllers. Unlike traditional radar systems, BRITE is similar to a television screen in that it can be seen in daylight. BRITE was so successful that the FAA has installed the new systems in towers, and even in some TRACONs. In fact, the invention of BRITE was so revolutionary that it launched a new type of air traffic facility ? the TRACAB, which is a radar approach control facility located in the tower cab of the primary airport, as opposed to a separate room.

In the many facilities without BRITE, the controllers use strictly visual means to find and sequence traffic. Towers that do have BRITE may have one of several different types. Some have only a very crude display that gives a fuzzy picture of blips on a field of green, perhaps with the capability of displaying an extra slash on transponder-equipped targets and a larger slash when a pilot hits the ident button. Next in sophistication are BRITEs that have alphanumeric displays of various types, ranging from transponder codes and altitude to the newest version, the DBRITE (digital BRITE). A computer takes all the data from the primary radar, the secondary radar (transponder information), and generates the alphanumeric data. DBRITE digitizes the image, and then sends it all, in TV format, to a square display in the tower that provides an excellent presentation, regardless of how bright the ambient light.

One of the most limiting factors in the use of the BRITE is in the basic idea behind the use of radar in the tower. The radar service provided by a tower controller is not, nor was it ever intended to be, the same thing as radar service provided by an approach control or Center. The primary duty of tower controllers is to separate airplanes operating on runways, which means controllers spend most of their time looking out the window, not staring at a radar scope.

RADAR COVERAGE

A full approach is a staple of instrument flying, yet some pilots rarely, if ever, have to fly one other than during initial or recurrency or proficiency training, because a full approach usually is required only when radar service is not available, and radar is available at most larger and busier instrument airports. Pilots come to expect radar vectors to final approach courses and that ATC will keep an electronic eye on them all the way to a successful conclusion of every approach. In addition, most en route flights are tracked by radar along their entire route in the 48 contiguous states, with essentially total radar coverage of all instrument flight routes except in the mountainous West. Lack of radar coverage may be due to terrain, cost, or physical limitations.

New developing technologies, like ADS-B, may offer ATC a method of accurately tracking aircraft in nonradar environments. ADS-B is a satellite-based air traffic tracking system enabling pilots and air traffic controllers to share and display the same information. ADS-B relies on the Global Positioning System (GPS) to determine an aircraft’s position. The aircraft’s precise location, along with other data such as airspeed, altitude, and aircraft identification, then is instantly relayed via digital datalink to ground stations and other equipped aircraft. Depending on the location of the ground based transmitters (GBT), ADS-B has the potential to work well at low altitudes, in remote locations, and mountainous terrain where little or no radar coverage exists.