FAA rolls out advanced radar system

The Federal Aviation Administration late last month began using a new surveillance radar system that will increase airport capacity by allowing planes to land simultaneously on closely spaced parallel runways.

The Precision Runway Monitor (PRM) system developed by AlliedSignal and now in use at the Minneapolis-St. Paul International Airport in Minnesota tracks and updates every second the position and speed of each approaching plane while current radar systems do this once about every five seconds.

With this real-time data controllers can land planes side by side - instead of staggering planes for landing - without compromising safety on parallel runways that are less than 4 300 feet apart. The simultaneous landing will increase the total number of planes that can land at any one airport - an important advance at a time when many of the largest airports have reached capacity and aviation travel is expected to continue to increase.

"PRM provides a quick scan that illuminates the target every second " said Jack Ryan vice president of air traffic management at the Air Transport Association. "Because the controller is seeing this target five times more often he has the ability to detect if the plane [shifts] from one runway [approach] to another. This allows the controller to react almost instantaneously. There is enough reaction time to keep these planes separated."

PRM also would help alleviate delays created by bad weather when controllers cannot maintain visual separation and must rely on radar. "In clear weather pilots can conduct independent parallel approaches but in bad weather they can't see the other approach path " said Bill Keys the business development manager for radar systems at AlliedSignal Electronic & Avionics Systems. "As a result air traffic control has to increase the separation of the aircraft.

PRM reduces the separation required in bad weather so airports gain back that capacity they [lost]. This can be done with regular radar with parallel runways spaced more than 4 300 feet apart. But parallel runways that are closer than that need PRM." The PRM system communicates with transponders on planes processes the replies and then provides controllers with the information graphically on a high-resolution color display.

The system also issues visual and verbal warnings to the controller if a plane has veered off the appropriate approach path and into the so-called no transgression zone. The controller can then take the appropriate action to get the aircraft back on course. What is unique about PRM is that it uses a stationary electronically steered antenna with no moving parts in contrast to current airport surveillance radar which moves. PRM is designed so that a target tracked on one approach path would not garble a target on a parallel approach path.

PRM is scheduled to be installed in five airports including Minneapolis-St. Paul which has parallel runways that are closer than 4 300 feet apart New York's John F. Kennedy Airport St. Louis Philadelphia and Atlanta. Several airports such as Charlotte Pittsburgh and Detroit have asked the FAA for PRM to help land planes simultaneously on three parallel runways.

The FAA sponsored the development and testing of PRM systems several years ago to improve radar for parallel-runway approaches. The FAA has invested about $127.9 million in PRM since 1990 according to FAA officials. This includes the demonstration of two different technologies at Raleigh-Durham Airport and Memphis Airport and five production systems. AlliedSignal is the sole contractor for PRM and received its contract in March 1992.