This description comes from the FAA's Technical Center and is dated April 1997.

The Precision Runway Monitor

The Precision Runway Monitor (PRM) System allows simultaneous, independent Instrument Flight Rules (IFR) approaches at airports with closely spaced parallel runways.

During instrument meteorological conditions, airports with parallel runways spaced less than 4,300 feet apart cannot conduct independent simultaneous operations due to existing equipment limitations. This results in decreased capacity during inclement weather. Congress mandated that the FAA procure and install five precision runway monitor systems to address this issue at qualifying airports.

The PRM program developed a highupdate-rate phased array, an electronically scanned monopulse beacon radar, and computer predictive displays that enable controllers to monitor aircraft on independent instrument flight rule approaches to dual- and triple-parallel runways spaced less than 4,300 feet apart.

PRM Antenna

Conducting independent approaches will enable airports to increase throughput capacity, reduce delays, and save fuel during reduced visibility. The electronically scanned antenna system (see photo) provides a faster update rate than conventional radars because 'it uses a computer-controlled electronic scanning sensor beam. The update rate requirement for parallel runways, down to 3,400 feet spacing, is 2.4 seconds or less. The FAA has awarded a sole-source contract for five limited production, electronically scanned units. These systems have a 1.0 second update rate with a capacity of 35 aircraft tracks and a mean azimuth accuracy of 1.0 milliradian, The system includes high-resolution displays with specific blunder alarms and three electronic cabinets (see photo as shown below) to enable a monitor controller to precisely monitor landing aircraft.

Efforts are continuing to develop air traffic control procedures and surveillance/ navigation requirements to support independent approaches to dual- and tripleparallel runways spaced as low as 3,000 feet apart. Results from real-time simulations indicate that using precision runway monitor systems and offset localizers will support independent approaches to dual-parallel runways spaced 3,000 feet apart.

This program also conducts research and development for a multi lateration, low-cost alternative to the electronically scanned system. The multilateration system will use small, strategically placed sensors outside the airport and on the airport surface to triangulate an aircraft's position based on transponder beacon replies. The multilateration approach will capitalize on work being performed in the Airport SurfaceTarget Identification System (ATIDS) program for future precision runway monitor requirements.

Five electronically scanned production systems will be deployed at Minneapolis-St. Paul, St. Louis, JFK, Philadelphia, and Logan International Airports with options for one to three more.

Accomplishments include the development of simulation and procedures at Atlanta, JFK, St. Louis, and Philadelphia airports. Also, the installation contract option for the St. Louis airport was awarded. Operational test and evaluation of the production PRM was completed in 1996. The first site was commissioned at Minneapolis-St. Paul International Airport in 1997. The demonstration of multilateration at Atlanta Hartsfield Airport was recently completed. Installations of the production PRM systems have begun at the St. Louis, Logan, and JFK International Airports.

Continue support of the installation of production PRM systems and future research and development and procurements activities is planned.

To find out more about the Precision Runway (PRIM) Program, contact:

Communications/Navigation/Surveillance
Engineering and Test Division
Surveillance Branch

Federal Aviation Administration
William J. Hughes Technical Center
Atlantic City International Airport, NJ 08405
Phone: (609) 485-5392
Fax: (609) 485-5995