Airport Development Reference Manual 172
F5.3.3 ATC Procedures and Equipment
The performance of radar equipment and ATC limitations sometimes impose a separation greater than the minima shown in Table F5.1. These limitations should be dealt with prior to considering investing in new runways.
F5.3.4 The Mix of Aircraft
As shown in Table F5.1, separation between aircraft depends on the aircraft category. Therefore, the mix of successive aircraft operating will have an impact on the overall separation and the runway capacity. For example, an airport operating with a majority of medium size aircraft will have an average arrival separation of 3NM. The same airport serving a mix of small, medium and heavy aircraft will have a separation of 3 to 6NM, depending on the sequence of arrivals, and will have a significantly reduced runway capacity.
F5.3.5 The Mix of Arrivals and Departures
An airport is part of a network and has a mix of arrivals and departures during the day. Aircraft that land at an airport will eventually take-off. The distribution of arrivals and departures has an impact on runway capacity. ATC not only needs to consider separation between successive arrivals and successive departures, but also gaps between arrivals preceded or followed by departures.
F5.3.6 The Mixed or Segregated Mode
Airports with two or more runways sometimes dedicate runways to departures and runways to arrivals. However, the arrival and departure peaks rarely coincide, and the separation between successive arrivals and successive departures are different. This results in gaps on one runway when another is at capacity; in these situations mixing arrivals and departures as if operating with a single runway can increase capacity.
F5.3.7 Runway Configuration
Parallel runways with adequate spacing (1035 m or more) can process independent arrivals. Interaction between runways is a constraint that limits capacity when the distance between runways does not meet the minimum distance requirement or runways intersect. Independent parallel runways are recommended for that reason.
F5.3.8 Precision Runway Monitor (FAA)
The PRM is a surveillance radar that updates essential aircraft target information 4 to 5 times more often than conventional radar equipment. PRM also predicts the aircraft track and provides alarms when an aircraft is within ten seconds of penetrating the non-transgression zone. Use of the PRM allows air traffic controllers to ensure safe separation of aircraft on the parallel approach courses and maintain an efficient rate of aircraft landings during adverse weather conditions. In December 2001, the FAA determined that the Traffic Alert and Collision Avoidance System (TCAS) may be operated in the resolution advisory (RA) mode when conducting a PRM approach.
The FAA has commissioned PRMs at Minneapolis and St. Louis, and at Philadelphia International Airport in September 2001. PRM's were scheduled for commissioning at San Francisco and John F. Kennedy in late-2002, Cleveland in late-2004, and Atlanta in 2006, coincident with the completion of the fifth parallel runway. The FAA has also approved procedures using a PRM to allow simultaneous instrument approaches in adverse weather