The Airfield Layout
Logan's airfield layout, illustrated in Figure 1, consists of six runways, which vary in length from 2,557 feet to 10,081 feet. Logan's runways are aligned in three directions with runway ends pointing toward six distinct compass headings. Aircraft must generally take off and land into the wind, so the availability of specific runway configurations is determined by wind speed and direction, and other weather conditions. The runway layout provides necessary operating flexibility given Logan's coastal location and highly variable wind conditions. Non-coastal airports that do not experience the same variation in wind conditions may have a simpler airfield layout and fewer required operating configurations.
Runway Use Configurations
There are several primary runway configurations in use at Logan, with over 80 operating subsets of these configurations. The operational capacities of Logan's existing configurations range from a maximum of approximately 120 operations per hour when the weather is good, winds are light, and three runways are available, to fewer than 60 hourly operations for a single runway.
Logan's highest capacity configurations have three active runways which allow FAA controllers to segregate arriving aircraft of different size classes into two arrival streams and to use the third runway for aircraft departures. High capacity runway configurations are available at Logan nearly 80 percent of the year. For the remaining part of the year, poor wind and weather conditions restrict the airport to low capacity configurations with just one or two available runways.
As shown in Figures 2 to 5, (figures are ordered top to bottom, please rollover over images for more information) the northeast-southwest-northwest configurations are the highest capacity configurations at Logan. These include the Runways 4L, 4R, and 9 configuration, Runways 22L, 22R, and 27 configuration and the Runways 33L, 32 and 27 configuration. With three available runways, these configurations maximizethe airports operating efficiency by providing two runways for arriving aircraft, which permits air traffic control to segregate aircraft of different size classes. Conversely, when the airport is restricted to a two-runway or one-runway configuration due to very strong winds, low visibility or snow conditions for example, with a single arrival stream, airfield capacity drops significantly.
Figure 6 illustrates the percentage of time that winds from different directions occur at Logan during a typical year. In light winds and good visibility, high capacity three-runway configurations are generally available. With moderate northeast and southwest winds, Logan can also operate on high capacity runway configurations. With northeast winds, the Runways 4L, 4R and 9 configuration is available for use (see Figure 2). When wind direction shifts to the southwest, the Runways 22L, 22R and 27 configuration is used (see Figure 3). When winds shift to the northwest, the Runways 33L, 32 and 27 configuration is used (see Figure 4). When winds are from the southeast, Runways 15R, 9, 14, and 15L are used (see Figure 5).