Airport Design in Software

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10 Sufficient distance must be provided to comfortably decelerate an aircraft after it leaves the runway It is suggested that for the present this distance be based on an average rate of deceleration of 33 ft/s2 This applies only to transport category aircraft Until more experience is gained with this type of operation the stopping distance should be measured from the edge of the runway A chart showing the relationship of exit speed to radii R1 and R2, and length of transition curve L1 is given in Fig 6-33 ICAO has indicated the relationship between aircraft speed and the radius of curvature of taxiway curves as illustrated in Table 6-22 For high-speed exit taxiways ICAO recommends a minimum radius

0 70

FIGURE 6-33

Source: International Civil Aviation Organization [4]

TABLE 6-22

of curvature for the taxiway centerline of 275 m (900 ft) for aerodrome code number 1 and 2 runways and 550 m (1800 ft) for aerodrome code number 3 and 4 runways This will allow exit speeds under wet conditions of 65 km/h (40 mi/h) for aerodrome code number 1 and 2 runways and 93 km/h (60 mi/h) for aerodrome code number 3 and 4 runways It also recommends a straight tangent section after the turnoff curve to allow exiting aircraft to come to a full stop clear of the intersecting taxiway when the intersection is 30 This tangent distance should be 35 m (115 ft) for aerodrome code number 1 and 2 runways and 75 m (250 ft) for aerodrome code number 3 and 4 runways [2, 4] A configuration for an exit speed of 60 mi/h and a turnoff angle of 30 is shown in Fig 6-34 The FAA recommends that the taxiway centerline circular curve be preceded by a 1400-ft spiral to smooth the transition from the runway centerline to the taxiway exit circular curve ICAO recommends the same geometry for both of these highspeed exits Right-angle or 90 exit taxiways, although not desirable from the standpoint of minimizing runway occupancy, are often

800' R (2

25' R (75 M)

50 M)

FIGURE 6-34

FIGURE 6-35

constructed for other reasons The configurations for a 90 exit and other common taxiway intersection configurations are illustrated in Fig 6-35 The dimensions labeled in Fig 6-35 are determined by the aircraft design group of the design aircraft These dimensional standards are provided in Table 6-23

The location of exit taxiways depends on the mix of aircraft, the approach and touchdown speeds, the point of touchdown, the exit speed, the rate of deceleration, which in turn depends on the condition of the pavement surface, that is, dry or wet, and the number of exits

I 75 50 60 75 50 55

V 150 250 85

Length of lead- L in to fillet Fillet radius for tracking centerline Fillet radius for judgmental oversteering symmetrical widening F

Letters correspond to the dimensions on Fig 6-35 Airplanes in airplane design group III with a wheelbase equal to or greater than 60 ft should use a fillet radius of 50 ft Dimensions for taxiway fillet designs relate to the radius of taxiway turn specified The center sketch of Fig 6-35 displays pavement fillets with symmetrical taxiway widening The lower sketch of Fig 6-35 displays a pavement fillet with taxiway widening on one side

TABLE 6-23

While the rules for flying transport aircraft are relatively precise, a certain amount of variability among pilots is bound to occur especially in respect to braking force applied on the runway and the distance from runway threshold to touchdown The rapidity and the manner in which air traffic control can process arrivals is an extremely important factor in establishing the location of exit taxiways The location of exit taxiways is also influenced by the location of the runways relative to the terminal area Several mathematical analyses or models have been developed for optimizing exit locations While these analyses have been useful