# Taxiway and Exit Taxiway Design Study Notes for Civil Engineering Exams

By Vishwajeet Sinha|Updated : October 6th, 2020

### Taxiway design

• where R is the radius of curve in m, V is ther speed in kmph and f is the coefficint of friction between the tyre and pavement surface the value of f may be assumed as 0.13.
• For airport serving large subsonic jet transports, minimum value of redius of curvature is 120 m whatever be the speed.
• For supersonic transports, a minimum radius at 180 m is suggested.
• Horonieff equation
Radius of taxiway in metre Where, W = Wheel base os aircraft in m.
T = Width of taxiway pavement in m.
S = distance between miodway point of the main gear and the sdge of the taxiway pavement in m.

Design of Exit Taxiway Connecting Runway and Parallel Taxiway

(1) The most significant factor effecting the turning radius is the exit speed of aircraft

(2) Slightly widened entrance of 30 m gradually tapering to the normal width of taxiway is preferred. The widened entrance given to the pilot more latitude in using the exit taxiway

(3) Total angle of turn of 30° to 45° can be negotiated satisfactiorily the smaller angle seems to be praferable because the langth of curved path is reduced.

(4) For dmooth and comfortable turn, the turning radius should be determined from the equation (5) At hight turn – off speeds of 65 to 95 kmph (40 to 60 kmph), a compounder curve is necessary to minimize the tire wear on the nose gear. Therefore the main curve radius R2 should be preceded by a large radius curve R1 as shown in figure. Aircraft path approximates a spiral but still a compound curve is preferred as it is relatively easier to establish it is the field and its shape is similar to that of a spiral.

The followwing radius were foumnd experimentally suitable. R1 = radius of entrance curve

L1 = length of entrance curve

R2 = radius of central curve

L2 = length of central curve Radius of curvature for exit taxiway

(6) The length of larger radius curve can be roughly obtained from the following relation The value of C is 0.39

(7) Sufficient distance must be provided to comfortably decelerate an aircraft after it leaves the runway. This distance may be based on an averge deceleration rate of 1 m/sec2 (33. Ft/sec2). The stopping distance may be obtained from the following equation: Where d is deceleration in m/sec2. The stopping distance woula be meadured from the edge of the runway pavement along the exit taxiway.

Fillets

• Fillets are provided at the junction or intersection of two or more number of traffic ways e.g. runways, taxiways of aprons.
• ICAO recommends that the radius of the fillet should not be less than the width of taxiway
• Typical Runway and Taxiway Fillets  For small airports  For large airports

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