Taxiway Design 295730

TAXIWAYS

TAXIWAY DESIGN

Taxiways • Taxiway provides access to the aircrafts from the runways to the loading apron or service hangar.

Factors controlling Taxiway Layout • Taxiways should be arranged that the aircrafts which have just landed & taxiing towards apron should not interfere with the aircrafts taxiing for take-off. • The taxiway should be located at various points along the runway so that the landing aircraft leaves the runway as early as possible. Such taxiways are called e it ta iwa s . • Exit taxiways should be designed for high turn off speeds of aircrafts so that runway occupancy time gets reduced. • The route should be a shortest distance from the apron to the runway end. • Intersection of taxiway & runway should be avoided.

GEOMETRIC DESIGN STANDARDS • • • • • • • •

Length of taxiway Width of taxiway Width of safety area Longitudinal gradient Transverse gradient Rate of change of longitudinal gradient Sight distance Turning radius

TAXIWAY GEOMETRICS AS PER ICAO Classifica tion by ICAO

Taxiway width

Max. Longitudinal gradient (%)

Mini. Transverse gradient (%)

Max. rate of change of longitudinal gradient per 30m (100ft) in %

Meter

Feet

A

22.5

75

1.5

1.5

1.0

B

22.5

75

1.5

1.5

1.0

C

15.0

50

3.0

1.5

1.0

D

9.9

33

3.0

2.0

1.2

E

7.5

25

3.0

2.0

1.2

Safety area width

Turfed or paved shoulders are not mandatory but are suggested if need exists.

EXIT TAXIWAYS Factors controlling location of exit taxiways – Number of exit taxiways – Exit speed – Type of aircrafts – Weather conditions – Topographical features – Pilot variability

AVERAGE ACCEPTANCE RATE

Optimum location of Exit Taxiways ARRIVAL RATE

WAVE-OFFS BALANCE PT. ACCEPTANCE RATE

ARRIVAL RATE

Acceptance rate of runway with a system of exit taxiways = Arrival rate of aircrafts

• The point beyond which the acceptance rate deviates from the ideal relationship of equal arrival and acceptance rate is balance point . • Balance point occurs when the runway is loaded to its full capacit and such situation is runway saturation . • At higher arrival rates, the runway cannot accept all aircrafts and hence few are waved off. For a given set of conditions, the exit taxiways should yield the highest possible rate of acceptance. Such location of e it ta iwa is Optimum location .

Separation Clearance • two parallel trafficways should be separated by an adequate distance from each other • depends upon – type of airport – wing span of aircraft – navigational aids

HOLDING APRON • These are also known as run-up or warm-up pads • located, where the aircrafts wait for their turn to take-off, and where they are finally checked before the take-off. • Holding aprons are usually provided near the runway ends • sufficiently large so that if one aircraft is unable to take-off another can it for the fake-off • size of holding apron – peak hour aircraft movements – aircraft size – ground maneuvering characteristics

• Holding apron may not be required if the volume of traffic is small

TURNAROUND OR BY TAXIWAY • Many airports in the initial stages have low airport traffic and are constructed without a parallel taxiway. • As the traffic increases, the need of a parallel taxiway may be felt although it may not always be feasible to provide it from economic considerations • As a substitute for parallel taxiway, sometimes a turnaround or by taxiway is constructed which also serves the purpose of a holding apron.