Transportation Engineering

1. Prof. Sudhanshu Sekhar Das
Department of Civil
Engineering,
VSSUT, Burla, Odisha, India
Runway Orientation
Niharika Pattanayak
Department of Civil Engineering,
VSSUT, Burla, Odisha, India

2. Runway Orientation
The orientation of a runway is defined by the direction, relative to magnetic
north, of the operations performed by aircraft on the runway.
Typically, runways can be oriented in such a manner that they may be used in
either direction. It is less preferred to orient a runway in such a way that
operating in one direction is precluded, normally due to nearby obstacles.
In addition to obstacle clearance considerations, runways are typically oriented
based on the area’s wind conditions. As such, an analysis of wind is essential for
planning runways. As a general rule, the primary runway at an airport should be
oriented as closely as practicable in the direction of the prevailing winds. When
landing and taking off, aircraft are able to manoeuvre on a runway as long as
the wind component at right angles to the direction of travel, the crosswind
component, is not excessive.

3. • Runway orientation depends on
• Cross wind
• Wind coverage
• Calm period
• Wind rose diagrams
• Runway configurations
Runway orientation

4. Runways
A runway is a rectangular area on the airport surface prepared for the
take-off and landing of aircraft.
An airport may have one runway or several runways which are sited,
oriented, and configured in a manner to provide for the safe and efficient
use of the airport under a variety of conditions.
Factors which affect the location, orientation, and number of runways at
an airport include local weather conditions, particularly wind distribution
and visibility, the topography of the airport and surrounding area, the type
and amount of air traffic to be serviced at the airport, aircraft performance
requirements, and aircraft noise.

5. • The runway orientation, the orientation of a runway depends upon the direction of the
wind and to some extent on the area available for development.
• The determination of a runway orientation is a critical task and effect in terms of planning
and designing of an airport.
• Runways are always orientated in the direction of the prevailing winds
• The reason is to utilizing the maximum force of the wind at the time of take-off and
landing of any aircraft.
• Lift and drag produced.
• The direction of the runway controls the layout of the other airport facilities such as
passenger terminals, taxiways, apron configurations, circulation roads and parking
facilities
• According to FAA standards, runways should be orientated so that aircraft can take-off
and or land at least 95% of the time without exceeding the allowable crosswinds.

6. Points needs to be considered in orienting Runway or Taxiway
• Avoiding delay in the landing, taxing and take-off operations with least
interference
• Providing the shortest taxi distance possible from the terminal area to the
end of the runway
• Making provision for maximum taxiway, so that the landing aircraft can leave
the runway as quickly as possible to the terminal area
• Provide adequate separation in the air traffic pattern

7. Data required
• Map of the area and contours to examine the flatness of the area and the
possible changes in the longitudinal profiles, so as to keep them within
permissible limits.
• Wind data and the wind data is required in three dimensions i.e. direction,
duration and intensity (Km/hr) in the vicinity of the airport
• Fog characteristics of the area

8. Wind direction
Wind direction keeps on varying throughout the year. It effect the aircraft
movements differently and depends on how wind acts
• Head wind
• Tail wind
• Cross wind

9. • Wind which is coming from the front side opposite to the movement of the aircraft
known as the head wind. It is creating effect on the head of the aircraft.
• Provides braking effect during landing and greater lift on the wings of the aircraft
during take-off.
• Thus the length of the runway gets reduced and this reduction maybe around
10%
• When wind is coming from the tail side, known as tail wind.
• Wind blowing in the same direction of landing or taking-off of the aircraft
(moving in the direction of the movement of the aircraft)
• Provides a push from the back, increasing the stop distance and lift-off distance
• May be dangerous for the nose diving aircrafts

10. • There can be another wind which is coming at an angle Ɵ with respect to the
longitudinal axis of the flight path of the aircraft. It has two components one
longitudinally moving in the direction of the aircraft or opposite to the direction of
the aircraft, depending on the angle of the theta whether it is less than 900 or it is
greater than 900, and the other component at transverse direction of the
movement of the aircraft which is termed as the cross wind component.
• Cross wind component is then the aircraft may not manoeuver safely, there will
be drifting effect.
• Aircraft will be move in the lateral direction away from the runway strip and if
the cross wind component is very large, all chances that during a take-off or
landing, the aircraft may move towards the shoulder or even away from that.
• Cross wind component is to be specified and remain below that, for the safe
and smooth operation of the aircrafts.

11. The maximum allowable cross wind depends on
• Size of the aircraft
• Wing configuration
• Condition of the pavement surface
For medium and light aircraft cross wind component is taken as less than or
equals to 25 kilometers per hour
ICAO recommended a maximum allowable cross wind component as per the
different field lengths

12. Wind coverage
Wind coverage or usability factor of airport can be defined as a percentage of
time in a year, during which the cross wind component remains within the limit
or runway system in not restricted, because of the excessive cross wind
component.
• ICAO and FAA both recommends the minimum wind coverage area of 95%
• When a single runway or a set of parallel runways cannot be oriented to
provide the required wind coverage, one or more than one cross wind
runways needs to be provided and the combined value of those runways
should be more than 95%

13. Calm period
Calm period is the one when the wind intensity remains below 6.4 kilometers per
hour
• This is common to all directions and hence can be added to wind coverage for
that direction.
• Calm period = 100 - Total wind coverage
= 100 - ∑percentage of time wind is blowing in any direction, with any
speed

14. Once the maximum permissible cross wind component is selected, the most desirable direction
of runway for cross wind coverage can be determined by examining the wind characteristics for
the following conditions
• The entire wind coverage regardless of visibility or cloud ceiling (normal condition)
• Wind condition when the cloud ceiling is at least 300 m and the visibility is at least 4.8 km and
this value during the concession period (visual metrological condition)
• Wind condition when the cloud ceiling is between 60 m and 300 m and or the visibility is
between 0.8 km and 4.8 km (instrument metrological conditions)
• When visibility approaches 0.8 km and the cloud ceiling is 60 m, there is very little wind
present, the visibility gets reduced due to fog, haze or smoke
• Sometimes, the visibility may be extremely poor, yet there is no distinct cloud ceiling.
• 95% wind coverage is applicable to all the conditions
Runway Orientation

15. Wind Rose
• To finding the orientation of the runway to achieve the desired wind coverage
• Area is divided in the case of the wind rose diagram into 16 parts using an angle of
22.5O.
• Average wind data of 5 to 10 years is used for preparing such type of wind rose
diagrams
Two types of the wind rose diagram
• Type - I shows direction and duration of wind,
• Type - II shows the direction, duration and intensity of wind. All the three parameters
are shown in the second case.

16. Wind rose diagram Type - I
• It is based on the direction and duration of the wind
• Minimum 8 directions are taken and optimum 16 directions
• Data will include the total percentage of time in each direction
• Concentric circles are drawn to scale according to the percentage of time wind is blowing
in a direction
• Total percentage of time in each direction is marked on the radial line drawn in that
direction
• These points on radial lines are joined together to form a duration map
• Best direction of runway is indicated along that direction of the longest line on the wind
rose diagram.

18. Wind rose diagram Type - II
• Based on direction, duration and intensity of wind
• Concentric circles are drawn to scale according to the wind velocity and not on the basis of
the percentage time as taken in Type – I.
• The influence of wind is assumed to spread at an angle of 22.5 degrees in a direction
• Radial lines from the centre are drawn up to the midpoint of the two directions, thus
dividing the space into 16 directions and 64 parts.
• The categorized duration is marked in the related cell
• A transparent rectangular template of length greater than the diameter of the diagram
width equal to the twice of allowable cross wind component is made

19. • Wind rose diagram is fixed in position and the template is placed above it such that the centre
of the template coincides with the centre of diagram and the centre line of template should
pass through the direction.
• The template is fixed in position and the sum of the duration shown in cells superimposed by
the template is calculated. Sum will become the percentage and represent the total wind
coverage for that direction.
• The template is then rotated and placed in next direction. The total wind coverage is
calculated for that direction too.
• Same procedure is adopted for all directions
• The direction giving maximum wind coverage is suitable direction for orientation of the runway
• If single runway is not sufficient to provide the necessary coverage, multiple runway can be
planed to get the desired coverage

21. The appropriate orientation of the runway or runways at an airport can be determined
through graphical vector analysis using a wind rose. A standard wind rose consists of a
series of concentric circles cut by radial lines using polar coordinate graph paper. The radial
lines are drawn to the scale of the wind magnitude such that the area between each pair
of successive lines is centered on the wind direction.

22. As an example, assume that the wind data for all conditions of visibility are those shown
in Table. This wind data is plotted to scale as indicated above to obtain a wind rose, as
shown in Fig.
The percentage of time the winds correspond to a given direction and velocity range is
marked in the proper sector of the wind rose by means of a polar coordinate scale for
both wind direction and wind magnitude. The template is rotated about the center of
the wind rose, as explained earlier, until the direction of the centerline yields the
maximum percentage of wind between the parallel lines.
Once the optimum runway direction has been found in this manner, the next step is to
read the bearing of the runway on the outer scale of the wind rose where the centerline
on the template crosses the wind direction scale. Because true north is used for
published wind data, this bearing usually will be different from that used in numbering
runways since runway designations are based on the magnetic bearing. As illustrated in
Fig. 6-9, a runway oriented on an azimuth to true north of 90° to 270° (N 90° E to S 90°
W true bearing) will permit operations 90.8 percent of the time with the crosswind
components not exceeding 15 km/h.

23. Sector True
Azimuth
Wind Speed Range, Km/h Total
4-15 15-20 20-25 25-35
Percentage of Time
N 0.0 2.4 0.4 0.1 0.0 2.9
NNE 22.5 3.0 1.2 1.0 0.5 5.7
NE 45.0 5.3 1.6 1.0 0.4 8.3
ENE 67.5 6.8 3.1 1.7 0.1 11.7
E 90.0 7.1 2.3 1.9 0.2 11.5
ESE 112.5 6.4 3.5 1.9 0.1 11.9
SE 135.0 5.8 1.9 1.1 0.0 8.8
SSE 157.5 3.8 1.0 0.1 0.0 4.9
S 180.0 1.8 0.4 0.1 0.0 2.3
SSW 202.5 1.7 0.8 0.4 0.3 3.2
SW 225.0 1.5 0.6 0.2 0.0 2.3
WSW 247.5 2.7 0.4 0.1 0.0 3.2
W 270.0 4.9 0.4 0.1 0.0 5.4
WNW 292.5 3.8 0.6 0.2 0.0 4.6
NW 315.0 1.7 0.6 0.2 0.0 2.5
NNW 337.5 1.7 0.9 0.1 0.0 2.7
Subtotal 60.4 19.7 10.2 1.6 91.9
Calms 8.1
Total 100.0

24. A common compass rose as
found on a hydrographic
chart showing both true
north (using a nautical
star symbol) and magnetic
north with magnetic
variation.

27. Runway Configurations
The term “runway configuration” refers to the number and relative
orientations of one or more runways on an airfield. Many runway
configurations exist. Most configurations are combinations of several basic
configurations. The basic configurations are
(1) single runways,
(2) parallel runways
(3) intersecting runways, and
(4) open-V runways.
(5) Combinations of Runway Configurations

31. Single runway configuration: San Diego International Airport

32. Parallel runway configuration: Orlando International Airport.

33. Intersecting runways: LaGuardia
Airport, New York
Open-V runways: Jacksonville
International Airport

34. Complex runway system: Chicago O’Hare International Airport