This document discusses how wind data is used to determine the optimal orientation of runways at airports. It describes how wind data including direction, speed, and duration is collected over many years and displayed on a wind rose diagram. The wind rose diagram shows the percentage of time winds blow from different directions at various speeds. To determine the best runway orientation, a strip representing the allowable crosswind component is placed along different directions on the wind rose. The direction that captures the highest percentage of winds within the strip, plus calm winds, is selected as the orientation for the runway. Having runways aligned properly reduces crosswinds and allows for safer takeoffs and landings.

1. Lecture 2
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Unit-IVAirportE
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2. Wind Effect on Aircraft Movement
Head wind is good for
both landing and take-off Dangerous!
Reference: http://www.physicsclassroom.com
Tail wind pushes the
landing aircraft-needing
longer runway to stop!
2

3. In landing, headwind provides necessary
drag force to slow down aircraft
3

4. In take-off, headwind provides lift
L
I
F
T
Reference: http://www.walluyo.com 4

5. V Sin(𝜽)
𝜽
Cross Wind Component
Wind Direction
Crosswind
Chaos
V
Cos(𝜽)
Head Wind/Tail Wind
Component

6. Crosswind Component Chaos
• It tends to drift the aircraft away from the runway
centerline.
• Its limiting values are prescribed by ICAO and FAA on
the basis of size of aircraft:
– Small: 15kmph
– Mixed: 25kmph
– Large: <35kmph
6

7. 7
Runway Orientation
• For runway orientation wind data is utilized
• Wind data comprises of:
– wind intensity,
– duration of movement of wind
– direction of movement of wind

8. 8
Typical Wind Data
Direction
Duration of Wind (%)
Total Percentage of
time wind blew
between 6.0 to
60kmph
6.0-25
kmph
25-40
kmph
40-60
kmph
N 7.4 2.7 0.2 10.3
NNE 5.7 2.1 0.3 8.1
NE 2.4 0.9 0.6 3.9
ENE 1.2 0.4 0.2 1.8
E 0.8 0.2 0 1
ESE 0.3 0.1 0 0.4
SE 4.3 2.8 0 7.1
SSE 5.5 3.2 0 8.7
S 9.7 4.6 0 14.3
SSW 6.3 3.2 0.5 10
SW 3.6 1.8 0.3 5.7
WSW 1 0.5 0.1 1.6
W 0.4 0.1 0 0.5
WNW 0.2 0.1 0 0.3
NW 5.3 1.9 0 7.2
NNW 4 1.3 0.3 5.6
Total 86.5

9. 9
Wind Data: Collection and Application
• Data collected over a period of, typically, 10
years.
• Systematically arranged on Wind Rose
diagram.

10. 10
Wind Rose Diagram
• It is a compass shaped diagram
• It exhibits wind direction, duration of wind
movement at different speed ranges
• It shows wind speeds
• It is used in working out the orientation of
runway

11. 11
Type of Wind Rose Diagrams
Type-I Shows
Direction and
Duration of
wind ONLY
Type-II Shows
Direction,
Duration and
Speed of wind

12. Types of Wind Rose Diagram
• Type 1:
– Concentric Circles: Wind DURATION
– Radial Lines: DIRECTION
• Type-2:
– Concentric Circles represent: WIND SPEED
– Numbers in Sectors: DURATION
– Radial Lines: DIRECTION

13. Components of Wind Rose: Type-I
Circles show
duration for
which wind blew
1
13
2
3
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
15
14
16
13
1
2
3
4
5
6
8
9
10
11
12
7
Procedure to use Wind Rose
Diagram Type-I
Step-1:
Draw concentric circles showing
wind durations
Step-2:
Divide the circles into 16
segments
Step-3:
Plot the wind duration along
respective directions and join
the points
Step-4:
Runway is oriented along the
longest line in the diagram

14. Wind Rose: Type-I
Direction
Duration of Wind
(kmph)
N 10.3
NNE 8.1
NE 3.9
ENE 1.8
E 1
ESE 0.4
SE 7.1
SSE 8.7
S 14.3
SSW 10
SW 5.7
WSW 1.6
W 0.5
WNW 0.3
NW 7.2
NNW 5.6
0
3
6
9
12
15
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
Runway
Orientation
14

15. 60kmph
15
6.0kmph 25kmph
40kmph
Wind Rose Type-II
Step 1: Draw concentric circles showing wind speed

16. Wind Rose Type-II
16
Step-2: Mark 16 directions, each with a wind coverage area of 22.5, as
shown in the next slide

17. Wind Coverage Angle and Area
1
2
3
4
N
5
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
22.5
17
The percentage of time in a year during which the crosswind component remained below the
specified value (See Slide no. 6).

18. Wind Rose Type-II
Step-3: Draw radial directions to show wind coverage area. This creates
segments in which wind coverage (% time) is written
18

19. Wind Rose Type-II
Step-4: Mark Calm Period
Calm
Period
Calm Period is
the percentage
of time during
which the wind
is blowing at a
speed less than
6.0kmph (For
this example).
Calculation on
next slide
19

20. Typical Wind Data
Direction
Duration of Wind (%)
Total Percentage of
time wind blew
between6.4 to
60kmph
6.0-25
kmph
25-40
kmph
40-60
kmph
N 7.4 2.7 0.2 10.3
NNE 5.7 2.1 0.3 8.1
NE 2.4 0.9 0.6 3.9
ENE 1.2 0.4 0.2 1.8
E 0.8 0.2 0 1
ESE 0.3 0.1 0 0.4
SE 4.3 2.8 0 7.1
SSE 5.5 3.2 0 8.7
S 9.7 4.6 0 14.3
SSW 6.3 3.2 0.5 10
SW 3.6 1.8 0.3 5.7
WSW 1 0.5 0.1 1.6
W 0.4 0.1 0 0.5
WNW 0.2 0.1 0 0.3
NW 5.3 1.9 0 7.2
NNW 4 1.3 0.3 5.6
Total 86.5
Calm Period = 100- 86.5 = 13.5 Percent 20

21. 7.4
5.7
2.4
1.2
0.8
0.3
4.3
5.5
9.7
6.3
3.6
1.0
0.4
0.2
5.3
4.0
Calm
Period
21
0.1
2.7 2.1
0.9
0.4
0.2
0.1
2.8
3.2
4.6
3.2
1.8
0.5
0.1
1.9
1.3
0.0
0.2
0.3
0.6
0.2
0.0
0.0
0.0
0.0
0.5
0.3
0.0
0.1
0.0
0.0
0.3
Filling Wind Durations
Step-5: Fill wind coverage in designated segment for each direction from
the wind data

22. 22
Step-6: Determination of Runway
Orientation
• Place transparent strip of width equal to the
crosswind component (at the same scale)
along a direction
• Add the wind coverage percentages
superimposed by the strip + Calm period.
• Then place the strip along all other directions
See This procedure in the next slides…

23. 7.4
5.7
2.4
1.2
0.8
0.3
4.3
5.5
9.7
6.3
3.6
1.0
0.4
0.2
5.3
4.0
0.1
2.7 2.1
0.9
0.4
0.2
0.1
2.8
3.2
4.6
3.2
1.8
0.5
0.1
1.9
1.3
0.0
0.2
0.3
0.6
0.2
0.0
0.0
0.0
0.0
0.5
0.3
0.0
0.1
0.0
0.0
0.3
Cross Wind
Component=25kmph
23
Strip placed
along the
North-South
direction
Count the area
of sector under
the strip

24. 7.4
5.7
2.4
1.2
0.8
0.3
4.3
5.5
9.7
6.3
3.6
1.0
0.4
0.2
5.3
4.0
0.1
2.7 2.1
0.9
0.4
0.2
0.1
2.8
3.2
4.6
3.2
1.8
0.5
0.1
1.9
1.3
0.0
0.2
0.3
0.6
0.2
0.0
0.0
0.0
0.0
0.5
0.3
0.0
0.1
0.0
0.0
0.3
24

25. 7.4
5.7
2.4
1.2
0.8
0.3
4.3
5.5
9.7
6.3
3.6
1.0
0.4
0.2
5.3
4.0
0.1
2.7 2.1
0.9
0.4
0.2
0.1
2.8
3.2
4.6
3.2
1.8
0.5
0.1
1.9
1.3
0.0
0.2
0.3
0.6
0.2
0.0
0.0
0.0
0.0
0.5
0.3
0.0
0.1
0.0
0.0
0.3
25

26. 7.4
5.7
2.4
1.2
0.8
0.3
4.3
5.5
9.7
6.3
3.6
1.0
0.4
0.2
5.3
4.0
0.1
2.7 2.1
0.9
0.4
0.2
0.1
2.8
3.2
4.6
3.2
1.8
0.5
0.1
1.9
1.3
0.0
0.2
0.3
0.6
0.2
0.0
0.0
0.0
0.0
0.5
0.3
0.0
0.1
0.0
0.0
0.3
26

27. 7.4
1.2
0.8
0.3
4.3
5.5
9.7
6.3
3.6
1.0
0.4
0.2
5.3 2.4
4.0 5.7
0.1
2.7 2.1
0.9
0.4
0.2
0.1
2.8
3.2
4.6
3.2
1.8
0.5
0.1
1.9
1.3
0.0
0.2
0.3
0.6
0.2
0.0
0.0
0.0
0.0
0.5
0.3
0.0
0.1
0.0
0.0
0.3
27

28. 7.4
5.7
2.4
1.2
0.8
0.3
4.3
5.5
9.7
6.3
3.6
1.0
0.4
0.2
5.3
4.0
0.1
2.7 2.1
0.9
0.4
0.2
0.1
2.8
3.2
4.6
3.2
1.8
0.5
0.1
1.9
1.3
0.0
0.2
0.3
0.6
0.2
0.0
0.0
0.0
0.0
0.5
0.3
0.0
0.1
0.0
0.0
0.3
28

29. 7.4
5.7
2.4
1.2
0.8
0.3
4.3
5.5
9.7
6.3
3.6
1.0
0.4
0.2
5.3
4.0
0.1
2.7 2.1
0.9
0.4
0.2
0.1
2.8
3.2
4.6
3.2
1.8
0.5
0.1
1.9
1.3
0.0
0.2
0.3
0.6
0.2
0.0
0.0
0.0
0.0
0.5
0.3
0.0
0.1
0.0
0.0
0.3
29

30. 7.4
5.7
2.4
1.2
0.8
0.3
4.3
5.5
9.7
6.3
3.6
1.0
0.4
0.2
5.3
4.0
0.1
2.7 2.1
0.9
0.4
0.2
0.1
2.8
3.2
4.6
3.2
1.8
0.5
0.1
1.9
1.3
0.0
0.2
0.3
0.6
0.2
0.0
0.0
0.0
0.0
0.5
0.3
0.0
0.1
0.0
0.0
0.3
30

31. 31
Final Orientation
• Wind Coverage = Sum of the percentages
under the strip for each direction + Calm
Period
• The direction with maximum wind coverage is
the direction along which runway is oriented
• In case wind coverage is less than 95% -
Another runway is constructed
• For busy airports, the wind coverage may be
increased to 98% or 100%.

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