3. Airfoil
Airfoil
If a horizontal wing is cut by a vertical plane the
resultant section is called the airfoil
An airfoil is a cross section of a wing.
4. The generation of lift and the stall
The generation of lift and the stall
characteristics of the wing strongly depend on
the geometry of the airfoil
the geometry of the airfoil
7. Leading Edge
Leading Edge
• The shape of the airfoil at the leading edge is
usually circular with a leading edge radius of
y g g
approximately 0.02c
• The leading edge of airfoils used in subsonic
applications is rounded with a radius that is on
applications is rounded with a radius that is on
the order of 1% of the chord length
9. 3.Chord Line
Straight line connecting the leading and
Straight line connecting the leading and
trailing edges
10. I i l th h d li f th i f il
In many airplanes the chord lines of the airfoil
sections are inclined relative to the vehicle axis
11. 4.Chord
The physical length of the Chord Line It is
The physical length of the Chord Line. It is
denoted by c
12. 5.Camber
The max. distance between the chord-line
The max. distance between the chord line
and the mean camber line, measured
perpendicular to the chord line.
perpendicular to the chord line.
13. 6.Mean Chamber Line
locus of points halfway between upper and
p y pp
lower surfaces as measured perpendicular to
mean chamber line itself
14. • The mean camber line is the major design
t f i f il
parameter of an airfoil
• The shape of mean camber line control the lift
and moment characteristics of airfoil
• Cambered airfoils in a subsonic flow generate
lift even at zero angle of attack
15. 7. Thickness
Thickness is the distance between the upper
Thickness is the distance between the upper
and lower surfaces also measured
perpendicular to chord line
p p
19. • As the angle of attack increases, the incoming
air is deflected more, resulting in increased lift.
, g
• For example, if you double the angle of attack
while the airspeed is constant you double the
while the airspeed is constant, you double the
amount of lift.
• In order to create the required lift the
• In order to create the required lift, the
airfoil must operate at a high angle of
attack
attack.
20. Relation between AOA & Lift
Relation between AOA & Lift
• Angle of attack is
Angle of attack is
directly proportional
to the lift coefficient
to the lift coefficient
Maximum limit which
is generally about 17o
is generally about 17
• After which the plane
After which the plane
stalls
22. Angle of incidence
It is the angle between the chord line of the
It is the angle between the chord line of the
wing where the wing is mounted to the
fuselage and the longitudinal axis of the
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fuselage.
23. Angle of incidence
Angle of incidence
• The angle of incidence is fixed in the design of
the aircraft by the mounting of the wing to the
the aircraft by the mounting of the wing to the
fuselage.
• Angle of incidence of about 6° are common on
• Angle of incidence of about 6 are common on
most general aviation designs.
24. Wing Geometry Parameters
Wing Geometry Parameters
• Wing Area
Wi S
• Wing Span
• Average Chord
A R i
• Aspect Ratio
• Root Chord
i h d
• Tip Chord
• Taper Ratio
• Sweep Angle
• Mean Aerodynamic Chord
• Dihedral Angle
25. Wi A A
Wing Area A
The wing area, A is the projected area
The wing area, A is the projected area
of the planform and is bounded by the
leading and trailing edges and the wing
leading and trailing edges and the wing
tips.
The shape of the wing, when viewed
from top looking down onto the wing, is
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called a planform.
28. For a rectangular wing, the chord length at
l i l h i h
every location along the span is the same.
Wing Area A = Span x Chord
A = b x c
29. Wing Area for Tapered Wings
Wi A Wi S A Ch d
Wing Area = Wing Span x Average Chord
A Ch d ( Ch d i Ch d ) ÷ 2
Average Chord = ( Root Chord + Tip Chord ) ÷ 2
30. Wing Area for Delta Wings
Delta Wing having a Tip Chord greater than 0
Delta Wing having a Tip Chord greater than 0
If a Delta Wing has a Tip Chord greater than 0
If a Delta Wing has a Tip Chord greater than 0
then use the formula for a tapered wing
31. Delta Wing having a Tip Chord of 0
If the Tip Chord is 0 then use the formula for a
triangle
Wing Area = 1/2 x Wing Span x Root Chord
32. • Wing Span b
The distance between the extreme wing tips
The distance between the extreme wing tips
It is the distance from one wingtip to the
It is the distance from one wingtip to the
other wingtip
The wingspan of an aircraft is always
measured in a straight line from wingtip to
measured in a straight line, from wingtip to
wingtip
33. For example, the Boeing 777 has a wingspan
of about 60 meters
of about 60 meters
34. Aspect Ratio AR
p
• The Aspect Ratio of a wing is defined as the
square of the span divided by the wing area
square of the span divided by the wing area
• For a rectangular wing, this reduces to the ratio
of the span to the chord length
of the span to the chord length
35. Low aspect ratio
Short and stubby wing. More efficient
structurally, less drag at high speeds They
y, g g p y
used in fighter aircraft, such as F-104
Starfighter
g
37. Moderate aspect ratio
General-purpose wing (e.g. the Lockheed P-80
Sh i S )
Shooting Star)
High aspect ratio
long and slender wing. More efficient
aerodynamically, having less drag, at low speeds.
They used in high-altitude subsonic aircraft (e.g.
the Lockheed U 2) subsonic airliners (e g the
the Lockheed U-2), subsonic airliners (e.g. the
Bombardier Dash 8) and by high-performance
sailplanes (e.g. Glaser-Dirks DG-500).
p ( g )
38. • The wing aspect ratio is the most telling
g p g
feature of an airplane’s purpose and
performance.
• It is the easiest way to say whether a plane is
built for transport, fighting, high-speed flight,
built for transport, fighting, high speed flight,
or astronautic applications.
• High aspect ratio wings have long spans
• High aspect ratio wings have long spans
• low aspect ratio wings have either short spans
(lik th F 16 fi ht ) thi k h d (lik th
(like the F-16 fighter) or thick chords (like the
Space Shuttle).
40. low aspect ratio wing
thi k h d S Sh ttl
thick chords - Space Shuttle
41. low aspect ratio wing
hi k h d S Sh l
thick chords - Space Shuttle
42. • The higher the aspect ratio, the lower the drag.
• So airplanes with very high-aspect-ratio wings
have very long range and especially a very
y g g p y y
long endurance, and are very fuel-efficient.
• They also cruise at slow speeds. Very high-
aspect-ratio wings mean an airplane is
p g p
supposed to stay in the air for a long, long
time.
43. • High aspect ratio wings abound in nature.
Most birds that fly long distances have wings
y g g
of high aspect ratio, and with tapered or
elliptical wingtips.
p g p
• This is particularly noticeable on soaring birds
such as eagles
such as eagles.
• Sparrow hawk have wings of low aspect ratio
(and long tails) for maneuverability
(and long tails) for maneuverability.
51. Root Chord Cr
r
The chord at the wing centre line
Tip Chord C
Tip Chord Ct
It is measured at tip
52. • Taper Ratio λ
• Taper Ratio λ
It is the ratio of the tip chord to the root
h d
chord
λ = Ct /Cr
Ct
Cr
53.
54. The taper ratio affects the lift distribution and
p
the structural weight of the wing
A rectangular wing has a taper ratio of 1.0
A rectangular wing has a taper ratio of 1.0
while the pointed tip delta wing has a taper
ratio of 0.0
ratio of 0.0
55. Lower taper ratios lead to lower wing weight.
Lower taper ratios result in increased fuel
Lower taper ratios result in increased fuel
volume
Larger root chords more easily accommodate
Larger root chords more easily accommodate
landing gear.
I i h i d lif
Increasing the taper ratio produces more lift
at the tips
56. • Sweep Angle Λ
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The angle between the line of 25% chord
and a perpendicular to the wing root.
and a perpendicular to the wing root.
θ
57.
58. Mean Aerodynamic Center (MAC)
It is the average for the whole wing
It is the average for the whole wing.
The computation of the mac depends on the
shape of the planform
shape of the planform.
59. To Locate the Mean Aerodynamic Chord
o ocate t e ea e ody a c C o d
• At the root of the wing, draw a line parallel to the
centerline of the fuselage extending forward from
g g
the leading edge and rearward from the trailing
edge. Both lines should be the length of the tip
h d
chord.
• Do the same thing at the tip but drawing the lines
the length of the root chord
the length of the root chord.
• Connect the ends of the lines so that they create
an "X" over the wing panel Where the two lines
an X over the wing panel. Where the two lines
intersect is the spanwise location of the Mean
Aerodynamic Chord.
62. Mean Aerodynamic Chord
Mean Aerodynamic Chord
Mean Aerodynamic Chord
Mean Aerodynamic Chord
Trapezoidal Wing
63.
64. Dihedral angle
Dihedral angle
The angle that the wing makes with the local
h i t l i ll d th dih d l l
horizontal is called the dihedral angle
65. • Dihedral angle is given to the wings for roll
stability
y
• A wing with some dihedral will naturally
return to its original position if it encounters a
return to its original position if it encounters a
slight roll displacement
• Most large airliner wings are designed with
• Most large airliner wings are designed with
dihedral
68. Anhedral angle
If the wing lies below the horizontal plane it is
called Anhedral
It i th i t ti dih d l l
It is the name given to negative dihedral angle,
that is, when there is a downward angle from
horizontal of the wings
g
70. Downwash
These wing-tip vortices of the wing induce a
small velocity component in the downward
small velocity component in the downward
direction, which is called Downwash
71. • Wash‐out is a reduction in camber or
Wash out is a reduction in camber or
incidence at the tip of a wing to reduce tip
stalling
stalling
72.
73. • The leaked flow around the tips creates a
The leaked flow around the tips creates a
trailing vortex
74. W h A l
Wash-out Angle
A reduction in the angle of incidence or
b f i ti th i ti t
camber of a wing section near the wing tip to
prevent tip stalling.
Wings often have less incidence at the tip than the root
Wings often have less incidence at the tip than the root
(wash-out) to reduce structural weight and improve
stalling characteristics.
