The document discusses the aerodynamic principles affecting aircraft performance, particularly focusing on the shapes of airfoils and their impact on lift and drag. It explains concepts such as angle of attack, camber, and the various types of drag that affect flight efficiency. Additionally, the document highlights the importance of streamlined shapes and the effects of airflow behavior around different wing designs.

1. 8.2 AERODYNAMICS
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2. Effect of Shapes on Streamlined Flow
(a) Flat Plate 100% Resistance (b) Sphere 50% Resistance
(c) Ovoid 15% Resistance (d) Streamlined 5% Resistance
STREAMLINED

3. Boundary Layer
Unaffected airflow
Each layer experience retardation until
some distance away from surface
Next layer slowed down but not stop
Airflow nearest the surface come to rest
STREAMLINED

4. Boundary Layer
STREAMLINED

5. Separation and turbulence at various
AOA
STALLING

6. AERODYNAMIC TERM
Stagnation point
Velocity = 0m/s
Wing tip vortices

7. Airfoil Shape
 Symmetrical – no lift at zero angle of attack
 Asymmetrical – lift created even at small angle
of attack
AIRFOIL

8. Airfoil Shape
• Medium and high speed aircraft – much less
curvature  lift comes from their additional speed
through the air.
• Low speed aircraft – cambered  not for high speed
(excess lift as well as drag)
AIRFOIL

9. CAMBER (CURVE)
• Camber  curvature of an aerofoil (wing)
above and below the chord line
Camber (curvature) of an aerofoil
PRODUCTION OF LIFT

10. AIRFOIL @ AEROFOIL
• Any surface which produces a reaction (lift) as air
passes over it
• The airfoil should provide this reaction (lift), whilst
having a shape which presents the least possible
resistance, or drag, to its passage through air
AIRFOIL

11. T/C AND FINENESS RATIO
Thicness/Chord ratio = CD
AB

12. MEAN AERODYNAMIC CHORD
• Average distance between leading and trailing
edge of wing
• Mean chord = Wing Area
Wing Span

13. ANGLE OF ATTACK
• The acute angle formed between the relative wind
striking an airfoil and the chord line.
• Increasing the angle from zero degree to a maximum
(between 15 degrees and 18 degrees) will increase
lift, but will also increases drag.
CENTER OF PRESSURE

14. ANGLE OF INCIDENCE
o Angle formed by the
intersection of the wing
chord line and the
horizontal plane or
longitudinal axis of aircraft
o Positive Angle of Incidence
(AOI) – leading edge higher
than trailing edge
o Correct AOI  low drag +
longitudinal stability
o ‘Wash out’ – higher AOI at
wing root than at wing tip
o ‘Wash in’ – higher AOI at
wing tip than at wing root
ANGLE OF INCIDENCE

15. WASH IN AND OUT
• Wash in :
– Angle of incident increase from root to tip
– Tip will stall 1st
• Wash out :
– Angle of incident decrease from root tip
– Root will stall 1st

16. CENTER OF PRESSURE (c.p)
 The position whereby the resultant force (lift) cuts
through chord line and considered to act
Total Lift
 Shape of airfoil and angle of attack influence the c.p
Position of lines denotes
location and direction direction of lift
Length of line denote
magnitude of lift
Direction
of airflow
Center of Pressure
CENTER OF PRESSURE

17. CENTER OF PRESSURE (c.p)
o Position of c.p varies during flight as the angle of attack (AOA)
altered
a. Increase AOA – c.p moves forward
b. Decrease AOA – c.p moves backward
o In normal flight the AOA usually between 2˚ and 4˚ (seldom
below 0˚ or above 16˚)
Small AOA Medium AOA Large AOA
Nose Heavy Balance OF PRESSURE
CENTER Flight Tail Heavy

18. WING SHAPE

19. ASPECT RATIO
• Ratio of aircraft wingspan to its mean chord
length

20. PRODUCTION OF LIFT
 To keep flying  aircraft must
produce a force equal to its
own weight
 Greater force – to lift the
aircraft from the ground
 Force (lift) is provided by the
wing
 The production of lift is based
on Bernoulli’s theory
PRODUCTION OF LIFT

21. Lift
Weight

22. Bernoulli’s theorem
• Air velocity increase – the pressure decreases (and vice
versa)
• The total energy of a moving fluid is made up of three
forms of energy:
 Potential Energy – due to height or position
 Kinetic Energy – due to motion
 Pressure Energy – due to pressure
• In a streamline flow of an ideal fluid, the sum of all those
energy is constant
Potential + Kinetic + Pressure = Constant
PRODUCTION OF LIFT

23. Venturi Effect
• A short circular tube with
large opening at both the
front and rear end +
restrictor between the
opening
• Venturi is a
convergent/divergent
duct
• Bernoulli’s Theory is
being proven by passing
a streamline flow of air
through a venturi duct
PRODUCTION OF LIFT

24. Venturi Effect
PRODUCTION OF LIFT

25. Venturi Effect
INLET CENTRE (THROAT) OUTLET
Airspeed normal Airspeed maximum Airspeed decrease
Pressure normal Pressure minimum Pressure increase
(equal to inlet area)
PRODUCTION OF LIFT

26. Camber (Curved)
• Airflow around the cambered wing behave exactly as airflow
in a venturi tube
PRODUCTION OF LIFT

27. Airflow on wing (Lift distribution)
Increased Speed Provide 70% of the wing’s Total Lift
Decreased Speed
Decreased pressure
70% of Total Lift
Increased pressure
Providing 30% of the wing’s Total Lift
Decreased Speed
Increased Speed
30% of Total Lift
PRODUCTION OF LIFT

28. STREAMLINED
 Streamline – shape or contour that presents a
minimum resistance to the air
 A perfect streamlined form is similar to the top view
of a fish
 Air flows around non-streamlined object  air swirls
into eddies + streamline distorted  disappear
 Airstream becomes turbulent
 Streamline air appears as smooth parallel lines
• Smoke jets – introduce smoke into air  to observe
and illustrate movement of air around object
STREAMLINED

29. Effect of Shapes on Streamlined Flow
STREAMLINED

30. DRAG
As an aircraft passes through the air, the air offers
a resistance to the passage.
This resistance, is known as ‘Drag’.
(Resistance to forward motion)
The total amount of drag on an aircraft is made
up of many types of drag forces.
• Common type of drag:-
i. Form drag
ii. Parasite drag
iii. Induced drag
DRAG

31. DRAG
RESISTANCE TO FORWARD MOTION
DRAG

32. FORM DRAG
Caused by the shape or form of the aircraft
• Reducing form drag
• Streamlining – aircraft shaped to produce least
resistance to the airflow
• For least resistance  object length between 3-4
times greater than maximum thickness
• Fineness ratio – ratio between length and maximum
thickness
DRAG

33. PARASITE DRAG
 A combination of many different drag forces
 Any exposed object on an aircraft offers some
resistance to the airflow, and the more objects in
the airstream, the more parasite drag
Reducing parasite drag
• reducing the number of exposed parts to as few as
practical and streamlining their shape.
DRAG

35. Streamlining
• Fixed landing gear

36. SKIN FRICTION DRAG
A type of parasite drag most difficult to reduce
Air particles in contact with surface of the aircraft
Reducing skin friction
glossy flat finishes
eliminating protruding rivet heads, roughness, and other
irregularities.
DRAG

37. INDUCED AND TOTAL DRAG
• Lift created by the airfoil also created drag 
induced drag
• Just as lift increases with an increase in angle of
attack, induced drag also increases as the angle of
attack becomes greater.
TOTAL DRAG
DRAG

38. THRUST AND WEIGHT
• Thrust is forward force produce by engine
• Determine by size and type use in propulsion
system
• Weight is a mass of aircraft act vertically
downward
• Determined by size and material used in
aircraft

39. FORCES ACTING ON AIRCRAFT IN
THRUST FLIGHT
• The aircraft’s propelling force LIFT
• Arranged symmetrically to the Acts at right angle to the line of
centre line flight & through the Centre of
• Act parallel to the line of flight Pressure of the wings
DRAG
• Opposes the forward motion
WEIGHT@ GRAVITY • Regarded as a rearward acting
Acts vertically downwards through force
the Centre of Gravity
FORCES ACTING ON AIRCRAFT IN FLIGHT

40. LIFT AND DRAG COEFFICIENT
• Theoritical value base on
airfoil shape
Lift = CL x 1/2ρv2 x S
Drag = CD x 1/2ρv2 x S
IDEAL ANGLE

41. POLAR CURVE
• Drag Polar is the relationship between the lift
and its drag interm on coefficeient

42. STALL
 ‘Sudden lost of lift’
i. Increase AOA – separation moves forward (turbulent)
– Insufficient pressure drop on upper surface  no
pressure differential to create lift
ii. Increase to higher AOA – excessive turbulence
– Drag increase higher than lift created
 Critical Angle of Attack – airflow separate + turbulence
 Critical AOA = 15˚ and above
STALLING

43. AIRFOIL CONTAMINATION
• Any contamination on wing will affect its
performance
• Need to provide method to remove the
contamination during flying
• Type of contamination :
– Ice
– Snow
– Frost