1. Theory of Flight 6.05 Lift and Drag References:
Transport Canada Study and Reference Guide Glider Pilot
FTGU pages 91-98

2. Review 1. Name the 4 forces acting on an aircraft.
2. What are Newton’s 3 laws?
3. Is an aircraft considered to be in a state of equilibrium when it is on the ground.
Answers:
Lift, Weight, Thrust, Drag
2. A body persists its state of rest or of uniform motion will stay in motion unless acted on by an external unbalanced force.
Force = mass x acceleration
For every action, there is an equal and opposite reaction
3. No

3. 6.05 Lift & Drag MTPs: Bernoulli’s Principle- how lift is created
Airfoil terms
Angle of attack versus lift
Angle of Incidence
Types of airfoils
Types of Drag
Wingtip Vortices
Streamlining

4. Bernoulli’s Principle
An increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.

5. Bernoulli’s Principle
Speed
Pressure
Speed
Pressure

6. Bernoulli’s Principle
Airfoils are shaped in a way to manipulate air pressure based on Bernoulli’s principle.
Air moves faster over the upper surface of the wing, decreasing pressure (or increasing suction)
Air moves slower over the lower surface of the wing and creates a higher pressure, or pushing force.

7. Airfoil Terms Terms related to airfoils Relative Airflow
Angle of Attack
Centre of Pressure

8. Relative Airflow
The direction of the airflow with respect to the wing.
It is created by the movement of the airplane as well as the movement of air.
Relative airflow is usually opposite to the flight path.
Relative airflow itself is not related to lift

9. Angle of Attack
The angle at which the airfoil meets the relative airflow

10. Centre of Pressure Is the average of the pressure on an airfoil
Sum of the distributed pressures on the airfoil acting through a single straight line
Moves forward on an airfoil as the angle of attack is increased

11. Centre of Pressure

12. A of A versus Lift Lift Increases Drag Increases
Now we know how we get lift but how much can we get?
One factor affecting lift is Angle of Attack
As the angle of attack increases, what happens to lift?
BUT… As the angle of attack increases, what happens to drag?
Lift Increases
Drag Increases

13. A of A versus Lift
Lift/ Drag
Angle of Attack

14. Angle of Incidence
The angle of incidence is the angle between the mean aerodynamic chord of the wing and the longitudinal axis of the aircraft
The angle of incidence impacts forward visibility, take-off and landing characteristics, and drag in level flight

15. Types of Airfoils Airfoil Airfoil – 2D vs. Wing – 3D
A two-dimensional surface designed to obtain a reaction from the air through which it moves.
The shape of an airfoil will affect how air flows over the wing
Airfoil – 2D vs. Wing – 3D

16. Types of Airfoils What are some functions of airfoils? Create lift
Create thrust
Attachment point for the control surfaces (including flaps, slots, slats, etc)
House fuel tanks and instrument components
Stability

17. Confirmation Check

18. Confirmation 1. Label where the high pressure and low pressure are:
2. Fill in the blanks
__________________: The angle at which the airfoil meets the relative airflow
__________________: airflow with respect to the wing
__________________:the average of the pressure on an airfoil

19. Confirmation 3. Lift acts 90o to the ________________.
4. Bernoulli’s principle states that:
An ____________ (increase/decrease) in the speed of a fluid occurs simultaneously with a _____________________ (increase/decrease) in pressure or a _______________ (increase/decrease) in the fluid's potential energy
5. As lift increases, drag _______________.

20. Drag
Is the resistance an airplane experiences in moving forward through the air

21. Types of Drag There are 2 main types of Drag:
Parasite Drag– This drag is further broken down
Form drag
Skin Friction
2. Induced Drag

22. Parasite Drag
Drag of all those parts the airplane which DO NOT contribute to lift
This drag is hard to eliminate but it can be minimized
Form drag is caused by the shape of the aircraft
Landing gear
Antennas
Struts
Wing tip fuel tanks

23. Parasite Drag Skin Friction
The tendency of air flowing over the body to cling to its surface
What causes it to resist motion?
Ice on the wings
Dirt build up

24. Induced Drag
Caused by those parts of an airplane which are active in producing lift
Cannot be eliminated
Lift Drag

25. Induced Drag
Induced drag can be reduced with a high aspect ratio

26. Due to the pressure changes
Wing Tip Vortices
Over the top of the wing the airflow goes inward
Under the bottom of the wing the airflow moves outward
Due to the pressure changes
This creates a swirling motion off the wing tip called a vortex

27. Streamlining The less drag you have…
Flying a glider: the further you can fly
Flying an airplane: the less fuel you use
Therefore streamlining is important
A design device by which a body is shaped to minimize drag

28. Confirmation Fill in the diagram
Is it possible to eliminate induced drag? Why or why not?

29. Wingtip Vortices