1. 4 2 .
How Lift is Created

2. Airfoils
An airfoil or airfoil section may be defined as any surface designed to obtain lift. It has been found that the most suitable shape for producing lift is a curved or cambered shape.
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3. Camber
The camber is the curvature of the upper and lower surfaces of an airfoil. Usually the upper surface has a greater camber than the lower.
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4. Equilibrium
When two forces are equal and opposite, the aircraft is said to be in a state of equilibrium. Therefore, when thrust and drag are equal and opposite, the aircraft will continue to move forward at the same uniform rate of speed. Equilibrium refers to steady motion and not to a state of rest.
If either of these forces become greater than the force opposing it, the state of equilibrium will be lost.
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5. Lift and Weight
When lift and weight are equal and opposite, the airplane will be in equilibrium.
However, if lift is greater than weight, the airplane will climb.
However, if weight is greater than lift, the airplane will sink.
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6. Thrust and Drag
When thrust and drag are equal and opposite, the airplane will be in equilibrium.
If thrust is greater than drag, the airplane will accelerate or gain speed.
If drag is greater than thrust, the airplane will decelerate or lose speed.
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7. Couples
When two forces are equal and opposite, the airplane is said to be in a state of equilibrium. When two forces such as lift and weight are equal and opposite, but parallel rather than passing through the same point, they are said to form a couple. A couple will cause a turning moment about a given axis (couples act around the C of G).
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8. Couples
If weight is ahead of lift, the couple created will turn the nose of the airplane down.
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9. Couples
If lift is ahead of weight, the couple created will turn the nose of the airplane up.
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10. Couples
If drag is above thrust, the couple formed will turn the nose of the airplane up.
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11. Couples
If thrust is above drag, the couple formed will turn the nose of the airplane down.
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12. NOTE: You must use the buttons in the Confirmation Stage
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13. Theory of Flight How Lift is Created
Let's try a few review questions on Theory of Flight:
Question #1 - When two forces are equal, opposite and parallel they are said to be a(n) A
Equilibrium B
Couple C
Camber D
Airfoil
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18. Theory of Flight How Lift is Created
Let's try a few review questions on Theory of Flight:
Question #2 - If thrust is above drag, how will the aircraft move? A
Accelerate B
Decelerate C
Climb D
Descend
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23. Relative Airflow
A term used to describe the direction of the airflow with respect to the wing.
Relative airflow, also known as relative wind, is created by the motion of the airplane though the air. It is also created by the motion of air past a stationary body or by a combination of both. Therefore, on a take-off roll, an airplane is subject to the relative airflow created by it’s motion along the ground and also by the moving mass of air (wind).
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24. Streamlining
Is a design device by which a body is so shaped that drag is minimized as the body moves forward through the air.
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25. Aileron Drag
When an aircraft banks to make a turn, one aileron is depressed and the other is raised.
The down going aileron being depressed into the compressed air flow, causes drag.
The up going aileron, moving up into a more streamlined position, causes less drag.
The result is a yaw in the opposite direction to which bank is applied.
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26. Lift and Drag Curves
The lift and drag of an airfoil depend not only on the angle of attack but also upon:
the shape of the airfoil
the plan area of the airfoil (wing area) = s
the square of the velocity (true airspeed) = V2
density of the air = p
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27. Lift and Drag Curves
Hence the lift of the airfoil can be expressed as a formula by:
CL*½pV2*S
And the drag by
CD*½pV2*S
CL = Coefficient of Lift
CD = Coefficient of Drag
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28. Lift Drag Ratio Best Lift-Drag Ratio
Used to express the relation between lift and drag and is obtained by dividing the lift coefficient by the drag coefficient
Reaches its maximum at 0° angle of attack, obtain the most lift for the least amount of drag.
Best Lift-Drag Ratio
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29. NOTE: You must use the buttons in the Confirmation Stage

30. Theory of Flight How Lift is Created
Let's try a few review questions on Theory of Flight:
Question #3 - What name is given to the direction of the airflow with respect to the wing? A
Aileron drag B
Air pressure C
Relative wind D
Drag air
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35. Theory of Flight How Lift is Created
Let's try a few review questions on Theory of Flight:
Question #4 - What is the best lift-drag ratio? A
Lift coefficient / drag coefficient B
0° AofA C
CL = pV2S D
CD = pV2S
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40. Theory of Flight How Lift is Created Congratulations!!
You have now completed the How Lift is Created lesson of the Theory of Flight Module. Of course, this lesson is always available to you for future reference if required.
You are now ready to move along to the next Theory of Flight lesson you have not completed or to any other module you wish. You can advance to the Self Test Module if you feel ready to challenge the final exam.
Good Luck!
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