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52 RCACS Ground School Theory of Flight PO 402 EO 4 How Lift is Created

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Introduction Teaching Points Teaching Points Terminology Terminology Review Review

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References Green FTGU pg 19 Green FTGU pg 19 Millennium Edition pg 21 Millennium Edition pg 21

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Terminology Airfoils 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 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 Camber 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 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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Airfoils and Camber

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Terminology Contd Equilibrium Equilibrium When two forces are equal and opposite, the aircraft is said to be in a state of equilibrium. Therefore, the aircraft will continue to move forward at the same uniform rate of speed. When two forces are equal and opposite, the aircraft is said to be in a state of equilibrium. Therefore, the aircraft will continue to move forward at the same uniform rate of speed. Lift Weight If Lift = Weight, then the aircraft is not climbing or descending, therefore, it is said to be in equilibrium Thrust Drag If Thrust = Drag, then the aircraft is not accelerating or decelerating, therefore, it is said to be in equilibrium

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Terminology Contd Centre of Gravity Centre of Gravity The point on the aircraft where all the weight acts through The point on the aircraft where all the weight acts through Centre of Pressure Centre of Pressure The point on the aircraft where all the lift acts through The point on the aircraft where all the lift acts through BIG NOTE: NOT ALWAYS THE SAME POINT BIG NOTE: NOT ALWAYS THE SAME POINT

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Terminology Contd Couples Couples When two equal forces act in opposite directions separated by a distance, that is said to form a couple When two equal forces act in opposite directions separated by a distance, that is said to form a couple Every couple has its moment Every couple has its moment W L W L Moment!

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Terminology Contd Relative Airflow Relative Airflow A term used to describe the direction of the airflow with respect to the wing A term used to describe the direction of the airflow with respect to the wing Is created by the motion of the airplane through the air. Is created by the motion of the airplane through the air. Direction of travel Relative Airflow

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Terminology Contd Streamlining Streamlining Is a device by which a body is so shaped that drag is minimized as the body moves forward through the air. Is a device by which a body is so shaped that drag is minimized as the body moves forward through the air.

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Terminology Contd Lift and Drag Curves Lift and Drag Curves The forces of Lift and Drag are dependent on: The forces of Lift and Drag are dependent on: The shape of the airfoil (C L or C D ) The shape of the airfoil (C L or C D ) The plan area of the airfoil S The plan area of the airfoil S The square of the velocity (true airspeed) V 2 The square of the velocity (true airspeed) V 2 Density of the air ρ Density of the air ρ Lift to Drag Ratio Lift to Drag Ratio Used to express the relation between lift and drag and is obtained by dividing the lift coefficient by the drag coefficient Used to express the relation between lift and drag and is obtained by dividing the lift coefficient by the drag coefficient

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Lift and Drag Curves Lift = C L · ½ · V 2 · S · ρ Drag = C D · ½ · V 2 · S · ρ

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Conclusion Terminology Terminology

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Questions ?

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