# 52 RCACS Ground School Theory of Flight PO 402 EO 4

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

Introduction Teaching Points Terminology Review

References Green FTGU pg 19 Millennium Edition pg 21

Terminology Airfoils Camber
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 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

Airfoils and Camber

Terminology Cont’d 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. 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”

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

Terminology Cont’d Couples
When two equal forces act in opposite directions separated by a distance, that is said to form a couple “Every couple has it’s moment”  Moment! W L W L

Terminology Cont’d Relative Airflow
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. Relative Airflow Direction of travel

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

Terminology Cont’d Lift and Drag Curves Lift to Drag Ratio
The forces of “Lift” and “Drag” are dependent on: The shape of the airfoil (CL or CD) The plan area of the airfoil “S” The square of the velocity (true airspeed) “V2” Density of the air “ρ” 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

Lift and Drag Curves Lift = CL · ½ · V2 · S · ρ
Drag = CD · ½ · V2 · S · ρ

Conclusion Terminology

Questions ?

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