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

52 RCACS52 RCACSGround SchoolGround School

Theory of FlightPO 402 EO 4

“How Lift is Created”

IntroductionIntroduction

Teaching PointsTeaching Points TerminologyTerminology ReviewReview

ReferencesReferences

Green FTGU pg 19Green FTGU pg 19

Millennium Edition pg 21Millennium Edition pg 21

TerminologyTerminology

AirfoilsAirfoils An airfoil or airfoil section may be An airfoil or airfoil section may be

defined as any surface designed to obtain defined as any surface designed to obtain lift. It has been found that the most lift. It has been found that the most suitable shape for producing lift is a suitable shape for producing lift is a curved or cambered shapecurved or cambered shape

CamberCamber The camber is the curvature of the upper The camber is the curvature of the upper

and lower surfaces of an airfoil. Usually and lower surfaces of an airfoil. Usually the upper surface has a greater camber the upper surface has a greater camber than the lowerthan the lower

Airfoils and CamberAirfoils and Camber

Terminology Cont’dTerminology Cont’d

EquilibriumEquilibrium When two forces are equal and opposite, When two forces are equal and opposite,

the aircraft is said to be in a state of the aircraft is said to be in a state of “equilibrium”. Therefore, the aircraft will “equilibrium”. Therefore, the aircraft will continue to move forward at the same continue to move forward at the same uniform rate of speed.uniform rate of speed.Lift

Weight

If Lift = Weight, then the aircraft is notclimbing or descending, therefore, it is said to be in “equilibrium”

Thrust

DragIf Thrust = Drag, then the aircraft is notaccelerating or decelerating, therefore, it is said to be in “equilibrium”

Terminology Cont’dTerminology Cont’d

Centre of GravityCentre of Gravity The point on the aircraft where all the The point on the aircraft where all the

weight acts throughweight acts through

Centre of PressureCentre of Pressure The point on the aircraft where all the The point on the aircraft where all the

lift acts throughlift acts through

BIG NOTE: NOT ALWAYS THE BIG NOTE: NOT ALWAYS THE SAME POINTSAME POINT

Terminology Cont’dTerminology Cont’d

CouplesCouples When two equal forces act in opposite When two equal forces act in opposite

directions separated by a distance, that is directions separated by a distance, that is said to form a couplesaid to form a couple

““Every couple has it’s moment” Every couple has it’s moment”

W

L

W

LMoment!

Terminology Cont’dTerminology Cont’d

Relative AirflowRelative Airflow A term used to describe the direction of the A term used to describe the direction of the

airflow with respect to the wingairflow with respect to the wing Is created by the motion of the airplane Is created by the motion of the airplane

through the air.through the air.

Direction of travel

RelativeAirflow

Terminology Cont’dTerminology Cont’d

StreamliningStreamlining Is a device by which a body is so shaped Is a device by which a body is so shaped

that drag is minimized as the body moves that drag is minimized as the body moves forward through the air.forward through the air.

Terminology Cont’dTerminology Cont’d

Lift and Drag CurvesLift and Drag Curves The forces of “Lift” and “Drag” are The forces of “Lift” and “Drag” are

dependent on:dependent on: The shape of the airfoil (CThe shape of the airfoil (CLL or C or CDD)) The plan area of the airfoil “S”The plan area of the airfoil “S” The square of the velocity (true airspeed) “VThe square of the velocity (true airspeed) “V22”” Density of the air “Density of the air “ρρ””

Lift to Drag RatioLift to Drag Ratio Used to express the relation between lift and Used to express the relation between lift and

drag and is obtained by dividing the lift drag and is obtained by dividing the lift coefficient by the drag coefficientcoefficient by the drag coefficient

Lift and Drag CurvesLift and Drag CurvesLift = CL · ½ · V2 · S · ρ

Drag = CD · ½ · V2 · S · ρ

ConclusionConclusion

TerminologyTerminology

QuestionsQuestions

?