Post on 26-Mar-2015
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
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