Lesson 3 - Airfoil, Aircraft Axes and Control, Lift

7/29/2019 Lesson 3 - Airfoil, Aircraft Axes and Control, Lift

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Basic Aerodynamics

& Theory of Flight

By

Ahmad Ahsan


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Any surface, such as a wing, propeller, rudder, or even a trim tab, which

provides aerodynamic force when it interacts with a moving stream of air.

FAA

The mean camber line is a line drawn midway between the upper and lower

surfaces

The chord line is a straight line connecting the leading and trailing edges of

the airfoil.

The Airfoil


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The angle of attack is the angle between the chord line and

the average relative wind.

Greater angle of attack creates more lift (up to a point).

Angle of Attack


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Four Forces of Flight

DRAG

WEIGHT

THRUST

LIFT


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Lift Lift is the upwards force created by the interaction between the wings and the

airflow.

Lift Formula: L= V2A CL

LIFT


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Weight Weight is the combined load of the aircraft, crew, fuel, passengers, and the

cargo. Weight acts through the aircrafts center of gravity (CG)

WEIGHT


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Thrust

Thrust is the forward force produced by the powerplant,propeller or rotor.

THRUST


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Drag Drag is a rearward acting force that resists the motion of aircraft through the

air.

Drag Formula: D= V2A CD

DRAG


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Outline Aircraft Axes

Control on three axes

Air Loads: loads during flight by maneuvers and gusts

Function of Aircraft Structure:

To transmit and resist loads.

To provide and maintain shape.

To protect passengers, payload, and systems from theenvironmental conditions.


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Three Axes of Movement

Axis of Roll (Longitudinal Axis)

Axis of Pitch (Lateral Axis)

Axis of Yaw (Vertical Axis)

Three Axes of Movement

Longitudinal Axis

Lateral Axis

Vertical Axis


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The Aileronscontrol movement on the lateral axis called rolling.

Control around the Longitudinal Axis




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Rudder The rudder controls the

movement around vertical axis

called yawing.

Control around the Vertical Axis

Moving rudder to the

right forces tail to the

left, nose to the right

Moving rudder to the

left forces tail to the

right, nose to the left.

Rudder The rudder controls the

movement around vertical axis

called yawing.

Control around the Vertical Axis

Moving rudder to

the right forces tail

to the left, nose tothe right

Moving rudder to

the left forces tail to

the right, nose tothe left.


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Elevators are used to control

movement about the lateral axis

called pitching

Control around the Lateral Axis

Elevators are used to control

movement about the lateral axis

called pitching

Control around the Lateral Axis


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Lift Definition:

Lift is the aerodynamic force that opposes the downward force ofweight, is produced by the dynamic effect of the air acting on the airfoil,

and acts perpendicular to the flightpath through the center of lift. (FAA)

Important Characteristics:

Aerodynamic Force Opposes Weight (downward)

Upward acting

Produced by dynamic effect of air on airfoil

Required elements become: Air, Airfoil & Motion

Perpendicular to the flightpath through center of lift.


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Lift Important Characteristics:

Lift is the force that directly opposes the weight of an airplane

Lift is generated by every part of the airplane, but most of the lift on a

normal airliner is generated by the wings

Lift is a mechanical aerodynamic force produced by the motion of the

airplane through the air Because lift is a force, it is a vector quantity, having both a magnitude and

a direction

Lift acts through the center of pressure of the object

It is directed perpendicular to the airflow


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Center of Pressure Center of pressure:A point along the wing chord line where lift is

considered to be concentrated. (FAA) For this reason, the center of pressure is commonly referred to as the

center of lift.

The pilot has no direct control over the location of forces acting on the

aircraft in flight except by controlling the center of lift ( by changing the

AOA) CL or CP


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Center of Pressure Center of pressure:A point along the wing chord line where lift is

considered to be concentrated. (FAA) For this reason, the center of pressure is commonly referred to as the

center of lift.

Can be considered average location of the pressure.

Center of pressure changes with AoA

CL or CP


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Center of Pressure

Source: NASA Glen Research Center


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Production of Lift There are many explanations for the generation of lift. Unfortunately,

many of the explanations are misleading and incorrect.

We will describe the various theories and how some of the popular

theories fail.

In simple terms:

Lift occurs when the airflow is turned by a solid object.

The airflow is turned in one direction, and the lift is generated in the

opposite direction, according to Newton's Third Law of action and

reaction.

The pilot can control the lift.

As the AOA increases, lift increases (all other factors being equal).

When the aircraft reaches the maximum AOA, lift begins to decrease

rapidly. This is the stalling AOA, known as CL-MAX critical AOA.


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Production of Lift Lift is generated by producing a greater pressure under the wing than

above it.

To produce this pressure difference, we require a surface that is: either

inclined to the relative air flow direction, or curved (cambered).

It is normal to use a combination of inclination (angle) and camber

(curvature) in most aircraft.

The shape used for a particular aircraft depends mainly on its speed range

and other operational requirements.


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Production of Lift Lift is generated by producing a greater pressure under the wing than

above it.

To produce this pressure difference, we require a surface that is: eitherinclined to the relative air flow direction, or curved (cambered).

It is normal to use a combination of inclination (angle) and camber

(curvature) in most aircraft.

The shape used for a particular aircraft depends mainly on its speed range

and other operational requirements.


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Production of Lift Almost any shape will generate lift if it is either cambered or inclined to

the flow direction.

Even a brick could be made to fly by inclining it and propelling it very fast. The production of lift depends on the viscosity or stickiness of air.

The upper and lower surface flows rejoin at the trailing edge, with no

sudden change of direction.

There is a difference in the average pressure between upper and lower

surfaces, and so lift is generated.


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Airfoil Section


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Production of Lift Almost any shape will generate lift if it is either cambered or inclined to

the flow direction.

Even a brick could be made to fly by inclining it and propelling it very fast.

R i i


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Revision Definition:

Lift is the aerodynamic force that opposes the downward force of

weight, is produced by the dynamic effect of the air acting on the

airfoil, and acts perpendicular to the flightpath through the center

of lift. (FAA)



Upward acting




R i i


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Revision Definition:

Lift is the aerodynamic force that opposes the downward force of

weight, is produced by the dynamic effect of the air acting on the

airfoil, and acts perpendicular to the flightpath through the center

of lift. (FAA)



Upward acting





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Assignment


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Assignment


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The End

Documents

Lesson 3 - Airfoil, Aircraft Axes and Control, Lift