lesson 3 - airfoil, aircraft axes and control, lift
TRANSCRIPT
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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
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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The Aileronscontrol movement on the lateral axis called rolling.
Control around the Longitudinal Axis
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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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The Aileronscontrol movement on the lateral axis called rolling.
Control around the Longitudinal Axis
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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The Aileronscontrol movement on the lateral axis called rolling.
Control around the Longitudinal Axis
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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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The Aileronscontrol movement on the lateral axis called rolling.
Control around the Longitudinal Axis
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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)
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.
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)
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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The Aileronscontrol movement on the lateral axis called rolling.
Control around the Longitudinal Axis
Assignment
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The Aileronscontrol movement on the lateral axis called rolling.
Control around the Longitudinal Axis
Assignment
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The End