Basic Aeronautics

1
Basic Aeronautics

• Know the principles of basic aeronautics.
• 1. Describe the theory of flight.
• 2. Describe airfoils and flight.
• 3. Describe the effects of relative wind.
• 4. Describe the effects of angle of attack.
• 5. Identify the four forces of flight.

2
Overview

• 1. Theory of Flight
• 2. Airfoils and Flight
• 3. Relative Wind
• 4. Angle of Attack
• 5. The Four Forces of Flight

3
Theory of Flight

• Aerodynamics
• The science relating to the effects produced by
  air or other gases.
• The term comes from the Greek words aero meaning
  air and dynamics meaning power.
• Ancient Greeks described air as having the
  qualities of moisture and heat. It was observed
  to shift in response to heating and cooling.

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Theory of Flight

• Aerodynamics
• A lifting force is required for heavier-than-air
  flying. An object can be pushed upward by
  applying muscle power, an explosion, a hoist, or
  other means of force.
• It cannot remain aloft without decreasing the air
  pressure from above and increasing lift pressure
  from below.
• Increasing the speed of the object can increase
  the flow of air.
• The flying object must be shaped to form an
  airfoil.
• Air flows faster over the curved surface of an
  airfoil.

5
Theory of Flight

• Aerodynamics
• Bernoulli principle
• As the air velocity increases, the pressure
  decreases and as the velocity decreases, the
  pressure increases.
• A major part of the knowledge base needed in the
  design and development of aircraft.
• Contributed to the work of G.B. Venturi, an
  Italian scientist, who first noted the effects of
  constricted channels on the flow of fluids. A
  round tube, such as a nozzle or jet engine,
  designed to increase the speed of flowing gases
  and liquids is called a venturi.

6
Theory of Flight

• Aerodynamics
• Aristotle
• The first useful studies of motion are attributed
  to Aristotle. He believed there were two kinds
  of motion natural and violent.
• He concluded, and later stated as a natural law,
  that the velocity or speed of an object depends
  entirely on the force being applied to it and the
  resistance it meets. This law was later proven
  to be inaccurate.

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Theory of Flight

• Aerodynamics
• Galileo Galilei
• Observed that an object in horizontal motion
  would continue to move at the same speed with no
  additional force.
• This truth was accepted by Sir Isaac Newton and
  became the first of three laws of motion stated
  by Newton.

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Theory of Flight

• Newtons Laws of Motion
• First Law of Motion
• A body at rest tends to remain at rest, and a
  body in motion tends to stay in motion, unless an
  outside force acts on the body. It is sometimes
  referred to as the Law of Inertia.
• One of the most common places people feel this
  law is in a fast moving vehicle. If you were
  standing inside a train and it suddenly stopped,
  you would continue to move forward even though
  the train had come to a stop.

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Theory of Flight

• Newtons Laws of Motion
• Second Law of Motion
• The acceleration of an object as produced by a
  net force, is directly proportional to the
  magnitude of the net force in the same direction
  as the net force and inversely proportional to
  the mass of the object.
• Hitting a golf ball is a common example of
  Newtons second law. The golf club is a force
  that causes the ball to move (overcoming
  inertia), and picks up speed (acceleration) and
  since the golf ball is relatively light, it picks
  up speed rapidly.

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Theory of Flight

• Newtons Laws of Motion
• Third Law of Motion
• Whenever one body exerts a force upon a second
  body, the second exerts an equal and opposite
  force upon the first body. Simply stated, For
  every action there is an equal and opposite
  reaction.

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Theory of Flight

• Newtons Laws of Motion
• Third Law of Motion
• This law is exemplified by what happens if you
  step off a boat onto the shore. As you move
  forward toward the shore, the boat tends to move
  in the opposite direction.

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Theory of Flight

• Acceleration
• The rate of increase in the velocity of
  something.
• Represents a change in velocity.
• Velocity
• The rate of motion in a given direction.
• The change of rate of motion in a given direction
  per unit of time.

13
Theory of Flight

• Force
• The power or energy exerted against a material
  body in a given direction.
• Force has both magnitude and direction.
• Mass
• The quantity of material (matter) contained in a
  body, while weight (which is often confused with
  mass) is really the amount of gravity being
  exerted on a quantity of matter.

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Theory of Flight

• The four forces in balance with one another hold
  the plane in the air.
• The four forces are lift, weight, thrust, and
  drag.

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Airfoils and Flight

• Airfoil Design
• An airfoil is designed to produce lift. An
  airfoil has a leading edge, a trailing edge, a
  chord, and camber.

16
Relative Wind

• The movement of the aircraft through the air
  creates the relative wind.
• The term relative wind means the wind that is
  moving past the airfoil and the direction of the
  wind is parallel to the flight path and relative
  to the attitude of position of the airfoil.
• The pilot controls the direction of the relative
  wind.

17
Angle of Attack

• Formed by the cord of the airfoil and the
  direction of the relative wind or between the
  chord line and the flight path.
• Is not constant during a flight. It changes as
  the pilot changes the attitude of the aircraft.
• One of the factors that determines the aircrafts
  rate of speed through the air.

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The Four Forces of Flight

• According to the Bernoulli Principle, there is an
  increase in the velocity of air as the airflow
  around an airfoil shape therefore, there is an
  increase of the relative wind as it flows above
  and below the surface of the airplane wing.

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The Four Forces of Flight

• Lift can be increased in two ways
• Increasing the forward speed of the airplane.
• Increasing the angle of attack.
• The pilot can increase the forward speed of the
  aircraft by applying more power.

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The Four Forces of Flight

• Lift Variables
• The pilot must have some way to control the
  amount of lift the airfoils generate.
• There are variables acting on the amount of lift
  generated.

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The Four Forces of Flight

• Angle of Attack

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The Four Forces of Flight

• Angle of Attack
• The sum of all the tiny forces over the surface
  of the wing is called the resultant.

23
The Four Forces of Flight

• Angle of Attack
• This resultant has magnitude, direction, and
  location. The point of intersection of the
  resultant with the chord of the wing is called
  the center of pressure (C/P).

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The Four Forces of Flight

• Angle of Attack
• The angle at which lift stops increasing and
  begins to decrease is called the burble point.

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The Four Forces of Flight

• Angle of Attack
• The point at which the amount of lift generated
  is no longer sufficient to support the aircraft
  in air is called the stalling point.

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The Four Forces of Flight

• Velocity of Relative Wind
• The velocity of the airfoil through the air is
  another important factor in determining the
  amount of lift generated.
• If an airfoil is made to travel faster through
  the air, greater pressure differences between the
  lower and upper surfaces of the airfoil result.

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The Four Forces of Flight

• Lift Variables
• Velocity of Relative Wind

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The Four Forces of Flight

• Air Density and Lift
• Lift varies directly with density. If flying at
  18,000 feet where the density is about half that
  at sea level, an aircraft will need to travel
  1.414 times as fast as it would at sea level to
  maintain altitude.
• If something reduces the lift by half, we will
  have to increase the speed so that the square
  root of the new velocity is twice the square of
  the original velocity.

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The Four Forces of Flight

• Airfoil Shape
• It is extremely important to preserve the
  characteristic curve that the designers built
  into the airfoil.
• Dents, mud, and ice are three common things that
  can spoil the built-in shape of the airfoil and
  interfere with the performance of the entire
  aircraft.

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The Four Forces of Flight

• Wing Area and Lift
• The greater the surface area of the wing, the
  greater the amount of lift that will be
  generated.
• Gliders and sailplanes are very good examples of
  how a large wing surface generates lift.

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The Four Forces of Flight

• Weight
• There is a point in the relationship of airfoil
  to angle of attack where lift is destroyed and
  the force of gravity (weight) takes command.
• Some of the most powerful jet fighter types and
  aerobatic sport airplanes can, for a short time
  and distance, climb straight up without any
  significant help from their airfoils.

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The Four Forces of Flight

• Weight
• There is another situation where lift can no
  longer overcome weight.
• The atmosphere becomes less and less dense as
  altitude increases.
• The airplane must be constructed of the lightest
  weight materials that can be used.
• The weight of whatever the airplane carries also
  receives very careful consideration.

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The Four Forces of Flight

• Weight
• Where the weight, or useful load, is placed in
  the airplane is another factor that has a
  pronounced effect on how well an airplane will
  fly.

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The Four Forces of Flight

• Thrust and Drag
• Thrust is the force that propels the aircraft
  forward.
• An airplane cannot gain altitude or maintain
  straight and level flight unless its engine is
  producing enough thrust.
• Without the needed thrust, weight has more
  influence than lift and pulls the airplane toward
  the ground.

35
The Four Forces of Flight

• Thrust and Drag
• Drag is present all the time and can be defined
  as the force that opposes thrust.
• The friction of air particles rubbing against all
  parts of the airplane causes part of the total
  drag.
• The shape of something may create low-pressure
  areas and turbulence that retard the forward
  movement of the aircraft.

36
Summary

• 1. Theory of Flight
• 2. Airfoils and Flight
• 3. Relative Wind
• 4. Angle of Attack
• 5. The Four Forces of Flight