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Theory of Flight
Objectives
• Four forces of flight
• Parts of an airfoil
• Bernoulli and Newton
• Three axis of control
All are demonstrated by the flight of the bird!
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Intro to Flight
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Upward force, opposes
gravity, supports weight of
aircraft
Artificial
Four Forces of Flight
Retards
forward
movement
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Artificial
Natural
Natural
Variable with
throttle — pulls
an aircraft
forward
Intro to Flight
Gravity - constant in level
unaccelerated flight,
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Important Terms
• Airfoil – component (such as a wing) designed to produce
lift, thrust or directional stability
• Wind - air in motion
• Relative wind - flow of air opposite flight path of an airplane
• Angle of attack – angle formed by the chord line and
relative wind
Flight Path
Angle of attack -- α
Relative wind
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Bernoulli’s Theorem (1750)
High speed low pressure
Ping pong ball
supported by
Bernoulli
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Air flowing
over paper…
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Factors affecting
Bernoulli’s
Induced lift
- Camber
- airspeed,
- angle of attack
Impact, planar
Downwash effect
(Isaac Newton’s Third
Law of Motion 1700)
- Angle of attack
“For every action there is an equal and opposite reaction”
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Mathematics of Flight
Coefficient – a factor that contributes to producing a result
Area of the wing
Coefficient of lift (airfoil design
(average chord x
and angle of attack)
wing span)
Lift = CL x R x (½Velocity)2 x A
Altitude (density
of air)
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Speed (doubling speed
provides 4 times lift)
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Stall—airflow
separation from
the wing
Caused by high
angles of attack
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Thrust--Basic Concepts
• Internal combustion engines derive power from changing
chemical energy into mechanical energy.
• A small amount of fuel is burned to produce a large
volume of hot gas.
• The gas pressure provides mechanical or reactive
movement.
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Four Stroke Engine
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What about Drag?
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What about Thrust & Drag
Power Available
(fixed pitch)
400 lbs.
Max Speed 100%
TAS 75% Power
Best Climb Vy
Stall Speed
Airspeed
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Intro to Flight
73
134
143
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Control Surfaces
Right Aileron
Rudder
Elevator
Left Aileron
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Three Axis of Control
A real or imaginary line on which an object rotates
Vertical Axis
Center of
Gravity
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Balancing the Airplane on the
Center of Pressure
Center of Lift (CP)
is behind the CG
CP
CG
Arm
Need for negative lift on
the horizontal stabilizer
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Defining the Essentials
Arm
Arm
Weight
Weight
Fulcrum
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Aircraft Stability
CP – Center of Pressure (Lift)
- Lift moves CG aft
CG – Center of Gravity
Determine
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Important Terms — A new Language
1.
2.
3.
4.
5.
6.
7.
aerodynamics - the forces of air in motion
aeronautics - science of flight in the atmosphere
aerospace - combination of aeronautics and space
AGL - Above Ground Level MSL – Mean Sea Level
air - mixture of gases 79% N, 19% O and 2% other
aircraft - machine capable of flying through the air.
airplane - kept aloft by aerodynamic forces on wings and is
thrust
8. airfoil - component, such as a wing designed to produce lift,
thrust or directional stability
9. aviation - art, science & technology of flight in the atmosphere
10. aviator -person operates aircraft during flight
11. camber -curved part of an airfoil (leading to the trailing edge)
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Important Terms
12. chord - line drawn from leading to its trailing edge
13. drag - force retards forward movement of an aircraft in flight
14. downwash- downward movement of air behind the wing
15. leading edge -the front part of an airfoil
16. lift - upward force, opposes gravity, supports weight of aircraft
17. relative wind - flow of air opposite flight path of an airplane
18. static - standing still, or without motion
19. supersonic - faster than the speed of sound.
20. Subsonic is below the speed of sound
21. thrust - the force which moves an aircraft forward in flight
22. trailing edge - the back part of an airfoil
23. wind - air in motion
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