The Physics of Flight

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24 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

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The Physics of Flight

Ancient Dreamers


Legends of flight attempts date to 2000 B.C.


Many believed flying was for the mythical gods


Others tried to copy bird flight
-
unsuccessfully


Chinese invented kites about 1000 B.C.


17
th

century A.D. kites carried soldiers aloft


Leonardo da Vinci, 15
th

century Italian artist


First recorded scientific study of aeronautics


Experimented to prove feasibility of mechanical flight


Drew sketches and plans to construct flying machines

Ancient Dreamers



Leonardo da Vinci


Daedalis & Icarus



Italian artist and scientist
Leonardo da Vinci

(1452
-
1519) gathered data on the flight of birds and
developed concepts of the propeller, the parachute,
and heavier
-
than
-
air craft.

The Quest for Flight


By 17th Century, ancient ideas inspired
scientific theories and experiments


Characteristics of the atmosphere and the
discovery of gasses and properties led to
lighter
-
than
-
air balloon experiments


Airships needed power and direction control


Glider flying increased the understanding of
flight forces, wing geometry & controls

Definition: Aerodynamics


Aerodynamics

is a
branch of fluid
mechanics that deals
with the motion of air
and other gaseous
fluids, and with the
forces acting on
bodies in motion
relative to such fluids

Bernoulli’s Principle


According to Bernoulli’s Principle, as the
velocity of a fluid increases the pressure
exerted by the fluid decreases.

Air Flow Past a Wing


The air speed is greater over the upper surface,
as indicated by the closer streamlines, the air
pressure is lower there and the wing is lifted



When the wing is angled upward, air deflected
from its lower surface provides additional lift.


If the angle is too great, turbulence reduces lift
and increases drag.


Powered Flight Breakthrough


Experiments showed basic ingredients of
flight are: sufficient power, lift , control


Wright’s successfully applied theories of lift
and drag to practical use in powered gliders


Progress (and a conventional designs) came
with lighter materials and drag reduction


Breakthrough


Sir Hiram Maxim


power, lift, control


Wright brothers


Glen Curtiss


Improved designs,
promoted aviation

December 17, 1903, near Kitty Hawk, North
Carolina, Wilbur and Orville Wright made the world's
first successful powered, free, controlled, sustained
flights in a heavier
-
than
-
air craft.

The Main Events

World War I


War speeds up
technology
development


Airplane speed,
loads increased


Large manufacturing
base developed

Congressional medal of Honor winner Captain Eddie
Rickenbacker went on to be a pioneer in civil aviation, too

The Main Events

After the War


Veteran pilots kept interest alive


Commercial aviation catches on


Dramatic design advances


Beginning of rocket flight


Invention of the jet engine


Four Forces of Flight


Lift


Weight


Thrust


Drag


Source: NASA Glen Research Center

Forces on an Airplane

Lift


Lift is an aerodynamic force


Lift must exceed weight for flight


Generated by motion of aircraft through
air


Created by the effects of airflow past
wing


The top of an airplane wing is curved, so
that air has to travel further to reach the
trailing end of the wing.


Therefore, the air on the underside of
the plane is exerting more pressure,
causing the plane to lift.

Weight


Weight is not constant


varies with passengers, cargo,
fuel load


decreases as fuel is consumed
or payload off
-
loaded


Direction is constant toward
earth’s center


May be assumed concentrated
at the center of gravity

Drag


An aerodynamic force


Drag is also called air resistance.


the force that pulls the plane backward.


Two broad drag classifications


Parasite drag: drag created by airplane design


Induced drag: by
-
product of lift generation


Acts through the center of pressure

Thrust


Forward
-
acting force opposes drag


Direction of thrust depends on design


Propulsion systems produce thrust


Equal to drag in straight, constant speed
flight

Stability


Center of Gravity


Center of Pressure


Longitudinal Stability


Lateral Stability


Directional Stability


Definition: Aeronautics


Aeronautics

is the
design and
construction of


aircraft and


The theory and
practice of aircraft
navigation


Definition: Aerospace Engineering


Aerospace
engineering

is
closely allied to
aeronautics and
aeronautical
engineering but


Includes the study
and development of
rocket engines,
satellites, and
spacecraft


Activities and Exercises


Build gliders for flight control experiments


Worksheets