A free Research Paper on How Airplanes Fly
Uploaded by nasuha7 on Nov 24, 2012
HOW AirPLANES FLY
Aerodynamic forces
Essentially there are 4 aerodynamic forces that act on an airplane in flight; these are lift, drag, thrust and gravity (or weight).
In simple terms, drag is the resistance of air (the backward force), thrust is the power of the airplane's engine (the forward force), lift is the upward force and gravity is the downward force. So for airplanes to fly and stay airborne, the thrust must be greater than the drag and the lift must be greater than the gravity (so as you can see, drag opposes thrust and lift opposes gravity).
This is certainly the case when an airplane takes off or climbs. However, when it is in straight and level flight the opposing forces of lift and gravity are balanced. During a descent, gravity exceeds lift and to slow an airplane drag has to overcome thrust.
The picture below shows how these 4 forces act on an airplane in flight
Thrust is generated by the airplane's engine (propeller or jet), gravity is a natural force acting upon the airplane and drag comes from friction as the plane moves through air molecules. Drag is also a reaction to lift, and this lift must be generated by the airplane in flight. This is done by the wings of the airplane...
The generation of lift is a widely discussed and sometimes disputed theory, but there are some key factors that nobody argues. A cross section of a typical airplane wing will show the top surface to be more curved than the bottom surface. This shaped profile is called an 'airfoil' (or 'aerofoil') and the shape exists because it's long been proven (since the dawn of flight) that an airfoil generates significantly more lift than opposing drag.
During flight air naturally flows over and beneath the wing and is deflected upwards over the top surface and downwards beneath the lower surface. Any difference in deflection causes a difference in pressure ('pressure gradient') and because of the airfoil shape the pressure of the deflected air is lower above the airfoil than below it, hence the wing is 'pushed' upwards by the higher pressure beneath.
One of the argued theories of lift generation is related to Newton's 3rd Law of Action & Reaction, whereby the air being deflected downwards off the lower surface of the wing creates an opposite reaction, effectively pushing the wing upwards. This may well be the case but it's the...