Fixed and Rotary Wing Aircraft
How Airplanes Fly
Airplanes fly because they are able to generate a force called Lift which normally moves the airplane upward. Lift is generated by the forward motion of the airplane through the air. This motion is produced by the Thrust of the engine(s).
The figure below is a simple diagram of the four forces acting on an airplane – Thrust, Lift, Drag and Weight. Drag is the force produced by the resistance of the air to the forward motion of the airplane. Swish your hand rapidly side-to-side and you will feel that resistance on your hand.
Weight is the force created by the pull of gravity toward the center of the earth. You will feel the effect of this force if you jump up from the floor. Your weight will force you back down.
When the Thrust produced by the engine(s) is greater than the force of Drag, the airplane moves forward. When the forward motion is enough to produce a force of Lift that is greater than the Weight, the airplane moves upward.
While any part of the airplane can produce Lift, the most Lift comes from the wings.
Fixed and Rotary Wing Aircraft
Now you are probably thinking that helicopters do not need to move forward in order to fly, and you are right. This is because helicopters are "rotary wing aircraft," meaning that the rotor which is turned around rapidly by the engine(s) is shaped like a narrow wing and provides the Lift necessary to overcome the Weight of the aircraft. This is different than a "fixed wing" aircraft where the wings are attached to the fuselage (fixed) and the Thrust of the engine(s) moves the plane forward to generate Lift. Tilting the rotor allows the helicopter to move forward and backward or side-to-side.
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