An aeroplane is heavier than air, and, in order to keep suspended, must be constantly in motion. The moment it stops moving forward it begins to fall downward.
There are several kinds of airships, but the principle ones are monoplanes and biplanes. Mono means one, and monoplane has but one set of "wings," being built much after the fashion of a bird.
A biplane, as the name indicates, consists of two sets of planes, one above the other. There are some triplanes, but they have not been very successful, and there are some freak aeroplanes built with as many as eight sets.
If you will scale a sheet of tin, or a thin, flat stone, or even a slate from a roof, into the air, you will have the simplest form of an aeroplane. The stone, or tin, is heavier than the amount of air it displaces, but it stays up for a comparatively long time because it is in motion. The moment the impulse you have given it by throwing fails, then it begins to fall.
The engine, or motor, aboard an aeroplane keeps it constantly in motion, and it glides along through the air, resting on the atmosphere, by means of the planes or wings.
If you will take a clam shell, and, holding it with the concave side toward the ground, scale it into the air, you will see it gradually mount upward. If you hold the convex side toward the ground and throw it, you will see the clam shell curve downward.
That is the principle on which airships mount upward and descend while in motion. In a biplane there is either a forward or rear deflecting rudder, as well as one for steering from side to side. The latter works an the same principle as does the rudder of a boat in the water. If this rudder is bent to the right, the craft goes to the right, because of the pressure of air or water on the rudder twisted in that direction. And if the rudder is deflected to the left, the head of the craft takes that direction.
Just as the curve of a clam shell helps it to mount upward, so the curve of the elevating or depressing rudder on an airship helps it to go up or down. If the rudder is inclined upward the aeroplane shoots toward the clouds. When the rudder is parallel to the plane of the earth's surface, the airship flies in a straight line. When the rudder is tilted downward, down goes the craft.
I hope I have not wearied you with this description, but it was, perhaps, needful, to enable those who have never seen an aeroplane to understand the working principle. One point more. A gasolene motor, very powerful, is used to whirl the wooden propeller blades that shove the airship through the air, as the propeller of a motor-boat shoves that craft through the water.
Faster and faster across the grassy ground went the biplane containing Dick Hamilton and the army officers. It was necessary to get this "running start" to acquire enough momentum so that the craft would rise, just as a heavy bird has sometimes to run along the ground a few steps before its wings will take it up.