TYPES OF AIRCRAFT

A. Modern heavier-than-air aircraft can be divided into two main classes according to the principle of flying: 1) aircraft flying due to aerodynamical action and 2) aircraft performing ballistic flight.

B. Aircraft of the first class are gliders, airplanes, helicopters, autogiros and winged missiles. Ballistic rockets belong to the second class.

C. Gliders have no power plant and are supported in the air by up and down air streams or air flows encountering the wing. The glider is lighter than the airplane and covers long distances with little loss of height. Thanks to them much of the early advance in aviation became possible. Now the gliders serve mostly for sport and training.

D. Airplanes are controllable machines and have engines which give power for forward motion. The lifting force of airplanes is created by the wing itself while it is propelled by the thrust produced by the airscrew or by a jet engine. The arrangement and number of the wings subdivide the airplanes into the classification as follows:

1) the biplane which is a two wing plane with an upper and lower of wings;

2) the monoplane which is an airplane with wings in one level.

These are divided into four general types according to the wing position:

a) the mid wing monoplane with the wing secured midway between the top and bottom of the fuselage;

b) the high wing monoplane having the wing attached to the top of the fuselage;

c) the low wing monoplane with the wing attached to the bottom of the fuselage;

d) the parasol wing monoplane having its wing placed a short distance above the
fuselage and attached to it by struts and braces.

E. Many airplanes are equipped to take off water and land on water. Such airplanes are called flying boats if the boat hull replaces the airplane fuselage, or seaplanes if floats take the place of wheels on a conventional land plane. If flying boats and seaplanes are also equipped with wheels for landing on the ground they are called amphibians.

F. At present VTOL and STOL aircraft are becoming popular but for vertical take-off it is necessary to produce the lift force exceeding the aircraft weight. The source of the lift is the energy developed by the propulsion system. The following methods of vertical take-off are suggested now:

a) the direct application of power plant thrust,

b) the application of lifting properties of airfoil.

G. The helicopter largely differs from the airplane. The main thing that distinguishes a helicopter from an airplane is that the necessary lift force for

helicopter is produced by a rotor instead of wings. The helicopter has a fuselage but there is no conventional propeller in the nose. Instead it has rotor blades on the top. The engine drives them. The power of a helicopter engine is transmitted to the rotor which produces the thrust for vertical take-off, hovering and forward propulsion. The helicopter is able to rise straight off the ground, fly forward, backward, sideward and descend vertically to the ground. Yet it has a few disadvantages. One of them is its inability to fly at high speed.

H. The autogiro is flying on the same principles, but the difference is that in addition to a rotor the autogiro has also a tractor airscrew. The power developed by the autogiro engine is transmitted to the airscrew while the rotor is freely revolving under the action of airflow, thus creating the lifting force.

I. Ballistic rockets (missiles) belong to the second class of aircraft. They do not require any lifting force produced by means of a wing. The rocket engine is to impart them the necessary energy for propulsion. The rocket engines are mostly operated on liquid or solid fuels.

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From the History of Flying	\|	Comprehension Check

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