As we all know, we usually call airplanes who own two wings the biplanes, and this is only the name and the form which we can see and observe from the basic level in the eyes of public. Besides, the biplane is a kind of airplane which possesses two units of wings whose upper wing is always paratactic and coordinates with the lower wing. Among all the biplanes, the airplanes whose front wing is often paratactic and coordinates with the rear wing are usually called the string-wing aircrafts.
Furthermore, the upper wing and the lower wing of these biplanes are usually made into a complete body which can bear the force by means of the struts and tension wires, and the complete structure of these biplanes is usually the space truss structure, and these biplanes are the airplanes in old times, and in the modern types of these airplanes, these small airplanes which possess the light and small airplane body and fast speed as well as limited loading and carrying capacity are the commonest airplanes in our daily life, and these biplanes are very rare.
Moreover, at the beginning of the development of these airplanes, the engine power was very lower, and in the meantime, the weight of the engine was usually very heavy, and the manufacturing materials of airplane body were almost the wood and cloths. In order to deal with and handle the flying problems of these airplanes, the wings whose total areas were very large and wide were really the must at that time, which can produce sufficient and enough flying power for these biplanes in order that these biplanes can well fly under the condition with lower speed. Also, these biplanes possess two wings, and the total areas of their wings are usually very larger than others.
With the rapid development and improvement of flying speed of these airplanes, the resistance and the obstructions of the struts and tension wires of these biplanes are becoming larger and larger, which become the main barriers of improving the flying speed of these biplanes. Thus, these biplanes are gradually replaced by modern airplanes step by step in modern times.
In addition, we really hope that all the important information mentioned above can be useful and helpful to all of you.