The two main supporting planes in the regular Farman models were 33 feet by 6-1/2 feet, set 7 feet apart, and with a total area of 430 square feet. These dimensions have been varied slightly in other machines. The elevating rudder, which was set well out in front of the body of the machine, was a horizontal plane controlled by a wire and lever. In the rear was a tail of two parallel surfaces, slightly curved like the main planes of the biplanes. These two surfaces steadied the machine from front to rear. At their two sides were two vertical surfaces, giving the tail the appearance of a box kite, so familiar in the Voisin. These two vertical surfaces, however, comprised the direction rudder, and were turned from side to side by the operator with a foot lever. In some of the later Farman biplanes the two vertical surfaces were done away with in favour of a single one, extending between the centres of the two horizontal surfaces of the tail. The side-to-side balance was maintained by ailerons in the form of wing tips set at the outer rear edges of the main planes. The tips were hinged and connected with wires which led to the lever that worked the elevating rudder. Thus by pulling this lever toward him the operator tilted the rudder up, and the machine rose, and by moving it from side to side the biplane was kept on an even keel. For instance, if the machine were to tip to the right he would move the lever to the left, pulling down the hinged ailerons on the right. The ones on the left would still remain standing straight out at the same angle as the main planes. The increase in the lifting power on the right side would cause that end to rise, righting the machine.
Most Farman biplanes these days are driven by the well known 7-cylinder Gnome rotary air-cooled engines, set at the rear of the main plane. They are directly connected with the single propeller, which is 8-1/2 feet in diameter. The seat for the aviator is in front of the engine at the front edge of the lower plane, and there also frequently are placed seats for two other passengers. The machine is mounted on wheels and skids.
The "Farman Militaire" type is one of the largest and heaviest machines made to date, having a total area of supporting plane of 540 square feet. The chief difference is that instead of two direction rudders there are three, and that the lower main plane is set at a dihedral angle. It was on such a machine ("Type Michelin") that Farman flew steadily for eight and a half hours. It also has made remarkable distance, endurance, and weight-carrying records, although it is a slow machine, making but 34 to 35 miles an hour. The "Type Michelin" is distinguished by the fact that the upper main plane has a spread of 49 feet, 3 inches, while the lower plane had a spread of only 36 feet.
MAURICE FARMAN BIPLANE
Soon after Henri Farman had become famous as an aviator and constructor of aeroplanes, his brother Maurice began to build air craft. The Maurice Farman biplane was the result. After conducting their business separately for several years the brothers consolidated, and each type is known by the name of the brother designing it. The Maurice Farman biplane has some remarkable records, among them the winning of the Michelin prize in 1910 by Tabuteau, who flew 362-1/2 miles in seven and a half hours without stopping.
The main planes have a spread of 36 feet and a depth of 7-1/2 feet. They have not as great a curve or camber as most biplanes, which increases their speed. The tail is of the well-known Farman cell formation—that is, it has four sides. The two vertical surfaces swing on pivots and are controlled by wires connecting with the direction steering wheel. The horizontal surfaces of the tail, except for the tips, are stationary, and steady the machine from front to rear. The rear tips of these two surfaces, however, work on pivots in connection with the main elevating plane which is set out in front. The elevator is a single plane controlled by a rod connected with the steering wheel, while the tips of the horizontal tail surfaces are controlled in unison with the main elevator by wires, also connected with the steering wheel. Ailerons are set into the rear outer tips of the main planes, for the control of the side-to-side balance, and these are worked by foot pedals. In order to give greater safety in case of the breakage of a wire, all the controlling parts in the Maurice Farman machine are duplicate, which is a big step toward the much-desired double controlling system in aeroplanes. The biplane is mounted on both skids and wheels. The operator sits well forward on the lower plane in a comfortable little pit enclosed in canvas. Thus, the Maurice Farman machine was the first to adopt this device for shielding the pilot from the wind. The engine used usually is an 8-cylinder air-cooled Renault, which drives a propeller nearly 10 feet in diameter.
BREGUET BIPLANE
Only slightly known in the United States but well and favourably known in Europe, particularly in France, is the Breguet biplane, which made wonderful records in the French Army tests in 1911. A brief description will show the difference between this machine and others of the biplane type. It has won many prizes for its stability and lifting powers, and also has shown great speed. The framework is mostly metal and is so elastic that it gives under the pulsations for the wind, so that the machine is not so badly strained by gusts as the more rigid kinds. Also it is thought the elasticity increases its lifting capacity. Of the two main planes the upper one spreads 43-1/2 feet, while the lower one spreads 32-1/2 feet. They are 5-1/2 feet deep, and set 7 feet apart. The body and tail of the machine are made on delicate graceful lines, terminating in the elevation and direction rudders at the rear. There are no rudders, vanes, or other rigging out in front. The lateral balance is maintained by warping the planes. The propeller is at the front of the machine, and is of the tractor type, pulling it through the air instead of pushing it. In the latest machines a metallic three-bladed Breguet propeller, the pitch of which is self-adjusting, is used, but in others a two-bladed wooden propeller, such as is familiar in this country. The long body, or fuselage, as the framework of the tail is called, is enclosed on the latest types of Breguets in use by the French Army, greatly adding to its gracefulness, and decreasing the wind pressure.
There are several other makes of biplanes that could be described to advantage but space prevents it, and the descriptions here given serve to illustrate the principle of the biplane type of aeroplane.