Learning to fly in the U.S. Army

by E. N. Fales

Speed 43 to 72 mi. per hr.; climbing ability 300 ft. per min.; 90 h.p.; weight fully loaded 1,890 lbs.

Types of Airplanes.—To suit the foregoing purposes flying machines exist in seven distinct different shapes at the present time, namely: monoplanes, biplanes, triplanes, single-motor tractors, single-motor pushers, double-motor machines and marine airplanes. The last four types may be either monoplanes, biplanes or triplanes. In order to understand the adoption of one or the other type for military use, it is well to run over the characteristics of the seven types mentioned.

Monoplanes.—The simplest form of airplane is the monoplane which is fashioned after the manner of a bird (see Fig. [34]). There are two things to say in favor of the monoplane: first, that the passengers have an unobstructed view forward and range of gun fire upward because there is no wing above them; second, the aerodynamic efficiency of the monoplane is superior to any other type. But when the bird design is applied to a man-carrying apparatus, it becomes impracticable to construct spars to take the place of the bird’s wing bones; and therefore to give the wings proper strength it becomes necessary to truss them with numerous tension wires stretching from the running gear out to various portions of the wings. There are also wires running from a vertical mast above the body to a point on the top part of the wing; these wires, while they give the wing no added strength during a flight, are necessary in order that the shock of landing shall not break the wings off sharp at the shoulder. It is characteristic of monoplane construction that from a point below the body and also from a point above the body a number of heavy wires run outward to various points on the wings; and it may be said that the strength to be secured from this construction is not all that could be desired.

Biplanes.—The biplane is an improvement over the monoplane from the latter standpoint; in the biplane there are two parallel surfaces separated by vertical sticks or struts, thus forming parallelograms which are susceptible of being trussed by means of tension-wire diagonals in a manner familiar and well understood in case of bridges. It is possible to build up biplane wings of great rigidity and strength by this system, much more easily than in case of monoplanes. However, the biplane type is from the standpoint of efficiency inferior to the monoplane. This is due to the fact that the vacuum above the bottom wing which is so necessary for high duty is somewhat interfered with by the upper wing; thus while in a biplane the upper wing operates about as efficiently as it would operate in a monoplane, yet the lower wing has its efficiency materially reduced and the resulting overall efficiency of a biplane compared area for area with the monoplane is about 85 per cent. as great. However, recent developments of the airplane have more or less put efficiency in the background and as a result today the biplane is more popular than the monoplane. In addition to the greater strength of biplane wings their span may be less than the monoplane for the same supporting area. This makes them less unwieldy. Moreover, for certain reasons a biplane machine of high speed may be landed at a lower speed than equivalent monoplanes.

Triplanes.—What is true of the biplane is more true in almost every item of the triplane, that is, it is comparatively strong, compact, and of low landing speed, but of reduced efficiency.

Fig. 8.—U. S. speed scout triplane, single seater.

(Curtiss Model S3), 55 to 115 mi. per hr.; climbing ability 900 ft. per min.; 100 h.p.; weight fully loaded 1,320 lbs.

Single-Motor Tractors.—The single-motor tractor received its name simply because the propeller is in front and draws the machine forward; but this location of the propeller necessitates a distinct type of airplane, wherein the power plant is located at the very nose of the machine. The tractor type has the pilot and passenger located in or to the rear of the wings in order that their weight may balance the weight of the motor. This means that the view and range of fire of the passengers is obstructed in a forward direction by the wings, and in machines such as the U. S. training machine, the passenger, who is practically in the center of the wings, can not look directly upward nor directly downward. Moreover, as concerns gun fire, the propeller of a tractor obstructs the range straight ahead. In the tractor the tail is supported at the rear and on the same body which contains the motor and passengers; this body constitutes a stream-line housing for the machinery, seats, etc., and therefore has low wind resistance. The tractor is a very shipshape design, compact and simple and is at present the prevailing type on the European war front. However, it has disadvantages which are only overcome in other types. One of these disadvantages is of course the obstruction to range of gun fire. The present practice in fighting airplanes is simply to shoot the gun straight through the circle of rotation of the propeller on the assumption that most of the bullets will get through and that those which hit the shank of the propeller blade will be deflected by proper armoring. An attempt is made to insure that all the shots will get through by connecting the gun mechanism mechanically to the motor shaft in such a way that bullets will be discharged only at the instant when their path is unobstructed by a propeller blade. This practice is possible of course only in guns which are fixed immovably to the airplane.