Aeroplane Construction and Operation

by John B. Rathbun

Chaser Armament. A single seat chaser is provided with one or two machine guns mounted on top of the fuselage, and directly in front of the pilot, the length of the barrel being parallel with the fore and aft center line. They may either be fixed rigidly to the fuselage top, or so that they can be pointed up, and over the top of the upper wing. With the machine guns fixed rigidly to the body, as in the early chaser monoplanes used by Garros and Vedrines, it was necessary at all times to fire directly through the disc area swept out by the propeller.

Two plans were tried for preventing the propeller from being broken by the bullets. The first consisted of a device operated by the motor that stopped the gun whenever the propeller blade came within the path of the bullets. This early mechanism proved unreliable, since the frequent stopping, with the propellers running 1200 revolutions per minute, soon put the apparatus out of order. Soon after the failure of this method, designers mounted curved protective steel plates on the inner portions of the propeller blades at points where they were likely to be struck with bullets. According to calculations in probability and chance, only one bullet out of every eighteen will strike the protective plate on the propeller blade, and hence only one out of eighteen bullets will be wasted. This, however, was a makeshift, and on modern machines the gun is driven, or "Synchronized" with the motor so that the bullets pass between the blades.

Curtiss Biplane in Flight. Taken from Another Machine. Courtesy "Aerial Age."

Many modern single seat chasers have the gun pivoted to the top of the fuselage so that the pilot can fire above the top plane and to either side of the body. This does away with the difficulty of keeping the machine headed directly at the enemy when in action, a method that is imperative with the fixed type of gun. Two seater chasers are generally arranged so that the gunner is seated back of the pilot, and the gun is so pivoted and supported that it can be swung through a wide radius both toward the front and on either side. This freedom of gun action at least partly compensates for the slower maneuvering qualities of the two seater type, since the gun may be swung with the target through quite a range of field, and without changing the flight direction of the machine. A gun of this type is provided with stops which prevent the gunner from shooting into the outlying parts of his own machine. The gun mounting in many cases of two seater construction consists of a light circular track that runs around the edge of the cockpit opening. The gun standard runs on this track, and the gun is pivoted at the upper end of the standard so that the muzzle can be raised or lowered. The gun turns in a horizontal plane by sliding on the track, and can be followed around by the gunner who is seated in the center on a pivoted seat. With this mounting it is possible to guard against a rear attack, to shoot straight up, or nearly straight down over the sides of the fuselage.

In a few machines of the two seater type, two machine guns are provided, one pivoted gun in the rear, and one gun rigidly fastened to the fuselage in front of the pilot. It is very seldom that both guns can be brought into action at once unless engaged with a number of enemy machines, although the front gun is handy in pursuit, and at a time when the rear gun is ineffective because of the pilot in front of him. Even with the double equipment, the superior maneuvering qualities of the single seater makes matters more even than would commonly be supposed. An added advantage of the single seater is that it is smaller and therefore more difficult to hit.

English speed scouts have largely adopted the American Lewis gun. The cartridges in this gun are arranged radially in a circular drum, and are fed to the gun as the drum revolves. The drum is mounted on the barrel near the breech and is operated automatically by the successive explosions. This feeds the cartridges and rejects the empty shells without the attention of the pilot. It fires about 600 shots per minute. When one drum is exhausted, another drum of new cartridges can be quickly and easily inserted. The French use the belt system to a large extent. In this system the cartridges are attached side by side on a cotton web belt as in the older types of army machine guns. As in the Lewis gun, the cartridges are fed automatically by the recoil of the explosions, and the belt moves through the breech with a step by step movement until the ammunition is exhausted. This is not nearly as compact an arrangement as the Lewis gun, and is more difficult to pivot on account of the dangling belts.

On the right hand side of the Nieuport body there is a drum on which the belt with the loaded cartridges is wound. The empty end of the belt is wound on a drum at the left, this drum being provided with a spring to keep the belt taut. The empty cartridges are discharged through a tube that passes through the side of the body. On the 1916 Fokker the gun is of the Maxim type, and is immovably fastened above the engine cowl and slightly to the right. To fire the gun, the pilot presses down a small lever fastened to the control column, and from this lever the connecting Bowden wire closes the motor clutch and starts the gun. A cam is fixed to the motor shaft in relation to the propeller blades. When firing, the elevator control is locked fore and aft, while the lateral control movement is operated by the pilot's knees. Steering is by the action of his feet on the rudder bar. Thus the pilot can balance laterally, and steer with his hands free for the manipulation of the gun, but he cannot change his elevation.

Aeromarine Training Seaplane