Power Plant of the Chaser. In the smaller speed scouts, the motor is of the rotary air cooled type, the output ranging from 80 to 110 horsepower, but as the power demands increased the water-cooled motor came into use, and at the present time has found favor with a large number of builders. When the power exceeds about 120 horsepower it is difficult to thoroughly cool the rotary engine, and although the Gnome, Clerget and Le Rhone are extremely desirable on a chaser because of their light weight, they cannot be used profitably on the larger scouts. Up to the present time, the Nieuport and Sopwith use the Clerget and Le Rhone rotary motors, but the S. P. A. D. and several others have adopted the water-cooled type. Nearly all of the German chasers, such as the Roland and Albatros, are water-cooled. Such motors must weigh well below 3 pounds per horsepower if there is to be sufficient power reserve for fast climbing. The Curtiss scouts are also water-cooled, although the rating is only 100 horsepower. The French and German machines are very heavily powered, motors of 175 horsepower being very common, even on single seaters. The fuel capacity is very limited, probably not exceeding 2.5 to 3 hours in any case.
General Dimensions of Scouts. The following table will give a better idea of the principal characteristics of these machines. It gives the overall dimensions, power, speed, climb, etc. It will be noted that the Nieuport biplane scouts have a smaller lower chord (*). The speeds given are the sea level speeds since a great change in altitude affects the performance to a marked degree.
Reconnaissance Type Arrangement. These machines are almost invariably of the two seater type, and are equipped either with one machine gun for the observer, or with a rigidly fixed gun for the pilot and a pivoted gun at the rear for the observer. In the majority of cases the observer is seated in the rear cockpit (Tractor types), and at a point where he has a greater visual radius and field of fire. With the pusher type, the observer is, of course, seated in the extreme front of the body, where he has an extremely wide angle of vision. The pilot in the rear seat of the pusher is effectually screened from any gun action, either from the front, side or rear, as the propeller cuts off the field at the back and the observer and interplane bracing blocks the way at the front and sides. The observer's cock-pit is equipped with the signalling apparatus, photographic equipment, map boards, etc., as well as the ammunition for the gun. The pilot's compartment contains the navigating instruments and controls.
Armament. At the beginning of the war nearly all of the French two seaters were of the pusher type, this arrangement, of course, resulted in almost a completely dead angle of fire in the rear, and a front horizontal angle that was practically restricted to 160 degrees. Owing to the forward position of the gun the vertical angle was quite good, 230 degrees or even better. In the tractor two seater, with a single movable gun mounted "En barbette" at the rear, the horizontal angle is about 180 degrees, but the vertical angle is less than with the pusher type. When the rear gun is supplemented with a front rigidly mounted gun, there is some protection at the front, but the rigid gun is far from being as effective as the pivoted rear gun. The front gun of course fires through the propeller. This armament is used by the German machines "Aviatic," "Rumpler," "Albatros," and "L. V. G." The forward rigid gun is usually of the infantry type, while the movable rear gun is lighter. The latter is fed by drums, or rolled bands on spools, so that reloading can be performed in the wind stream.
With the two seater type used in reconnaissance, artillery spotting, or photography, the power is generally in the neighborhood of 220-260 horsepower, and the speed varies from 85 to 100 miles per hour. The area is approximately 400 to 480 square feet. A single engine is generally used.
General Dimensions and Speeds. Reconnaissance machines of various types and makes are listed in the following table. A pusher is indicated by (P) and a tractor by (T). The German aeroplanes (G), and the Allied aeroplanes (A), are both listed for comparison: It will be noted that several types of machines have been made by the same firms, and that in some cases the same machines have different power plants. The Albatros C-III has been furnished with both the 170 and 220 Mercedes motor. The Ago biplane has a tapering wing, and the chord width (*) given is taken at the body. While very recent machines cannot be described, because of certain restrictions, the horsepower of the latest two seaters will average about 240 horsepower. If the dates and power items are noted, it will be seen that the machines used in 1917 have much larger motors than those built in 1916. The weight per square foot of surface will average about 6.5 pounds. The loading per horsepower rarely exceeds 17.0 pounds.
Bombing Type Aeroplanes. These large aeroplanes are fitted with either two or three independent power plants. The German bombers are represented by the Gotha, A. E. G., Friedrichshafen, and Rumpler G, while the Allied bombers are the Caproni, Handley-Page, Farman, Voisin, etc. The speed is about that of the reconnaissance type, and will seat three or more men. The motors average 500 560 horsepower per power plant, and the wing area is usually well over 1,000 square feet. The small two seaters are generally equipped with two pivoted machine guns, while the three seaters have a third machine gun arranged so that it can be lowered and fired through a trap door in the bottom of the body. Defense may thus be had from the rear, or below. In some of the pusher types, a rapid fire gun of comparatively heavy caliber is mounted at the front of the body in place of the usual machine gun. This is usually the case with the sea planes used for submarine chasing.
