AIR FORCES - UNITED STATES When in April 1917 the United States entered the World War, but little had been done by the country toward the creation of an air component for either the army or the navy. The aviation personnel consisted of 65 officers and 1,120 men in the army, 35 officers and 163 men in the navy. There were on hand no planes but those used for training, and of these only about 300, some of which were of inferior types. Aviation in,the army was then a function of the Signal Corps, whose prime mission was to provide means of communication, telephone and telegraph systems in the theatre of military operations. In the navy there was no well defined agency charged with the development of aviation. During the war the aviation section of the Signal Corps was abolished and instead there was created in the United States under the War Department, the division of military aeronautics, while in France the air component of the army was organized as the Air Service, with an officer, chief of the Air Service, in charge. In the navy, in March 1918 aviation was placed under the chief of naval operations, and was administered by an officer called the director of naval aviation.
At the Armistice in Nov. 1918 the army aviation personnel consisted of 20,000 officers, 60o cadets and 164,00o men; that of the navy, 6,716 officers and 30,692 men. There had been delivered in the United States about 8,500 training planes; there had been built for the army some 3,30o service type observation planes, the so-called De Haviland 4's, for the navy 1,60o anti submarine flying boats, while 15,700 motors for training planes and 13,396 Liberty motors had been produced. The Liberty motor development was one of the most strikingly successful projects undertaken during the war. Service type aircraft, that is, those actually used in military operations, were frequently and greatly changed, modified and improved during the war. This was especially true of the smaller, single-seater pursuit or fighting planes. Acting upon the best advice obtainable, the production efforts of the United States were concentrated upon planes of the larger types mentioned above which were not likely to be superseded so quickly, and upon the production of motors.
In addition to airplanes, lighter-than-air craft, dirigibles or air ships, are employed in both military and commercial operations. These are in use in both the army and the navy, though their development has been carried on more extensively by the latter service. Congress in 1928 authorized the navy to contract for two airships, each of about 5,000,000 cu.ft. capacity, at a cost of about $8,000,000.
The best way in which the air effort of the United States should be organized and administered has been much discussed. There were those who advocated the creation of a department of aeronautics, under a cabinet officer, charged with the conduct of all aviation activities, military and civil. Others urged the set ting up of a department of national defence, with a cabinet officer at the head, and under him three assistants in charge respectively of the land, the sea and the air forces. Still another view ad vanced was that the air components of the army and navy should remain separate, each under the control of the corresponding department head, and up to 1928 this view prevailed. Naval aviation, under the secretary of the Navy, is administered by the bureau of aeronautics, created in 1922, with a navy officer as its chief. Army aviation was made a separate combat arm, called the Air Service, by act of Congress in June 192o. This organization is under the secretary of War, an army officer its chief. In 1926 the name was changed to the Air Corps. In that year, 1926, Congress created in the Department of Commerce an aeronautical section charged with all matters concerning civil or commercial aviation, with an assistant secretary of Commerce at its head, and also provided additional assistant secretaries of War and of the Navy, each to have charge of aviation, under the secretary, in his own department.
During the session which ended July 2, 1926, Congress adopted definite continuing programmes to govern the development of army and navy aviation during the following five-year period. The necessary money was not appropriated until the next session, so that the carrying out of these programmes could not be started until July I, 1927. In accordance with this legislation, it was intended that by June 30, 1932, the Army Air Corps should have a total of 1,518 officers and 16,000 men, and 1,80o airplanes of the most modern designs, with provision for annual replace ments of about 400 planes; the navy, 85o officers and men, with not less than i,000 planes, likewise of up-to-date designs.
As of June 30, 1928, the Army Air Corps consisted of 1,o16 officers, 9,494 men, with 511 post-war built planes; the navy of 750 officers, about io,000 men, with 428 such planes; a total for the United States of 1,766 officers, 19,494 men, and 939 service type planes. Training planes are not included in these figures. (M. M. P.) air carburetted with the vapour of a highly vola tile hydrocarbon, such as petrol (gasolene). This product, origi nated about half a century ago, can be generated in a simple plant, operated by weights on a small scale, or by shafting, elec tric motor, or water-power for greater capacities, with self-regu lation according to the quantity of gas consumed. About 500 cubic feet of air-gas may be produced from a gallon of good petrol, one cubic foot giving 16 candle-power per hour. A special spirit, which leaves practically no residue, is used. Benzene may also be used.
The figure shows a simple weight-driven apparatus. As the weight descends it pulls the cord wound around the drum of the ma chine, chain-connected to a wheel inside the casing, standing upon the petrol tank. The wheel has cups that pass through the petrol, pick it up in measured quantities, and discharge it through a pipe into the obliquely-set carburettor. This compresses and carburets the air, using an archimedean screw that rotates and prevents irregular carburation, due to the cold produced by the rapid evaporation of the petrol. Cessation of action automatically occurs from the fact of a vacuum being set up when the bell of the gasholder has risen to a certain height. The machine thus generates rapidly or slowly according to the number of burners in use, and stops if they are all turned off. The larger electrically driven outfits will produce as many as 2,25o cu. ft. per hour. A product called gas-machine gas is used in America for mak ing air-gas. Gas-machine gas is a special "cut" or fraction of natural gasolene. This last-named product is isolated from the majority of natural gas produced in America by compression and cooling, or either by oil absorption or charcoal adsorption ftnd subsequent heating. From the natural gasolene thus produced, the gas-machine gas is obtained by a well-controlled distillation, to ensure having a highly volatile material with no residue when carburetted.
Air-gas, commonly known in America as gasoline-gas, consists of air charged with gasoline vapor to a point in excess of the maximum percentage which can form an explosive mixture. It is widely used for isolated plants in villages and country houses for lighting and other purposes. It is rarely used in larger com munities. The mixture commonly found most desirable (for a flame source in the Welsbach burner) is about 6 gallons of gaso lene per thousand cubic feet of air. The illuminating power of such air-gas compares favorably with that of ordinary commercial gas. The following table shows theoretical combining proportions for various gases (used as fuels) at room temperature: a gun in which the force employed to propel the bullet is the elasticity of compressed atmospheric air. It has attached to it, or constructed in it, a reservoir of compressed air, a portion of which, liberated into the space behind the bullet when the trigger is pulled, propels the bullet from the barrel by its ex pansion. The common forms of air-gun, which are merely toys, are charged by compressing a spiral spring, one end of which forms a piston working in a cylinder ; when released by a pull on the trig ger, this spring expands, and the air forces out the bullet.
In factories and other places where a supply of compressed air is available, its use for operating lifting tackle is much favoured, because of the cleanliness, absence of noise, and ease of connection with flex ible hose. The direct hoist, raising a load 4 or and deal ing with from r oo to 7,000lb. in different sizes, is the simplest. It comprises a cylinder, a piston, a rod attached thereto and carry ing the lifting hook at the bot tom, and an operating valve, con trolled by pendant chains. An eyebolt at the top affords means of suspension to a fixed beam, or a swinging jib, or to a trolley running on a girder, either sta tionary or forming part of a jib or travelling crane.
The hoist shown in the dia gram is controlled by balanced pressure. The full air pressure of ioolb. per sq. in. is maintained at the underside of the piston throughout all the operations of lifting, lowering and remaining stationary. For lifting, the at tendant manipulates the valve so that air leaks off the top piston.
Another way of applying air power is to use a special pulley block to which is attached a small pneumatic motor, the cylinders of which actuate connecting-rods and so drive a crankshaft, this being geared to the rope drum in order to gain power. Loads up to r o tons can be lifted in this way.
For colliery service, another class of air-hoist is built, a winch or haulage engine, the rope drum being driven through gears from a pneumatic motor. This is es sential in circumstances where compressed air is the power supply in use. Some of the engines can be run either with air or steam.
a system of lifting liquids by compressed air without a pump. For Artesian-wells the method consists in carrying down a smaller air-pipe either within the water delivery pipe or alongside it, and connecting up an air-compressor. The compressed air forms with the water a mixture of lower specific gravity than the surrounding water in the well or bore-hole, with the result that the mixture of air and water in the tube is forced by the weight of the surrounding water to the point of discharge (see next page). When the supply flowing into a well is not enough to give constant delivery, waste of energy may be avoided by a governor. Some air-lifts yield as many as 285,000 gals. per hour per well.
The Shone ejector, another form of air-lift, is utilized for raising sewage and other liquids automatically from one or any number of points, and forcing to any spot desired. The differ ence between this and the well lift just described is that the liquid gravitates into a bell-shaped casting through an inlet pipe and rises until the vessel is nearly full. Then the air trapped up at the top becomes slightly compressed, and acts on a metal cup that lifts a valve and admits a supply of compressed air into the vessel. This drives the sewage out through an outlet pipe to reach a higher level or any distance away; a fresh supply enters through the inlet pipe, which has been automatically closed during the discharge, and the cycle commences again.