NAVAL aviation confined its activities to training and to coastal patrol during the World War. This limited operation was necessitated by the small amount of materiel suitable for operation over water, the strategical and geographical situation which determined the nature of the naval operations, the very limited performance of seaplanes of that period, and the fact that warships were not equipped for handling aircraft or prepared for aircraft cooperation. At the end of the War, naval aviation was made part and parcel of the fleet.
Fighting airplanes are required to gain and maintain control of the air. Observation airplanes are used for short-range scouting and also for controlling long-range fire of capital ships by reporting the fall of shot to the ship by radio. For torpedo and bombing work, the first requirement is large weight-carrying capacity. A definite need exists for scouting and patrol operations at great distances from the fleet or base, requiring flights of great range and duration. In the present state of development, the multiple-engine flying-boat seems best suited for this purpose. Training airplanes need have only limited performance and require some skill on the part of the pilot. They should have low first and maintenance costs but weight, within reasonable limits, is not considered as being especially important.
The two accepted arrangements of aircraft engines for naval use at present are the radial and the in-line, and the cooling is by air or by water. An analysis of troubles experienced with water-cooled engines shows that a large proportion are due to failures of some part of the water system. The weight per horsepower, dry, of the most modern types of engine, is approximately the same, but it is a misleading comparison in that the chief concern is the weight of the powerplant when ready to fly. Air-cooling eliminates the troubles and the additional weight due to water-cooling. In the matter of mechanical dependability, there seems to be little choice between the engines proper of the two types. From the viewpoint of fuel economy, the two types are equally good.
Three distinct types of engine are now being produced for the Navy. Two models, practically identical in design and construction, are Packard engines of from 500 to 600 hp., and of 770 hp. respectively. Each is a 12-cylinder 60-deg-V type. The Wright nine-cylinder Model J-5 radial air-cooled engine and the Pratt & Whitney engines are the other two types.
After detailing various phases of flight experience, the author discusses superchargers, starters, ignition, the fire hazard of airplanes, gearing of airplane engines, heavy-oil solid-injection compression-ignition engines for aircraft use, and steam powerplants for the same purpose. He said that the solid-injection engine lends itself most favorably to the propulsion of rigid airships and that the steam powerplant is not worthy of serious consideration for aviation purposes in any form which has been devised to date.
Steady progress in engine design and engine building has resulted in a line of excellent powerplants produced to meet naval needs; one engine to date has found much favor with commercial users; and a line of engines has been developed that should fill commercial as well as naval needs.
The discussion cites some further features of engine lubrication, including a brief description of a centrifuge and its action.