MORE and more is being demanded of Navy airplanes beyond the requirements of commercial planes. Catapulting and deck landings are required of some planes and corrosion must be guarded against. Bombers and fighting planes each have their special requirements, and planes must be able to land safely on either land or water.
The most important developments in aerodynamics now going on are to restrict the travel of the center of pressure of the wings as the angle of attack changes; but widespread adoption of slotted wings and other results of experimental development may be expected.
Metal is being used more than formerly in structural work but there are as yet no all-metal service-types in the Navy. Chrome-molybdenum steel is replacing mild carbon-steel in the tubular frames of fuselages, and there is a tendency to seek substitutes for welded joints. Duralumin is slowly replacing steel where welding is not required, but its adoption is retarded because of corrosion. Spruce, mahogany and plywood are used for wing structures and fabric is still the standard covering-material.
Heat-treated aluminum-alloy castings and forgings are beginning to be used to a large extent. Stainless steel is expensive and not thoroughly reliable in every respect, but it may be used more as these objections are eliminated.
The five classes of planes required for the Navy are training, fighting, gunnery observation, three purpose, and patrol. Each of these classes has one or two service-types and most classes have several experimental types. The uses and features of these various types are briefly described and the development of powerplant accessories is outlined.
Slots at the leading edge and flaps at the trailing edge, which reduce landing and take-off speeds in experiment, will be especially valuable in deck-landing airplanes when they are fully developed. Torque-equalized brakes are being developed for these planes.
Reduction of resistance is being studied by making various parts retractable, by improving the sections and profiles of other parts and by developing cantilever wings.
Adjustable-pitch and reversible propellers are desirable but offer mechanical difficulties. Provision for floating wheel-type airplanes in case of forced landings on water is being made.