The purpose of the paper is to point out the basic policies which have resulted in the fostering of air-cooled-engine development by the Navy, and to indicate where the development has led. Two roles played by naval aviation are designated “air service” and “air force.” The former term refers to the functions of naval aircraft which are contributory to the ships of the fleets, such as scouting and the control of gun-fire. The latter term refers to the functions which involve the use of aircraft as an integral and component part of the Navy's striking force, such as combat, bombing and torpedo launching.
Seven different types of aircraft are required by the Navy for its different purposes, these being airplanes for training, fighting, observation, scouting, torpedoing, bombing, and patrol use. Scouting, torpedoing, bombing and patrol functions have been combined into one type in the past, but any airplane which combines multiple functions must suffer in its performance of the individual functions and it is desirable to provide a specific type for each required function.
Subsequent to specifying the engines now used in the airplanes for training, for fighting and for observation and saying that water-cooled engines in the 200-hp. field have been definitely supplanted by the air-cooled type, the author passes to a recitation of pertinent features connected with airplane tests conducted by the Bureau of Aeronautics with air-cooled engines installed in high-speed aircraft suitable for fighting. He states that the air-cooled engine has entered the pursuit field definitely to challenge the water-cooled engine and then discusses supercharging with Roots-blower-type superchargers, following this with description regarding recent application of the air-cooled engine to the bombing and the torpedoing-airplane classes.
The statement that the tendency to increase power is not sound is analyzed, as well as the preference in the Navy's development for radial rather than in-line air-cooled engines. The Navy is rapidly obtaining a line of three air-cooled engines that will meet most of its requirements. The large air-cooled engines are now equipped with 2 to 1 reduction-gears and can be installed with geared or with direct drive in twin-engined patrol-airplanes. Thus, the Navy then has the entire range of its aircraft air-cooled.
Since the approval of the basic policy to make naval aviation an integral and component part of the fleet that must go to sea with the fleet, the outlining of the types of aircraft required and their general characteristics, all the Navy's engines for aircraft have been developed for a specific purpose and it now has water-cooled engines of from 200 to 800 hp. and air-cooled engines of from 200 to 500 hp., the service ratings of which are shown in a chart. The requirements are low weight per horsepower, high economy in fuel, maximum dependability, maximum durability, maximum ease in maintenance, minimum cost, and easy adaptability to quantity production. With these requirements in mind, the author estimates the progress that has been made in naval-aircraft development, considering fuel economy, cooling efficiency, powerplant economy, dependability, durability, maintenance, cost, and production.
