No Carburetor

The famous flights of Macready and Kelly indicated that the body of the airplane, its structure and flying controls are sound, its heart--the power plant--is weak and constantly giving trouble. Navy Department statistics indicate that the Liberty motor must be overhauled after approximately 72 hours of flight at a cost of 300 man-hours and over $600. The Navy has been giving the question of improved engine reliability the most concentrated attention, and, without great modifications in principle, by better detail design and more skillful use of materials has greatly raised engine endurance. Engines now are expected to run continuously for 300 hours without deterioration.

Now, however, the Navy Department is studying a radical departure in airplane motors. Working on the famous Diesel engine principle, air may be compressed to 600 pounds per square inch or more than 40 times atmospheric pressure before delivery to the cylinder. With this enormous pressure liquid gasoline may be injected directly into the cylinder with the compressed air, without the necessity for a carburetor. The temperature of the mixture of fuel and air is so high that it will ignite spontaneously without any ignition system. The carburetor and the ignition systems are the great terrors of the flyer, as they are of the motorist, and their removal may mark a new era in airplane reliability.

The air compressors required on this system are tremendously heavy and bulky, however. It remains to be seen if weight and size can be sufficiently reduced for use in the airplane.