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The author describes in a general way the three classes of battleplanes-the fighting, the reconnaisance and the bombing machines-and outlines the service for which each type is best fitted. The tests of engines and airplanes, prior to acceptance for the French Army, are cited. Among the difficulties of construction, those relating to the plane itself are relatively less serious than those relating to the engine. The greatest difficulty is to secure a reliable engine weighing only about 2 lb. per hp. The qualities of rotary and fixed-type engines are compared. The paper is concluded with a few remarks about aviators and mechanics and the relation of one to the other. The author has reserved some of his most interesting observations for the discussion, in which he describes vividly some actual airplane attacks and refers to night flying and night landing, concluding with suggestions as to “what America must do.”

Starting with the statement that command of the air in warfare rests largely with the side that produces the best single-seater fighter, the author proceeds to outline some of the problems confronting the designer of fighting airplanes, and particularly the smaller ones. Considering better performance and better fighting qualities as the main desiderata, the author discusses means of obtaining them by: (1) increasing the horsepower-weight ratio; (2) decreasing the wing or structure resistances; (3) devising a new arrangement of the supporting planes, with regard to the position of pilot or crew, or by a combination of the above. Considerable space is devoted to methods of decreasing wing resistance, principally by employing low-resistance aerofoils, and the shaping of wing tips is also referred to.

The author calls attention to the unreliability of the magnetic compass when used for aerial navigation and to the possible development of the gyroscopic compass for this purpose. He then explains how the drift of an airplane in flight makes it difficult to follow with accuracy a given course devoid of landmarks, unless an accurate drift indicator using the principle of the stroboscope is available. The development of such an instrument is then described, as are also means for synchronizing it with the compass. The use of the automatic synchronized instrument in flight over land is outlined, and its application to flight over water is described in considerable detail. Rules for aerial navigation over water, observation as to movement of wave crest and determination of wind velocity and direction are considered in their relation to the use of the instrument.

This paper first traces the early development of aviation engines in various countries. The six-cylinder Mercedes, V-type twelve-cylinder Renault, and six-cylinder Benz engines are then described in detail and illustrated. Various types of Sunbeam, Curtiss, and Austro-Daimler are also described. The effect of offset crankshafts, as employed on the Benz and Austro-Daimler engines, is illustrated by pressure and inertia diagrams and by textual description. The paper concludes with a section on the requirements as to size of aviation engines, four curves showing the changing conditions which affect the engine size requirements. These curves relate to variations of temperature, air density, engine speed, airplane speed and compression ratio required to compensate for decrease in air density, all as related to varying altitude.