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HIGHER volatility is required in an aircraft-engine fuel than in the ordinary internal-combustion-engine fuel, and provision must be made for easy starting, good distribution, freedom from vapor lock and decreased fire hazard. Each of these requirements requires the evaporation or non-evaporation of a certain percentage of the fuel under given temperature and pressure conditions that vary from one engine to another and with atmospheric-temperature changes. Changes in fuel volatility to suit the engine have no appreciable effect on performance, but small differences in the engine, particularly those that are found in the induction system, overshadow to a far greater degree any change that might occur in the volatility of the fuel. The ideal fuel is one whose boiling point is sufficiently high to avoid vapor lock and minimize the fire hazard but which will evaporate approximately 20 per cent at the initial boiling-point.

WHILE much experimental work has been done on the controllable-pitch propeller, complexity of existing devices has prevented their being placed on the market. After reviewing briefly the difficulties encountered, due to propeller and engine characteristics, the author discusses the effect of camber ratio and of angle of attack on the speed at which burble occurs, following this with comments on the efficiency of propellers as static-thrust producers, the use of the method of momentum to compute thrust and the application of adjustable-pitch propellers to supercharged engines. The causes of the forces required to operate the control adjustments are given as (a) friction, (b) twisting moments produced by centrifugal force and (c) twisting moments produced by air pressure.

WHAT can be done to increase safety, efficiency and comfort in flight of aircraft now in use? In answer, the author describes several devices designed to bring about this result and supplements this with the results of wind-tunnel research. Detailed descriptions of the particular devices mentioned are not included, the object of this paper being to show the great possibilities of their use and the resulting improvement in performance.

SELECTION of the proper crude is an important consideration in the manufacture of aviation-engine oils. The authors class petroleum into asphalt-base, paraffin-base and mixed-base crudes, stating that scientific research and actual-performance tests have demonstrated the advantages of paraffin-base oils over asphalt-base oils for aviation engines, and that their superiority is now conceded by most authorities. Much attention has been given recently to the dewaxing and fractionating of lubricating oils, and this has resulted in an improvement in their quality and in their unrestricted use as “all-weather aero oils.” After quoting statements from several authorities who agree that an oil which will meet both summer and winter requirements is desirable, the authors give the definitions of viscosity, fluidity, consistency and plasticity determined by the American Society for Testing Materials and then discuss the fluidity or consistency of aviation-engine oils below their A. S. T.

THE monocoque type of fuselage construction seems to promise satisfaction of the three requisites of prime importance; namely, high strength-weight ratio, “streamlined” form, and unobstructed interior, according to the author. The conventional method of building a fuselage consists, first, in the construction of a “form” of the required shape, upon which a layer of veneer is fastened. Other layers are applied, and thus a fuselage shell of two or three plies is completed. But the process is expensive and laborious, involving the handling and individual fitting of many small pieces. In the process described by the author, a wooden form of the exact shape of one half of the fuselage body, divided on a vertical plane passing through the center line, is built. This form, or pattern, is next suspended in a large box in which reinforcing bars previously have been woven, and concrete is poured in.

THE fundamental electrical and mechanical requirements of ignition equipment for aircraft engines are outlined and the special requirements peculiar to this service and that apply, in general, equally to military and commercial aircraft, are described. Brief descriptions are given of various new types of both magneto and battery ignition and the developments in each are pointed out. Characteristics of an ideal ignition system are enumerated as a basis for further development. Among the general requirements reliability is given place of first importance, followed by light weight, compactness, low cost and adaptability of a single model to engines of different types. The chief design-requirements are speed, ruggedness, simple mounting, light rotating-parts, resistance to vibration, ample lubrication, protection against moisture, and fire-proof ventilation. Each of these subjects is dealt with specifically.

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.

The experiences of the author in flying over an air-mail route are graphically portrayed. Although general practices hold for all routes, each route is said to present its own problems; special methods used in flying between any two points are not entirely effective in flying between any other two points. Conditions along the New York City-Cleveland route are therefore described and such topics as lights and beacons, terminal fields, emergency landing-fields, and the various aids in locating the position of the airplane when the beacons are obscured, are discussed. Among these aids are the general appearance of cities and the direction of their main streets, large factories, blast-furnaces, amusement parks, lighted railroad trains, automobile headlights on main highways, railroad roundhouses, mountains, and rivers. In nightflying, much depends on the airplane, which must meet definite requirements.

The author discusses commercial-airplane design in general terms, considering the subject under the main divisions of economy, safety, speed and comfort. Under economy, mention is made of possible reductions of first cost by designing for long life and reliability, the effect of the former on the depreciation allowance being obviously advantageous. Airplane size is debated also, the trend of progress being seemingly toward the giant airplane. Safety is stated to be dependent upon reliability, structural strength, stability, control, fire prevention and reduction of risk of injury to passengers in the event of a crash. Minimizing the results of a crash is considered suggestively. Speed is governed almost solely by the ratio of wing loading to power loading; hence, speed will always be kept as low as possible without loss of business to competing transportation enterprises. Included among desirable measures to secure comfort are adequate ventilation and the elimination of noise.

This paper is illuminative and affords an opportunity for better comprehension of the remarkable progress and accomplishment made in Europe along the lines of commercial aviation. Reviewing the present European routes now in regular or partial operation, the author stresses the essentialness of the attitude of the press in general being favorable if commercial aviation is to become wholly successful. The airship appears most practical for long-distance service, to the author, and he mentions the possibility of towns and cities growing up around “air ports.” The cost of airship travel is specified, although it is difficult to figure costs and necessary charges because so few data on the depreciation of equipment are available. Regarding successful operation, much depends upon the efficiency of the ground personnel and organization.

The very complete laboratory tests of airplane engines at ground level were of little aid in predicting performance with the reduced air pressures and temperatures met in flight. On the other hand, it was well-nigh impossible in a flight test to carry sufficient apparatus to measure the engine performance with anything like the desired completeness. The need clearly was to bring altitude conditions to the laboratory where adequate experimental apparatus was available and, to make this possible, the altitude chamber of the dynamometer laboratory at the Bureau of Standards was constructed. The two general classes of engine testing are to determine how good an engine is and how it can be improved, the latter including research and development work.

THIS paper describes the various types of radiator installations in use. Tabulated data on several makes of radiation and on successful airplane radiator installations are given. A brief review of laboratory tests is made and the features to be considered in design and manufacture are discussed. The author concludes by cautioning engineers against attempting to base new designs entirely upon experimental data, without comparing the tentative design with existing successful installations.

THE impression that recent aircraft experience should have taught engineers how to revolutionize automobile construction and performance, is not warranted by the facts involved. Aircraft and automobiles both embody powerplants, transmission mechanisms, running gear, bodies and controls, but their functions are entirely different. The controls of an airplane, except in work on the ground, act upon a gas, whereas with an automobile the resistant medium is a relatively solid surface. Similarly, the prime function of the fuselage is strength, weight considerations resulting in paying scant attention to comfort and convenience, which are the first requirements of an automobile body. Aircraft running-gear is designed for landing on special fields, and is not in use the major portion of the time. The running-gear is the backbone of an automobile, in use continuously for support, propulsion and steering; hence its utterly different design.

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.