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The present rapid increase in the number of light aircraft and private pilots will undoubtedly lead to a more general use of these aircraft. This will also mean more frequent operation under extremes of weather and operating conditions, and will increase the tendency on the part of many users to utilize automotive rather than aviation gasoline as an engine fuel because of its wider availability. Both these factors bring the problem of fuel vapor lock closer, hence it became desirable to study light aircraft fuel systems from the standpoint of vapor handling capacity. The vapor lock limits of a typical fuel system are presented, and an analysis is made of the factors which control vapor formation and the vapor handling capacity of the system. The limits found indicate that present 7 psi. Reid vapor pressure aviation fuels can be safely used under all practical conditions in a properly designed gravity feed fuel system but diaphragm fuel pump systems are marginal.

FOR preliminary design work on transport airplanes, a graphical method is outlined for determining the effect which changes in a set of chosen major design variables will have on the airplane's ability to meet a given set of specifications and regulations. Engines, propellers, and wing geometry are selected. Then for each condition laid down as a specification or regulation, a limiting curve of maximum weight allowed by the condition is plotted as a function of wing area. These curves are developed from basic data and standard equations. If it is possible to meet all the conditions, the limiting curves - when plotted together on one graph - will enclose an area on the “allowable” side of all curves.

BY relatively simple mathematics, it is possible to include the effects of mass, flexibility, valve-spring force, and gas pressure in designing valve cams for automobile or aircraft engines. First, a curve of ideal valve motion having suitable lift area and minimum acceleration properties is specified. Then, with the valve assumed to be executing this motion at a chosen speed, the sum of the inertia, gas pressure, and valve-spring forces can be computed at any point in the cycle. The driving force to overcome these resistances is created by compressing the valve linkage. The amount of deflection needed at any time can be found. These deflections are added to the valve motion to find the correct cam lift.

THE authors have found that of the many factors influencing ground and direct costs, these five have the greatest effect: 1. Payload. 2. Ratio of payload to number of passengers. 3. Number of ground stations. 4. Average length of passenger journey. 5. Administrative policy and efficiency. The effects of these factors on a sample airline are shown in a series of graphs.