From Introduction: "The object of this investigation was to determine the characteristics of various types of wings having sufficient depth to entirely inclose the wing bracing, and also to provide data for the further design of such sections. Results of the investigation of the following subjects are given: (1) effect of changing the upper and lower camber of thick aerofoils of uniform section; (2) effect of thickening the center and thinning the tips of a thin aerofoil; (3) effect of adding a convex lower surface to a tapered section; (4) effect of changing the mean thickness with constant center and tip sections; and (5) effect of varying the chord along the span."
From Report: "The question of the influence of a supercharged engine on airplane performance is treated here in a first approximation, but one that gives an exact idea of the advantage of supercharging. Considered here is an airplane that climbs first with an ordinary engine, not supercharged, and afterwards climbs with a supercharged engine. The aim is to find the difference of the ceilings reached in the two cases. In the case of our figure, the ceiling from 25,000 feet is increased to 37,000 feet, the supercharging maintaining the power only up to 20,000 feet. This makes, in comparison with an engine without supercharging, an increase of about 50 percent."
Report presents descriptions, schematics, and photographs of the altitude laboratory for the testing of aircraft engines constructed at the Bureau of Standards for the National Advisory Committee for Aeronautics.
Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, Congressional report, summaries of the committee's activities and research accomplished, expenditures, problems, recommendations, and a compilation of technical reports produced.
Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, Congressional report, summaries of the committee's activities and research accomplished, expenditures, and a compilation of technical reports produced.
Report develops a fundamental conception and partial application of a method for calculating the pressure-volume relationships to be expected for any given engine design. It outlines a method of computing and interpreting low-pressure indicator cards.
Tests were conducted at the altitude laboratory erected at the Bureau of Standards for the National Advisory Committee for Aeronautics to determine the changes in engine performance with changes in atmospheric temperature and pressure at various levels above the earth's surface, with special reference to (a) the variables affecting the functioning of the carburetor and (b) the changes in performance resulting from variables in the carburetor itself. This report constitutes a concise statement of the difficulties to be encountered in this branch of carburetion.
This report gives the results of an investigation made into the fundamental physical characteristics of high-tension ignition magnetos, and also describes the methods used for measuring the quantities involved.
Among the fuels which will operate at compression ratios up to at least 8.0 without preignition or "pinking" is hecter fuel, whence a careful determination of its performance is of importance. For the test data presented in this report the hecter fuel used was a mixture of 30 per cent benzol and 70 per cent cyclohexane, having a low freezing point, and distilling from first drop to 90 per cent at nearly a constant temperature, about 20 degrees c. below the average distillation temperature ("mean volatility") of the x gasoline (export grade). The results of these experiments show that the power developed by hecter fuel is the same as that developed by export aviation gasoline at about 1,800 r.p.m. at all altitudes. At lower speeds differences in the power developed by the fuels become evident. Comparisons at ground level were omitted to avoid any possibility of damaging the engine by operating with open throttle on gasoline at so high a compression. The fuel consumption per unit power based on weight, not volume, averaged more than 10 per cent greater with hecter than with x gasoline. The thermal efficiency of the engine when using hecter is less than when using gasoline, particularly at higher speeds. A generalization of the difference for all altitudes and speeds being 8 per cent. A general deduction from these facts is that more hecter is exhausted unburnt. Hecter can withstand high compression pressures and temperature without preignition. (author).
Given here is a description of the design of a scientific recording wind tunnel balance. It was decided that the most satisfactory arrangement would be a rigid ring completely surrounding the tunnel or wind stream, so that the model could be supported from it by wires or any arrangement of spindles. The forces and moments acting on this ring can then be recorded by suitable weighing apparatus. The methods available for recording forces on the arms are explained. The proposed type of balance will support the model rigidly in a variety of ways, will make a complete test without attention, and will plot the results so that all computations are avoided.
Report describes the development of a suitable speed nozzle for the first few thousand airplanes made by the United States during the recent war in Europe, and to furnish a basis for more mature instruments in the future. Requirements for the project were to provide a suitable pressure collector for aircraft speed meters and to develop a speed nozzle which would be waterproof, powerful, unaffected by slight pitch and yaw, rugged and easy to manufacture, and uniform in structure and reading, so as not to require individual calibration.
Discussed here are computations of drag or negative traction of geared down supporting propellers in the downward vertical glide of a helicopter. By means of Frounde's Theory, the maximum value of the drag of a windmill is calculated. For wooden propellers, the author finds that the difference between the drag and the weight is proportional to the number of blades and is larger for propellers of small diameter; thus it is 25 kg. for a six blade propeller with a diameter of 2 m. 50. The author notes that if we are to adopt large propellers, we must have recourse to a different method of construction, resulting in large dimension propellers much lighter than those made of wood. In discussing insufficient drag, the author notes that the question of the drag of geared down supporting propellers can only be decided by experiment.
As an airplane rises to high altitudes the decrease in the density and the temperature of the air have important effects on the performance of the radiator. This report gives the results of a study of the effect of reduced pressure and temperature upon the capacity of airplane radiators. A method is presented by which the performance of a radiator at an altitude may be estimated for a particular speed of the airplane at a particular altitude.
This report is a very complete treatise on the comparative strength of air and kiln dried wood. The series of tests includes 26 species of wood, approximately 100 kiln runs, and over 10,000 mechanical tests.
This report presents the results of an investigation which was to determine how the voltage necessary to produce the proper spark discharge varies with the pressure and temperature of the gas in which the discharge takes place.
I. The development of the gear wheels: (a) bending stresses; (b) compressive stresses; (c) heating; (d) precision of manufacture. II. General arrangement of the gearing. III. Vibration in the shaft transmission. An overview is given of experience with geared propeller drives for aviation engines. The development of gear wheels is discussed with emphasis upon bending stresses, compressive stresses, heating, and precision in manufacturing. With respect to the general arrangement of gear drives for airplanes, some principal rules of mechanical engineering that apply with special force are noted. The primary vibrations in the shaft transmission are discussed. With respect to vibration, various methods for computing vibration frequency and the influence of elastic couplings are discussed.
Report presents the results of wind tunnel tests of propellers that examined the influence of the following characteristics: (1) nominal pitch ratio 1.3 combined with a certain number of the more common or standard forms and proportions; (2) driving face slightly rounded or convex; (3) change in the location of the maximum thickness ordinate of the blade section; (4) pushing forward the leading edge of the blade, thus giving a rounded convex surface on the leading side of the driving face. (5) a series of values for the constant "angle of attack" in forming propellers with radially increasing pitch. In accordance with these purposes tests were carried out on 28 propellers.
The study of aeronautical fabrics has led to a consideration of the best methods of attaching and fastening together such materials. This report presents the results of an investigation upon the proper methods of attaching fabrics to airplane wings. The methods recommended in this report have been adopted by the military services.
Report describes the generation of hydrogen by the reaction between ferrosilicon, sodium hydroxide, and water. This method known as the ferrosilicon method is especially adapted for use in the military field because of the relatively small size and low cost of the generator required to produce hydrogen at a rapid rate, the small operating force required, and the fact that no power is used except the small amount required to operate the stirring and pumping machinery. These advantages make it possible to quickly generate sufficient hydrogen to fill a balloon with a generator which can be transported on a motor truck. This report gives a summary of the details of the ferrosilicon process and a critical examination of the means which are necessary in order to make the process successful.
This report was prepared for the National Advisory Committee for Aeronautics and presents the results of investigations conducted by the Forest Products Laboratory of the United States Forest Service on the manufacture, preparation, application, testing and physical properties of the different types of glues used in wood airplane parts.
Given here is a brief description of the Göttingen wind tunnel for the testing of aircraft models, preceded by a history of its development. Included are a number of diagrams illustrating, among other things, a sectional elevation of the wind tunnel, the pressure regulator, the entrance cone and method of supporting a model for simple drag tests, a three-component balance, and a propeller testing device, all of which are discussed in the text.
Part 1 deals with the head resistance of a number of common types of radiator cores at different speeds in free air, as measured in the wind tunnel at the bureau of standards. This work was undertaken to determine the characteristics of various types of radiator cores, and in particular to develop the best type of radiator for airplanes. Some 25 specimens of core were tested, including practically all the general types now in use, except the flat plate type. Part 2 gives the results of wind tunnel tests of resistance on a model fuselage with a nose radiator. Part 3 presents the results of preliminary tests of head resistance of a radiator enclosed in a streamlined casing. Special attention is given to the value of wing radiator and of the radiator located in the open, especially when it is provided with a properly designed streamlined casing.
From Resume: "This report describes a method developed at the Bureau of Standards for measuring the total energy liberated as heat in a spark gap by an ignition system. Since this heat energy is obtained from the electromagnetic energy stored in the windings of the magneto or coil, it is a measure of the effectiveness of the device as an electric generator." Part 2 gives the results of measurements in absolute units of the total heat supplied to a spark gap by ignition systems of different types operating at various speeds, under conditions substantially equivalent to those in the cylinder of a high-compression aviation engine.
Described here is a method by which high average fuel economy has been achieved in aircraft engines. Details are given of the design of certain foreign engines that employ an unusual type of fuel-air ratio control in which the change in power produced by a mixture change is due almost entirely to the change in the power producing ability of the unit weight of the mixture. The safety and performance features of this type of control are explained.
Report discusses the calculations that can be used to show why pressures inside an engine during preignition are higher than average. This information can be used to design a safer engine that is able to contain the increased pressure and heat generated during preignition.
With the advent of the V type engine, a new method to measure the clearance volume in cylinders was needed. It was suggested that this measurement could be made by a process which consisted essentially of simultaneously changing both a known and unknown volume of gas by a known amount and then calculating the magnitude of the unknown from the resulting difference in pressure between the two. An instrument based on this design is described.
The experimentation presented in this report falls in two divisions: first, the determination of the relation between back pressure in the exhaust line and consequent power loss, for various combinations of speed and throttle positions of the engine; second, the construction and trial of muffler designs covering both type and size. Report deals with experiments in the development of a muffler designed on the principle which will give the maximum muffling effect with a minimum loss of power. The main body of the work has been done on a Curtiss OX eight-cylinder airplane engine, 4 by 5 inches, rated 70 horsepower at 1,200 revolutions per minute. For estimation of the muffling ability and suppression of "bark" of individual exhausts, the "Ingeco" stationary, single cylinder, 5 1/2 by 10 inch, throttling governed gasoline engine, and occasionally other engines were used.
Given here are the results of experiments conducted by Colonel Costanzi of the Italian Army to determine the influence of the surrounding building in which a wind tunnel was installed on the efficiency of the installation, and how the efficiency of the installation was affected by the design of the tunnel. Also given are the results of a series of experiments by Eiffel on 34 models of tunnels of different dimensions. This series of experiments was started in order to find out if, by changing the shape of the nozzle or of the diffuser of the large tunnel at Auteuil, the efficiency of the installation could be improved.
Report describes experiments conducted on a new method of producing high-grade aviation gasoline at a test laboratory established at Charleston, W. Va. For the National Advisory Committee for Aeronautics.
Report defines the principal terms which have come into use in the development of aeronautics. It was prepared in cooperation with a committee engaged upon a similar undertaking in Great Britain. As a result this nomenclature is in substantial agreement with the one which has been adopted by the aeronautical authorities of Great Britain.
Report detailing studies of longitudinal stability and balance on five airplanes: the JN4H, DH4, VE7, USAC-11, and Martin Transport. The methods of measurement, methods of correcting instability, and potential modifications for the elevator of the planes is described.
Given here are the rules officially adopted by the Aeronautical Commission of the Aero Club of France for a flight competition to be held in France in 1920 at the Villacoublay Aerodrome. The prize will be awarded to the pilot who succeeds in obtaining the highest maximum and lowest minimum speeds, and in landing within the shortest distance.
The author examines the current theory on the importance of reducing slip in airplane propellers. The author feels an exaggerated importance is attached to this supposition and feels that the increase in friction by an increase in propeller area or number of revolutions can't be discounted.
This report deals with the problem of increasing the speed range of an airplane by varying the camber of a wing surface. The variable camber wing offers many advantages over the variable incidence type of speed range.
Methods and equipment for recording small and sometimes rapid motions by photographic means are described, and the efficacy of photographic recording in such instances is evaluated. The optical system consisting of the light source, the mirror or prism for transmitting motion to the emergent beam, and a means of bringing the rays into focus on the film are discussed. Attention is given to the critical issue of mirror mounting. The film holder and the driving motor for the recording drum are described in detail. The authors conclude that the optical methods they describe are far more satisfactory than the recording pen, in compactness, in high natural period, and in elimination of friction. Costs are similar to mechanical methods. The development and reproduction of the record is an added complication, but the ease of duplicating the records is a decided advantage.
Report presents the summation of results obtained in the testing of fuels of various compositions and characteristics in the altitude laboratory. The data upon which this report is based has had an important influence upon the writing of specifications for the various grades of aviation fuels.
Results are presented for a series of tests made by the Advisory Committee's staff at Langley Field during the summer of 1919 with the objectives of determining the characteristics of airplanes in flight and the extent to which the actual characteristics differ from those predicted from tests on models in the wind tunnel, and of studying the balance of the machines and the forces which must be applied to the controls in order to maintain longitudinal equilibrium.
Report discussing some of the issues regarding the design and operation of helicopters and the theoretical basis behind them. Some particular issues covered include propeller blade design, helicopters in forced descent, horizontal travel, and stability and control.
From Report: "In terminating the study of the adaptation of the engine to the airplane, we will examine the problem of the turbo-compressor, the first realization of which dates from the war; this will form an addition to the indications already given on supercharging at various altitudes. This subject is of great importance for the application of the turbo-compressor worked by the exhaust gases. Assuming that the increase of pressure in the admission manifold is the same in both cases, the pressure in the exhaust manifold would be greater in the case in which the compressor is worked by the exhaust gas and there would result a certain reduction of engine power which we must be able to calculate. On the other hand , if the compressor is controlled by the engine shaft, a certain fraction of the excess power supplied is utilized for the rotation of the compressor. In order to compare the two systems, it is there-fore necessary to determine the value of the reduction of power due to back pressure when the turbine is employed."
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