Latest content added for UNT Digital Library Collection: National Advisory Committee for Aeronautics (NACA)https://digital.library.unt.edu/explore/collections/NACA/browse/?sort=date_a&fq=untl_institution:UNTGD&fq=str_title_serial:NACA+Technical+Notes&display=brief2011-11-17T22:13:23-06:00UNT LibrariesThis is a custom feed for browsing UNT Digital Library Collection: National Advisory Committee for Aeronautics (NACA)Notes on Longitudinal Stability and Balance2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53683/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53683/"><img alt="Notes on Longitudinal Stability and Balance" title="Notes on Longitudinal Stability and Balance" src="https://digital.library.unt.edu/ark:/67531/metadc53683/small/"/></a></p><p>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.</p>Airplane Performance as Influenced by the Use of a Supercharged Engine2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53684/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53684/"><img alt="Airplane Performance as Influenced by the Use of a Supercharged Engine" title="Airplane Performance as Influenced by the Use of a Supercharged Engine" src="https://digital.library.unt.edu/ark:/67531/metadc53684/small/"/></a></p><p>"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" (p. 1).</p>Notes on the Theory of the Accelerometer2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53698/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53698/"><img alt="Notes on the Theory of the Accelerometer" title="Notes on the Theory of the Accelerometer" src="https://digital.library.unt.edu/ark:/67531/metadc53698/small/"/></a></p><p>Report discusses several types of accelerometers and how they function. Methods for reducing error and determining the source of the error, including the best placement for the device, are included.</p>The Problem of the Helicopter2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53699/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53699/"><img alt="The Problem of the Helicopter" title="The Problem of the Helicopter" src="https://digital.library.unt.edu/ark:/67531/metadc53699/small/"/></a></p><p>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.</p>Relation of Rib Spacing to Stress in Wing Planes2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53685/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53685/"><img alt="Relation of Rib Spacing to Stress in Wing Planes" title="Relation of Rib Spacing to Stress in Wing Planes" src="https://digital.library.unt.edu/ark:/67531/metadc53685/small/"/></a></p><p>The stress relations to the fabric and the rib consequent upon a change of spacing between ribs in a wing plane are discussed. Considering the wing plane as a static structure, and ignoring the question of aerodynamic efficiency, it appears that the unit stress in the rib and fabric will remain constant for constant p if the linear dimensions of both rib and fabric are increased alike, viz., if wing and fabric remain geometrically similar. Since the bulge and the structural dimensions remain geometrically similar, the whole distended plane remains so, and hence should have the same pressure distribution and efficiency.</p>Duralumin2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53690/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53690/"><img alt="Duralumin" title="Duralumin" src="https://digital.library.unt.edu/ark:/67531/metadc53690/small/"/></a></p><p>Various properties of duralumin as used in aircraft construction are discussed, including the effects of temperature, working, tempering, and strength.</p>Notes on the Design of Supercharged and Over-dimensioned Aircraft Engines2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53689/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53689/"><img alt="Notes on the Design of Supercharged and Over-dimensioned Aircraft Engines" title="Notes on the Design of Supercharged and Over-dimensioned Aircraft Engines" src="https://digital.library.unt.edu/ark:/67531/metadc53689/small/"/></a></p><p>The author discusses the limited benefits of supercharging motors and some of the factors that make supercharging less beneficial than it initially appears.</p>Static Testing and Proposed Standard Specifications2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53686/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53686/"><img alt="Static Testing and Proposed Standard Specifications" title="Static Testing and Proposed Standard Specifications" src="https://digital.library.unt.edu/ark:/67531/metadc53686/small/"/></a></p><p>Static tests fall into two groups, the first of which is designed to load all members of the structure approximately in accordance with the worst loads which they carry in flight, while the second is directed to the testing of specific members which are suspected of weakness and which are difficult to analyze mathematically. The nature of the loading in the second type is different for every different test, but the purpose of the first is defined clearly enough to permit the adoption of some standard set of loading specifications, at least for airplanes of normal design. Here, an attempt is made to carry through an analysis leading to such a standard, the goal being the determination of a load which will simultaneously impose on every member of the airplane structure a stress equal to the worst it will carry in flight.</p>Theory of Lifting Surfaces2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53693/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53693/"><img alt="Theory of Lifting Surfaces" title="Theory of Lifting Surfaces" src="https://digital.library.unt.edu/ark:/67531/metadc53693/small/"/></a></p><p>The general basis of the theory of lifting surfaces is discussed. The problem of the flow of a fluid about a lifting surface of infinite span is examined in terms of the existence of vortexes in the current. A general theory of permanent flow is discussed. Formulas for determining the influence of aspect ratio that may be applied to all wings, whatever their plane form, are given.</p>Increase in Maximum Pressures Produced by Preignition in Internal Combustion Engines2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53694/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53694/"><img alt="Increase in Maximum Pressures Produced by Preignition in Internal Combustion Engines" title="Increase in Maximum Pressures Produced by Preignition in Internal Combustion Engines" src="https://digital.library.unt.edu/ark:/67531/metadc53694/small/"/></a></p><p>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.</p>The Problem of the Turbo-Compressor2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53703/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53703/"><img alt="The Problem of the Turbo-Compressor" title="The Problem of the Turbo-Compressor" src="https://digital.library.unt.edu/ark:/67531/metadc53703/small/"/></a></p><p>"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" (p. 1).</p>Soaring Flight in Guinea2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53687/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53687/"><img alt="Soaring Flight in Guinea" title="Soaring Flight in Guinea" src="https://digital.library.unt.edu/ark:/67531/metadc53687/small/"/></a></p><p>Report discusses information obtained from studying large birds that fly by soaring, which involves using the wind without moving their wings. An Egyptian vulture and African white-backed vulture were observed and their relative air speed, upward air velocity, lift, and drag were noted. The experimental methods for measuring these values are described.</p>Theory of Lifting Surfaces, Part 22011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53695/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53695/"><img alt="Theory of Lifting Surfaces, Part 2" title="Theory of Lifting Surfaces, Part 2" src="https://digital.library.unt.edu/ark:/67531/metadc53695/small/"/></a></p><p>A mathematical model is presented towards a theory of lifting and resistance on wings. It consists hide
of a theory of multiplanes, conditions of flow at a great distance from the wing, lifting systems of minimum resistance, and free stream and stream limited by walls.</p>Drag or Negative Traction of Geared-Down Supporting Propellers in the Downward Vertical Glide of a Helicopter2011-11-14T22:28:08-06:00https://digital.library.unt.edu/ark:/67531/metadc54438/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc54438/"><img alt="Drag or Negative Traction of Geared-Down Supporting Propellers in the Downward Vertical Glide of a Helicopter" title="Drag or Negative Traction of Geared-Down Supporting Propellers in the Downward Vertical Glide of a Helicopter" src="https://digital.library.unt.edu/ark:/67531/metadc54438/small/"/></a></p><p>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.</p>The Dynamometer Hub2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53712/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53712/"><img alt="The Dynamometer Hub" title="The Dynamometer Hub" src="https://digital.library.unt.edu/ark:/67531/metadc53712/small/"/></a></p><p>The construction of the dynamometer hub is illustrated and explained, and its electrical and aviation motor tests, as well as those in free flight, described.</p>Experience With Geared Propeller Drives for Aviation Engines2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53702/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53702/"><img alt="Experience With Geared Propeller Drives for Aviation Engines" title="Experience With Geared Propeller Drives for Aviation Engines" src="https://digital.library.unt.edu/ark:/67531/metadc53702/small/"/></a></p><p>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.</p>Recent Efforts and Experiments in the Construction of Aviation Engines2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53715/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53715/"><img alt="Recent Efforts and Experiments in the Construction of Aviation Engines" title="Recent Efforts and Experiments in the Construction of Aviation Engines" src="https://digital.library.unt.edu/ark:/67531/metadc53715/small/"/></a></p><p>It became evident during World War I that ever-increasing demands were being placed on the mean power of aircraft engines as a result of the increased on board equipment and the demands of aerial combat. The need was for increased climbing efficiency and climbing speed. The response to these demands has been in terms of lightweight construction and the adaptation of the aircraft engine to the requirements of its use.</p>Notes on Specifications for French Airplane Competitions2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53700/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53700/"><img alt="Notes on Specifications for French Airplane Competitions" title="Notes on Specifications for French Airplane Competitions" src="https://digital.library.unt.edu/ark:/67531/metadc53700/small/"/></a></p><p>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.</p>Tests of the Daimler D-IVa Engine at a High Altitude Test Bench2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53701/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53701/"><img alt="Tests of the Daimler D-IVa Engine at a High Altitude Test Bench" title="Tests of the Daimler D-IVa Engine at a High Altitude Test Bench" src="https://digital.library.unt.edu/ark:/67531/metadc53701/small/"/></a></p><p>Reports of tests of a Daimler IVa engine at the test-bench at Friedrichshafen, show that the decrease of power of that engine, at high altitudes, was established, and that the manner of its working when air is supplied at a certain pressure was explained. These tests were preparatory to the installation of compressors in giant aircraft for the purpose of maintaining constant power at high altitudes.</p>Development of the Inflow Theory of the Propeller2011-11-17T22:13:23-06:00https://digital.library.unt.edu/ark:/67531/metadc59643/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc59643/"><img alt="Development of the Inflow Theory of the Propeller" title="Development of the Inflow Theory of the Propeller" src="https://digital.library.unt.edu/ark:/67531/metadc59643/small/"/></a></p><p>Report discusses the theory of inflow of the propeller and the fact that both suctional axial velocity and suctional tangential velocity must be considered when calculating the maximum efficiency.</p>Göttingen Wind Tunnel for Testing Aircraft Models2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53751/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53751/"><img alt="Göttingen Wind Tunnel for Testing Aircraft Models" title="Göttingen Wind Tunnel for Testing Aircraft Models" src="https://digital.library.unt.edu/ark:/67531/metadc53751/small/"/></a></p><p>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.</p>Horizontal Buoyancy in Wind Tunnels2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53717/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53717/"><img alt="Horizontal Buoyancy in Wind Tunnels" title="Horizontal Buoyancy in Wind Tunnels" src="https://digital.library.unt.edu/ark:/67531/metadc53717/small/"/></a></p><p>Note presenting an examination of horizontal buoyancy in wind tunnels, including an examination of the relative flow, static pressure gradient, horizontal buoyancy computation, and methods of computation in practical use are provided.</p>Italian and French Experiments on Wind Tunnels2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53707/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53707/"><img alt="Italian and French Experiments on Wind Tunnels" title="Italian and French Experiments on Wind Tunnels" src="https://digital.library.unt.edu/ark:/67531/metadc53707/small/"/></a></p><p>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.</p>The Photographic Recording of Small Motions2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53706/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53706/"><img alt="The Photographic Recording of Small Motions" title="The Photographic Recording of Small Motions" src="https://digital.library.unt.edu/ark:/67531/metadc53706/small/"/></a></p><p>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.</p>Design of Recording Wind Tunnel Balances2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53711/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53711/"><img alt="Design of Recording Wind Tunnel Balances" title="Design of Recording Wind Tunnel Balances" src="https://digital.library.unt.edu/ark:/67531/metadc53711/small/"/></a></p><p>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.</p>High thermal efficiency in airplane service2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53714/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53714/"><img alt="High thermal efficiency in airplane service" title="High thermal efficiency in airplane service" src="https://digital.library.unt.edu/ark:/67531/metadc53714/small/"/></a></p><p>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.</p>Instrument for measuring engine clearance volumes2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53696/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53696/"><img alt="Instrument for measuring engine clearance volumes" title="Instrument for measuring engine clearance volumes" src="https://digital.library.unt.edu/ark:/67531/metadc53696/small/"/></a></p><p>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.</p>Progress Made in the Construction of Giant Airplanes in Germany During the War2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53709/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53709/"><img alt="Progress Made in the Construction of Giant Airplanes in Germany During the War" title="Progress Made in the Construction of Giant Airplanes in Germany During the War" src="https://digital.library.unt.edu/ark:/67531/metadc53709/small/"/></a></p><p>The construction of giant airplanes was begun in Germany in August, 1914. The tables annexed here show that a large number of airplanes weighing up to 15.5 tons were constructed and tested in Germany during the War, and it is certain that no other country turned out airplanes of this weight nor in such large numbers. An examination of the tables shows that by the end of the War all the manufacturers had arrived at a well-defined type, namely an airplane of about 12 tons with four engines of 260 horsepower each. The aircraft listed here are discussed with regard to useful weight and aerodynamic qualities.</p>The Steadiness Factor in Engine Sets2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53718/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53718/"><img alt="The Steadiness Factor in Engine Sets" title="The Steadiness Factor in Engine Sets" src="https://digital.library.unt.edu/ark:/67531/metadc53718/small/"/></a></p><p>Technical notes discussing the steadiness factor in engines and the calculations that can be used to arrive at it. Factors affecting the steadiness factor are detailed, including the mass of parts, torque, engine rotation, and power.</p>A Variable Speed Fan Dynamometer2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53722/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53722/"><img alt="A Variable Speed Fan Dynamometer" title="A Variable Speed Fan Dynamometer" src="https://digital.library.unt.edu/ark:/67531/metadc53722/small/"/></a></p><p>Fan brakes used as absorption dynamometers in testing internal combustion engines have the disadvantage that a given fan will run only at one speed when the engine is delivering full power. In order to be able to vary the speed at which a given power will be absorbed, English manufacturers have for some time been using a cylindrical housing around the fan with one or two variable openings in the periphery. Here, results are given of tests conducted to determine how great a range of speed can be obtained from such a device.</p>The 300 H.P. Benz Aircraft Engine2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53726/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53726/"><img alt="The 300 H.P. Benz Aircraft Engine" title="The 300 H.P. Benz Aircraft Engine" src="https://digital.library.unt.edu/ark:/67531/metadc53726/small/"/></a></p><p>This report provides a description of the Benz 300 H.P. aircraft engine containing 12 cylinders placed at a 60° angle. It includes a detailed description of the development of the constructional points, particularly the cylinders, pistons, and connecting rods, as well as the engine fitting, lubrication, oil pumps, bearings, oil tank, fuel pump, carburetors, and cooling system. There are seven pages of illustrative figures at the end of the report.</p>N.A.C.A. Langley field wind tunnel apparatus: The tilting manometer2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53735/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53735/"><img alt="N.A.C.A. Langley field wind tunnel apparatus: The tilting manometer" title="N.A.C.A. Langley field wind tunnel apparatus: The tilting manometer" src="https://digital.library.unt.edu/ark:/67531/metadc53735/small/"/></a></p><p>A description is given of a tilting manometer designed to meet the requirements of a manometer for use in the wind tunnel at the Langley Memorial Aeronautical Laboratory. This gauge was designed to meet the requirements of a manometer in use in connection with a static pressure plate to indicate the wind speed in the tunnel. The requirements are noted. The sensitivity of the gauge must be made inversely proportional to the pressure to be measured. The gauge must be accurately and quickly set for any desired pressure.</p>The determination of downwash2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53782/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53782/"><img alt="The determination of downwash" title="The determination of downwash" src="https://digital.library.unt.edu/ark:/67531/metadc53782/small/"/></a></p><p>It is obvious that, in accordance with Newton's second law, the lift on an aerofoil must be equal to the vertical momentum communicated per second to the air mass affected. Consequently a lifting aerofoil in flight is trailed by a wash which has a definite inclination corresponding to the factors producing the lift. It is thought that sufficient data, theoretical and experimental, are now available for a complete determination of this wash with respect to the variation of its angle of inclination to the originating aerofoil and with respect to the law which governs its decay in space.</p>The determination of the effective resistance of a spindle supporting a model aerofoil2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53708/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53708/"><img alt="The determination of the effective resistance of a spindle supporting a model aerofoil" title="The determination of the effective resistance of a spindle supporting a model aerofoil" src="https://digital.library.unt.edu/ark:/67531/metadc53708/small/"/></a></p><p>An attempt was made to determine the effect of spindle interference on the lift of the airfoil by measuring moments about the axis parallel to the direction of air flow. The values obtained are of the same degree as the experimental error, and for the present this effect will be neglected. The results obtained using a U.S.A. 15 wing (plotted here) show that the correction is nearly constant from 0 degrees to 10 degrees incidence and that at greater angles its value becomes erratic. At such angles, however, the wing drag is so high that the spindle correction and its attendant errors become relatively small and unimportant.</p>Measurements of Rudder Moments on an Airplane During Flight2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53720/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53720/"><img alt="Measurements of Rudder Moments on an Airplane During Flight" title="Measurements of Rudder Moments on an Airplane During Flight" src="https://digital.library.unt.edu/ark:/67531/metadc53720/small/"/></a></p><p>Tests indicated that: 1) C airplanes with two struts are extremely susceptible to aileron maneuvers, slight alterations of the aileron sufficing to compensate great unequalized moments; 2) great unequalized moments can be produced or neutralized by the unequalized alternation of the angle of attack below the outer and inner struts. Adjustment below the outer strut is the more effective of the two. 3) When a load of bombs is suspended beyond the center of the airplane, below the wings, the bombs need not be dropped simultaneously. 4) The propeller wash of a wide open engine has considerable influence on the position and operation of the elevator. The elevator is more susceptible in flight with the engine running than in gliding flight. 5) Adjustable tail planes are not advisable for D airplanes, nor for the C type, but they are, on the other hand, to be recommended for large size and giant airplanes in which the center of gravity changes during flight. 6) The aileron values obtained by wind tunnel measurements are about 10 percent too low, though otherwise applicable. For the elevator, the results of such measurements should be taken as mean values between flight with the engine running and gliding flight.</p>On the Resistance of Spheres and Ellipsoids in Wind Tunnels2011-11-17T22:13:23-06:00https://digital.library.unt.edu/ark:/67531/metadc65029/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc65029/"><img alt="On the Resistance of Spheres and Ellipsoids in Wind Tunnels" title="On the Resistance of Spheres and Ellipsoids in Wind Tunnels" src="https://digital.library.unt.edu/ark:/67531/metadc65029/small/"/></a></p><p>Note presenting a study of the influence exercised on the results of measurements by the dimensions and type of the tunnels used in aerodynamic laboratories, and on the comparison of the results with observations made in motionless and unlimited air.</p>The optical wing aligning device of the Langley Field tunnel2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53728/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53728/"><img alt="The optical wing aligning device of the Langley Field tunnel" title="The optical wing aligning device of the Langley Field tunnel" src="https://digital.library.unt.edu/ark:/67531/metadc53728/small/"/></a></p><p>Described here is a convenient and accurate method of aligning the wing chord with the airflow. The device was developed to permit rapid and accurate alignment of airfoils and models with the airstream passing through the tunnel. It consists of three main parts: a projector, a reflector, and a target. The arrangement, which is shown in a figure, has proven satisfactory in operation. It is far better than the old method of sighting across a long batten, as the operator of a balance may see the target and correctly judge the accuracy of his alignment. Whereas the old method required two operators and several minutes time to align to within 1/10 degree, this method enables one operator to align a wing to within 1/100 of a degree in a few seconds. This method also has the advantage of being able to measure the angle of the wing while the tunnel is running. Thus, the true angle of incidence is shown.</p>Causes of cracking of ignition cable2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53716/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53716/"><img alt="Causes of cracking of ignition cable" title="Causes of cracking of ignition cable" src="https://digital.library.unt.edu/ark:/67531/metadc53716/small/"/></a></p><p>From Summary: "The experiments described here show that the cracking at sharp bends, observed in the insulation of internal combustion engine high tension ignition wires after service, is due to a chemical attack upon the rubber by the ozone produced by the electric discharge that takes place at the surface of the cable. This cracking does not occur if the insulating material is not under tension, or if the cable is surrounded by some medium other than air. But it does occur even if the insulation is not subjected to electric stress, provided that the atmosphere near the cable contains ozone. The extent of this cracking varies greatly with the insulating material used. The cracking can be materially reduced by using braided cable and by avoiding sharp bends."</p>The Effect of the Nature of Surfaces on Resistance as Tested on Struts2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53719/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53719/"><img alt="The Effect of the Nature of Surfaces on Resistance as Tested on Struts" title="The Effect of the Nature of Surfaces on Resistance as Tested on Struts" src="https://digital.library.unt.edu/ark:/67531/metadc53719/small/"/></a></p><p>The chief concern was to measure the variations of resistance brought about by the nature of the surface of the struts. The struts were spanned with aviation linen, and then covered with one coat of varnish. The top surface was not perfectly smooth after this treatment, being slightly rough owing to the threads and raised fibers of the fabric. The results of the measurements of the surfaces are shown by the dotted lines of the curves plotted in several figures.</p>Effect of the Reversal of Air Flow Upon the Discharge Coefficient of Durley Orifices2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53761/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53761/"><img alt="Effect of the Reversal of Air Flow Upon the Discharge Coefficient of Durley Orifices" title="Effect of the Reversal of Air Flow Upon the Discharge Coefficient of Durley Orifices" src="https://digital.library.unt.edu/ark:/67531/metadc53761/small/"/></a></p><p>Experiments were conducted to obtain information on the relationship between the coefficients for flow in two directions through thin plate orifices at low velocities. The results indicate that the ratio of the orifice discharge coefficient from standard orifice C(sub s)(sup 1) to the discharge coefficient from the reverse flow C(sub s) is always less than unity with increasing ratio of box area to orifice area. Even for areas as low as twenty, the ratios of the coefficients are not much less than unity. It is probable, however, that when the ratio of box area is less than twenty, the ratio of discharge coefficients would be greatly reduced. Specific results are given for the case of an apparatus for the laboratory testing of superchargers.</p>Effect of the Reversal of Air Flow Upon the Discharge Coefficient of Durley Orifices2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53927/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53927/"><img alt="Effect of the Reversal of Air Flow Upon the Discharge Coefficient of Durley Orifices" title="Effect of the Reversal of Air Flow Upon the Discharge Coefficient of Durley Orifices" src="https://digital.library.unt.edu/ark:/67531/metadc53927/small/"/></a></p><p>Note presenting an experiment to obtain information regarding the relationship between the coefficients for flow in the two directions through an inlet. The results indicate that the ratio of the orifice discharge coefficient from standard orifice to the discharge coefficient from reverse flow is always less than unity, but approaches unity with increasing ratio of box area to orifice area, and that even for a ratio of areas as low as twenty the ratios of the coefficients is not much less than unity.</p>Loads and Calculations of Army Airplanes2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53704/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53704/"><img alt="Loads and Calculations of Army Airplanes" title="Loads and Calculations of Army Airplanes" src="https://digital.library.unt.edu/ark:/67531/metadc53704/small/"/></a></p><p>By comparing airplanes of known strength that have resisted all the usual and even extreme air loads with those that under like conditions were found to be insufficiently strong, the researchers, aided by scientific investigations, developed standards which are satisfactory for the calculation of airplane structures. Given here are standards applicable to loads on wing trusses, load factors for use in stress analysis, load factors required in sand testing, loads on control surfaces, loads on wing ribs, loads on landing gear, and rigidity of materials.</p>Note on the Resistance of Polished Cylinders (and Cylindrical Wires) With Generatrices Perpendicular to the Airstream2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53793/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53793/"><img alt="Note on the Resistance of Polished Cylinders (and Cylindrical Wires) With Generatrices Perpendicular to the Airstream" title="Note on the Resistance of Polished Cylinders (and Cylindrical Wires) With Generatrices Perpendicular to the Airstream" src="https://digital.library.unt.edu/ark:/67531/metadc53793/small/"/></a></p><p>Report presenting a review of currently published documents regarding the resistance of polished cylinders with generators perpendicular to the airstream. The discrepancies between these various studies are pointed out.</p>Airplane Crashes: Engine Troubles: A Possible Explanation2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53738/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53738/"><img alt="Airplane Crashes: Engine Troubles: A Possible Explanation" title="Airplane Crashes: Engine Troubles: A Possible Explanation" src="https://digital.library.unt.edu/ark:/67531/metadc53738/small/"/></a></p><p>The aim was to bring attention to what might be the cause of some aircraft accidents for which there was no satisfactory explanation. The author notes that in testing aircraft accidents at the Bureau of Standards, it happened frequently that the engine performance became erratic when the temperature of the air entering the carburetor was between 0 C and 20 C. Investigation revealed the trouble to have been caused by the formation and collection of snow somewhere between the entrance to the carburetor and the manifold, probably at the throttle.</p>Extract From a Report on the Resistance of Spheres of Small Diameter in an Airstream of High Velocity2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53800/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53800/"><img alt="Extract From a Report on the Resistance of Spheres of Small Diameter in an Airstream of High Velocity" title="Extract From a Report on the Resistance of Spheres of Small Diameter in an Airstream of High Velocity" src="https://digital.library.unt.edu/ark:/67531/metadc53800/small/"/></a></p><p>Much attention is given here to the design of the wind tunnel and the experimental set-up. In comparing their results on the wind resistance of spheres to the results of other researchers, the authors find wide discrepancies. They are unable to explain the cause of the discrepancies, concluding, as they do, that the differing results could not be explained by the action of the wind tunnel walls.</p>The Factors That Determine the Minimum Speed of an Airplane2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53737/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53737/"><img alt="The Factors That Determine the Minimum Speed of an Airplane" title="The Factors That Determine the Minimum Speed of an Airplane" src="https://digital.library.unt.edu/ark:/67531/metadc53737/small/"/></a></p><p>The author argues that because of a general misunderstanding of the principles of flight at low speed, there are a large number of airplanes that could be made to fly several miles per hour slower than at present by making slight modifications. In order to show how greatly the wing section affects the minimum speed, curves are plotted against various loadings. The disposition of wings on the airplane slightly affects the lift coefficient, and a few such cases are discussed.</p>Influence of Span and Load Per Square Meter on the Air Forces of the Supporting Surface2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53767/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53767/"><img alt="Influence of Span and Load Per Square Meter on the Air Forces of the Supporting Surface" title="Influence of Span and Load Per Square Meter on the Air Forces of the Supporting Surface" src="https://digital.library.unt.edu/ark:/67531/metadc53767/small/"/></a></p><p>"It should be clear that in order to obtain a lift it is necessary that the air which flows past an aerofoil be given a downward acceleration; indeed the lift can be only the reaction produced by the downward acceleration of the flowing air. The motion of the air in the neighborhood of an aerofoil may be followed theoretically with great exactness. In the following, it will be undertaken to make understood, through the simplest possible considerations, the effect of span and loading on the air force on an aerofoil, and while these do not form a strong proof of the correctness of the formulae developed, yet they explain the essential features of the phenomena" (p. 1).</p>Gordon Bennett Airplane Cup 19202011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53727/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53727/"><img alt="Gordon Bennett Airplane Cup 1920" title="Gordon Bennett Airplane Cup 1920" src="https://digital.library.unt.edu/ark:/67531/metadc53727/small/"/></a></p><p>The characteristics of the airplanes built for the Gordon Bennett Airplane Cup race that took place on September 28, 1920 are described. The airplanes are discussed from a aerodynamical point of view, with a number of new details concerning the French machines. Also discussed is the regulation of future races. The author argues that there should be no limitations on the power of the aircraft engines. He reasons that in the present state of things, liberty with regard to engine power does not lead to a search for the most powerful engine, but for one which is reliable and light, thus leading to progress.</p>On the Resistance of the Air at High Speeds and on the Automatic Rotation of Projectiles2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53724/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53724/"><img alt="On the Resistance of the Air at High Speeds and on the Automatic Rotation of Projectiles" title="On the Resistance of the Air at High Speeds and on the Automatic Rotation of Projectiles" src="https://digital.library.unt.edu/ark:/67531/metadc53724/small/"/></a></p><p>Here, the laws governing the flow of a compressible fluid through an opening in a thin wall are applied to the resistance of the air at high speeds, especially as applied to the automatic rotation of projectiles. The instability which we observe in projectiles shot into the air without being given a moment of rotation about their axis of symmetry, or without stabilizing planes, is a phenomenon of automatic rotation. It is noted that we can prevent this phenomenon of automatic rotation by bringing the center of gravity sufficiently near one end, or by fitting the projectile with stabilizing planes or a tail.</p>Recent European Developments in Helicopters2011-11-11T19:22:00-06:00https://digital.library.unt.edu/ark:/67531/metadc53807/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc53807/"><img alt="Recent European Developments in Helicopters" title="Recent European Developments in Helicopters" src="https://digital.library.unt.edu/ark:/67531/metadc53807/small/"/></a></p><p>Descriptions are given of two captured helicopters, one driven by electric power, the other by a gasoline engine. An account is given of flight tests of the gasoline powered vehicle. After 15 successful flight tests, the gasoline powered vehicle crashed due to the insufficient thrust. Also discussed here are the applications of helicopters for military observations, for meteorological work, and for carrying radio antennas.</p>