Latest content added for UNT Digital Library Collection: National Advisory Committee for Aeronautics (NACA)http://digital.library.unt.edu/explore/collections/NACA/browse/?fq=str_title_serial:NACA+Technical+Reports&display=list2014-09-25T20:32:43-05:00UNT LibrariesThis is a custom feed for browsing UNT Digital Library Collection: National Advisory Committee for Aeronautics (NACA)A Comparison of Theory and Experiment for High-Speed Free-Molecule Flow2014-09-25T20:32:43-05:00http://digital.library.unt.edu/ark:/67531/metadc172515/<p><a href="/ark:/67531/metadc172515/"><img alt="A Comparison of Theory and Experiment for High-Speed Free-Molecule Flow" title="A Comparison of Theory and Experiment for High-Speed Free-Molecule Flow" src="/ark:/67531/metadc172515/thumbnail/"/></a></p><p>Comparison of free-molecule-flow theory with the results of wind-tunnel tests performed to determine the drag and temperature-rise characteristics of a transverse circular cylinder.</p>The Lagrangian Multiplier Method of Finding Upper and Lower Limits to Critical Stresses of Clamped Plates2014-03-30T18:00:15-05:00http://digital.library.unt.edu/ark:/67531/metadc279603/<p><a href="/ark:/67531/metadc279603/"><img alt="The Lagrangian Multiplier Method of Finding Upper and Lower Limits to Critical Stresses of Clamped Plates" title="The Lagrangian Multiplier Method of Finding Upper and Lower Limits to Critical Stresses of Clamped Plates" src="/ark:/67531/metadc279603/thumbnail/"/></a></p><p>The theory of Lagrangian multipliers is applied to the problem of finding both upper and lower limits to the true compressive buckling stress of a clamped rectangular plate. The upper and lower limits thus bracket the truss, which cannot be exactly found by the differential-equation approach. The procedure for obtaining the upper limit, which is believed to be new, presents certain advantages over the classical Raleigh-Rite method of finding upper limits. The theory of the lower-limit procedure has been given by Trefftz but, in the present application, the method differs from that of Trefftz in a way that makes it inherently more quickly convergent. It is expected that in other buckling problems and in some vibration problems problems the Lagrangian multiplier method finding upper and lower limits may be advantageously applied to the calculation of buckling stresses and natural frequencies.</p>Lifting-surface-theory aspect-ratio corrections to the lift and hinge-moment parameters for full-span elevators on horizontal tail surfaces2014-03-30T18:00:15-05:00http://digital.library.unt.edu/ark:/67531/metadc279678/<p><a href="/ark:/67531/metadc279678/"><img alt="Lifting-surface-theory aspect-ratio corrections to the lift and hinge-moment parameters for full-span elevators on horizontal tail surfaces" title="Lifting-surface-theory aspect-ratio corrections to the lift and hinge-moment parameters for full-span elevators on horizontal tail surfaces" src="/ark:/67531/metadc279678/thumbnail/"/></a></p><p>A limited number of lifting-surface-theory solutions for wings with chordwise loadings resulting from angle of attack, parabolic-ac camber, and flap deflection are now available. These solutions were studied with the purpose of determining methods of extrapolating the results in such a way that they could be used to determine lifting-surface-theory values of the aspect-ratio corrections to the lift and hinge-moment parameters for both angle-of-attack and flap-deflection-type loading that could be used to predict the characteristics of horizontal tail surfaces from section data with sufficient accuracy for engineering purposes. Such a method was devised for horizontal tail surfaces with full-span elevators. In spite of the fact that the theory involved is rather complex, the method is simple to apply and may be applied without any knowledge of lifting-surface theory. A comparison of experimental finite-span and section value and of the estimated values of the lift and hinge-moment parameters for three horizontal tail surfaces was made to provide an experimental verification of the method suggested. (author).</p>Icing-protection requirements for reciprocating-engine induction systems2014-03-30T18:00:15-05:00http://digital.library.unt.edu/ark:/67531/metadc279668/<p><a href="/ark:/67531/metadc279668/"><img alt="Icing-protection requirements for reciprocating-engine induction systems" title="Icing-protection requirements for reciprocating-engine induction systems" src="/ark:/67531/metadc279668/thumbnail/"/></a></p><p>None</p>Preliminary report on the problem of the atmosphere in relation to aeronautics2014-03-30T18:00:15-05:00http://digital.library.unt.edu/ark:/67531/metadc279504/<p><a href="/ark:/67531/metadc279504/"><img alt="Preliminary report on the problem of the atmosphere in relation to aeronautics" title="Preliminary report on the problem of the atmosphere in relation to aeronautics" src="/ark:/67531/metadc279504/thumbnail/"/></a></p><p>A report to the Weather Bureau, Washington DC, from the chairman of the Subcommittee on the Atmosphere in Relation to Aeronautics describing the activities accomplished and the proposal of work to be undertaken by the subcommittee.</p>Nomenclature for Aeronautics2014-03-30T18:00:15-05:00http://digital.library.unt.edu/ark:/67531/metadc279570/<p><a href="/ark:/67531/metadc279570/"><img alt="Nomenclature for Aeronautics" title="Nomenclature for Aeronautics" src="/ark:/67531/metadc279570/thumbnail/"/></a></p><p>The nomenclature for aeronautics presented in this Report No. 474 is a revision of the last previous report on this subject (i.e., Report no. 240.) This report is published for the purpose of encouraging greater uniformity and precision in the use of terms relating to aeronautics, both in official documents of the Government and in commercial publications. Terms in general use in other branches of engineering have been included only where they have some special significance in aeronautics, or form an integral part of its terminology.</p>The Measurement of Fuel-Air Ratio by Analysis for the Oxidized Exhaust Gas2014-03-30T18:00:15-05:00http://digital.library.unt.edu/ark:/67531/metadc279515/<p><a href="/ark:/67531/metadc279515/"><img alt="The Measurement of Fuel-Air Ratio by Analysis for the Oxidized Exhaust Gas" title="The Measurement of Fuel-Air Ratio by Analysis for the Oxidized Exhaust Gas" src="/ark:/67531/metadc279515/thumbnail/"/></a></p><p>An investigation was made to determine a method of measuring fuel-air ratio that could be used for test purposes in flight and for checking conventional equipment in the laboratory. Two single-cylinder test engines equipped with typical commercial engine cylinders were used. The fuel-air ratio of the mixture delivered to the engines was determined by direct measurement of the quantity of air and of fuel supplied and also by analysis of the oxidized exhaust gas and of the normal exhaust gas. Five fuels were used: gasoline that complied with Army-Navy fuel Specification No. AN-VV-F-781 and four mixtures of this gasoline with toluene, benzene, and xylene. The method of determining the fuel-air ratio described in this report involves the measurement of the carbon-dioxide content of the oxidized exhaust gas and the use of graphs for the presented equation. This method is considered useful in aircraft, in the field, or in the laboratory for a range of fuel-air ratios from 0.047 to 0.124.</p>The effect of cowling on cylinder temperatures and performance of a Wright J-5 engine2014-03-30T18:00:15-05:00http://digital.library.unt.edu/ark:/67531/metadc279502/<p><a href="/ark:/67531/metadc279502/"><img alt="The effect of cowling on cylinder temperatures and performance of a Wright J-5 engine" title="The effect of cowling on cylinder temperatures and performance of a Wright J-5 engine" src="/ark:/67531/metadc279502/thumbnail/"/></a></p><p>This report presents the results of tests conducted to determine the effect of different amounts and kinds of cowling on the performance and cylinder temperatures of a standard Wright J-5 engine. These tests were conducted in conjunction with drag and propeller tests in which the same cowlings were used. Four different cowlings were investigated varying from the one extreme of no cowling on the engine to the other extreme of the engine completely cowled and the cooling air flowing inside the cowling through an opening in the nose and out through an annular opening at the rear of the engine. Each cowling was tested at air speeds of approximately 60, 80, and 100 miles per hour.</p>A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System2014-03-30T18:00:15-05:00http://digital.library.unt.edu/ark:/67531/metadc279589/<p><a href="/ark:/67531/metadc279589/"><img alt="A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System" title="A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System" src="/ark:/67531/metadc279589/thumbnail/"/></a></p><p>The relation between the elevator hinge moment parameters and the control forces for changes in forward speed and in maneuvers is shown for several values of static stability and elevator mass balance. The stability of the short period oscillations is shown as a series of boundaries giving the limits of the stable regions in terms of the elevator hinge moment parameters. The effects of static stability, elevator moment of inertia, elevator mass unbalance, and airplane density are also considered. Dynamic instability is likely to occur if there is mass unbalance of the elevator control system combined with a small restoring tendency (high aerodynamic balance). This instability can be prevented by a rearrangement of the unbalancing weights which, however, involves an increase of the amount of weight necessary. It can also be prevented by the addition of viscous friction to the elevator control system provided the airplane center of gravity is not behind a certain critical position. For high values of the density parameter, which correspond to high altitudes of flight, the addition of moderate amounts of viscous friction may be destabilizing even when the airplane is statically stable. In this case, increasing the viscous friction makes the oscillation stable again. The condition in which viscous friction causes dynamic instability of a statically stable airplane is limited to a definite range of hinge moment parameters. It is shown that, when viscous friction causes increasing oscillations, solid friction will produce steady oscillations having an amplitude proportional to the amount of friction.</p>Stability of the parachute and helicopter2014-03-30T18:00:15-05:00http://digital.library.unt.edu/ark:/67531/metadc279530/<p><a href="/ark:/67531/metadc279530/"><img alt="Stability of the parachute and helicopter" title="Stability of the parachute and helicopter" src="/ark:/67531/metadc279530/thumbnail/"/></a></p><p>This report deals with an extension of the theory of stability in oscillation to the case of aircraft following a vertical trajectory, and particularly to the oscillations of parachutes.</p>