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Safeguards Against Flutter of Airplanes
This report is a compilation of practical rules, derived at the same time from theory and from experience, intended to guide the aeronautical engineer in the design of flutter-free airplanes. Rules applicable to the wing, the ailerons, flaps, tabs,tail surfaces, and fuselage are discussed.
Date:
August 1956
Creator:
De Vries, Gerhard
System:
The UNT Digital Library
Gas Jets
"A brief summary of the contents of this paper is presented here. In part I the differential equations of the problem of a gas flow in two dimensions is derived and the particular integrals by which the problem on jets is solved are given. Use is made of the same independent variables as Molenbroek used, but it is found to be more suitable to consider other functions. The stream function and velocity potential corresponding to the problem are given in the form of series" (p. 1).
Date:
August 1944
Creator:
Chaplygin, S.
System:
The UNT Digital Library
Self-Ignition and Combustion of Gases
This paper attempts to state laws for the self-ignition and combustion of gases in a comprehensive manner. The primary focus is recent investigations in which new combustion phenomena or new methods of studying them experimentally are brought out and investigations that throw new light on already known phenomena.
Date:
August 1942
Creator:
Sokolik, A. S.
System:
The UNT Digital Library
Cones in Supersonic Flow
"In the case of cones in axially symmetric flow of supersonic velocity, adiabatic compression takes place between shock wave and surface of the cone. Interpolation curves betwen shock polars and the surface are therefore necessary for the complete understanding of this type of flow. They are given in the present report by graphical-numerical integration of the differential equation for all cone angles and airspeeds" (p. 1).
Date:
August 1947
Creator:
Hantzsche, W. & Wendt, H.
System:
The UNT Digital Library
Lateral Control by Spoilers at the DVL
"The present report describes the development of spoiler control at the DVL from the end of 1936 until the beginning of 1939. The authors are fully aware that the present report also forms only a contribution to the problem of spoiler control and offers at best a possibility of extrapolation regarding the behavior of the control in modern airplanes. A modern airplane (Me 109) is being reconstructed for conversion to spoiler control" (p. 1).
Date:
August 1951
Creator:
Kramer, Max; Zobel, Theodor W. & Esche, C. G.
System:
The UNT Digital Library
Three Papers From Conference On "Wing and Tail-Surface Oscillations: March 6-8, 1941, Munich
Memorandum presenting three papers regarding aerodynamic balance of control surfaces. The specific topics covered include some general remarks regarding aerodynamically balanced control surfaces, aerodynamically equivalent systems for various forms of control surfaces within the scope of two-dimensional wing theory, and comparative calculations concerning aerodynamic balance of control surfaces.
Date:
August 1951
Creator:
Söhngen, Heinz; Schwarz, L. & Dietze, F.
System:
The UNT Digital Library
The Flow of Gases in Narrow Channels
Measurements were made of the flow of gases through various narrow channels a few microns wide at average pressures from 0.00003 to 40 cm. Hg. The flow rate, defined as the product of pressure and volume rate of flow at unit pressure difference, first decreased linearly with decrease in mean pressure in the channel, in agreement with laminar-flow theory, reached a minimum when the mean path length was approximately equal to the channel width, and then increased to a constant value. The product of flow rate and square root of molecular number was approximately the same function of mean path length for all gases for a given channel.
Date:
August 1951
Creator:
Rasmussen, R. E. H.
System:
The UNT Digital Library
The Ground Effect on Lifting Propellers
In what follows an estimate will be made of the magnitude of the ground effect. For the two cases where the distance a of the propeller from the ground is very small, and very large, respectively, in comparison with the propeller radius r(sub o) the relations may be simply expressed. We consider first the effect of the ground, assuming that the thrust is held constant, as may be done by a suitable change in the propeller speed.
Date:
August 1937
Creator:
Betz, A.
System:
The UNT Digital Library
Pressure Distribution on a Wing Section With Slotted Flap in Free Flight Tests
"The pressure distribution was measured in flight on a wing section with a slotted flap for several flap deflections, and the results obtained are presented. The test apparatus and the procedure employed in obtaining the results are also described. A Fieseler type F 5 R airplane was used for the tests" (p. 1).
Date:
August 1937
Creator:
Kiel, Georg
System:
The UNT Digital Library
Automatic Stabilization
This report concerns the study of automatic stabilizers and extends it to include the control of the three-control system of the airplane instead of just altitude control. Some of the topics discussed include lateral disturbed motion, static stability, the mathematical theory of lateral motion, and large angles of incidence. Various mechanisms and stabilizers are also discussed.
Date:
August 1936
Creator:
Haus
System:
The UNT Digital Library
Calculation of Wing Spars
The author presents a comparison and combination of the numerical and geometrical determinations of the maximum M, when calculating the maximum bay moment.
Date:
August 1921
Creator:
Müller-Breslau, H.
System:
The UNT Digital Library
Investigations of Lateral Stability of a Glide Bomb Using Automatic Control Having No Time Lag
The investigation of the lateral stability of an automatically controlled glide bomb led also to the attempt of clarifying the influence of a phugoid oscillation or of any general longitudinal oscillation on the lateral stability of a glide bomb. Under the assumption that its period of oscillation considerably exceeds the rolling and yawing oscillation and that c(sub a) is, at least in sections, practically constant, the result of this test is quite simple. It becomes clear that the influence of the phugoid oscillation may be replaced by suitable variation of the rolling-yawing moment on a rectilinear flight path instead of the phugoid oscillation.
Date:
August 1950
Creator:
Sponder, E. W.
System:
The UNT Digital Library
Lift and Drag of Wings with Small Span
The lift coefficient of a wing of small span at first shows a linear increase for the increasing angle of attack, but to a lesser degree then was to be expected according to the theory of the lifting line; thereafter the lift coefficient increases more rapidly than linearity, as contrasted with the the theory of the lifting line. The induced drag coefficient for a given lift coefficient, on the other hand, is obviously much smaller than it would be according to the theory. A mall change in the theory of the lifting line will cover these deviations.
Date:
August 1947
Creator:
Weinig, F.
System:
The UNT Digital Library
Flow Measurement by Means of Light Interference
"There has been under development for the high-speed wind tunnel of the LFA an optical measuring arrangement for the qualitative and quantitative investigation of flow. By the use of interference measurements, the determination of density at the surface of the bodies being tested in the air stream and in the vicinity of these bodies can be undertaken. The results obtained so far in the simple preliminary investigations show that it is possible, even at a low Reynolds number, to obtain the density field in the neighborhood of a test body by optical means" (p. 1).
Date:
August 1949
Creator:
Zobel
System:
The UNT Digital Library
The Frictional Force with Respect to the Actual Contact Surface
"Hardy's statement that the frictional force is largely adhesion, and to a lesser extent, deformation energy is proved by a simple experiment. The actual contact surface of sliding contacts and hence the friction per unit of contact surface was determined in several cases. It was found for contacts in normal atmosphere to be about one-third t-one-half as high as the macroscopic tearing strength of the softest contact link, while contacts annealed in vacuum and then tested, disclosed frictional forces which are greater than the macroscopic strength" (p. 1).
Date:
August 1944
Creator:
Holm, Ragnar
System:
The UNT Digital Library
Concerning the Velocity of Evaporation of Small Droplets in a Gas Atmosphere
"The evaporation velocity of liquid droplets under various conditions is theoretically calculated and a number of factors are investigated which are neglected in carrying out the fundamental equation of Maxwell. It is shown that the effect of these factors at the small drop sizes and the small weight concentrations ordinarily occurring in fog can be calculated by simple corrections. The evaporation process can be regarded as quasi-stationary in most cases" (p. 1).
Date:
August 1947
Creator:
Fuchs, N.
System:
The UNT Digital Library
Distribution of Structural Weight of Wing Along the Span
"In the present report the true weight distribution law of the wing structure along the span is investigated. It is shown that the triangular distribution and that based on the proportionality to the chords do not correspond to the actual weight distribution, On the basis of extensive data on wings of the CAHI type airplane formulas are obtained from which it is possible to determine the true diagram of the structural weight distribution along the span from a knowledge of only the geometrical dimensions of the wing" (p. 1).
Date:
August 1946
Creator:
Savelyev, V. V.
System:
The UNT Digital Library
DVL Angular Velocity Recorder
"In many studies, especially of nonstationary flight motion, it is necessary to determine the angular velocities at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular velocity for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated" (p. 1).
Date:
August 1944
Creator:
Liebe, Wolfgang
System:
The UNT Digital Library
Equations for Adiabatic but Rotational Steady Gas Flows Without Friction
This paper makes the following assumptions: 1) The flowing gases are assumed to have uniform energy distribution. ("Isoenergetic gas flows," that is valid with the same constants for the the energy equation entire flow.) This is correct, for example, for gas flows issuing from a region of constant pressure, density, temperature, end velocity. This property is not destroyed by compression shocks because of the universal validity of the energy law.
Date:
August 1947
Creator:
Schäefer, Manfred
System:
The UNT Digital Library
Measurements on Compressor-Blade Lattices
From Summary: "At the end of 1940 an investigation of a guide-vane lattice for the compressor of a TL unit [NACA comment: Turbojet] was requested. The greatest possible Mach number had to be attained. The investigation was conducted with an annular lattice subjected to axial flow. A direct-current shunt motor with a useful output of 235 horsepower at an engine speed of 1800 qm was available for driving the necessary blower."
Date:
August 1948
Creator:
Weinig, F.
System:
The UNT Digital Library
Determination of the Actual Contact Surface of a Brush Contact
"The number of partial contact surfaces of a brush-ring contact is measured by means of a statistical method. The particular brush is fitted with wicks - that is, insulated and cemented cylinders of brush material, terminating in the brush surface. The number of partial contact surfaces can be computed from the length of the rest periods in which such wicks remain without current" (p. 1).
Date:
August 1944
Creator:
Holm, Ragnar
System:
The UNT Digital Library
The Surface Structure of Ground Metal Crystals
"The changes produced on metallic surfaces as a result of grinding and polishing are not as yet fully understood. Undoubtedly there is some more or less marked change in the crystal structure, at least, in the top layer. Hereby a diffusion of separated crystal particles may be involved, or, on plastic material, the formation of a layer in greatly deformed state, with possible recrystallization in certain conditions" (p. 1).
Date:
August 1944
Creator:
Boas, W. & Schmid, E.
System:
The UNT Digital Library
Papers on Shimmy and Rolling Behavior of Landing Gears Presented at Stuttgart Conference October 16 and 17, 1941
Report presenting a compilation of papers on shimmy and rolling behavior of landing gears.
Date:
August 1954
Creator:
Fromm, H.; Hoffman, E.; Harling, R.; Schrode, H.; Kraft, P.; Scheubel, Franz Nikolaus et al.
System:
The UNT Digital Library
On the Representation of the Stability Region in Oscillation Problems With the Aid of the Hurwitz Determinants
This report concerns the use of the Hurwitz determinants in defining boundaries of regions where oscillatory phenomena are to be stable or unstable. A simplification is suggested as an aid in reducing the computations usually required, although it is emphasized that point checks in the various regions defined are required using the complete set of Hurwitz determinants or some other complete stability determination.
Date:
August 1952
Creator:
Sponder, E.
System:
The UNT Digital Library