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Supplement to Comparison of Automatic Control Systems

Description: "This analysis deals with the indirect regulator, wherefrom the behavior of the direct regulator is deduced as a limiting case. The prime mover is looked upon as "independent of the load": a change in the adjusting power (to be applied) for the control link (as, for example, in relation to the adjusting path (eta) with pressure valves or the rudder of vessels) does not modify the actions of the prime mover. Mass forces and friction are discounted; "clearance" also is discounted in the transmission links of the regulator" (p. 1).
Date: August 1941
Creator: Oppelt, W.
Partner: UNT Libraries Government Documents Department

The Transformation of Heat in an Engine

Description: This report presents a thermodynamic basis for rating heat engines. The production of work by a heat engine rests on the operation of supplying heat, under favorable conditions, to a working fluid and then taking it away.
Date: April 1929
Creator: Neumann, Kurt
Partner: UNT Libraries Government Documents Department

Lift Theory of Supporting Surfaces: Second Article

Description: Memorandum presenting a description of the hydrodynamic lift theory of supporting services. This report is mainly about the task of finding suitable wing sections for given lift conditions. Formulas are given for lift magnitude and moment, which make it possible to obtain solutions of great simplicity and clearness.
Date: September 1921
Creator: von Mises, R.
Partner: UNT Libraries Government Documents Department

The Boundary Layer as a Means of Controlling the Flow of Liquids and Gases

Description: According to one of the main propositions of the boundary layer theory the scarcely noticeable boundary layer may, under certain conditions, have a decisive influence on the form of the external flow by causing it to separate from the wing surface. These phenomena are known to be caused by a kind of stagnation of the boundary layer at the point of separation. The present report deals with similar phenomena. It is important to note that usually the cause (external interference) directly affects only the layer close to the wall, while its indirect effect extends to a large portion of the external flow.
Date: March 1930
Creator: Schrenk, Oskar
Partner: UNT Libraries Government Documents Department

The critical velocity of a body towed by a cable from an airplane

Description: It is sufficient to consider only the equations of motion of the towed body whereas those of the cable may be left out of consideration. The result obtained makes it possible to determine which factors affect the critical velocity and what modifications of the instrument are necessary for extending the upper limit of that velocity.
Date: July 1937
Creator: Koning, C. & DeHaas, T. P.
Partner: UNT Libraries Government Documents Department

Airplane Drag

Description: It has been less well understood that the induced drag (or, better said, the undesired increase in the induced drag as compared with the theoretical minimum calculated by Prandtl) plays a decisive role in the process of taking off and therefore in the requisite engine power. This paper seeks to clarify the induced drag.
Date: December 1929
Creator: Töpfer, Carl
Partner: UNT Libraries Government Documents Department

Airplane Flight in the Stratosphere

Description: This brief survey of the problems encountered in high-altitude flight deals in particular with the need for high lift coefficient in the wings, large aspect ratios in the wings, and also the problem of hermetically sealing the cabin.
Date: February 1932
Creator: de Caria, Ugo
Partner: UNT Libraries Government Documents Department

Air Transport

Description: Report presenting the development in air transport that has taken place since civil aviation between England and Europe started at the end of August 1919. The primary subjects explored include the character of loads on aircraft, routes operated, results in passengers carried and efficiency of the service, costs of the service, question of subsidies, and probable future developments.
Date: 1924
Creator: Page, F. Handley
Partner: UNT Libraries Government Documents Department

Investigation of the Variations in the Velocity of the Air Flow About a Wing Profile

Description: Memorandum presenting an investigation to determine the variations in the velocity of the air when it was obliged to flow about a wing profile. Special interest was paid to the determination of velocity as compared with that of the undisturbed flow and of the velocity drop in successive planes perpendicular to the flow direction at increasing distances from the wing profile.
Date: July 1930
Creator: Repenthin, Walter
Partner: UNT Libraries Government Documents Department

Some German Gliders of 1920-1923

Description: Memorandum presenting a review of some of the German gliders produced from 1920-1923. The designs, flight characteristics, and descriptions of successful flights are provided.
Date: October 1927
Creator: Gymnich, Alfried
Partner: UNT Libraries Government Documents Department

The Transference of Heat From a Hot Plate to an Air Stream

Description: The object of the present study was to define experimentally the field of temperature and velocity in a heated flat plate when exposed to an air stream whose direction is parallel to it, then calculate therefrom the heat transference and the friction past the flat plate, and lastly, compare the test data with the mathematical theory. To ensure comparable results, we were to actually obtain or else approximate: a) two-dimensional flow; b) constant plate temperature in the direction of the stream. To approximate the flow in two dimensions, we chose a relatively wide plate and measured the velocity and temperature in the median plane.
Date: April 1931
Creator: Elias, Franz
Partner: UNT Libraries Government Documents Department

Longitudinal Balancing of Airplanes

Description: The object of the present communication is to determine the best method for locating the center of lift of an airplane and to provide a method for making corrections. The method employed is very simple, being based on the positions given the elevator during flights at different speeds.
Date: February 1923
Creator: Eteve, Albert
Partner: UNT Libraries Government Documents Department

Impact Tests on Rubber Compression Springs for Airplane Landing Gears

Description: The present report gives the results of tests which were made for the purpose of solving the problem of whether diagrams obtained from pressure tests could be conclusive for the determination of the safe impact coefficients. It is first established that the rubber rings adhere firmly to the compression surfaces during deformation. Suggestions are thus obtained for a constructive simplification of the rubber rings. The hysteresis phenomenon is ascribed to external and internal friction forces. A device for falling tests is then described with which the process of shock absorption with rubber rings was tested.
Date: July 1930
Creator: Hohenemser, K.
Partner: UNT Libraries Government Documents Department

Lautal as a Material for Airplane Construction

Description: Lautal is a refinable aluminum alloy which, unlike duralumin, contains no magnesium. According to the statements of the Lauta Works, lautal contains: aluminum, 94%; copper, 4%; silicon, 2%. The use of lautal as a construction material is discussed in relation to specific weight, production methods, and riveting tests.
Date: August 1929
Creator: Brenner, Paul
Partner: UNT Libraries Government Documents Department

Load Assumptions for Calculating the Strength of Airplanes

Description: "The following load assumptions shall be taken as the basis of the strength calculations. Certain definite load conditions (e.g. of flight, control, landing and transport) shall be assumed. The loads shall be assumed to be safe loads, constant or only slowly variable, and the inertia forces due to elastic deformation are accordingly disregarded. The external forces, the force of gravity and the inertia forces on the whole airplane shall produce a condition of equilibrium" (p. 1).
Date: September 1930
Partner: UNT Libraries Government Documents Department

Landing Impact of Seaplanes

Description: The theory of landing impact is briefly stated and the applicability of a previously suggested formula is extended. Theoretical considerations regarding impact measurements on models and actual seaplanes are followed by a brief description of the instruments used in actual flight tests. The report contains a description of the strength conditions and deals exhaustively with force measurements on the float gear of an "HE 9a" with flat-bottom and with V-bottom floats. The experimental data are given and compared with the theoretical results.
Date: June 1931
Creator: Pabst, Wilhelm
Partner: UNT Libraries Government Documents Department

Liquid Cooling of Aircraft Engines

Description: This report presents a method for solving the problem of liquid cooling at high temperatures, which is an intermediate method between water and air cooling, by experiments on a test-stand and on an airplane. A utilizable cooling medium was found in ethylene glycol, which has only one disadvantage, namely, that of combustibility. The danger, however is very slight. It has one decided advantage, that it simultaneously serves as protection against freezing.
Date: December 1931
Creator: Weidinger, Hanns
Partner: UNT Libraries Government Documents Department

Report on Commercial Air Transportation Activities in England, France, Germany and Holland

Description: The following pages present a review of the air transportation activities of England, France, Germany and Holland, based on an inspection trip during the summer of 1924. The different components described include operating companies, nature of transportation services, air traffic, flying equipment, government relations, and general remarks.
Date: June 1925
Creator: Van Zandt, J. Parker
Partner: UNT Libraries Government Documents Department

Remarks on Building of Low-Powered Airplanes

Description: "If the low-powered airplane is to be used advantageously by private individuals, the most important consideration is a smaller fuel consumption and, hence, a lower engine power. From experiments with gliders, it appears entirely possible, by utilizing ascending winds (on the weather side of mountains and those generated by the heat of the sun) and by employing engine flight intermittently, as required to fly long distances over land" (p. 1).
Date: January 1924
Creator: Langsdorff, Werner v.
Partner: UNT Libraries Government Documents Department

Resistance of Plates and Pipes at High Reynolds Numbers

Description: It was learned that the law of resistance for high R values does not follow the simple powers, and that the powers, which can be obtained approximately for the velocity distribution, gradually change. Since, moreover, very important investigations have recently been made on the resistance of plates at very high R values, it seemed of interest to apply the above line of reasoning to the new general law of resistance. For this purpose, the resistance and velocity distribution along the plate must always be equal to the values of the pipe flow at the corresponding Reynolds number.
Date: January 1931
Creator: Schiller, L. & Hermann, R.
Partner: UNT Libraries Government Documents Department

Nieuport-Astra Parachute Contest

Description: Report presenting a description of a parachute design contest. The object of this contest was to obtain a parachute of light weight and small bulk, suitable for airplanes. The primary areas of focus were safety, ability to be installed on airplanes, speed, materials, and behavior of the parachutes in the air.
Date: October 1923
Creator: Philippe, J.
Partner: UNT Libraries Government Documents Department

Nomogram for Correcting Drag and Angle of Attack of an Airfoil Model in an Air Stream of Finite Diameter

Description: In experimenting with airfoil models in a wind tunnel, the magnitude of the forces acting on the model is affected by the fact that the air stream in which the model is suspended, has a restricted cross-section. In order to utilize the results for an airplane in an unlimited quantity of air, a correction must be made. The magnitude of this correction was determined by Prandtl by the application of his wing theory.
Date: December 1924
Partner: UNT Libraries Government Documents Department