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High-speed wind tunnels
Wind tunnel construction and design is discussed especially in relation to subsonic and supersonic speeds. Reynolds Numbers and the theory of compressible flows are also taken into consideration in designing new tunnels.
Aerodynamic Heat-Power Engine Operating on a Closed Cycle
"Hot-air engines with dynamic compressors and turbines offer new prospects of success through utilization of units of high efficiencies and through the employment of modern materials of great strength at high temperature. Particular consideration is given to an aerodynamic prime mover operating on a closed circuit and heated externally. Increase of the pressure level of the circulating air permits a great increase of limit load of the unit. This also affords a possibility of regulation for which the internal efficiency of the unit changes but slightly. The effect of pressure and temperature losses is investigated" (p. 1).
Investigations on Wings With and Without Sweepback at High Subsonic Speeds
Drag tests at zero lift have been made at Mach numbers from 0.7 to approximately 0.95 in the high speed wind tunnel of the Institute of Aerodynamics, ETH, Zurich, on a group of untapered wings of aspect ratio 3.25, having sweep angles of 0 degree and 35 degrees. For each sweep angle, a series of geometrically similar models was tested at a constant Reynolds number to provide a verification of computed tunnel blocking corrections. Tests were also made for wings having thickness ratios of 0.09 and 0.12 and the results compared with results predicted by von Karman's similarity law.
Variable Pitch Propellers
In this report are described four different types of propellers which appeared at widely separated dates, but which were exhibited together at the last Salon de l'Aeronautique. The four propellers are the Chaviere variable pitch propeller, the variable pitch propeller used on the Clement Bayard dirigible, the variable pitch propeller used on Italian dirigibles, and the Levasseur variable pitch propeller.
The "Universal" Adjustable and Reversible Propeller Built by Paragon Engineers, Inc., Baltimore, MD
"A device which does for the aircraft what change speed gears do for the automobile is the invention of Spencer Heath. It comprises a system of special blades and a mechanism for varying the pitch of the blades from zero to 360 degrees, while in flight or otherwise. By adjusting the pitch, either before starting or while the engine is running, to a less than normal angle, the engine is allowed to pick up speed and deliver its maximum power which is necessary in taking-off with a heavier load than the same airplane could otherwise normally carry" (p. 1).
Experiments on Airfoils With Aileron and Slot
The present report contains the results of a few experiments on three airfoils to which the rear portions, having chords respectively 1/4, 1/3, and 2/5 of the total chords, are hinged so as to form ailerons, especial attention being given to the shape of the slot between the aileron and the main portion of the aileron.
A Method for the Direct Determination of Wing-Section Drag
In order that the method may be more easily understood, we will first consider the simpler case when there is no lift, but only drag, and when the streamlines at the measuring point behind the obstacle are nearly parallel. Moreover, the flow is assumed not to deviate much from the two-dimensional flow.
Approximate Calculation of the Static Longitudinal Stability of Airplanes
It seems desirable to have some simple method for calculating quickly and with sufficient accuracy: 1) the correct position of the center of gravity; 2) the requisite tail-group dimensions; 3) and the course of the wing and tail-group moments. In out deductions, we will first replace the biplane (disregarding the effect of stagger, decalage and induced drag) by an equivalent monoplane, whose dimensions and position in space can be approximately determined in a simple manner.
How to Lay Out and Build an Airplane Landing Field: Notes on Shape and Size of Plot, Runway Details, Type and Arrangement of Buildings, Drainage of Field, Best Kind of Grass and Proper Marking to Aid Pilots
Report presenting a description of considerations that go into the layout and building of an aircraft landing field or airstrip. Some of the elements considered include the shape and size of the plot, general arrangement, buildings present near the airstrip, runways, grass, roadways and railroad tracks, field markings, and some miscellaneous factors are provided.
Determination of the Elastic Constants of Airplane Tires
For determination of the elastic constants of airplane tires which are required for the numerical calculations of the shimmy properties of nose and tail wheels, deformation measurements were carried out on four different tires. For this purpose, the tires were loaded in each case with a normal load and then with a lateral force, a tangential force, and a moment. Moreover, the weight and the mass moment of inertia about a vertical axis were determined for the various tires.
Aeronautic Instruction in Germany
This report contains a list of the courses relating to aeronautics announced in Germany, both in the technical high schools and in the universities.
On the Take-Off of Heavily Loaded Airplanes
This report examines the take-off conditions of airplanes equipped with tractive propellers, and particularly the more difficult take-off of airplanes heavily loaded per unit of wing area (wing loading) or per unit of engine power (power loading).
Safety in Airplane Flight
This report presents methods to reduce the incidence of aviation accidents. Some of the methods discussed include enlistment and training of aviators, improvement of controls and control surfaces, and upgrading of power plants.
Measurement of Oil-Film Pressures in Journal Bearings under Constant and Variable Loads
"In a study of journal bearings, the measurement of the oil-film strength produces some significant information. A new instrument is described by means of which the pressure of the oil film in bearings (under constant or alternating load) can be measured and recorded. With this device, the pressure distribution in the lubricating film of a bearing bushing was measured (under different operating conditions on a journal bearing) in the pulsator-bearing-testing machine" (p. 1).
Effect of Threaded and Serrated Holes on the Limited Time and Fatigue Strength of Flat Light-Alloy Strips
"The investigation was made for the purpose of ascertaining the notch sensitivity of flat strips of light alloy with cylindrical holes under initial tension stress, with special attention to the change in notch-effect factors with the number of load cycles. Then the studies were extended to similar flat strips with pin-loaded holes (tension lugs). This report deals with fatigue tests under initial tension load on flat test specimens of 3116.5 duralumin and AZM 3510.1 electron with plain unloaded and pin-loaded holes (tension lugs) of different forms" (p. 1).
Note on a New and Simple Method of Dead Reckoning in Aerial Navigation
Memorandum presenting a method of calculating the dead reckoning in aerial navigation.
Combustion of Gaseous Mixtures
This report not only presents matters of practical importance in the classification of engine fuels, for which other means have proved inadequate, but also makes a few suggestions. It confirms the results of Withrow and Boyd which localize the explosive wave in the last portions of the mixture burned. This being the case, it may be assumed that the greater the normal combustion, the less the energy developed in the explosive form. In order to combat the detonation, it is therefore necessary to try to render the normal combustion swift and complete, as produced in carbureted mixtures containing benzene (benzol), in which the flame propagation, beginning at the spark, yields a progressive and pronounced darkening on the photographic film.
The American Airship ZR-3
This airship was built by the Zeppelin Airship Company at Friedrichshafen in 1923-4, for the United States Navy, as the reparations service of the German Government in fulfillment of the treaty of peace. A description of the design, components, flight characteristics, blueprints, and photographs are provided.
Method Rendering It Possible, in Testing Airplane Wing Models at the Eiffel Laboratory, to Obtain Comparable Polars, Whether the Supports Are Attached to the Upper or Lower Side of Model
Report presenting an examination of the errors that result from testing an aircraft model and applying the results to full-sized airplanes. An investigation is carried out to determine how to obtain comparable polars regardless of whether the supports are attached to the upper or lower side of the model.
A New Simple Interferometer for Obtaining Quantitatively Evaluable Flow Patterns
"The method described in the present report makes it possible to obtain interferometer records with the aid of any one of the available Schlieren optics by the addition of very simple expedients, which fundamentally need not to be inferior to those obtained by other methods, such as the Mach-Zehnder interferometer, for example. The method is based on the fundamental concept of the phase-contrast process developed by Zernike, but which in principle has been enlarged to such an extent that it practically represents an independent interference method for general applications. Moreover, the method offers the possibility, in case of necessity, of superposing any apparent wedge field on the density field to be gauged" (p. 1).
On the Determination of Certain Basic Types of Supersonic Flow Fields
A discussion is given of the application of Fourier series techniques to the problems of linearized supersonic flow. The formulation presented is an extension of the doublet type of "fundamental solution" to higher order types of singularity. The equations developed have application to wing theory but are primarily of importance in wing-body interaction problems. A specific example of a wing-body interference problem is discussed in light of the presented methods.
On the Motions of an Oscillating System Under the Influence of Flip-Flop Controls
"So-called flip-flop controls (also called "on-off-course controls") are frequently preferred to continuous controls because of their simple construction. Thus they are used also for the steering control of airplanes. Such a body possesses-even if one thinks, for instance, only of the symmetric longitudinal motion - three degrees of freedom so that a study of its motions under the influence of an intermittent control is at least lengthy. Thus, it is suggested that an investigation of the basic effect of such a control first be made on a system with one degree of freedom" (p. 1).
The effect of the slipstream on an airplane wing
The conditions which must be met at the slipstream boundary are developed, after which it is shown with the aid of the reflection method how these limiting conditions may be complied with in the case of an airfoil in a propeller slipstream in horizontal flow as well as for the propeller in yaw and with allowance for the slipstream rotation. In connection herewith, it is shown how the effective angles of attack and the circulation distribution with due regard to slipstream effect can be predicted and what inferences may be drawn therefrom for the distribution of lift, drag, and pitching moment.
Wind-Tunnel Investigations of Diving Brakes
Unduly high diving speeds can be effectively controlled by diving brakes but their employment involves at the same time a number of disagreeable features: namely, rotation of zero lift direction, variation of diviving moment, and, the creation of a potent dead air region.
Mathematical treatise on the recovery from a flat spin
In this mathematical investigation, made in collaboration with Dr. Wilhelm Schmidt, we interpret the temporary change (due to some disturbance) in the quantities which define the position of the airplane while in a flat spin. We further examine the effect of this change, of the means resorted to to produce the disturbance, and thus reveal the expedients available for recovering from a flat spin.
Static Soaring Flight Over Flat Sea Coasts
Static soaring flight has hitherto been accomplished by means of two sources of energy: ascending air currents in the vicinity of obstacles and those produced by unequal heating. The latter has not yet been practically tested in soaring flight.
Mathematical and Experimental Investigation of Heat Control and Power Increase in Air-Cooled Aircraft Engines
In order to understand the numerical relations between the air velocity, temperature of the cylinder walls, heat dissipation, cylinder dimensions and type of construction an experimental plant was installed in the Siemens and Halske laboratory. The experimental cylinder was exposed to the air stream of a wind tunnel. The compression chamber was heated by an electrically heated oil bath kept constantly in motion by a stirrer. The wall temperatures were measured by thermocouples.
Tests of Artificial Flight at High Altitudes
"If we wish to form an accurate idea of the extraordinary progress achieved in aeronautics, a comparison must be made of the latest altitude records and the figures regarded as highest attainable limit some ten years ago. It is desirable, for two reasons, that we should be able to define the limit of the altitudes that can be reached without artificial aid. First, to know to what extent the human body can endure the inhalation of rarified air. Second, the mental capacity of the aviator must be tested at high altitudes and the limit known below which he is able to make reliable observations without being artificially supplied with oxygen" (p. 1).
Universal Logarithmic Law of Velocity Distribution as Applied to the Investigation of Boundary Layer and Drag of Streamline Bodies at Large Reynolds Number
In the present paper we shall consider a figure of revolution, so that the formulas applicable to the more simple cases as, for example, a wing or flat plate will follow from our equations as corollaries. For checking the results of our theory, we made use of the data derived from the tests of Freeman on a 1/40-scale model of the airship "Akron" conducted in the large NACA wind tunnel. In the first part we shall derive the fundamental equation for a body of revolution according to the Karman theory in its original form, and in the second part we shall give all the comparisons of the results of tests with the modified theory.
Structural Details of German Gliders
The structural details such as wings, fuselage, landing gear, and steering organs of German gliders are detailed in this report.
Type of Engine to Employ
The engine of a commercial airplane must, above all, be sure and durable. It seems therefore, that we must use engines with vertical cylinders or in the V form with quite a small angle.
Heat Transfer by Free Convection From Horizontal Cylinders in Diatomic Gases
"The case of the horizontal cylinder is of particular importance in the study of heat transfer by free convection for the following reasons: In the first place, next to the rectangular plate it represents the simplest two-dimensional case; and second, a very wide range of measurements is possible, from the finest electrically heated glow lamp wires to pipes heated by liquids or gases flowing through them" (p. 1).
Riveted Joints in Thin Plates
The method of riveting by forming the closing head under increasing pressure or by a series of hammer blows is investigated. The question as to the best edge distance, i.e. that distance from the rivet center to the plate edge below which it is unadvisable to go and, at the same time useless to go beyond, was examined. The slippage of plates which occurs under the effect of a certain stress, does not completely disappear on unloading.
Influence of Static Longitudinal Stability on the Behavior of Airplanes in Gusts
The equations of motion for an airplane penetrating a gust are derived using a few simplifying assumptions. Calculations of loads for different static longitudinal stability on two German airplane models, HC 45 and HS 122, are compared with flight tests. Good agreement is obtained between the trend of the flight tests and the calculated values; however no absolute comparison was possible between the flight tests and calculations.
The danger of stalled flight and an analysis of the factors which govern it
A definition of "stalled fight" is presented as well as a detailed discussion on the how and why it occurs. Some suggestions are made to prevent its occurrence such as carrying an air speed instrument in the airplane.
Metallography of Aluminum and Its Alloys: Use of Electrolytic Polishing
Recent methods are described for electropolishing aluminum and aluminum alloys. Numerous references are included of electrolytic micrographic investigations carried out during the period 1948 to 1952. A detailed description of a commercial electrolytic polishing unit, suitable for micrographic examination of aluminum and its alloys, is included.
Resistance of a Plate in Parallel Flow at Low Reynolds Numbers
The present paper gives the results of measurements of the resistance of a plate placed parallel to the flow in the range of Reynolds numbers from 10 to 2300; in this range the resistance deviates from the formula of Blasius. The lower limit of validity of the Blasius formula is determined and also the increase in resistance at the edges parallel to the flow in the case of a plate of finite width.
Principle of the Boerner Airship
"The Boerner airship is built on entirely different principles from ordinary airships, of which the Zeppelin is the best known type. Mr. Boerner has abandoned the rigid body of the Zeppelin and has adopted a body with a double keel forming a rigid platform for attaching the gas ballonets, which must support the whole in the air" (p. 1).
Establishment of Aviation Schools
Report presenting a discussion of the creation of a suitable aviation school and some of the characteristics that should be considered in terms of hiring personnel, creating a curriculum, and obtaining equipment.
Aerodynamic forces and moments of a seaplane on the water
From Introduction: "This report gives the results of wind-tunnel tests with a seaplane model as a contribution to the solution of the aerodynamic problems."
Measurement of Visibility From the Pilot's Cockpit on Different Airplane Types
A process for the measurement of the visibility of airplanes from the pilot's cockpit is developed. The apparatus necessary for the measurements was suitably constructed and measurements of the fields of vision were made with it. The visibilities of six airplanes of different types of construction and use were measured, as well as the visibility of an automobile for comparison. An attempt was made to establish minimum visibility requirements and to express the excellence of visibility by means of a numerical coefficient.
Relations Between the Modulus of Elasticity of Binary Alloys and Their Structure
A comprehensive survey of the elastic modulus of binary alloys as a function of the concentration is presented. Alloys that form continuous solid solutions, limited solid solutions, eutectic alloys, and alloys with intermetallic phases are investigated. Systems having the most important structures have been examined to obtain criteria for the relation between lattice structure, type of binding, and elastic behavior.
Concerning the Flow About Ring-Shaped Cowlings Part 2: Annular Bodies of Infinite Length With Circulation for Smooth Entrance
The investigations carried out in a previous report (NACA TM 1325) concerning the flow about ring-shaped cowlings were extended by taking a circulation about the cowling into consideration. The present second report treats bodies of infinite length with approximately smooth entrance. The circulation was caused by distributing vortex rings of constant density over a stream surface extending to infinity. Furthermore, the influence of a hub body on such cowlings was dealt with.
Aeroelastic Problems of Airplane Design
The technical memorandum briefly summarizes the growth of interest in aeroelastic phenomena as aircraft speed increased and wing designs changed for faster aircraft. Different types of aircraft vibrations are then introduced, and the mathematical basis for the theory behind them is described. Special attention is given to static oscillations, wing flutter, and the flutter of skin panels. The last section of the memorandum deals with the prevention of flutter by design specifications.
Practical Tests With The "Auto Control Slot" Part 1: Lecture
"The effect of a slotted wing depends essentially on the fact that a secondary flow branches off from the main flow and passes to the suction side of the profile. It is thus possible to delay the separation greatly and increase the lift. The practical aspect of the slotted wing is less known in Germany, especially the results obtained during the last three years since the introduction of the 'auto control slot'" (p. 1).
Practical Tests With The "Auto Control Slot" Part 2: Discussion
"For some time the D.V.L. has been investigating the question of applicability of Handley Page slotted wings to German airplanes. Comparitive gliding tests were made with open and closed slots on an Albatros L 75 airplane equipped with the Handley Page "auto control slots." This investigation served to determine the effect of the auto control slot on the properties and performances of airplanes at large angles of attack. The most important problems were whether the angle of glide at small angles of attack can be increased by the adoption of the auto control slot and, in particular, as to whether the flight characteristics at large angles of attack are improved thereby and equilibrium in gliding flight is guaranteed even at larger than ordinary angles of attack" (p. 1).
Definition of Terms Used in Connection With Commercial Aircraft Engines
To facilitate standardization of certain terms and definitions relating to engines and airplanes a list of definitions is provided.
Tests for the Determination of the Stress Condition in Tension Fields
"The present experiments treat the stress of actual tension fields within the elastic range. They give the magnitude of the flexural stresses due to wrinkling. They also disclose, particularly by slightly exceeded buckling load, the marked unloading - as compared with the tension-field theory - of the uprights as a result of the flexural stiffness of the web plate. The test sheets were clamped at the edges and brought to buckling through shearing and compressive stresses applied in the direction of the long sides" (p. 1).
Measurements of Vertical Air Currents in the Atmosphere
To summarize, the experiments with balloons, sailplanes and light airplanes conducted thus far, reveal the vertical velocities of the air to be primarily dependent on the vertical temperature distribution. Stable stratifications result in up-and-down currents forced by the contour of the ground, which are readily recognized in flight and, if need be, may be avoided.
The Constructional Design of Metal Flying-Boat Hulls: Part 1 & Workshop Notes on the Building of Metal Hulls: Part 2
Part I of this paper covers the constructional design of metal flying-boat hulls and does not elaborate any further. Part II deals with the actual construction process of the hull.
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