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A resume of the advances in theoretical aeronautics made by Max M. Munk

Description: In order to apply profitably the mathematical methods of hydrodynamics to aeronautical problems, it is necessary to make simplifications in the physical conditions of the latter. To begin with, it is allowable in many problems, as Prandtl has so successfully shown, to treat the air as having constant density and as free of viscosity. But this is not sufficient. It is also necessary to specify certain shapes for the solid bodies whose motion through the air is discussed, shapes suggested by the actual solids - airships or airfoils - it is true, but so chosen that they lead to solvable problems. In a valuable paper presented by Dr. Max M. Munk, of the National Advisory Committee for Aeronautics, Washington, to the Delft Conference in April, 1924, these necessary simplifying assumptions are discussed in detail. It is the purpose of the present paper to present in as simple a manner as possible some of the interesting results obtained by Dr. Munk's methods.
Date: January 1, 1926
Creator: Ames, Joseph S
Item Type: Report
Partner: UNT Libraries Government Documents Department

Experiments on autorotation

Description: This article deals principally with Professor Bairstow's experiments on autorotation, in which the wing is free to rotate about an axis in its plane of symmetry, which axis is parallel with the direction of the wind.
Date: September 1, 1926
Creator: Anderlik, E
Item Type: Report
Partner: UNT Libraries Government Documents Department

The stresses in columns under combined axial and side loads

Description: The problem before us is to determine the total stresses in an axially loaded column of any degree of restraint which is also subject to transverse bending both from a uniformly distributed load and from concentrated loads.
Date: July 1, 1922
Creator: Arnstein, Karl
Item Type: Report
Partner: UNT Libraries Government Documents Department

Some principles governing the establishment of meteorological stations along air routes

Description: The organization of a meteorological service for an air route involves the solution of two distinct problems: distribution and grouping of meteorological stations and communications. Experience gained in the establishment of two lines, Paris-Warsaw and Constantinople-Bucharest enables us to establish certain principles, which may be of interest to note here.
Date: March 1, 1922
Creator: Aujames, P
Item Type: Report
Partner: UNT Libraries Government Documents Department

Langley Field wind tunnel apparatus

Description: The difficulties experienced in properly holding thin tipped or tapered airfoils while testing on an N.P.L. type aerodynamic balance even at low air speeds, and the impossibility of holding even solid metal models at the high speeds attainable at the National Advisory Committee's wind tunnel, necessitated the design of a balance which would hold model airfoils of any thickness and at speeds up to 150 m.p.h. In addition to mechanical strength and rigidity, it was highly desirable that the balance readings should require a minimum amount of correction and mathematical manipulation in order to obtain the lift and drag coefficients and the center of pressure. The balance described herein is similar to one in use at the University of Gottingen, the main difference lying in the addition of a device for reading the center of pressure directly, without the necessity of any correction whatsoever. Details of the design and operation of the device are given.
Date: October 1, 1921
Creator: Bacon, D L
Item Type: Report
Partner: UNT Libraries Government Documents Department

Preliminary experiments to determine scale and slip-stream effects on a 1/24th size model of a JN4H biplane

Description: This work was undertaken to obtain results on a small model of a complete airplane which might be used for comparison with corresponding tests made in full flight. Somewhat similar tests have been previously made at various other laboratories; but as certain discrepancies exist between corresponding tests in different tunnels, it has been deemed advisable to obtain a direct comparison for this particular installation. The present work covers tests on a one-twenty-fourth scale model at speeds varying from 6.7 m/sec. (15 m.p.h.) to 40.2 m/sec, (90 m.p.h.). A slip stream correction has been obtained by the use of a small belt-driven propeller mounted in front of the model, and force coefficients thus obtained are compared with the measurements of the same forces made in full flight on a geometrically similar airplane. This report gives lift, drag, and longitudinal moment values obtained in tests of a particularly accurate model over a wide range of speeds. A measure of the slip stream corrections on lift and drag forces was obtained by the use of a power-driven model propeller. Measurements were also made of forces and longitudinal moments for all angles from 0 degree to 360 degrees.
Date: January 1, 1923
Creator: Bacon, D L
Item Type: Report
Partner: UNT Libraries Government Documents Department

The resistance of spheres in wind tunnels and in air

Description: To supplement the standardization tests now in progress at several laboratories, a broad investigation of the resistance of spheres in wind tunnels and free air has been carried out by the National Advisory Committee for Aeronautics. The subject has been classed in aerodynamic research, and in consequence there is available a great mass of data from previous investigations. This material was given careful consideration in laying out the research, and explanation of practically all the disagreement between former experiments has resulted. A satisfactory confirmation of Reynolds law has been accomplished, the effect of means of support determined, the range of experiment greatly extended by work in the new variable density wind tunnel, and the effects of turbulence investigated by work in the tunnels and by towing and dropping tests in free air. It is concluded that the erratic nature of most of the previous work is due to support interference and differing turbulence conditions. While the question of support has been investigated thoroughly, a systematic and comprehensive study of the effects of scale and quality of turbulence will be necessary to complete the problem, as this phase was given only general treatment.
Date: January 1, 1924
Creator: Bacon, D L & Reid, E G
Item Type: Report
Partner: UNT Libraries Government Documents Department

The distribution of lift over wing tips and ailerons

Description: This investigation was carried out in the 5-foot wind tunnel of the Langley Memorial Aeronautical Laboratory for the purpose of obtaining more complete information on the distribution of lift between the ends of wing spars, the stresses in ailerons, and the general subject of airflow near the tip of a wing. It includes one series of tests on four models without ailerons, having square, elliptical, and raked tips respectively, and a second series of positively and negatively raked wings with ailerons adjusted to different settings. The results show that negatively raked tips give a more uniform distribution of air pressure than any of the other three arrangements, because the tip vortex does not disturb the flow at the trailing edge. Aileron loads are found to be less severe on wings with negative application to the calculation of aileron and wing stresses and also to facilitate the proper distribution of load in sand testing. Contour charts show in great detail the complex distribution lift over the wing.
Date: January 1, 1924
Creator: Bacon, David L
Item Type: Report
Partner: UNT Libraries Government Documents Department

Model supports and their effects on the results of wind tunnel tests

Description: The airflow about a model while being tested is often sufficiently affected by the model support to lead to erroneous conclusions unless appropriate corrections are used. In this paper some new material on the subject is presented, together with a review of the airfoil support corrections used in several other laboratories.
Date: February 1, 1923
Creator: Bacon, David L
Item Type: Report
Partner: UNT Libraries Government Documents Department

The "Universal propeller": built by Paragon Engineers, Inc., Baltimore, Md

Description: At the request of the N.A.C.A. the "Universal Propeller" was operated and explained by the inventor, Mr. Spencer Heath, for the purpose of demonstrating the following features of design: 1) Elimination of continuously running gears, collars or bearings in the pitch control mechanism; 2) The use of engine power in place of manual labor in changing blade angle; 3) The absence of any structural limitation to the range of blade angles available and the possibility of limiting the blade travel between any two predetermined extreme positions; 4) Continuous indication on the instrument board of the blade position; 5) Automatic throttling of the engine while the propeller is passing through the position of neutral pitch.
Date: March 1, 1922
Creator: Bacon, David L
Item Type: Report
Partner: UNT Libraries Government Documents Department

Atmospheric waves and their utilization in soaring flight

Description: In soaring flight, ascending air currents are utilized and the interesting question is raised whether there are such currents which extend to any considerable distance and which can be utilized practically.
Date: March 1923
Creator: Baldit, M Albert
Item Type: Report
Partner: UNT Libraries Government Documents Department

Wind tunnel tests on an airfoil equipped with a split flap and a slot

Description: The investigation described in this report is concerned with the changes in the aerodynamic characteristics of an airfoil which are produced by a gauze-covered suction slot, located near the leading edge, and connected by an air passage to a split flap at the trailing edge. The tests were conducted at the Langley Memorial Aeronautical Laboratory. At the larger values of lift coefficient where the action of the slot might be expected to be most effective, the pressure differences were such that the air flowed out of the slot rather than in through it, and in consequence, the maximum lift coefficient was decreased.
Date: October 1, 1929
Creator: Bamber, Millard J
Item Type: Report
Partner: UNT Libraries Government Documents Department

The decay of a simple eddy

Description: The principal result obtained in this report is a generalization of Taylor's formula for a simple eddy. The discussion of the properties of the eddy indicates that there is a slight analogy between the theory of eddies in a viscous fluid and the quantum theory of radiation. Another exact solution of the equations of motion of viscous fluid yields a result which reminds one of the well-known condition for instability in the case of a horizontally stratified atmosphere.
Date: January 1, 1923
Creator: Bateman, H
Item Type: Report
Partner: UNT Libraries Government Documents Department

The Inertial Coefficients of an Airship in a Frictionless Fluid

Description: This report deals with the investigation of the apparent inertia of an airship hull. The exact solution of the aerodynamical problem has been studied for hulls of various shapes and special attention has been given to the case of an ellipsoidal hull. In order that the results for this last case may be readily adapted to other cases, they are expressed in terms of the area and perimeter of the largest cross section perpendicular to the direction motion by means of a formula involving a coefficient K which varies only slowly when the shape of the hull is changed, being 0.637 for a circular or elliptic disk, 0.5 for a sphere, and about 0.25 for a spheroid of fineness ratio 7. For rough purposes it is sufficient to employ the coefficients, originally found for ellipsoids, for hulls otherwise shaped. When more exact values of the inertia are needed, estimates may be based on a study of the way in which K varies with different characteristics and for such a study the new coefficient possesses some advantage over one which is defined with reference to the volume of fluid displaced. The case of rotation of an airship hull has been investigated also and a coefficient has been defined with the same advantages as the corresponding coefficient for rectilinear motion.
Date: January 1, 1924
Creator: Bateman, H
Item Type: Report
Partner: UNT Libraries Government Documents Department

Diagrams of airplane stability

Description: In this report a study is made of the effect on longitudinal and lateral oscillations of an airplane of simultaneous variations in two resistance derivatives while the remainder of the derivatives are constant. The results are represented by diagrams in which the two variable resistance derivatives are used as coordinates, and curves are plotted along which the modulus of decay of a long oscillation has a constant value. The same type of analysis is also carried out for the stability of the parachute. In discussing the stability of the helicopter it is concluded that the gyroscopic effect on stability will be greater than in the case of the airplane.
Date: January 1, 1921
Creator: Batemen, H
Item Type: Report
Partner: UNT Libraries Government Documents Department

Stability of the parachute and helicopter

Description: 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.
Date: January 1, 1920
Creator: Batemen, H
Item Type: Report
Partner: UNT Libraries Government Documents Department