Note presenting an investigation of the Karman vortex street, which is a flow arrangement occurring behind a plate. The equations governing the flow and some of the hypotheses behind it are provided.

"This collection of data on aerofoils has been made from the published reports of a number of the leading aerodynamic laboratories of this country and Europe. The information which was originally expressed according to the different customs of the several laboratories is here presented in a uniform series of charts and tables suitable for the use of designing engineers and for purposes of general reference. The absolute system of coefficients has been used, since it is thought by the National Advisory Committee for Aeronautics that this system is the one most suited for international use, and yet is one for which a desired transformation can be easily made" (p. 423).

"This investigation is an extension of NACA report no. 75 for the purpose of studying the effect of various modifications in a given wing section, including changes in thickness, height of lower camber, taper in thickness, and taper in plan form with special reference to the development of thick, efficient airfoils. The method consisted in testing the wings in the NACA 5-foot wind tunnel at speeds up to 50 meters (164 feet) per second while they were being supported on a new type of wire balance. Some of the airfoils developed showed results of great promise" (p. 521).

This report is Section two of a series of reports on aeronautic instruments (Technical Report nos. 125 to 132, inclusive). This section discusses briefly barometric altitude determinations, and describes in detail the principal types of altimeters and barographs used in aeronautics during the recent war. This is followed by a discussion of performance requirements for such instruments and an account of the methods of testing developed by the Bureau of Standards. The report concludes with a brief account of the results of recent investigations. For accurate measurements of altitude, reference must also be made to thermometer readings of atmospheric temperature, since the altitude is not fixed by atmospheric pressure alone. This matter is discussed in connection with barometric altitude determination.

Part 1 contains a discussion and description of the various types of air speed measuring instruments. The authors then give general specifications and performance requirements with the results of tests on air speed indicators at the Bureau of Standards. Part 2 reports methods and laboratory apparatus used at the Bureau of Standards to make static tests. Methods are also given of combining wind tunnel tests with static tests. Consideration is also given to free flight tests. Part 3 discusses the problem of finding suitable methods for the purpose of measuring the speed of aircraft relative to the ground.

Part one points out the adequacy of a consideration of the steady state gyroscopic motion as a basis for the discussion of displacements of the gyroscope mounted on an airplane, and develops a simple theory on this basis. Part two describes a new type of stabilizing gyro mounted on top of a spindle by means of a universal joint, the spindle being kept in a vertical position by supporting it as a pendulum of which the bob is the driving motor. Methods of tests and the difficulties in designing a satisfactory and reliable compass for aircraft use in considered in part three. Part four contains a brief general treatment of the important features of construction of aircraft compasses and description of the principal types used.

Part 1 gives a general discussion of the uses, principles, construction, and operation of airplane tachometers. Detailed description of all available instruments, both foreign and domestic, are given. Part 2 describes methods of tests and effect of various conditions encountered in airplane flight such as change of temperature, vibration, tilting, and reduced air pressure. Part 3 describes the principal types of distance reading thermometers for aircraft engines, including an explanation of the physical principles involved in the functioning of the instruments and proper filling of the bulbs. Performance requirements and testing methods are given and a discussion of the source of error and results of tests. Part 4 gives methods of tests and calibration, also requirements of gauges of this type for the pressure measurement of the air pressure in gasoline tanks and the engine oil pressure on airplanes. Part 5 describes two types of gasoline gauges, the float type and the pressure type.

This report outlines briefly the methods of aerial navigation which have been developed during the past few years, with a description of the different instruments used. Dead reckoning, the most universal method of aerial navigation, is first discussed. Then follows an outline of the principles of navigation by astronomical observation; a discussion of the practical use of natural horizons, such as sea, land, and cloud, in making extant observations; the use of artificial horizons, including the bubble, pendulum, and gyroscopic types. A description is given of the recent development of the radio direction finder and its application to navigation.

This report contains statements as to amount of oxygen required at different altitudes and the methods of storing oxygen. The two types of control apparatus - the compressed oxygen type and the liquid oxygen type - are described. Ten different instruments of the compressed type are described, as well as the foreign instruments of the liquid types. The performance and specifications and the results of laboratory tests on all representative types conclude this report.

While the reliability of predictions is poor the author still attempts to gauge the future speeds of airplanes.

In an investigation described in NACA Technical Report 110, it was shown that under certain conditions, particularly for the relatively low-speed flight of airships, the data obtained were not sufficiently accurate. This report describes an investigation in which the data obtained were sufficiently accurate and complete to enable the viscosity correction to be deduced quantitatively for a number of the air-speed pressure nozzles in common use. The report opens with a discussion of the theory of the performance of air-speed nozzles and of the calibration of the indicators, from which the theory of the altitude correction is developed. Then follows the determination of the performance characteristics of the nozzles and calibration constants used for the indicators. In the latter half of the report, the viscosity correction is computed for the Zahm Pitot-venturi nozzles.

Topographic map of a portion of Texas from the United States Geological Survey (USGS) project. The map includes towns, historic or notable sites, bodies of water, and other geologic features. Scale 1:62500

From Introduction: "The analyses given in this bulletin are of samples of delivered coal. This bulletin gives the results of analyses of samples delivered coal collected from July 1, 1915 to January 1, 1922."

From Introduction: "This chapter indicates the methods of determining several of the alloy metals when occurring together in the same sample. Most materials seldom contain more than two or three of these elements, but considerable time may be saved if determinations can be combined. Details of the analyses and separations are not given here, as they have been covered more fully in other chapters. Whenever possible, reference is made to the particular chapter. Only sufficient directions have been given to outline the method of procedure, actual conditions for the separations being presented on other pages."

Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, Congressional report, summaries of the committee's activities and research accomplished, and expenditures.

Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, congressional report, summaries of the committee's activities and research accomplished, and expenditures.

The report gives, rather briefly, in part one an introduction to hydrodynamics which is designed to give those who have not yet been actively concerned with this science such a grasp of the theoretical underlying principles that they can follow the subsequent developments. In part two there follows a separate discussion of the different questions to be considered, in which the theory of aerofoils claims the greatest portion of the space. The last part is devoted to the application of the aerofoil theory to screw propellers. A table giving the most important quantities is at the end of the report. A short reference list of the literature on the subject and also a table of contents are added.

Topographic map of a portion of Texas from the United States Geological Survey (USGS) project. The map includes towns, historic or notable sites, bodies of water, and other geologic features. Scale 1:62500

Report giving instructions for designing and building barns for cattle. Considerations include the location, size, arrangement, and ventilation of barns. Different barn designs are provided.

This report describes the theory of calculating the principal stresses in the envelope of a nonrigid airship used by the Bureau of Aeronautics, United States Navy. The principal stresses are due to the gas pressure and the unequal distribution of weight and buoyancy, and the concentrated loads from the car suspension cables. The second part of the report deals with the variations of tensions in the car suspension cables of any type of airship, with special reference to the rigid type, due to the propeller thrust or the inclination of the airship longitudinally.

From Introduction: "This bulletin is the sixth in the series of petroleum bibliographies published by the Bureau of Mines, Bulletins 149, 165, 180, 189, and 216 being compilations for the years 1915, 1916, 1917, 1918, and 1919-20 respectively. In this bulletin the same general plan has been followed in arranging the references, but one or two additions have been made in the classification."

Report issued by the Bureau of Mines consisting of bibliographies for petroleum bulletins. The bibliographies for bulletins published between 1919 and 1920 are presented.

In presenting this bulletin to the public it is the desire of the Department of Agriculture to furnish cotton growers of the state such information as to the best methods of fighting the boll weevil, as scientific investigation have discovered.

From Forward: "The first edition of the record setting forth the history of the boundaries of the United States and the several States and Territories was prepared by Henry Gannett, assisted by Franklin G. Butterfield, and was published as Bulletin 13 of the United States Geological Survey in 1885. The present bulletin is a revision and enlargement of Bulletin 226 and includes additional matter incidentally connected with boundaries."