Report presenting the Bureau of Mines' investigation into acid processes of extracting alumina. The paper discusses the sulphuric acid processes and other work with hydrochloric and nitric acids so that the comparative advantages can be appreciated.

Report discussing before proceeding to discuss the preparation of dope solutions, it will be necessary to consider some of the essential properties which should be possessed of a dope film, deposited in and on the surface of an aero fabric. The first is that it should tighten the material and second it should withstand weathering.

This report contains the aerodynamic properties of the wing sections U.S.A. 5, U.S.A. 27, U.S.A. 35 A, U.S.A. 35 B, Clark Y, R.A.F. 15, and Gottingen 387, as determined at various Reynolds numbers up to an approximately full scale value in the variable density wind tunnel of the National Advisory Committee for Aeronautics. It is shown that the characteristics of the wings investigated are affected greatly and in a somewhat erratic manner by variation of the Reynolds number. In general there is a small increase in maximum lift and an appreciable decrease in drag at all lifts.

This report presents a description of the design of the Cuatro Vientes wind tunnel.

In this report is described an experimental method which the writer has evolved for dealing with air-cooled engines, and some of the data obtained by its means. Methods of temperature measurement and cooling are provided.

From Summary: "The purpose of this test was to compare six well-known airfoils, the R.A.F 15, U.S.A. 5, U.S.A. 27, U.S.A. 35-B, Clark Y, and Gottingen 387, fitted to the Sperry Messenger model, at full scale Reynolds number as obtained in the variable density wind tunnel of the National Advisory Committee for Aeronautics; and to determine the scale effect on the model equipped with all the details of the actual airplane. The results show a large decrease in minimum drag coefficient upon increasing the Reynolds number from about one-twentieth scale to full scale. A comparison is made between the results of these tests and those obtained from tests made in this tunnel on airfoils alone."

Report discussing the air forces on a systematic series of biplane and triplane cellule models which are measured in the atmospheric density tunnel.

From Summary: "Tests have been made in the atmospheric wind tunnel of the National Advisory Committee for Aeronautics to determine the effects of pitching oscillations upon the lift of an airfoil. It has been found that the lift of an airfoil, while pitching, is usually less than that which would exist at the same angle of attack in the stationary condition, although exceptions may occur when the lift is small or if the angle of attack is being rapidly reduced. It is also shown that the behavior of a pitching airfoil may be qualitatively explained on the basis of accepted aerodynamic theory."

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, bibliographies, and financial report.

The calculations in this paper afford an approximate solution of the static stability. A derivation of the formulas for moment coefficient of a wing, moment coefficient of elevator, and the total moment of the combined wing and elevator and the moment coefficient with reference to the center of gravity are provided.

"The significance attaching to "column effect" in airplane wing spars has been increasingly realized with the passage of time, but exact computations of the corrections to bending moment curves resulting from the existence of end loads are frequently omitted because of the additional labor involved in an analysis by rigorously correct methods. The present report represents an attempt to provide for approximate column effect corrections that can be graphically or otherwise expressed so as to be applied with a minimum of labor. Curves are plotted giving approximate values of the correction factors for single and two bay trusses of varying proportions and with various relationships between axial and lateral loads" (p. 485).

This is an all metal aircraft, including the wing coverings. Both the framework and the sheet-metal coverings are Alferium, made by Schneider Co. A description of the wing, fuselage, landing gear, engines, fuel tanks, characteristics, drawings, and photographs are provided.

Circular describing the Avro Gosport 504 R, which is a new training airplane that is lighter than other Avro training airplanes but is strong enough to withstand rough handling that may be encountered in training. Details of the fuselage, construction, ailerons, tail, struts, landing gear, fuel tanks, performance, characteristics, and photographs are provided.

The Bluebird is a two seat, side by side biplane, designed primarily for training and pleasure flying. A description of the construction and flight characteristics is provided.

The Boeing Mail Airplane is a biplane with cloth covered wings of wood and wire construction, a top speed of 130 MPH, and a fuel capacity of 100 gallons in two tanks.

The building and flying of a glider is possible for anyone who can use a few basic tools. This report presents some plans and techniques for building your own glider.

I am now proposing a method for the preliminary approximate calculation of the thrust distribution and efficiency of air propellers under any operating conditions. Our task becomes the following, namely, to determine the speed relations and the forces developed on a section with a given direction and velocity of the air current, a problem which can be solved with the aid of the momentum theory.

The Caproni 73 is a biplane with medium thick wings, a rigid central section, and with each lateral extension forming a single cell and is powered by two 500 Isotta Fraschini "Asso" Engines.

This report presents the results of an investigation of the planing and get-away characteristics of three representative types of seaplanes, namely, single float, boat, and twin float. The experiments carried out on the single float and boat types have been reported on previously. This report covers the investigation conducted on the twin-float seaplane, the DT-2, and includes as an appendix, a brief summary of the results obtained on all three tests. At low-water speeds, 20 to 30 miles per hour, the seaplane trims by the stern and has a high resistance. Above these speeds the longitudinal control becomes increasingly effective until, with corresponding speeds of 56 to 46 miles per hour. It was further determined that an increase in the load caused little if any change in the water speed at which the maximum angle and resistance occurred, but that it did produce an increase in the maximum angle.

"This investigation was made for the purpose of determining the characteristics of five full-scale propellers in flight. The equipment consisted of five propellers in conjunction with a VE-7 airplane and a Wright E-2 engine. The propellers were of the same diameter and aspect ratio. Four of them differed uniformly in thickness and pitch and the fifth propeller was identical with one of the other four with exception of a change of the airfoil section" (p. 267).

Report examining the aerodynamic characteristics of three airfoil sections as determined in the variable density wind tunnel. Particular attention is given to the relation of the characteristics to the angle of attack and their use in airplane design.

The object of this report was to indicate that we frequently only make use of 50 percent of the maximum brake horsepower of the engine in taking off the ground, that this loss is not inevitable, and that the effort to get engines of low weight per horsepower by boosting revolutions is of very little use to bombers and commercial airplanes.

From Introduction and Summary: "This bulletin describes the third series of coal-dust explosion tests by the Bureau of Mines in its experimental mine and covers a period from 1919 to the end of 1924, inclusive. A few related tests made in 1925 are also included."

Report compiled by the U.S. Bureau of Mines including statistics on fatalities in coal mines located in the United States as well as data regarding the various operations (e.g., number of miners employed and average production). The information is organized into tables for comparison and the text draws some overall conclusions in the summary.