Circular presenting a description of the Bernard 120, which is a seaplane. Descriptions of the structural elements, engine, and fuel distribution system are provided.

Circular presenting a description of the Bleriot 110 which is a long-distance airplane mainly distinguished by its fineness and lightness. Details of the fuselage, shape, wing, and power plant are provided.

Circular presenting a description of the Wibault 280 T.10, which is an all-metal cantilever low-wing monoplane. The flight characteristics, design, blueprints, and photographs are provided.

Circular describing the Polish P.I and P.VIII airplanes, which are both all-metal gull-type wing monoplanes that differ in the type of engine used, their wing area, and their landing gears. Details of the components, design, differences, characteristics, load distribution, performance, drawings, and photographs are provided.

The stability conditions of Ente (duck) airplanes are investigated in this report. In developing the formulas, which afford an approximate solution, the unimportant effect of the height of the C.G. and the moment of the residual resistance are neglected. The effect of downwash from the forward horizontal empennage on the wing are also disregarded.

This report details the Elmira, New York soaring contest of 1930 and provides up-current maps, experiences in piloting, distance flights, and a few details on glider design.

Report issued by the Bureau of Mines over the Salt Flat fields in East Central Texas. As stated in the introduction, "this report deals with the development and production history of the Salt Flat field and gives comparative data on five outstanding fault fields. Two of these fields are producing from limestone and three from sandstone reservoirs" (p. 2-3). This report includes tables, maps, photographs, and illustrations.

Report issued by the U.S. Bureau of Mines on the coal mine related deaths during the month of February, 1931. The number of fatalities and the causes of each are presented. This report includes tables.

"The deformation of aircraft wings is measured by photographically recording a series of bright shots on a moving paper band sensitive to light. Alternating deformations, especially vibrations, can thus be measured in operation, unaffected by inertia. A handy recording camera, the optograph, was developed by the static division of the D.V.L. (German Experimental Institute for Aeronautics) for the employment of this method of measurement on airplanes in flight" (p. 1).

The variation of the coefficient of discharge with the length-diameter ratio of the orifice was determined for nozzles having single orifice 0.008 and 0.020 inch in diameter. Ratios from 0.5 to 10 were investigated at injection pressures from 500 to 5,000 pounds per square inch. The tests showed that, within the error of the observation, the coefficients were the same whether the nozzles were assembled at the end of a constant tube or in an automatic injection valve having a plain stem.

The first flights of the Oehmichen helicopter are detailed as well as various aspects of the construction.

Report issued by the U.S. Bureau of Mines discussing the mine stations and safety cars used to reach miners in distress. As stated in the report, "the purpose, equipment, personnel, and construction of its safety cars" is presented. This report includes an illustration, and a map.

This report deals with the theory of the vortex street which enables the reproduction of the mechanism of the form resistance with suitable approximation under stated conditions, although such a resistance is precluded in a fluid which is perfectly inviscid. Disregarding for the present the origination of the vortex, the stream attitude in the wake of the body may be described approximately correct by the representation of individual vortices, without transgressing the law governing the motion of such vortices in an ideal fluid. Another striking example is the theory of the induced drag of wings, which likewise shows the extent of applying the vortex equations without overstepping the bounds of the dynamics of ideal fluids.

This report presents an introduction to the extensive literature on turbulence, with especial consideration of L. Prandtl's theories.

"This report gives the results of pressure-distribution tests made to study the effects on lateral stability of changing the span-load distribution on a rectangular monoplane wing model of fairly thick section. Three methods of changing the distribution were employed: variation in profile along the span to a thin symmetrical section at the tip, twist from +5 degrees to -15 degrees at the tip, and sweepback from +20 degrees to -20 degrees. The tests were conducted in a 5-foot closed-throat atmospheric wind tunnel" (p. 567).

"In connection with the study of aircraft and propeller noises, the National Advisory Committee for Aeronautics has developed an instrument for sound-frequency analysis which differs fundamentally from previous types, and which, owing to its simplicity of principle, construction, and operation, has proved to be of value in this investigation. The method is based on the well-known fact that the Ohmic loss in an electrical resistance is equal to the sum of the losses of the harmonic components of a complex wave, except for the case in which any two components approach or attain vectorial identity, in which case the Ohmic loss is increased by a definite amount" (p. 605).

"Formulas are derived for computing the instantaneous pressures delivered by a fuel pump. The first derivation considers the compressibility of the fuel and the second, the compressibility, elasticity, and inertia of the fuel. The second derivation follows that given by Sass; it is shown to be the more accurate of the two. Additional formulas are given for determining the resistance losses in the injection tube" (p. 621).

This report presents the results of deceleration tests conducted for the purpose of determining the drag characteristics of six airships. The tests were made with airships of various shapes and sizes belonging to the Army, the Navy, and the Goodyear-Zeppelin Corporation. Drag coefficients for the following airships are shown: Army TC-6, TC-10, and TE-2; Navy Los Angeles and ZMC-2; Goodyear Puritan. The coefficients vary from about 0.045 for the small blunt airships to 0.023 for the relatively large slender Los Angeles. This variation may be due to a combination of effects, but the most important of these is probably the effect of length-diameter ratio.

"Data are presented on the kinematic viscosity, in the temperature range -50 degrees to +30 degrees C. of pure liquids and of solutions of animal oils, vegetable oils, mineral oils, glycerine, and ethylene glycol in various low freezing point solvents. It is shown that the thermal coefficient of kinematic viscosity as a function of the kinematic viscosity of the solutions of glycerine and ethylene glycol in alcohols is practically independent of the temperature and the chemical composition of the individual liquids. This is similarly true for the mineral oil group and, for a limited temperature interval, for the pure animal and vegetable oils. The efficiency of naphthol, hydroquinone, and diphenylamine to inhibit the change of viscosity of poppyseed and linseed oils was also investigated" (p. 679).

From Summary: "The pressure in the cabin of a Fairchild cabin monoplane was surveyed in flight, and was found to decrease with increased air speed over the fuselage and to vary with the number and location of openings in the cabin. The maximum depression of 2.2 inches of water (equivalent pressure altitude at sea level of 152 feet) occurred at the high speed of the airplane in level flight with the cabin closed."