It is sufficient to consider only the equations of motion of the towed body whereas those of the cable may be left out of consideration. The result obtained makes it possible to determine which factors affect the critical velocity and what modifications of the instrument are necessary for extending the upper limit of that velocity.

Circular presenting a description of the Hanriot-Biche 110 C1 airplane, which is a French all-metal low-wing pursuit monoplane. Details regarding the wing, girders and tail surfaces, pilot's cockpit, power plant, landing gear, flying qualities, and photographs are provided.

Circular presenting a description of the Comte A.C. 3, which is a high-wing monoplane with tow tandem 600 hp Hispano-Suiza engines mounted above the fuselage. Details of the design, fuel tanks, fuselage, pilot seating, engine, wings, safety factors, and flight qualities are provided.

Circular presenting a description of the Bernard 80 aircraft. Details are provided on the body shape, wings, ribs, fuel requirements, and flight characteristics.

Circular describing the Comper Streak single-seat low-wing cantilever monoplane. Details of the fuselage, construction, wing, stabilizer, engine, landing gear, characteristics, drawings, and photographs are provided.

Circular presenting a description of the Farman night bombers 211 and 212, which are four-engine high-wing monoplanes that are equipped with different engines. Details of the wing structure, fuselage, tail surface and controls, landing gear, power plant, characteristics, performance, drawings, and photographs are provided.

This report will present ideas closely related to the vortex conception and illustrate them in the simplest possible terms. In addition to these general considerations, this report will attempt to show the application of the vortex theory in connection with the wing theory.

Memorandum presenting an investigation to determine the variations in the velocity of the air when it was obliged to flow about a wing profile. Special interest was paid to the determination of velocity as compared with that of the undisturbed flow and of the velocity drop in successive planes perpendicular to the flow direction at increasing distances from the wing profile.

Results of an investigation wherein the change of the normal force coefficient with Reynolds Number was obtained statically for a 15.5-centimeter hemispherical cup.

Circular presenting a description of the Caproni 90 P.B., which is the largest airplane in existence at the time of the report. Details of the weight, construction, wings, controls, fuselage, tail, landing gear, flying qualities, and photographs are provided.

Circular presenting a description of the Mono-Spar light airplane, which is a small twin-engined low-wing cabin monoplane. A description of the design, structural features, characteristics, flying qualities, photographs, and drawings are provided.

"This thesis presents the method of moment distribution modified to include the effect of axial load upon the bending moments. This modification makes it possible to analyze accurately complex structures, such as rigid fuselage trusses, that heretofore had to be analyzed by approximate formulas and empirical rules. The method is simple enough to be practicable even for complex structures, and it gives a means of analysis for continuous beams that is simpler than the extended three-moment equation now in common use" (p. 1).

Circular describing the Avro Commodore, which is a cabin biplane of metal construction that is designed for comfort rather than performance. Details regarding the fuselage, wings, landing gear, controls, characteristics, drawings, and photographs are provided.

Report issued by the U.S. Bureau of Mines on studies of the known natural gas reserves in central Michigan sandstone deposits. The geology and methods used to estimate the reserves are presented. This report includes tables, illustrations, and maps.

Report issued by the U.S. Bureau of Mines on the oil and gas production of the Eunice oil field in southeastern New Mexico. Properties of the oil field, and analysis of the oil and gas produced are presented. This report includes tables, maps, illustrations, and photographs.

Report issued by the U.S. Bureau of Mines on the leaching of copper ores. The different strengths and cycles of solvents to extract impurities from the ore are presented. This report includes tables and graphs.

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

The following discussion is at first restricted to the light-oil engines now in use. We shall consider how far it is possible to reduce fire hazards by changes in the design of the engines and carburetors and in the arrangement of the fuel pipes.

The present report gives the results of tests which were made for the purpose of solving the problem of whether diagrams obtained from pressure tests could be conclusive for the determination of the safe impact coefficients. It is first established that the rubber rings adhere firmly to the compression surfaces during deformation. Suggestions are thus obtained for a constructive simplification of the rubber rings. The hysteresis phenomenon is ascribed to external and internal friction forces. A device for falling tests is then described with which the process of shock absorption with rubber rings was tested.

This report deals first with the fundamental data required for the investigation. These are chiefly the aerodynamic forces and moments acting on an airplane in a flat spin. It is shown that these forces and moments depend principally on the angle of attack and on the rotation about the path axis, and can therefore either be measured in a wind tunnel or calculated from wind-tunnel measurements of lift, drag and moment about the leading edge of the wing of an airplane model at rest.

The downwash velocity distribution behind the wing was determined for the free jet and for the closed tunnel of both circular and elliptic cross sections. The wing was placed at the center of the tunnel. The theory makes it possible to determine the downwash at any point in the jet. The computations were performed for points in the plane determined by the jet axis and the center-of-pressure line of the wing.

"In this report are presented the results of wind-tunnel tests of retractable spoilers on the upper surface of a Clark Y wing, which have been made as part of an investigation of lateral control devices being conducted by the National Advisory Committee for Aeronautics. Spoilers with chords up to 15.0 percent of the wing chord were tested in several locations on a plain rectangular wing and in two locations on the same wing equipped with a 20.0 percent chord split flap down 60 degrees. Charts are given for four representative angles of attack from which values of rolling- and yawing-moment coefficients may be obtained for spoilers up to 15.0 percent chord located on the upper surface of a Clark Y wing" (p. 1).

"NACA model 11-C was tested with four different depths of step to obtain information as to the effect of the depth of step on the water performance. The depths of step were selected to cover the practicable range of depths and in each case the included angle between the forebody and afterbody keels was kept the same 6-1/2 degrees. Small depths of step were found to give lower resistance at speeds below and at the hump speed of the model and greater depths of step lower resistance at high speeds" (p. 1).

"Wind-tunnel and flight tests have been made of a Fairchild 22 airplane equipped with a wing having external-airfoil flaps that also perform the function of ailerons. Lift, drag, and pitching-moment coefficients of the airplane with several flap settings, and the rolling- and yawing-moment coefficients with the flaps deflected as ailerons were measured in the full-scale tunnel with the horizontal tail surfaces and propeller removed. The effect of the flaps on the low speed and on the take-off and landing characteristics, the effectiveness of flaps when used as ailerons, and the forces required to operate them as ailerons were determined in flight" (p. 1).