"In order to find an airfoil for a predetermined pressure distribution, the problem must be posed so that the pressure distribution creates no drag. Another fundamental difficulty is that it is impossible to specify a pressure distribution without first knowing the place where these pressures are to be applied, i.e., the wing-section shape. This difficulty may be avoided by directing the pressure distribution along the contour of the wing section. Then it becomes possible to define the change in wing-section shape which effects a certain modification of the wing-section shape" (p. 1).

"The stability of an airplane can be easily determined by wind-tunnel tests, especially by simple tests with models mounted wind-vane fashion. However, each stability curve plotted by this method is valid only for a certain setting of the corresponding control surface, i.e., it characterizes the stability of the airplane with the control stick in a given position. The problems thus defined are studied from the point of view of longitudinal and transverse stability. Directional stability is not included in this study" (p. 1).

This report analyzes the action of a cantilever T beam with a tension flange so thin it can only carry tensile stresses.

The present report is a description of systematic tests at maximum lift on airfoils with and without split flap and of profile drag at low lift. In order to obtain an opinion as to the suitability of the airfoils with flaps, the maximum-lift measurements were repeated on airfoils with split flaps. The profile drag at low lift was arrived at by direct weighing and momentum measurements and, since the profiles were of unusual depth, extended to large Reynolds numbers.

The models designated "Torino 30, 31, 32" are horizontal tail surfaces of rectangular, triangular, and elliptical plan form and all of the same profile section. Tests were carried out with the object being to determine the effect of the propeller slipstream on the aerodynamical characteristics of the horizontal stabilizer. The results presented correspond to a first series of tests made without an interposed wing and in which the distance between the plane of the propeller disk and the tail was maintained constant.

This report was made to study the velocity distribution in an open, in a partially open, and in a partially expanding jet. The open-jet observations reveal minor systematic discrepancies from Tollmien's theoretical velocity distribution. The shearing-stress distribution for the partially open jet was determined. The value derived for the ratio of mixing distance to jet width was found to be in close agreement with the corresponding value for the open-jet boundary.

The object of the present paper is to consider the interaction of engine, propeller, and airplane for the low-power range. The discussion is presented in a form so as to provide the engine builder with a basis in his selection in the type of engine required, a suitable selection being possible only in connection with considerations on the best possible propeller.

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.

"To investigate the process of ignition and combustion in the case of spray injection into heated air, a new form of apparatus is developed and the tests carried out with it described. Photographs of the spray before and after ignition are obtained at frequencies of 500 pictures per second. Pressures and temperatures are simultaneously recorded on oscillograms. Information on the initial conditions, ignition time lag, period of complete combustion, place where ignition starts, and general course of the combustion is obtained" (p. 1).

"A number of German airplanes have a gap between elevator and stabilizer. The effect of this open space is not generally known, although English wind-tunnel experiments have shown that even a very small gap exerts a profound influence on the elevator action. The purpose of the present free-flight measurements is to ascertain whether fairing over the gap would actually result in an appreciable improvement" (p. 1).

In the following report a complete theory of twisting failure by the energy method is developed, based on substantially the same assumptions as those employed by Wagner and Bleich. Problems treated in detail are: the stress and strain condition under St. Venant twist and in twist with axial constraint; the concept of shear center and the energy method for problems of elastic stability.

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.

The report contains a description of the DVL wind tunnel. According to the cones fixed, an elliptical stream with axes 5 by 7 meters and length 9 meters, or a stream 6 by 8 meters in cross section and 11 meters in length is available. The top speed with the smaller cone is 65 meters per second. The testing equipment consists of an automatic six-component balance and a test rig for propellers and engines up to 650 horsepower.

"An investigation is made of the mutual interference of the wings of a biplane under the general assumption that each wing may be replaced by a vortex system of the type given by the Prandtl wing theory. The additional velocities induced at each wing by the presence of the other are determined by the Biot-Savart law and converted into an equivalent change in the angle of attack, the effect being that of an additional twist given to the wings in changing their lift distributions. The lift distributions computed in this manner for several airplane types are compared with the results of measurement" (p. 1).

"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).

"Proceeding from the basic assumptions of the Batho-Bredt theory on twisting failure of thin-walled columns, the discrepancies most frequently encountered are analyzed. A generalized approximate method is suggested for the determination of the disturbances in the stress condition of the column, induced by the constrained warping in one of the end sections" (p. 1).

"Development of a method for calculating the volumetric efficiency of piston engines with intake pipes. Application of this method to the scavenging pumps of two-stroke-cycle engines with crankcase scavenging and to four-stroke-cycle engines. The utility of the method is demonstrated by volumetric-efficiency tests of the two-stroke-cycle engines with crankcase scavenging. Its practical application to the calculation of intake pipes is illustrated by example" (p. 1).

This report presents a detailed analysis and history of the construction and operation of the aeronautical laboratory of the Stockholm Technical Institute. Engines and balances are discussed and experimental results are also given.

Test equipment is described that includes a system of three quartz indicators whereby three different pressures could be synchronized and simultaneously recorded on a single oscillogram. This equipment was used to test the reliction of waves at ends of valve spring, the dynamical stress of the valve spring for a single lift of the valve, and measurement of the curve of the cam tested. Other tests included simultaneous recording of the stress at both ends of the spring, spring oscillation during a single lift as a function of speed, computation of amplitude of oscillation for a single lift by harmonic analysis, effect of cam profile, the setting up of resonance, and forced spring oscillation with damping.

"Various methods have been proposed for determining the inherent stresses in structural components by disturbing their stress equilibrium through a mechanical device and measuring the resulting deformations. The methods used have disadvantages because they can be used only with specially shaped pieces (those with round or rectangular cross sections), that every form of test piece requires another kind of injury and hence of calculation, and the tested parts are rendered useless. The new test method, which seeks to eliminate these disadvantages, is likewise based on a disturbance of the equilibrium of forces, and indeed by drilling a hole which, however, is so small that the part can be used again" (p. 1).

"On the basis of a systematic investigation of Gottingen wind-tunnel data on Joukowski type and related airfoils, it is shown in what manner the profile drag coefficient is dependent on the lift coefficient. The individual factors for the construction of the profile drag polars are given. They afford a more accurate calculation of the performance coefficients of airplane designs than otherwise attainable with the conventional assumption of constant drag coefficient" (p. 1).

The Rateau supercharger investigated had, under normal operating conditions, an adiabatic efficiency of 52 percent, the CINA constant-pressure altitude being 6,240 m and the corresponding CINA compression ratio being 2.22. In order to understand the flow conditions in the supercharger, the air velocities at various points, the theoretical delivery heads and a few characteristics were calculated.

Providing information that will make possible a favorable compromise between landing impact and planing resistance is the immediate problem in experimental float development. A description of equipment to perform dropping tests are included as well as how to determine the landing impact.

The apparatus consists of a universal balance with transmission at variable speeds from 300 to 5,000 rpm and a group directly coupled to the model for speeds of 5 to 30,000 revolutions. This new apparatus was also designed with a torsion meter for measuring the torque. Tests were conducted on the effect of the angle between the propeller axis and the wind direction. The results presented correspond to a first series of tests made without an interposed wing and in which the distance between the plane of the propeller disk and the tail was maintained constant.