The most important factors in evaluating performance of gliders are minimum sinking speed and minimum gliding angle. To assure their optimum value the energy necessary for flight, that is, the energy of lift and friction must be kept very low, or in other words, weight and total drag which have a decisive effect on the sinking speed and on the gliding angle, must be kept to a minimum. How great the effect of a reduction of these two quantities will be shown in the following.

The rules and regulations for the International Touring Competition are presented as well as the technical characteristics that proved advantageous for the successful competitors.

Report discussing a description of the balance in the Aachen wind-tunnel.

"On the premise of a rectangular velocity wave arriving at the valve, the equation of motion of a spring-loaded valve stem is developed and analyzed. It is found that the stem oscillates, the oscillation frequency being consistently above the natural frequency of the nozzle stem alone, and whose amplitudes would increase in the absence of damping. The results are evaluated and verified on an example" (p. 1).

"This report presents the results of an investigation to determine the behavior of dural strip with flanged holes in the center when subjected to shear stresses. They buckle under a certain load just as a flat sheet. There is one optimum hole spacing and a corresponding buckling load in shear for each sheet width, sheet thickness, and flange form. Comparison with non-flanged sheets revealed a marked increase of buckling load in shear due to the flanging and a slightly greater displacement" (p. 1).

"The author gives a survey of the principles of stress analysis and design of airplane structures, and discusses the fundamental strength specifications and their effect on the stress analysis as compared with the safety factors used in other branches of engineering" (p. 1).

"The change of induced wing drag due to the field of flow of the propeller was analyzed quantitatively. The field of flow of the propeller is represented by a uniform distribution of sinks over the propeller disk area, whose strength is determined by the increase in speed in the slipstream. The superposition of this sink flow on the basic flow reproduces the actual field of flow outside of the slipstream with close approximation" (p. 1).

This report presents a detailed examination of the factors that went into the design of the Stipa monoplane. The model tested in the wind tunnel was made dissymmetrical externally, in order to produce a lift even at an angle of attack of 0 degrees with respect to the longitudinal axis of the tube.

From Summary: "The purpose of this investigation was to explore the influence of weights of the controls on the stability with elevator released. The available test data were extended to stability with elevator locked. In this connection the study of the propeller effect seemed of vital importance."

"The rudder effect of a sport airplane at high angles of attack was to be improved. This made it necessary to make a cut-out in the center of the continuous elevator so as to enlarge the rudder downward. This cut-out which reduced the rudder area by 12.5 percent changed the static stability of the airplane as well as the elevator effect" (p. 1).

"This report describes the equipment and method developed for recording the boundary layers on the surface of an airfoil in free flight. The results are in close agreement with the wind-tunnel tests of other experimenters. The intensity of the turbulent boundary layer, even at the much higher Reynolds Numbers reached, is determinable with Gruschwitz's formulas, although it was impossible to definitely establish a direct relationship between the turbulent boundary layer and the Reynolds Number within the limits of the obtained accuracy. The observations on the transition from laminar to turbulent flow check with previous wind-tunnel tests and calculations" (p. 1).

"Following a qualitative discussion of the complicated process involved in a short-period, longitudinal force applied to an originally not quite straight bar, the actual process is substituted by an idealized process for the purpose of analytical treatment. The simplifications are: the assumption of an infinitely high rate of propagation of the elastic longitudinal waves in the bar, limitation to slender bars, disregard of material damping and of rotatory inertia, the assumption of consistently small elastic deformations, the assumption of cross-sectional dimensions constant along the bar axis, the assumption of a shock-load constant in time, and the assumption of eccentricities on one plane" (p. 1).

The problem of autorotation has been attacked by various authors, in particular Fuchs and Schmidt who applied the so-called strip method which is based upon the assumption that the forces and moments per unit length acting in each section of the wing are equal to those on an infinite cylindrical wing of equal section in an air flow of intensity and direction resulting from the apparent relative motion of this section with respect to the surrounding air. In other words they disregarded the induced velocities, which, however, are of such importance that their omission is bound to result in appreciable errors, as we attempt to prove in this report.

"Following the development of the well-known differential equations of the problem and their resolution for failure in tension, the bending (transverse) oscillations of an originally not quite straight bar hinged at both ends and subjected to a constant longitudinal force (shock load) are analyzed. To this end the course of the bar form is expanded in a sinusoidal series, after which the investigation is carried through separately for the fundamental oscillation and the (n-1)the higher oscillations. The analysis of the fundamental oscillation distinguishes three cases: shock load lower, equal to, or higher than the Eulerian load" (p. 1).

This report details the designs of high-speed aircraft from various countries from 1931 on, with special emphasis on the United States and Germany.

This report details the design and construction of the Heinkel 70 mailplane and its comparison with the Lockheed "Orion".

"The present report gives a method for computing the torsion of boxes with thin shear-resistant or simply tension-resistant walls under any torsional load, support and dimension. The final stress condition is developed from that of a principal system with unconstrained sectional warping corresponding to Bredt's formula and an additional stress condition due to constrained cross-sectional warping. This is computed by means of the deflection condition of the principal system from a statically indeterminate calculation" (p. 1).

The discussion of the structural methods for obtaining lateral stability discloses the remarkable influence of the constant fuselage and wing proportions to the yawing moments. For the effectiveness of modifications in vertical tail surfaces and tail length, these quotas - little observed heretofore, in this connection - are decisive. This also applies to the amount of dihedral of the wing with regard to the roll stability of the complete wing already existing without angle of the dihedral.

This report was undertaken to give a brief summary of the laws governing the fatigue stresses and of the most important strength coefficients necessary for the correct dimensioning of the structural members. With consideration of the known fatigue strengths, the most important of which for airplane and engine materials are included in the paper, the fatigue strength of the structural parts can at least be approximately estimated.

In connection with the DVL Report 272 on the theory of the lateral stability of airplanes, the formal results are here amplified in some respects and their technical significance again briefly explained. Three numerical examples show how model tests for checking the lateral stability are to be evaluated and supplemented, if necessary, and how the stability limits depend on the design of the airplane and on the conditions of flight.

"This investigation treats the conversion of energy in conically divergent channels with constant opening ratio and half included angle of from 2.6 to 90 degrees, the velocity distribution in the entrance section being varied from rectangular distribution to fully developed turbulence by changing the length of the approach. The energy conversion is not completed in the exit section of the diffuser; complete conversion requires a discharge length which depends upon the included angle and the velocity distribution in the entrance section. Lastly, a spiral fan was mounted in the extreme length and the effect of the spiral flow on the energy conversion in the cross-sectional divergence explored" (p. 1).

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.

A previous report discusses the experimental program of a systematic exploration of all questions connected with the planing problem as well as the first fundamental results of the investigation of a flat planing surface. The present report is limited to the conversion of the model test data to full scale.

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.