The limitation of the 1929 contest to performance gliders necessitated the establishment of a formula which would make it possible to distinguish between performance gliders and school and training gliders. The sinking speed was therefore adopted as the basis for such a distinction, and the requirement was made that the sinking speed of a performance glider should not exceed 0.8 m/s. The rest of the report details the different entries with regard to design and performance.

Report presenting testing in the full-scale wind tunnel on a model of a large 4-engine monoplane to determine the overall aerodynamic efficiency of a conventional wing-nacelle-engine installation as compared with power-plant installations enclosed in the wing with extension shafts to the propellers. Results regarding power-on and power-off performance for the installations as well as propeller noise are provided.

"The effect on airfoil characteristics of surface roughness of varying degrees and types at different locations on an airfoil was investigated at high values of the Reynolds number in a variable density wind tunnel. Tests were made on a number of National Advisory Committee for Aeronautics (NACA) 0012 airfoil models on which the nature of the surface was varied from a rough to a very smooth finish. The effect on the airfoil characteristics of varying the location of a rough area in the region of the leading edge was also investigated" (p. 1).

"The main purpose of this investigation is to make available to the designer useful information with regard to the aerodynamic drag of various types of flying-boat hull models. The present report is the first in a series covering investigation in this field. Through close cooperation between hydrodynamics and aerodynamics divisions it is hoped that results leading to improvements in hull design obtained" (p. 1).

Progress in the scientific and practical fields of aviation has caused the Swiss Institute of Technology to organize lectures and practical training courses in all three branches of aeronautics and to found centers of scientific research, laboratories, etc., in order to supply the government and industries with scientifically and technically trained engineers.

This report presents the results of an investigation undertaken to determine the feasibility of making glide landings in gusty air. Wind velocities were measured at several stations between the ground and a height of 51 feet, and flight tests were made to determine the actual influence of gusts on an airplane gliding close to the ground.

"This paper deals with the analysis of 2-spar cantilever wings in torsion, taking cognizance of the fact that the spars are not independent, but are interconnected by ribs and other structural members. The principles of interaction are briefly explained, showing that the mutual relief action occurring depends on the "pure torsional stiffness" of the wing cross section. Various practical methods of analysis are outlined" (p. 45).

Report presents an analysis of the factors that determine the periodic twist of a rotor blade under the action of the air forces on it. The results of the analysis show that the Fourier coefficients of the twist are linear expressions involving only the tip-speed ratio, the pitch setting, the inflow coefficient, the pitching-moment coefficient of the blade airfoil section, and the physical characteristics of the rotor blade and machine.

Based upon Kirchoff's theory of free jets the flow through different screen arrangements of flat plates, as chiefly encountered with turbines in the cavitation zone is defined. It is shown by experiments that these theoretical results are very well representative in most cases of the conditions of discharge from water in air and consequently by cavitation. In addition, the experiments reveal a picture of the discrepancies between the actual flow and the theory of discharge of air in air (of water in water without cavitation).

"The problem of the skin-stringer combinations used as axially loaded panels or as covers for box beams is considered from the point of view of the practical stress analyst. By a simple substitution the problem is reduced to the problem of the single-stringer structure, which has been treated in NACA Report no. 608. The method of making this substitution is essentially empirical; in order to justify it, comparisons are shown between calculations and strain-gage tests of three beams tested by the author and of one compression panel and three beams tested and reported elsewhere" (p. 469).

The system of linear differential equations which indicated the approach of separation and the so-called "boundary-layer thickness" by Gruschwitz is extended in this report to include the case where the friction layer is subject to centrifugal forces. Evaluation of the data yields a strong functional dependence of the momentum change and wall drag on the boundary-layer thickness radius of curvature ratio for the wall. It is further shown that the transition from laminar to turbulent flow occurs at somewhat higher Reynolds Numbers at the convex wall than at the flat plate, due to the stabilizing effect of the centrifugal forces.

The tendency toward economy of material and lightness of structure has long since led to the increased application of beams having large ratios of moment of area W to cross-sectional area F. This paper tries to provide an answer to how thin the beams can be.

Circular presenting a description of the Boulton and Paul P.64 high-performance mail-carrier. It is a two-engine tractor biplane that has been designed to give the specified normal speed with each engine throttled down to approximately half its output. Details of the landing gear, structural features, pilots' compartment, accommodation for mails, controls, power plant, and some flying qualities are provided.

Circular presenting a description of the C.A.M.S. 60, which is a twin-engine monoplane with a medium-thickness wing and two floats. Details of the wings, engines, fuselages, floor, rear cabin, floats, and flying qualities are provided.

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.

Circular presenting a description of the Caudron P.V. 200 touring amphibian, which is a two-place cantilever monoplane with folding wings and dual controls. Details of the wing, fuselage, controls, landing gear, flying qualities, and photographs are provided.

"According to Mr. L.D. Bell, of the Consolidated Aircraft Corporation, certain undesirable spinning characteristics of a commercial airplane were eliminated by the addition of a filler to the forward part of the wing to give it a sharp leading edge. To ascertain what aerodynamic effects result from such a change of section, two airfoils having sharp leading edges were tested in the variable-density wind tunnel. Both sections were derived by modifying the Gott. 398. The tests, which were made at a large value of the Reynolds Number, were carried to very large angles of attack to provide data for application to flight at angles of attack well beyond the stall" (p. 1).

In this report charts are given showing the relation between time, velocities, and altitude for airplanes having various terminal velocities diving in a standard atmosphere. The range of starting altitudes is from 8,000 to 32,000 feet, and the terminal velocities vary from 150 to 550 miles per hour. A comparison is made between an experimental case and the results obtained from the charts. Examples pointing out the use of the charts are included.

"The present paper describes a device whereby rapid flame movement within an internal-combustion engine cylinder may be recorded and determined. By the aid of a simple cylindrical contact and an oscillograph the rate of combustion within the cylinder of an airplane engine during its normal operation may be measured for gas intake velocities of from 30 to 35 m/s and for velocities within the cylinder of from 20 to 25 m/s. With it the influence of mixture ratios, of turbulence, of compression ratio and kind of fuel on combustion velocity may be determined" (p. 1).

The air flow in combustion chambers is divided into three fundamental classes - induced, forced, and residual. A generalized resume is given of the present status of air flow investigations and of the work done at this and other laboratories to determine the direction and velocity of air movement in auxiliary and integral combustion chambers. The effects of air flow on engine performance are mentioned to show that although air flow improves the combustion efficiency, considerable induction, friction, and thermal losses must be guarded against.

A method is developed with no neglect of certain factors in mass flow of air and in the drag of the heated radiator, i.e., one under actual operating conditions, as compared with the corresponding values in the cold state, may be simply computed. Although a symmetrical duct radiator has been used to bring out the flow relations, the results apply equally as well to the unsymmetrical radiator shapes usual in airplane construction.

Measurements were made of the cooling on the fronts of model cylinders in a conventional cowling for cooling in both the ground and the cruising conditions. The mechanisms of front and rear cooling are essentially different. Cooling on the rear baffled part of the cylinders continually increases with increasing fin width. For the front of the cylinder, an optimum fin width was found to exist beyond which an increase in width reduced the heat transfer. The heat transfer coefficient on the front of the cylinders was larger on the side of the cylinder facing the propeller swirl than on the opposite side. This effect became more pronounced as the fin width was increased. These results are introductory to the study of front cooling and show the general effect of several test parameters.

This report gives formulas for analyzing the critical shear load of a simply supported square, isotropic (simple flat plate), or orthogonal anisotropic plate (a plate in which the rigidity in two directions perpendicular to each other is different, i.e. plywood or corrugated sheet), these formulas, although arrived at by approximation method, seem to agree fairly well with experimental results.

Following a summary of the multiplicity of domestic and foreign floats and a brief enumeration of the requirements of floats, the essential form parameters and their effect on the qualities of floats are detailed. On this basis a standard float design is developed which in model families with varying length/beam ratio and angle of dead rise is analyzed by an experimental method which permits its best utilization on any airplane.