"The present paper evaluates the shear buckling stresses of rectangular flat plates with simply supported edges more accurately than previous work on this problem. Both symmetric (odd number of buckles) and antisymmetric (even number of buckles) patterns were considered. A curve is presented from which the critical stresses may be obtained when the dimensions of the plate are known" (p. 1).

Presented here are the summary charts of the collapsed results of general tank tests of about 100 flying boat hull models. These summary charts are intended to be used as an engineering tool to enable a flying boat designer to grasp more quickly the significance of various hull form parameters as they influence his particular airplane. The form in which the charts are prepared is discussed in some detail in order to make them clearer to the designer. This is a data report, and no attempt has been made to produce conclusions or correlations of the usual sort. However, some generalizations are put forward on the various methods in which summary charts may be used.

Note presenting an investigation to compare the 14S-T with 24S-T in extruded stiffeners for stiffened flat sheet panels. The tests were made with stiffened flat sheet panels with three hat-shape stiffeners. Data is provided on the strength of the two alloys as well as the effect of sheet thickness on relative stiffener strengths.

Note presenting an investigation of the buckling of a simply supported rectangular flat plate under combinations of shear and direct stress by means of an energy method. The critical combinations of stress for several length-width ratios were determined to an accuracy of about 1 percent in conjunction with a modified matrix iteration method. Results regarding the shear and longitudinal stress and shear and transverse stress are provided.

Report presenting a series of tensile-strength and shear-strength tests made on age-hardened 17S-T rivets machine-countersunk in 75S-T sheets. The results of the tests indicated that the joints can be made satisfactorily with regard to both flushness and strength if the ratio of buck to diameter is kept to a certain value.

Note presenting the utilization of an extended form of the Ackeret iteration process to calculate the compressible flow at high subsonic velocities past an elliptical cylinder. The expression for the moment acting on the elliptical cylinder is derived and shows a first-step improvement of the Prandtl-Glauert approximation. A second-step improvement is obtained in the Prandtl-Glauert approximation for the lifting force acting on the elliptic cylinder.

Report presenting the results of a cooling investigation using an 18-cylinder, radial, air-cooled engine installed on a dynamometer test stand to determine the effects of exhaust pressure on the engine-cooling characteristics. Testing covered a wide variety of engine operating conditions.

Note presenting an investigation to determine the effect of exhaust pressure on the performance of an 18-cylinder air-cooled radial engine equipped with a conventional exhaust collector ring. The engine power increased at a diminishing rate as exhaust pressure decreased.

Note presenting a formula for the pressure distribution on an oscillating lifting surface of finite span under the assumption of a ratio of span to average chord that is not too small. It is found that the effect of three-dimensionality of the flow may be incorporated in the results of the two-dimensional theory by adding a correction factor to the basic function of the two-dimensional theory.

Note presenting a theoretical investigation made to determine the effect of the product-of-inertia terms in the lateral equations of motion on the lateral-stability boundaries. The product of inertia results from the inclination of the principal longitudinal axis of the airplane to the flight path. The results indicated that the product-of-inertia terms should be included in the lateral equations of motion to determine the lateral stability of an airplane.

Report presenting testing at Reynolds numbers up to 8,000,000 to determine the effectiveness of a reflex-cambered mean line in shifting the low-drag range of a sweptback wing without affecting the longitudinal stability. Two models were tested, one with symmetrical airfoil sections and one with a reflex-cambered mean line. Results regarding the effect of camber, roughness, and variation of aerodynamic characteristics with Reynolds number are provided.

Note presenting an approximate theory of the effect of slipstream rotation on the forces on a fuselage without a wing, which represents the slipstream rotation by the flow about a vortex aligned with the longitudinal axis. A wind-tunnel investigation was made primarily to check the predictions for the lateral force on a fuselage shaped as a body of revolution.

"A resume is given of an investigation of the influence of plastic deformation and of annealing temperature on the tensile and shear elastic properties of high strength nonferrous metals and stainless steels in the form of rods and tubes. The data were obtained from earlier technical reports and notes, and from unpublished work in this investigation. There are also included data obtained from published and unpublished work performed on an independent investigation" (p. 1).

Report describing experiments to determine the conditions that cause surging in compressors and to determine the effect of various installations and operating conditions on the character of the velocity and pressure variations occurring during surging. Surging was found to be a periodic variation of pressures and velocities that may occur when the slope of the compressor characteristic curve is positive.

Note presenting results of strain surveys around four reinforced circular cut-outs successively made in an axially loaded skin-stringer tension panel. Curves are presented which show the distribution of stringer and shear stresses in the panel and bending stresses in the reinforcing rings.

Report presenting information about a series of modifications incorporated into light airplanes to increase safety, including decreasing the wing incidence, increasing the wing washout, increasing the area and aspect ratio of the horizontal and vertical tails, moving the elevators out of propeller slipstreams, depressing the thrust axis, and limiting the rudder travel. The new inherent safety characteristics and effects on the airplane's performance are provided.

Report presenting an investigation at subsonic Mach numbers in the rectangular high-speed tunnel on five supersonic airfoils and, for comparison, on two subsonic airfoils. Two-dimensional data were obtained by pressure measurements and schileren photographs at angles of attack from 0 to 4 degrees for a range of Mach numbers between 0.30 and 0.90. Results regarding pressure distributions, normal-force coefficients, pitching-moment of normal-force about the quarter-chord point, drag coefficient, and unusual flow at high Mach numbers are provided.

Note presenting an analysis of nonviscous unsteady channel flow in order to gain some insight into instability resulting from shock-free deceleration in order to provide more information on the factors determining the minimum shock intensity for a stable flow and to study in general the formation and motion of shocks in channel flows.

Note presenting a frequency-response method for determining the critical control-gearing and hunting oscillations of airplanes with automatic pilots. The method is graphical and has several advantages over the standard numerical procedure based on Routh's discriminant. Several examples are worked out to illustrate the application of the frequency-response method in determining the effect of automatic-pilot lag or lead on critical control gearing and in determining the amplitude and frequency of hunting.

From Summary: "By means of the general solutions of the hodograph equations for compressible fluids, certain solutions corresponding to solutions of the hodograph equations of an incompressible fluid are used to find flow patterns of compressible fluids. When the adiabatic equation of state is used, only a general method is outlined. The method appears to lead to the solution of the problem of subsonic flows with circulation around arbitrary bodies, as the method of Theodorsen does for incompressible fluids."

Note presenting an investigation of a radial-inlet impeller based on two-dimensional-flow theory to establish correlation between flow theory and impeller performance. The simplifying assumptions of an infinite number of blades and an incompressible fluid were made for the impeller design. Results regarding performance characteristics based on standard overall measurements, performance characteristics based on static-pressure measurements, and hydraulic-efficiency characteristics are provided.

"A general description of the field operations of the U.S. Weather Bureau thunderstorm project conducted in the vicinity of Orlando, Florida during the summer month of 1946 is given. The participation of NACA in this project is described and measurements of atmospheric turbulence taken by NACA are presented for one of the flights. The results indicate that some regions of thunderstorms may present no great hazard to flight, while exceptionally severe conditions of atmospheric turbulence may occur in other regions, or even in the same region, at about the same time" (p. 1).

Note presenting an investigation to develop ceramic coatings that will prolong the life of alloys used in turbines, especially the blades, or permit their use at higher temperatures than would otherwise be predictable. Several steps were taken in order to establish whether or not protective coatings can be developed that will effect such an improvement.

"A method for determining the streamwise flow pattern of a nonviscous incompressible fluid about an oblique airfoil from the corresponding flow pattern about the airfoil in normal position is presented and illustrated in two examples. The method can be extended to account approximately for compressibility effects by applying the Prandtl-Glauert correction factor to the flow pattern that is normal to the leading edge of the airfoil. The method is expected to be useful in determining the shape of a fuselage or nacelle having a minimum of interference with the flow over a swept-back wing" (p. 1).