Report presenting knock testing of a sensitive fuel and a relatively insensitive fuel in a full-scale air-cooled cylinder. Six engine variables were investigated: fuel-air ratio, compression ratio, inlet-air temperature, spark advance, exhaust pressure, and cylinder temperature.

Note presenting three internally cooled exhaust valves with the same external dimensions but different throat designs were investigated to determine a method of obtaining increased coolant-flow area with increasing stresses. The valves were statistically loaded to simulate stresses in the throat region caused by valve closure.

"The theory of small disturbances is applied to the calculation of the pressure distribution and drag of a closed body of revolution traveling at supersonic speeds. It is shown that toward the rear of the body the shape of the pressure distribution is similar to that for subsonic flow. For fineness ratios between 10 and 15 the theoretical wave drag is of the same order as probable values of the frictional drag" (p. 1).

Report presenting the load capacities of four aluminum-alloy radial-engine crank-pin bearings determined in a centrifugal bearing test machine. Chemical analysis made after the bearings had been tested to failure showed that the actual composition of each aluminum alloy was different from the chemical specifications.

From Summary: "A method of increasing the compressive strength of 24S-T aluminum-alloy sheet by flexure rolling was investigated. In this method, the sheet was alternately bent and then straightened by rolling a four-step procedure. The results showed that the greatest increase was in compressive yield stress in the with-grain direction regardless of the direction of rolling; the increase was greater as the radius of flexure rolling became smaller and as the number of steps was increased. The tensile properties, however, were little affected."

Report presenting an investigation of the cooling of an 18-cylinder, twin-row, radial, air-cooled engine in a high-performance pursuit airplane for variable engine and flight conditions at a range of altitudes to provide a basis for predicting high-altitude cooling performance from sea-level or low-altitude test results.

Report presenting experiments to determine the shearing rigidity of curved panels under compression, particularly in that region of loading where the panels are in a buckled state. For the preliminary tests four, and for the final test series eight, circular cylinders were built of aluminum alloy sheet. Results regarding the uniformity of compressive strain, buckling of the panels, distribution of shear strain, calculation of the effective shear modulus, shear rigidity versus compressive strain curves, nondimensional shear rigidity curves, and failure of the cylinders are provided.

Report presenting testing regarding the effectiveness of ducted head baffles in reducing temperatures of rear-row exhaust-valve seats using a two-row radial engine. Two types of ducted head baffle were investigated on a test stand and the better of the two was tested in flight. Results regarding the preliminary test stand investigation with two baffles and a flight investigation on five rear-row cylinders are provided.

Note presenting the Izod-impact strengths and flexural properties of several types of plastic laminates, which are either in use or have potential application in aircraft structures and parts, and were determined at different temperatures. The materials investigated were unsaturated-polyester laminates reinforced with glass fabric and phenolic laminates reinforced with asbestos fabric, high-strength paper, rayon fabric, and cotton fabric.

Note presenting an investigation of the effects on the aerodynamic characteristics of skin wrinkles on the forward part of the upper surface of two NACA airfoils. The results showed that no appreciable change in normal-force or pitching-moment characteristics over the range of Mach numbers tested was noted. The drag was greater on the wrinkled sections than the smooth sections, however.

Report presenting a two-dimensional wind tunnel investigation for the purpose of developing a suitable double slotted flap on a 14-percent-thick modified NACA 66-series-type airfoil section. Section aerodynamic characteristics of the airfoil with various double-slotted-flap arrangements are presented. Results regarding the airfoil with the flap retracted and flap deflected are provided.

"Experiments by Deming at the Langley Memorial Aeronautical Laboratory confirm completely the formula of Gutin, which permits the convenient calculation of the sound level of any airplane propeller at low forward speeds. A simplification of the Gutin formula has been achieved by the use of a set of functions giving the sound level in the direction of maximum intensity. The sound level can be read from graphs of the functions for various numbers of blades and tip speeds. Two numerical examples and one experimental example are included; also, a radical fan-type propeller is tentatively treated" (p. 1).