Report presenting a theory regarding engine-cooling variables from a previous report, which was used as a basis for the development of a semi-empirical equation to correlate exhaust-valve temperature with engine conditions. Results regarding the determination of constants, influences of operating variables on mean effective gas temperatures, thermal-resistance factor, and accuracy of correlating equation are provided.

Report presenting pressure-distribution measurements obtained from the horizontal tail surfaces of the Curtiss P-40K airplane during low-speed pull-ups to abrupt stall in which tail buffeting was experienced. The chordwise load distributions during buffeting are similar to those experienced during angle-of-attack changes. The location of the stall and frequency of stall disturbances are also described.

Report discussing the use of variable-ratio geared tabs with an experimental elevator to improve stick-force characteristics in turning flight. The stick forces with the tabs were found to be satisfactory for a variety of center-of-gravity ranges. The ability of pilots to use the controls is also described.

"In Mach range of 0.25 - 0.69, boundary-layer measurements were made on upper wing surface at 25% semi-span, pressure-distribution measurements made on upper surface at 63% semi-span, and wake surveys made at 63% semi-span. The minimum profile-drag coefficient of 0.0062 was indicated for smooth section at 63% semi-span. Critical mach number was exceeded by 0.04, but no compressibility shocks appeared. In slipstream, boundary layer transition occurred as far back as 20% chord on upper surface at low lift coefficients" (p. 1).

Report presenting an analysis to compare longitudinal stability and control characteristics obtained with a conventional fixed-stabilizer, an adjustable-stabilizer, and an all-movable horizontal tail. The tail-area requirements, control forces required in the critical landing condition, static margin, control-force gradients in a dive recovery, and elevator-free stability are investigated.

Report presenting an investigation to determine the knock-limited performance of AN-F-28, Amendment-2, fuel in a DCFR engine when water solutions of the following aliphatic amines were added as internal coolants: monomethylamine, dimethylamine, ethylendiamine, diethylamine, triethylamine, and butylamine. Results regarding the mean effective pressure, indicated specific fuel competition, indicated specific liquid consumption, and knock-limited inlet-air pressure plotted against fuel-air ratio are presented for each fuel and amine combination.

Report presenting testing of two deep inducers as separate components and in combination with an impeller as part of an investigation to correlate design requirements of inducers and impellers. Both inducers, when tested as separate components at a speed corresponding to an impeller tip speed of 1000 feet per second, had a peak adiabatic efficiency of approximately 82 percent. Results regarding the inducers as separate components, inducer-impeller units, and a comparison of inducer performance as a separate and as an integral impeller component are provided.

Report presenting a program of tests to determine the effect of an integral front shroud on the performance characteristics of a centrifugal supercharger impeller. The impellers tested included a modification of a commercial semishrouded impeller and a fully shrouded impeller, which was the same as the semishrouded one except for an integral front shroud.

Report presenting a flight investigation made of boundary-layer and profile-drag characteristics of smooth wing sections of a P-47D airplane. Measurements were made at three stations on the wing: boundary-layer measurements, pressure-distribution measurements, and wake surveys. The results indicated that a minimum profile-drag coefficient of 0.0062 for the smooth section at 63 percent semispan was obtained.

Report presenting a number of tests on the effect of service stresses on impact resistance, X-ray diffraction patterns, and the microstructure of the 25S aluminum alloy.

"For a simple diffraction pattern, the time required to calculate interplanar distances from measurements of the pattern is not excessive. If more than a few lines are present, however, or if several patterns are to be studied, it is very advantageous to have available a table giving interplanar spacings directly in terms of the linear measurements made on the film of the lines appearing on the diffraction pattern. The preparation of the table given here was undertaken when the expansion of research activities involving X-ray diffraction techniques indicated that such a table would greatly decrease the time required to analyze diffraction patterns" (p. 1).

"A semiempirical equation correlating exhaust-valve temperatures with engine operating conditions and exhaust-valve design has been developed. The correlation is based on the theory correlating engine and cooling variables developed in a previous NACA report. In addition to the parameters ordinarily used in the correlating equation, a term is included in the equation that is a measure of the resistance of the complex heat-flow paths between the crown of the exhaust valve and a point on the outside surface of the cylinder head" (p. 103).

"Stress concentration factors for shear stresses around cut-outs in the webs of beams having shear resistant webs were determined by the photoelastic method. Webs with circular, square, and rectangular cut-outs were tested. The effect of reinforcements around square and circular cut-outs was investigated" (p. 1).

A summary of the results of wind-tunnel tests to determine the high-speed aerodynamic characteristics of six model wings having NACA 65sub1-series sections is presented in this report. The 8-percent-thick wings were superior to the 10-percent and 12-percent-thick wings from the standpoint of power economy during level flight for Mach numbers above 0.76. However, airplanes that are to fly at Mach numbers below 0.76 will gain aerodynamically if the percentage thickness of the wing and the aspect ratio are both increased. The lift-curve slopes for the 8-percent-thick wings at 0.85 Mach number were roughly twice their low-speed values.

Several methods of predicting the compressible-flow pressure loss across a baffled aircraft-engine cylinder were analytically related and were experimentally investigated on a typical air-cooled aircraft-engine cylinder. Tests with and without heat transfer covered a wide range of cooling-air flows and simulated altitudes from sea level to 40,000 feet. Both the analysis and the test results showed that the method based on the density determined by the static pressure and the stagnation temperature at the baffle exit gave results comparable with those obtained from methods derived by one-dimensional-flow theory. The method based on a characteristic Mach number, although related analytically to one-dimensional-flow theory, was found impractical in the present tests because of the difficulty encountered in defining the proper characteristic state of the cooling air. Accurate predictions of altitude pressure loss can apparently be made by these methods, provided that they are based on the results of sea-level tests with heat transfer.

Investigations were made to determine the cowling and cooling characteristics of the Ranger V-770-8 engine installation in an observation seaplane. Final cowl configurations possessed ample engine and oil-cooler pressure drops for cooling in the critical normal-power climb condition with any of the three baffle configurations tested. The indicated critical Mach number of the cowling was found to be 0.70 as determined by the pressure on the lower lip of the inlet.

Report presenting an investigation to develop a general method of determining bearing loads for crankpins. Results regarding the idea design of the bearing, bearing operating temperature, and the calculations for determining ideal operating conditions for V-type engines and production V-type engines are provided.

Report presenting a dimensional analysis method of analyzing bearing loads as applied to the blade bearing of a V-type aircraft engine.

Report presenting tests conducted with two liquid-cooled cylinders in order to isolate the effects of the various engine and coolant variables on cylinder temperatures and to obtain engine-cooling data required for a fundamental study of the heat-transfer processes in liquid-cooled engines. Cylinder temperatures were obtained for a large range of engine speeds, manifold pressures, carburetor-air temperatures, fuel-air ratios, spark advances, coolant-flow rates, average coolant temperatures, and coolant pressures with water and AN-E-2 ethylene glycol and other ethylene glycol-water mixtures as coolants.

Engine temperature data and cooling correlating analyses of the engine and oil cooler are presented in connection with an investigation of the cowling and cooling of the ranger V-770-8 engine installation in the Edo XOSE-1 airplane. Three types of baffles were installed in the course of the tests: the conventional, the turbulent-flow, and the NACA diffuser baffles. Each of the types was of merit in cooling a different region on the cylinder. Incorporation of the best features of the three types into one baffle, a method which appears to be feasible, would provide improvements in cylinder cooling.

"A test-stand investigation was conducted to determine the mixture distribution of a conventional double-row radial engine for a wide range of engine speeds, powers, and fuel-air ratios and to evaluate its effect on engine performance. The fuel was injected into the combustion-air stream by a rotating spray ring located near the impeller entrance. Fuel-air ratios of the individual cylinders were determined from chemical analyses of the exhaust gas" (p. 1).

"Information published in chemical journals from 1933 to 1939 on the thermodynamic properties of the component gases of exhaust gases based on spectroscopic measurements were used as data for computing the ideal values of work, mass flow, nozzle velocity, power, and temperature change involved in the thermodynamic properties of a gas turbine. Curves from which this information can conveniently be obtained are given. An additional curve is included from which the heat flow may be calculated for nonadiabatic processes" (p. 1).

From Summary: "This report suggests a method whereby information on the strength under repeated stresses of aircraft materials or structural parts can be used in conjunction with information on service loadings as a means of comparing alternative designs."

Report discussing testing of six airfoil sections for the wing of the Vega XP2V-1 airplane in a smooth condition and with standard leading-edge roughness. Information about the lift, drag, pitching-moment characteristics, and sensitivity to roughness is provided. No airfoil was found to be superior to the others in all categories.