The methods of NACA TN No. 995 have been slightly modified and extended in include flows with circulation by considering the alteration of the singularities of the incompressible solution due to the presence of the hypergeometric functions in the analytic continuation of the solution. It was found that for finite Mach numbers the only case in which the nature of the singularity can remain unchanged is for a ratio of specific heats equal to -1. From a study of two particular flows it seems that the effect of geometry cannot be neglected, and the conventional "pressure-correction" formulas are not valid, even in the subsonic region if the body is thick, especially if there is a supersonic region in the flow.

Note presenting a theoretical investigation made of the hydrodynamic pitching moments experienced by V-bottom seaplanes during step-landing impacts. The entire immersion process is analyzed from the instant of initial contact until the seaplane rebounds from the water surface.

From Introduction: "In references 1, 2, and 3, flight measurements of the performance of a conventional, single-rotor helicopter equipped with its production fabric-covered main rotor blades are presented."

Report presenting an investigation to study the effects of changes in fuel-nozzle carbon deposition on the combustion efficiency of a single tubular-type, reverse-flow, turbojet combustor. The investigation was conducted because of the need to improve the reproducibility of combustion data for fuel-research purposes.

"An investigation was made to determine the effect of longitudinal stiffeners on the buckling load of long flat plates under shear. Tests were made of long flat plates reinforced by one and by two longitudinal stiffeners. A theoretical study of the buckling load of such plates, made by the energy method, is presented in the appendix. The results of the tests and the results of the theory are compared and are found to be in fair agreement" (p. 1).

Report presenting theoretical pressure distributions and experimental aerodynamic characteristics at low speeds for a group of NACA four-digit series airfoil sections. Results regarding lift, drag, and pitching moment are provided.

Report presenting flight measurements of structure temperatures occurring in the wing outer panel of the airplane in order to improve the design of thermal ice-prevention systems. Results indicate that structure temperatures increased almost in direct proportion with an increase in heated-air temperature.

Report presenting computations of the horsepower and specific fuel consumption of a compound engine composed of an exhaust-gas turbine and an auxiliary supercharger geared to the crankshaft of a 12-cylinder liquid-cooled engine. Results regarding the engine exhaust pressure, engine speed, fuel-air ratio, inlet-manifold pressure, turbine, auxiliary-supercharger, and drive-gear efficiency, effect of altitude, comparison of compound and turbosupercharged engines, performance at high-power levels, effect of afterburning, and characteristics of a modified system are provided.

Note presenting an investigation conducted to determine the applicability of statistical methods as an approach to the evaluation of materials for use in gas turbines by determining the frequency distribution of time until failure of gas-turbine blades. Two wheels, each incorporating 142 inserted blades of a cast cobalt-base heat-resistant alloy, were tested. The results indicated that the time for first failure may not generally be taken as an accurate indication of the performance of the average blade.

"A list of standard symbols for rotating-wing aircraft is presented. The list of symbols is subdivided for ready reference under appropriate headings, the symbols being restricted to those most generally used in studies of helicopter aerodynamics" (p. 1).

Note presenting an extensive investigation of the cooling characteristics of a multicylinder, liquid-cooled aircraft engine of 1710-cubic-inch displacement. The results of the investigation are presented showing the variation of the cylinder-head temperature and the coolant heat rejection with the pertinent engine and coolant variables. Results regarding the relations between cylinder temperatures, effect of engine variables on average cylinder-head temperature between exhaust valves, coolant-flow distribution, effect of engine variables on heat rejection to coolant, and effect of coolant variables on coolant heat rejection are provided.

Report presenting an experimental investigation to determine the effect of design factors on the performance of collectors for axial-flow compressors, which consisted of airflow studies of an experimental collector on which six different outlet configurations were used. The size and number of outlet pipes had little effect on the static-pressure distribution at the collector inlet.

Report presenting a method for quantitative analysis of ternary mixtures of naphthalene, 1-methylnaphthalene, and 2-methylnaphthalene on the basis of ultraviolet absorption in the region from 3000 to 3300 A and the effect of interference by a fourth absorber. Twelve synthetic ternary mixtures of three naphthalenes were analyzed with an average error of 0.8 percent of the alkylnaphthalenes present.

Report presenting the results of flame-speed measurements of quiescent fuel-air mixtures in a 2.5-centimeter horizontal glass tube of 16 straight-chain hydrocarbons of paraffin, olefin, diolefine, and acetylene series and four cyclic hydrocarbons presented in graphical form. Results regarding peak flame velocity and uniform flame velocity are provided.

Report presenting a method for determining aromatics in several fractions of crude petroleum. A general curve for analysis of cuts of crude petroleum with molal average boiling points near 218 degrees Celsius is presented.

Report presenting the effect of landing flaps and landing gear on the spin and recovery characteristics of airplanes as determined from investigations of the spinning characteristics of 58 models in the 15-foot and 20-foot free-spinning tunnels. Lowering flaps was generally found to cause an increase in inward sideslip, an increase in the angle of attack, and a decrease in the rate of rotation of the model in the spin.

Note presenting gust data obtained during the U.S. Weather Bureau thunderstorm project in Orlando, Florida in 1946, which is analyzed statistically to determine the effects on the gust measurements of the several pilots and the several airplanes of the same model. The results indicate that, for three of the pilots and two of the airplanes, the effects on the gust measurements may introduce average errors of about 10 percent.

Report presenting a low-speed wind tunnel investigation of an exploratory nature in order to determine a satisfactory location for a spoiler lateral-control device for a sweptback wing. The semispan wing used for the tests had 42 degrees sweepback referred to the wing leading edge and an aspect ratio of 4.01. The best location appeared to be near the trailing edge of the wing, slightly inboard from the wing tip, and skewed with reference to the wing so as to be perpendicular to the free-stream air flow.

Note presenting pressure measurements on a triangular wing with an aspect ratio of 2 and an NACA 0012 airfoil section parallel to the center line. The wing angle of attack was varied from 4.3 to 48.1 degrees with the airspeed held constant at approximately 100 miles per hour. Results regarding chordwise pressure distribution, section lift characteristics, span load distribution, centers of pressure, and comparison of pressure data with force-test data are provided.

"The theory of supersonic flow in nozzles is discussed, emphasis being placed on the physical rather than the mathematical point of view. Methods, both graphic and analytic, for designed nozzles are described together with a discussion of design factors. In addition, the analysis of given nozzle shapes to determine velocity distribution and possible existence of shock waves is considered" (p. 1).

Report presenting an investigation of the interference effects between an airfoil of high critical speed with no sweepback and a nacelle of high critical speed mounted in various positions with respect to the wing. The main objective was to obtain a wing-nacelle combination which has the force break occurring at a Mach number as high as for the wing alone. Results regarding the wings alone, pressure contours on wing and nacelle, influence of wing on nacelle, influence of nacelle on wing, and leading-edge modifications are provided.

Report presenting results to show the effects on the flutter characteristics of mounting concentrated weights at various positions on an untapered wing model. The moment of inertia, chordwise position of the weight, and spanwise position of the weight were varied. Results regarding the flutter parameters, flutter-speed ratio, flutter-velocity coefficients, and curves of ratio of first-bending frequency to torsion frequency and second-bending frequency to torsion frequency and provided.

Note presenting a study to gain information as to the fundamental mechanism of fretting corrosion. The specific questions to be answered were whether chemical action played an important role in fretting of metal surfaces and whether any such action would improve the corrosion resistance of the metal investigated. The results indicated that the chemical action is of primary importance in fretting-corrosion effects and oxide formation does not give any protection to the metals but rather increases the rate of wear.

Report presenting an investigation to determine the effect of leading-edge flaps on the maximum lift coefficient of an NACA 64-009 airfoil and to compare the results with data obtained from previous testing of a similar flap. Two types of flaps, one intended to slide forward on the upper surface and one hinged at the center of the airfoil leading-edge radius, were tested. Results regarding lift characteristics, pitching-moment characteristics, and effect of leading-edge roughness are provided.