A connected account is given of the Possio theory of non-stationary flow for small disturbances in a two-dimensional supersonic flow and of its application to the determination of the aerodynamic forces on an oscillating airfoil. Further application is made to the problem of wing flutter in the degrees of freedom - torsion, bending, and aileron rotations. Numerical tables for flutter calculations are provided for various values of the Mach number greater than unity. Results for bending-torsion wing flutter are shown in figures and are discussed. The static instabilities of divergence and aileron reversal are examined as is a one-degree-of-freedom case of torsional oscillatory instability.

"The well-known methods of thin-airfoil theory have been extended to oblique or sweptback airfoils of finite aspect ratio moving at supersonic speeds. The cases considered thus far are symmetrical airfoils at zero lift having plan forms bounded by straight lines. Because of the conical form of the elementary flow fields, the results are comparable in simplicity to the results of the two-dimensional thin-airfoil theory for subsonic speeds" (p. 267).

An extended form of the Ackeret iteration method, applicable to arbitrary profiles, is utilized to calculate the compressible flow at high subsonic velocities past an elliptic cylinder. The angle of attack to the direction of the undisturbed stream is small and the circulation is fixed by the Kutta condition at the trailing end of the major axis. The expression for the lifting force on the elliptic cylinder is derived and shows a first-step improvement of the Prandtl-Glauert rule. It is further shown that the expression for the lifting force, although derived specifically for an elliptic cylinder, may be extended to arbitrary symmetrical profiles.

"An investigation of the cooling of an 18-cylinder, twin-row, radial, air-cooled engine in a high-performance pursuit airplane has been conducted for variable engine and flight conditions at altitudes ranging from 5000 to 35,000 feet in order to provide a basis for predicting high-altitude cooling performance from sea-level or low altitude experimental results. The engine cooling data obtained were analyzed by the usual NACA cooling-correlation method wherein cylinder-head and cylinder-barrel temperatures are related to the pertinent engine and cooling-air variables. A theoretical analysis was made of the effect on engine cooling of the change of density of the cooling air across the engine (the compressibility effect), which becomes of increasing importance as altitude is increased" (p. 267).

"The theory of Lagrangian multipliers is applied to the problem of finding both upper and lower limits to the true compressive buckling stress of a clamped rectangular plate. The upper and lower limits thus bracket the true stress, which cannot be exactly found by the differential-equation approach. The procedure for obtaining the upper limit, which is believed to be new, presents certain advantages over the classical Rayleigh-Ritz method of finding upper limits" (p. 213).

From Introduction: "A collection balanced-aileron test data is given in reference 1. Reference 2 presents a collection of data applicable to the design of tail surfaces. The results of analyses of data for control surfaces with internal balances, plain-overhang and Frise balances, beveled trailing edges, and unshielded horn balances have already been published in references 3 to 6."

From Introduction: "It is the purpose of this paper to describe the physical properties that are necessary to specify mixture quality in a system containing fuel and dry air and to evaluate the theoretical rolation between these properties and the physical properties of the mixture."

Report presenting a number of calculations of bending-torsion wing flutter at two Mach numbers and a comparison of the results. The results indicated that the effect of compressibility on flutter speed for subsonic speeds with no shocks, although complicated, is relatively small in the usual cases.

"A single chart has been prepared that simplifies the calculation of the thermodynamic properties of air, various octene-air mixtures, and mixtures of those with their products of combustion at all temperatures below which chemical dissociation becomes unimportant. The chart is based on the use of 1 pound mol of mixture, and examples of its use are given in the form of the calculation of a turbocompressor power plant and a supercharged Otto engine cycle" (p. 1).

"Column and plate compressive strengths of extruded 14S-T aluminum alloy were determined both within and beyond the elastic range from tests of flat-end H-section columns and from local-instability tests of H-, Z-, and channel-section columns. These tests are part of an extensive research investigation to provide data on the structural strength of various aircraft materials. The results are presented in the form of curves and charts that are suitable for use in the design and analysis of aircraft structures" (p. 1).

Note presenting an investigation of the use of aluminum alloy 14S-T in heavy-duty structural applications and aircraft. The column data presented in this report have been obtained on extruded shapes and on rolled and drawn rod of the alloy.

Web stresses and flange stresses were measured in three built-up beams: one of constant depth with flanges of constant cross-section, one linearly tapered in depth with flanges of constant cross section, and one linearly tapered in depth with tapered flanges. The measured stresses were compared with the calculated stresses obtained by the methods outlined in order to determine the degree of accuracy that may be expected from the stress analysis formulas. These comparisons indicated that the average measured stresses for all points in the central section of the beams did not exceed the average calculated stresses by more than 5 percent. It also indicated that the difference between average measured flange stresses and average calculated flange stresses on the net area and a fully effective web did not exceed 6.1 percent.

Report presenting several methods of predicting the compressible-flow pressure loss across a baffled aircraft-engine cylinder that were analytically and experimentally investigated on a typical air-cooled aircraft-engine cylinder. Results regarding the evaluation of data, comparative accuracy of correction methods, and ability to apply information about heat transfer to compressible-flow pressure-drop predictions are provided.

Note presenting static tests made on machine-countersunk riveted joints in 24S-T, X75S-T, and Alclad 75S-T sheet using A17S-T and 24S-T rivets. In order to intensify the cutting action of the rivets, all specimens were made with the depth of countersink just equal to the thickness of the sheet.

Note presenting pressure distributions and schileren photographs for the high-speed flow about a symmetrical airfoil at zero lift in open and closed jets in order to show the nature of the jet-boundary interference. Results regarding the application of jet-boundary-interference theory, analysis of experimental wall-interference data and comparison with theory, conditions near choking, and change of velocity ratio with Mach number are provided.

Tests were made to determine the effect of brake forming on the strength of 24S-T aluminum alloy sheet that had been formed to an inside bend radius of three times the sheet thickness. The results for both directions of the grain of the material showed that the compressive yield stresses were appreciably increased, that the tensile yield stresses were moderately increased, that the ultimate tensile stresses were only slightly increased, that the elongations were considerably reduced, and that the shapes of the tensile and compressive stress-strain curves were markedly changed.

Report presenting compressibility effects on the aerodynamic section characteristics of an airfoil with a round-nose slotted Frise aileron for various pressure distributions and angles of attack. Previous testing with sharp-nose ailerons demonstrated heavy stick forces at large aileron deflections, leading to testing on the round-nose aileron. Results regarding control effectiveness characteristics, aileron hinge-moment coefficient, Frise aileron critical speeds, section aileron loads, and other airfoil characteristics are provided.

For the normal range of engine power the impeller provided marked improvement over the standard spray-bar injection system. Mixture distribution at cruising was excellent, maximum cylinder temperatures were reduced about 30 degrees F, and general temperature distribution was improved. The uniform mixture distribution restored the normal response of cylinder temperature to mixture enrichment and it reduced the possibility of carburetor icing, while no serious loss in supercharger pressure rise resulted from injection of fuel near the impeller outlet. The injection impeller also furnished a convenient means of adding water to the charge mixture for internal cooling.

Note presenting an experimental radial-discharge impeller designed to have, by comparison with conventional impellers, a long radius of axial-plane curvature, a large axial depth, and a small inlet-blade root diameter. The impeller was tested as part of an investigation to improve the flow capacity of radial impellers. Results regarding the comparative volume-flow characteristics of the basic experimental impeller, effect of passage-area variation on performance of the basic experimental impeller, and overall performance characteristics of the basic experimental impeller are provided.

Report presenting the results of experiments with a technique for investigating the spray characteristics of flying-boat models. The forebody of a pointed-step flying boat hull was used for testing, and the effects of varying trim, propeller position, and amount of power were investigated. Either of the two types of spray that emanate from a forebody can limit the gross load of a flying boat depending on the configuration.

Note presenting a criterion for selecting foam inhibitors from insoluble liquids that form emulsions with the foaming liquid. By determining the surface tensions of the foaming liquid and of the additive saturated with that liquid and the interfacial tension between them, spreading and entering coefficients may be calculated. A mechanism of foam inhibition is also described.

Report discussing a mock-up injection impeller created to investigate the hydraulic characteristics and limitations of the NACA injection impeller currently in use. Information about the form and magnitude of critical factors of fuel-transfer leakage and peripheral fuel distribution is provided as well as the effects of design variations of components on hydraulic characteristics. Several revisions in portions of the impeller are suggested to improve its fuel-transfer, fuel-pumping, and fuel-equalizing characteristics.

Report presenting an investigation of the transition of the boundary layer from the laminar to the turbulent region on a flat plate, on the concave and convex side of a plate with a 20-foot radius of curvature, and on the convex side of a plate with a 30-inch radius of curvature.

Tests show that at inlet-air temperatures of 250 deg F and 100 deg F the knock-limited performance of the base fuel of blends, leaded with 4 ml TEL per gallon and containing 20 percent spiropentane, was reduced at fuel/air ratios below 0.085. The 20 percent methylenecyclobutane reduced the knock-limited power of the base fuel at fuel/air ratios below 0.112. Di-tert-butyl ether, methyl-tert-butyl ether, and triptane increased the knock-limited power of the base fuel at all fuel/air ratios and at both temperatures.