A summary is given of information on atmospheric electrical discharges to aircraft and associated meteorological conditions. Information is given that is designed to give a fairly comprehensive view of the underlying principles of meteorology and atmospheric electricity. Of special interest to pilots are lists of procedures of flight conduct and aircraft maintenance recommended foe avoiding or minimizing the hazards of disruptive electrical discharges and other severe conditions near thunderstorms.

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.

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.

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.

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.

Note presenting a series of diagonal-tension beams tested to determine the accuracy of previously published design charts and formulas for beams of 24S-T aluminum alloy when used to analyze beams of 75S-T aluminum alloy. Results regarding stresses in the uprights, failure of the uprights, and web failure of beam 8 are provided.

The problem treated here is that of the stresses in a torsion box with a large rectangular cut-out. The theoretical treatment is confined to stresses termed the 'primary stresses.' Comparison of the theoretical results with strain gage data for a series of cut-outs indicates that the primary stresses are probably adequate for designing the major part of the structure, the only important exception being in the design of the cover sheet in the full section adjacent to the cut-out.

Note presenting an investigation of the effect of wing location, power, and flap deflection on the effective dihedral of a typical single-engine fighter-airplane model. The model, which was tested in the 7- by 10-foot tunnel, had provisions for placing the wing in either one of two vertical locations. The results are presented as curves of lateral-stability derivatives against lift coefficient.

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 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.

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.

Report presenting tests conducted in tank no. 2 on models of an unconventional flying-boat hull called a planing-tail hull to determine the effects on resistance of varying a number of afterbody parameters. The effects of varying length, width, and plan-form taper of the afterbody are explored. Results regarding the effect of decreasing width of the afterbody, effect of increasing length of the afterbody, effect of tapering afterbody, and a comparison of planing-tail hulls with a conventional hull are also provided.

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.

Note presenting a low-wing, single-engine airplane model tested in the stability tunnel to obtain data showing the effect of canopy size and shape on the directional stability characteristics of the model. Generally, the addition of a canopy to the model decreased the directional stability of the model.

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.

"The theorems of Bjerknes and Crocco are of great interest in the theory of flow around airfoils at Mach numbers near and above unity. A brief note shows how both theorems are developed by short vector transformations" (p. 1).

Report presenting testing to determine the aerodynamic characteristics of a full-scale semispan horizontal tail surface of a fighter airplane at a range of mach numbers. The results presented show the effects of elevator nose shape, elevator trailing-edge angle, and trailing-edge strips on the aerodynamic characteristics.

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 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.

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."

Note presenting damping data obtained from free-flight-tunnel tests of 13 models; the results are analyzed and compared with calculated results. The contributions of the wing, flaps, fuselage, tail surfaces, and power to the damping in pitch and yaw were studied. For complete models, fairly good agreement was obtained between experimental and calculated values for power-off, flaps-neutral conditions.

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.

Note presenting an investigation of the electromagnetic-analogy method used to provide lifting-surface-theory solutions applicable to the determination of aspect-ratio corrections for the slope of the curve of hinge-moment coefficient against flap deflection. A comparison of the results of the present measurements with those of previous tests indicated that the increment of induced downwash at the 0.5-chord line over the value predicted by lifting-line theory is a linear function of the center-of-pressure coefficient.

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."