Memorandum presenting investigation on reductions of friction on wings, especially by means of boundary-layer suction. The report is broken up into several sections, including: causes of transition, laminar profiles with the transition taking place, laminar boundary-layer suction, investigation of the laminar pressure increase, investigation of the slot flow for laminar boundary-layer suction with single slots, tests about keeping a boundary layer for high Reynolds laminar with the aid of boundary-layer suction, and an investigation of a slightly-cambered laminar suction profile of 10.5-percent thickness.

Note presenting a discussion of the integral relations for flow of the boundary-layer type. It is shown that the characteristic laws of spread of jets, wakes, and so forth, can be obtained directly for the laminar case and, with the help of dimensional reasoning, for the turbulent case as well. Measurements of the mean velocity, the intensity and scale of the turbulent fluctuations, and of the turbulent shear in a two-dimensional mixing zone are presented.

Report presenting the results of an investigation of a specific tail configuration in the 15-foot free-spinning tunnel in order to supplement the existing published data on hinge moments of elevators and rudders in spins. Hinge-moment measurements are presented for a balanced elevator equipped with trim tabs and for a balanced rudder. Results regarding elevator hinge moments, rudder hinge moments, and application of hinge-moment data are provided.

Report presenting information regarding the velocity potential, lift force, moment, and propulsive force on a two-dimensional airfoil in a stream of periodically varying angle of attack, as well as an application of the theoretical results.

Note presenting results of a flight investigation conducted on a fighter-type airplane to determine the factors which affect the loads and load distributions on the vertical tail surfaces in maneuvers. An analysis is made of the data obtained in steady flight, rudder kicks, and fishtail maneuvers.

Note presenting data from flight measurements of the meteorological factors related to the intensity of icing conditions. The physical factors that establish the distribution of liquid water in clouds of various types are discussed and the results of the analysis are used to formulate certain rules for the forecasting of icing intensity. Discussion of the results includes the problem of forecasting icing conditions and the problem of defining the physical characteristics of icing conditions for the purpose of the design of ice-protection equipment.

Report presenting a method for determining, by step-by-step integration, the trajectories of water drops around any body in two-dimensional flow for which the streamline velocity components are known or can be computed. The equations are presented in general form and then water-drop trajectories are calculated about a 12-percent-thick symmetric Joukowski profile.

Report presenting a flight investigation of a scout-bomber airplane with 4.7 degrees and 10 degree geometric dihedral in the wing outer panels in order to obtain flight test results pertaining to the upper limit of the wing-dihedral angle for satisfactory handling qualities. No unusual or undesirable lateral control characteristics were observed with the combinations of stability parameters obtained with the two dihedral angles used.

Report presenting the results of high-speed wind-tunnel research on the effects of modifications to the horizontal tail profile on the static longitudinal stability and control of a pursuit airplane at high speeds. Two symmetrical stabilizers, two flat-sided elevators, and three elevators with bulged profiles were investigated. The pitching-moment and elevator hinge-moment characteristics with various tails are shown.

Report presenting an investigation to obtain a record of any chemical changes directly associated with knock in a spark-ignition engine on a greatly magnified time scale by means of coordinated high-speed motion pictures and spectrograms.

Report presenting design charts for 24S-T and 75S-T aluminum-alloy flat compression panels with longitudinal extruded Y-section stiffeners. Comparisons are also made among panels designed from these charts and 24S-T aluminum-alloy panels with formed Z-section stiffeners designed from available design charts.

Report presenting an investigation to determine the effects of compressibility on the aerodynamic characteristics of a 5-inch-chord NACA 16-009 airfoil with a 32.9-percent-chord flap with a nose overhang and an unsealed gap. Airfoil lift and pitching moment and flap hinge moments were obtained for a range of angles of attack, flap angle ranges, and Mach numbers.

Report presenting the optical principle of the NACA ultrahigh-speed camera. Simplified sketches are included illustrating the optical principle and main design features of the camera, but without minor design details. A detailed description of the camera is provided as well as some sample photographs taken with the camera.

Report presenting a method for the determination by use of charts of mass-flow coefficient and associated flow parameters from pressure surveys in internal-flow systems. The charts presented cover a wide range of specific parameters through the complete range of subsonic Mach numbers. The equations have also been evaluated for flows that involve the adding of mechanical or thermal energy, such as flows behind radiators or propellers.

Report presenting a wind-tunnel investigation to determine the practicability of the dropped-aileron-type lateral-control device on NACA low-drag airfoils. Section aerodynamic characteristics of an NACA 66(215)-216 airfoil with an aileron of normal profile and an aileron of straight-sided profile with a modified nose shape are presented for various aileron locations, hinge centers, and aerodynamic balances.

From Summary: "This report presents a rough correlation of the dimensions of water rudders of various actual seaplanes and flying boats as related to their behavior. The correlation should be useful for determining the size of a water rudder which will give adequate control for maneuvering at low speeds."

"Tests of a partial-span model of a large bomber-type airplane were conducted to determine the aerodynamic characteristics of the wing equipped with full-span flaps and a retractable spoiler end aileron lateral control system. The arrangement consisted of (1) a double slotted flap extending over aproximate1y 86 percent of the wing semispan, (2) a 20-percent constant-percentage-chord aileron extending from the outboard end of the flap to the wing tip, and (3) a retractable spoiler, located at the 65-percent wing-chord station and extending from approximately 63 percent of the wing semispan to the wing tip. In addition, tests were made of a wing vent (of 1 and 2 percent of the wing chord located directly behind the spoiler), perforations in the spoiler, a blot or cut-out along the lower edge of the spoiler and spoilers of various spans" (p. 1).

Note presenting a discussion of the performance characteristics of the compound engine, the turbine-propeller engine, the turbojet engine, the turbo ramjet engine, the ramjet engine, and the rocket engine. Insight is provided into the proper position of each of these engine types in the speed-range spectrum of aircraft operation. It is shown that the compound engine, which has the greatest weight per unit thrust and also the lowest specific fuel consumption, gives the longest range.

Report presents the results of an investigation conducted to determine some of the effects of airfoil section and washout on the experimental and calculated characteristics of 10-percent-thick wings. Three wings of aspect ratio 9 and ratio of root chord to tip chord 2.5 were tested. One wing had NACA 64-210 sections and 2 degree washout, the second had NACA 65-210 sections and 2 degree washout, and the third had NACA 65-210 sections and 0 degree washout. It was found that the experimental characteristics of the wings could be satisfactorily predicted from calculations based upon two-dimensional data when the airfoil contours of the wings conformed to the true airfoil sections with the same high degree of accuracy as the two-dimensional models.

Note presenting flight measurements of thrust losses due to shanks on a flared-shank two-blade propeller mounted on an airplane with a streamline slender nose. Thrust losses due to the shanks were found to be high; they were of the order of 9 percent at an airplane Mach number of 0.7 when the propeller was operating at the highest test power coefficient of 0.17 per blade.

Report presenting an investigation to determine whether a safety fuel with a flash point of 122 degrees Fahrenheit could be successfully used in a high-power radial aircraft engine without individual cylinder fuel-injection equipment. The safety fuel was injected into the combustion-air stream in three different ways. Results regarding the standard powers, effect of average fuel-air ratio on mixture distribution, effect of combustion-air temperature on mixture distribution, general engine performance, and idling and starting are provided.

"The knock-limited power at various blend compositions for several aromatics and cycloparaffins individually blended with paraffinic base stocks, as determined in an air-cooled aircraft-engine cylinder at fuel-air ratios of 0.07 and 0.10 is presented. An analysis of the data leads to the conclusion that the extended reciprocal blending relation suggested in a previous NACA report is not generally applicable to such nonparaffinic components, but might possibly be useful as an approximation over a limited range of composition for aromatic blends" (p. 1).

Note presenting a method for determining, by step-by-step integration, the trajectories of water drops around any body in two-dimensional flow for which the streamline velocity components are known or can be computed. The equations are presented in general form and then, to illustrate the procedure, water-drop trajectories are calculated about a 12-percent-thick symmetrical Joukowski profile chosen to simulate an NACA 0012 section. The method provides a means for the relatively rapid calculation of the trajectory of a single drop without the utilization of a differential analyzer.

An investigation was conducted to furnish data on the effect of tab balance on tab and control-surface characteristics. The airfoil tested had a modified NACA 65(1)-012 contour with a plain flap having a chord equal to 25 percent of the wing chord and with a tab having a chord equal to 25 percent of the flap chord and having several nose shapes and overhang lengths. The results of the investigation indicated that, in general, tab balance affected tab hinge-moment characteristics in much the same manner that flap balance affects flap hinge-moment characteristics. A moderate amount of tab balance did not seem to have any adverse effect on flap hinge-moment characteristics.