Report presenting an investigation of the exhaust of corrosive attack in an aluminum alloy wing employing an exhaust-gas-air mixture as a heating medium for ice prevention. There were no cases of structurally serious corrosion on either painted or plain specimens removed from the wing for detailed microscopic and metallurgic examination.

From Summary: "By the use of a form of the Prandtl-Glauert method that is valid for three-dimensional flow problems, the value of the maximum incremental velocity for compressible flow about thin ellipsoids at zero angle of attack is calculated as a function of the Mach number for various aspect ratios and thickness ratios. The critical Mach numbers (within the accuracy of the Prandtl-Glauert method) of the various ellipsoids are also determined. The results indicate an increase in critical Mach number with decrease in aspect ratio which is large enough to explain experimental results on low-aspect-ratio wings at zero lift."

Rotating-cylinder measurements of the icing conditions encountered in flight during the winter of 1947-48 are presented. Liquid water content, drop size, and temperature data are shown to be consistent with previously measured conditions and with proposed maximum icing conditions in supercooled layer-type clouds. Cumulative frequency graphs of meteorological parameters indicate the frequency with which various icing conditions have been encountered in the Great Lakes area and surrounding states.

Report presenting tests in the gust tunnel of the 30 degree sweptback wing model to provide information on some of the problems encountered in the prediction of gust loads for airplanes incorporating swept wings. The results indicate that within the scope of the data and the values of gradient distance investigated, the maximum acceleration increment depends on the slope of the lift curve of an equivalent straight wing multiplied by the cosine of the angle of sweep and on the effect of gradual penetration of the sweptback wing into the gust.

Note presenting some of the basic general equations governing the three-dimensional compressible flow of gas through a compressor or a turbine in terms of velocity components, total enthalpy, and entropy. The equations are applied to investigate the maximum compatible number of the radial variations of the gas properties between successive blade rows that a designer is free to specify.

Report presenting an investigation of the take-off and landing behavior in waves of models of a hypothetical flying boat with hull length-beam ratios of 6 and 15. The flying boat had a design gross weight of 75,000 pounds, a wing loading of 41.1 pounds per square foot, and a power loading of 11.5 pounds per brake horsepower for take-off. Results regarding the landing behavior, spray characteristics, and taxiing and take-off behavior are provided.

Note presenting an investigation of a two-blade and a three-blade propeller on a slender-nose fighter airplane in climb and at high speed.

Report presenting comparisons of the structural efficiency of panels with straight-web and curved-web Y-section stiffeners. In the high-stress region in which failure is at least in part associated with local buckling, panels with curved-web Y-section stiffeners have higher structural efficiencies than panels with straight-web Y-section stiffeners, which is evidenced by higher average stresses at failure, smaller stiffener heights, or wider average spacing of rivet lines.

"A method developed in a previous report for finding the induced velocity field behind a supersonic wing with known load distribution is used to find the downwash behind a triangular wing with subsonic leading edges. Results are given for the chord plane in the extended vortex wake of the wing and for the vertical plane of symmetry up to about 20 percent of the wing span above the plane of the wing" (p. 1).

Report presenting an investigation to determine the underlying causes of the undesirable longitudinal characteristics of a 45 degree swept-forward wing in the moderate and high lift-coefficient range. Several methods were used to create a detailed correlation between separation phenomena and longitudinal characteristics of the wing. Both turbulent and leading-edge separation need to be postponed in order to improve the longitudinal characteristics of this wing.

Note presenting calculations, based on linearized supersonic flow theory and on the additional assumption that the Mach cones yaw with the wing, to determine the effect of thickness on the lateral force and yawing moment of a sideslipping delta wing at supersonic speeds. Generalized equations are derived for delta wings with rhombic profile and constant thickness ratio.

Report presenting the flying qualities problems of current helicopters, including instability with angle of attack in forward flight, control sensitivity in hovering, and control forces following control movement in maneuvers. Some possible solutions to these issues are presented.

Report presenting a spin investigation in the 20-foot free-spinning tunnel of a model of a twin-tail low-wing personal-owner-type airplane with linked and unlinked rudder and aileron controls. The model was tested for two wing loadings and three mass distributions. When the rudders and ailerons were linked for two-control operation, the model generally would not spin.

Note presenting a wind-tunnel investigation made of the lateral-control characteristics of a thin, low-drag, semispan wing equipped with three configurations of circular plug ailerons and a full-span, 25-percent-chord, slotted flap. The investigation was performed through a Mach number range of 0.13 to 0.61. Results regarding wing aerodynamic characteristics, aileron control characteristics, comparison of lateral-control characteristics of the three configurations of circular plug aileron, comparison of lateral-control characteristics of the circular plug ailerons, a conventional plug aileron, and a retractable aileron, and a comparison of lateral-control characteristics of the circular plug ailerons with those of a sealed plain aileron are provided.

Note presenting landing tests made with the PB2Y-6 flying boat to determine the effect of production step vents and forebody longitudinal steps on skipping. Skipping was found to occur at higher landing trims without either step vents or longitudinal steps. The steps were found to constitute a powerful method for improving the landing stability.

Note presenting the boundary-layer equation of motion and the boundary-layer energy equation for the compressible and steady laminar boundary layer on two-dimensional bodies and bodies of revolution in a nondimensional form and to provide a clearer indication of the effects of Mach number, Reynolds number, and the properties of the gas.

Note presenting a method by which the pressure distribution on a slender, arbitrary body of revolution moving at supersonic speeds at zero angle of attack may be calculated with an appreciable saving of time as compared with that required by other methods. It is essentially a graphical computing technique based on the assumption that a body may be represented satisfactorily by a relatively small number of point sources and sinks. The method gives results for parabolic bodies in excellent agreement with results obtained by the method of Jones and Margolis.

Note presenting a prismatic-float forebody with an angle of dead rise of 40 degrees that was subjected to smooth-water impacts in the impact basin. The tests were made at fixed trims of 3, 6, 9, and 12 degrees for a range of flightpath angles from approximate 2 to 22 degrees. The data are presented and converted into dimensionless variables for correlation of the experimental results with hydrodynamic impact theory and for comparison of the runs among themselves.

Note presenting the stability derivatives valid for a limited range of supersonic speeds for a series of sweptback wings tapered to a point with sweptback or sweptforward trailing edges. The wings were derived by modifying the trailing edge of a basic triangular wing so that it coincided with lines drawn from the wing tips to the wing axis of symmetry.

"Direct-reading design charts are presented for 24S-T aluminum-alloy flat compression panels having longitudinal straight-web Y-section stiffeners. These charts make possible the direct determination of the stress and all the panel proportions required to carry a given intensity of loading with a given skin thickness and effective length of panel" (p. 1).

"Direct-reading design charts are presented for 24S-T aluminum-alloy flat compression panels having longitudinal formed Z-section stiffeners. These charts make possible the direct determination of the stress and all the panel proportions required to carry a given intensity of loading with a given skin thickness and effective length of panel" (p. 1).

Report presenting a landing investigation with a flying boat with a conventional configuration to determine the applicability of hydrodynamic impact theory in defining full-scale water impact loads. The results indicated that in addition to chine flare and angular rotation, there are many other factors that may affect overall load, such as elasticity effects, sustained pressures on the area behind the chine, and the effect of variation of wing lift during impact.

Report presenting complete pressure-distributions measurements over a 24-inch-chord NACA 65,1-115 airfoil equipped with 20-percent-chord plain ailerons with aerodynamically smooth surfaces. Characteristics determined included airfoil normal-force, pitching-moment, aileron normal-force, and hinge-moment coefficients for a variety of Mach numbers, angles of attack, and aileron deflections. The aileron effectiveness parameter and section pitching-moment parameter are calculated.

Note presenting a study of conditions in the Pacific Ocean to investigate several characteristics in the sea and wind that are of importance in the structural design of flying boats and seaplanes: wave height and frequency of occurrence, wave length-height ratio and frequency of occurrence, wave velocity and its relation to wave lengths, wind velocity, and wave shape.