"The effect of two-dimensional bumps and surface waviness on the pressure distribution over airfoils is considered. It is shown that the results of the analysis may be useful in evaluating the effects of accidental or intended surface distortions on the drag and critical Mach number of airfoils" (p. 1).

Report issued by the U.S. Bureau of Mines on studies conducted at the Magnolia oil fields in Columbia County, Arkansas. History, geology, and methods are presented. This report includes tables, graphs, maps, and illustrations.

Report presenting hinge moment, lift, and pressure-distribution measurements made on a Frise aileron on an NACA 23012 airfoil in the two-dimensional test section of the stability tunnel. Speeds up to 360 miles per hour corresponding to a Mach number of about 0.470 were used.

Report presenting a series of related flying-boat hull forms with various combinations of aerodynamic and hydrodynamic requirements that were tested in an NACA tank and high-speed tunnel. Effects explored included varying the height of the bow, varying the height of the stern, increasing the angle of dead rise at the bow, decreasing the angle of dead rise on the afterbody, increasing the depth of step, increasing the angle of afterbody keel, adding chine flare, adding a third planing surface, and rounded chines at the bow.

From Summary: "Tests were made of an 0.309-chord double-slotted flap on an NACA 65, 3-118, a equals 1.0 airfoil section to determine drag, lift, and pitching-moment characteristics for a range of flap deflections. Results indicate that combination of a low-drag airfoil and a double-slotted flap, of which the two parts moved as a single unit, gave higher maximum lift coefficients than have been obtained with plain, split, or slotted flaps on low-drag airfoils. Pitching moments were comparable to those obtained with other high-lift devices on conventional airfoils for similar lift coefficients."

"Two methods are presented for determining the horizontal location of the stick-fixed neutral point from wind-tunnel data. One method involves the solution of a mathematical equation; whereas the other method is a graphical solution for the same mathematical equation. The combined horizontal and vertical variation of the neutral point completely describes the stick-fixed longitudinal stability of airplanes that have large allowable center-of-gravity shifts" (p. 1).

Report presenting vibration tests of six- and eight-blade tractor and seven- and eight-blade pusher dual-rotating propellers conducted in the 16-foot high-speed tunnel to determine the severity of vibrations excited by blade passages. Measurements of vibratory stresses were made for engine-speed ranges at low, intermediate, and high engine powers. Few vibrations caused by blade passages were detected, and those vibrations were not serious.

Report presenting tests in the two-dimensional low-turbulence tunnel to determine the drag characteristics of two configurations of a 0.0476-scale nacelle and oil-cooler scoop for the Hughes-Kaiser cargo airplane. The nacelles were found to have a slightly favorable effect on the maximum lift coefficient.

"This is the sixth of a series of reports covering an investigation of the general instability problem by the California Institute of Technology. This report and the succeeding reports of this series cover the work done on other loading conditions under the sponsorship of the National Advisory Committee for Aeronautics. This report summarizes the work that has been carried on in the experimental investigation of the problem of general instability of stiffened metal cylinders subjected to combined bending and transverse shear at the C.I.T." (p. 1).

"Panels of aluminum alloy sheets, framed by side and end stiffeners, were subjected to combined loading by means of offset knife edges applying loads to top and bottom end plates with reacting forces against the end plates supplied by laterally acting rollers. The test specimens were 17S-T aluminum alloy shoots 0.040 inch thick in panels of 10-inch width and three different lengths (approximately 10, 26, and 30 inch). Data were obtained for the bowing of transverse and longitudinal ribs of rectangular cross section and varying depths mounted on one side of the sheet only, for several ratios of compression to shear loads" (p. 1).

"The results of tests of 56 cylinders of D cross section conducted in the Aeronautical Laboratory of the University of Maryland are presented in this report. These cylinders were subjected to pure bending and torsional moments of varying proportions to give the strength under combined loading conditions. The average buckling stress of these cylinders has been related to that of circumscribing circular cylinders for conditions of pure torsion and pure bending and the equation of the interaction curve has been determined for conditions of combined loading" (p. 1).

"An iteration method is employed to obtain the flow of a compressible fluid past a curved surface. The first approximation which leads to the Prandtl-Glauert rule, is based on the assumption that the flow differs but little from a pure translation. The iteration process then consists in improving this first approximation in order that it will apply to a flow differing from pure translatory motion to a greater degree. The method fails when the Mach number of the undisturbed stream reaches unity but permits a transition from subsonic to supersonic conditions without the appearance of a compression shock" (p. 305).

"A formula is given for the critical compressive stress for slightly curved sheet with equal elastic restraints against rotation along the unloaded edges. The theory of small deflections is used and the formula reduces to that given by Timoshenko for the case of simply-supported edges. For larger curvatures, a modification of Redshaw's formula to include the effect of edge restraint is suggested" (p. 1).

Report discussing an investigation of the flight qualities of the Bell P-39D-1 airplane. Information about the longitudinal stability and control characteristics, lateral and directional stability and control, stalling characteristics, and control friction is provided.

Bulletin presenting the development and testing of airfoil sections that have small or zero pitching-moment coefficients and high lift-drag ratios. Because the new airfoil sections have small pitching moments and low profile-drag coefficients at moderate lift coefficients, they may be suitable for use on the rotor blades of rotating-wing aircraft.

"The effect of variations in the type of mean line on the section characteristics of several representative NACA low-drag airfoils was investigated. The test results are compared with theoretical predictions and indicate trends that facilitate the choice of mean line in the absence of tests" (p. 1).

Report presenting aerodynamic and hydrodynamic tests of a 1/10-scale wing-hull model and a 1/10-scale float-strut model of the proposed arrangement of the Hughes-Kaiser cargo airplane. The aerodynamic tests were made primarily to study the drag characteristics of these models as originally designed and to determine how the design could be improved. Results regarding the wing-hull model and float-strut model are provided.

Report discussing strain measurements made on a box beam of triangular cross section and on two beams of D-section under transverse bending. Information about the arrangement of the beams and experimental and calculated stresses for different boxes.

Report presenting results of flight tests to determine the turning performance of a Navy F2A-3 airplane over a range of speeds for three flap deflections at two altitudes. The results are correlated with an analytical study of turning performance in which the effect of thrust on maximum lift coefficient was considered.

Report discussing an investigation of cooling ducts at various positions on a model of a typical pursuit airplane in the NACA full-scale tunnel. Results in the report are given for a duct located on the bottom of the fuselage with the inlet behind the leading edge of the wing. Due to the thick boundary layers at the inlets of the rear underslung fuselage duct and the serious pressure losses that resulted, a special vane was also installed to avoid boundary-layer separation.

Report discusses five tests related to seaplane skipping and attempts to prevent it by changing the depths of step to avoid large suction force on the afterbody generated by the flow behind a shallow step. Flying boats of various sizes and weights were tested during landing and several degrees of trim were tested for boats that had a particularly shallow step. Design suggestions for future flying boats are also included.

Report discusses the results of analyses and test results of the porpoising characteristics of flying boats. Equations for calculating stability limits with given hull forms under various combinations of loading and aerodynamic conditions and for modifications of the afterbody are provided.

The following report discusses measurements for slow and fast neutrons from cadmium coated ionization chambers.

A report on the SOM-vanadium occurrences of the Huerfano Park District.