Report presenting information about a series of modifications incorporated into light airplanes to increase safety, including decreasing the wing incidence, increasing the wing washout, increasing the area and aspect ratio of the horizontal and vertical tails, moving the elevators out of propeller slipstreams, depressing the thrust axis, and limiting the rudder travel. The new inherent safety characteristics and effects on the airplane's performance are provided.

Report presenting a series of tensile-strength and shear-strength tests made on age-hardened 17S-T rivets machine-countersunk in 75S-T sheets. The results of the tests indicated that the joints can be made satisfactorily with regard to both flushness and strength if the ratio of buck to diameter is kept to a certain value.

"A method for determining the streamwise flow pattern of a nonviscous incompressible fluid about an oblique airfoil from the corresponding flow pattern about the airfoil in normal position is presented and illustrated in two examples. The method can be extended to account approximately for compressibility effects by applying the Prandtl-Glauert correction factor to the flow pattern that is normal to the leading edge of the airfoil. The method is expected to be useful in determining the shape of a fuselage or nacelle having a minimum of interference with the flow over a swept-back wing" (p. 1).

Note presenting results of strain surveys around four reinforced circular cut-outs successively made in an axially loaded skin-stringer tension panel. Curves are presented which show the distribution of stringer and shear stresses in the panel and bending stresses in the reinforcing rings.

Note presenting a frequency-response method for determining the critical control-gearing and hunting oscillations of airplanes with automatic pilots. The method is graphical and has several advantages over the standard numerical procedure based on Routh's discriminant. Several examples are worked out to illustrate the application of the frequency-response method in determining the effect of automatic-pilot lag or lead on critical control gearing and in determining the amplitude and frequency of hunting.

"A general description of the field operations of the U.S. Weather Bureau thunderstorm project conducted in the vicinity of Orlando, Florida during the summer month of 1946 is given. The participation of NACA in this project is described and measurements of atmospheric turbulence taken by NACA are presented for one of the flights. The results indicate that some regions of thunderstorms may present no great hazard to flight, while exceptionally severe conditions of atmospheric turbulence may occur in other regions, or even in the same region, at about the same time" (p. 1).

This document details 100 Areas technical activities in reactor physics research and operation for the month of February 1947.

None

It was desired to establish the adaptability of iron box sludge, a residue recovered in the initial concentration of domestic ores, as a raw material from the production of high purity U{sub 3}O{sub 8}. This report summarizes the experimental work on the extraction of uranium from iron box sludge and that on the removal of V{sub 2}O{sub 5} and P{sub 2}O{sub 5} from the solutions.

It was desired to determine the distribution of boron in the various steps of the processing of domestic ore concentrates containing high percentages of boron. The experiments described in this report were directed toward that end. Summary of this report are: (1) a black oxide containing 0.6 ppm of boron was prepared from material containing 350 ppm; (2) less than 0.02% of the boron in the original material appeared in the black oxide; (3) the iron step did not remove appreciable amounts of boron; (4) the bulk of the extracted boron was removed in the soda salt precipitation; and (5) some of the boron was removed in the acid leach and calcination steps.

The object of this project is to reduce the impurities and raise the density of rejected slugs and briquetted turnings from these slugs by recasting the material. Summary and conclusions are (1) slugs and briquettes made from turnings produced when these slugs were machined can be recast with great improvement in quality; (2) casting this material is quite hard on graphite crucibles, but a long-range program might point the way to better graphite usage; (3) this metal run alone gives fair yields (88.8% to 94.8%) if heated to 2500 F and then cooled to 2400 F before pouring. Mixing with virgin metal improves the final quality, but does not materially increase the yield; (4) briquettes should not be mixed with magnesium before recasting.

Both acid and alkaline dissolutions of Be/sub 3/N/sub 2/ were carried The recommended alkaline dissolution procedure is outlined. (M.H.R.)

Abstract: Test distillations were made with Kinney and diffusion pump oils under vacuum in order to determine accurately the temperature range over which satisfactory distillate may be collected. Also recommendations are made as to the most advisable type of heating equipment necessary to produce the required heat and maintain the desired temperature. In addition, several important refinements in the distillation equipment were checked for operational characteristics and for their efficiency in aiding the production of uranium-free distillates.

This report for March, 1947 describes progress regarding chemical and spectrographic analysis, chemical work, physical methods of analysis, and ore dressing and pyrometallurgical studies,

From Summary: "By means of the general solutions of the hodograph equations for compressible fluids, certain solutions corresponding to solutions of the hodograph equations of an incompressible fluid are used to find flow patterns of compressible fluids. When the adiabatic equation of state is used, only a general method is outlined. The method appears to lead to the solution of the problem of subsonic flows with circulation around arbitrary bodies, as the method of Theodorsen does for incompressible fluids."

Note presenting an investigation to compare the 14S-T with 24S-T in extruded stiffeners for stiffened flat sheet panels. The tests were made with stiffened flat sheet panels with three hat-shape stiffeners. Data is provided on the strength of the two alloys as well as the effect of sheet thickness on relative stiffener strengths.

Report presenting a summary of the available information on lateral control. Some of the topics include the criterions used in lateral-control specifications, the factors involved in obtaining satisfactory lateral control, and the methods employed in making lateral-control investigations in flight and wind tunnels.

Note presenting an approximate theory of the effect of slipstream rotation on the forces on a fuselage without a wing, which represents the slipstream rotation by the flow about a vortex aligned with the longitudinal axis. A wind-tunnel investigation was made primarily to check the predictions for the lateral force on a fuselage shaped as a body of revolution.

Report presenting testing at Reynolds numbers up to 8,000,000 to determine the effectiveness of a reflex-cambered mean line in shifting the low-drag range of a sweptback wing without affecting the longitudinal stability. Two models were tested, one with symmetrical airfoil sections and one with a reflex-cambered mean line. Results regarding the effect of camber, roughness, and variation of aerodynamic characteristics with Reynolds number are provided.

Presented here are the summary charts of the collapsed results of general tank tests of about 100 flying boat hull models. These summary charts are intended to be used as an engineering tool to enable a flying boat designer to grasp more quickly the significance of various hull form parameters as they influence his particular airplane. The form in which the charts are prepared is discussed in some detail in order to make them clearer to the designer. This is a data report, and no attempt has been made to produce conclusions or correlations of the usual sort. However, some generalizations are put forward on the various methods in which summary charts may be used.

Note presenting an investigation of a radial-inlet impeller based on two-dimensional-flow theory to establish correlation between flow theory and impeller performance. The simplifying assumptions of an infinite number of blades and an incompressible fluid were made for the impeller design. Results regarding performance characteristics based on standard overall measurements, performance characteristics based on static-pressure measurements, and hydraulic-efficiency characteristics are provided.

Report presenting an investigation of the principles for designing the optimum hull for a large long-range flying boat to meet the requirements of seaworthiness, minimum drag, and ability to take off and land at all operational gross loads. The aerodynamic and hydrodynamic qualities of the model were investigated in Langley tank no. 1.

Report presenting an investigation at subsonic Mach numbers in the rectangular high-speed tunnel on five supersonic airfoils and, for comparison, on two subsonic airfoils. Two-dimensional data were obtained by pressure measurements and schileren photographs at angles of attack from 0 to 4 degrees for a range of Mach numbers between 0.30 and 0.90. Results regarding pressure distributions, normal-force coefficients, pitching-moment of normal-force about the quarter-chord point, drag coefficient, and unusual flow at high Mach numbers are provided.

Note presenting an analysis of nonviscous unsteady channel flow in order to gain some insight into instability resulting from shock-free deceleration in order to provide more information on the factors determining the minimum shock intensity for a stable flow and to study in general the formation and motion of shocks in channel flows.