From Summary: "The purpose of this test was to compare six well-known airfoils, the R.A.F 15, U.S.A. 5, U.S.A. 27, U.S.A. 35-B, Clark Y, and Gottingen 387, fitted to the Sperry Messenger model, at full scale Reynolds number as obtained in the variable density wind tunnel of the National Advisory Committee for Aeronautics; and to determine the scale effect on the model equipped with all the details of the actual airplane. The results show a large decrease in minimum drag coefficient upon increasing the Reynolds number from about one-twentieth scale to full scale. A comparison is made between the results of these tests and those obtained from tests made in this tunnel on airfoils alone."

"In this report a formula for calculating the induced drag of multiplanes with end plates is derived. The frictional drag of the end plates are used, is sufficiently large to increase the efficiency of the wing. Curves showing the reduction of drag for monoplanes and biplanes are constructed; the influence of gap-chord ratio, aspect ratio, and height of end plate are determined for typical cases. The method of obtaining the reduction of drag for a multiplane is described" (p. 253).

"This report describes an investigation made in order to determine the effect of tip speed on the characteristics of a thin-bladed metal propeller. The propeller was mounted on a VE-7 airplane with a 180-HP E-2 engine, and tested in the 20-foot propeller research tunnel of the National Advisory Committee for Aeronautics. It was found that the effect of tip speed on the propulsive efficiency was negligible within the range of the tests, which was from 600 to 1,000 feet per second (about 0.5 to 0.9 the velocity of sound in air)" (p. 465).

This report presents the results of full-scale tests made on a 10-foot 5-inch propeller on a geared J-5 engine and also on a similar 8-foot 11-inch propeller on a direct-drive J-5 engine. Each propeller was tested at two different pitch settings, and with a large and a small fuselage. The investigation was made in such a manner that the propeller-body interference factors were isolated, and it was found that, considering this interference only, the geared propellers had an appreciable advantage in propulsive efficiency, partially due to the larger diameter of the propellers with respect to the bodies, and partially because the geared propellers were located farther ahead of the engines and bodies.

This paper gives some quantitative measurements of wind tunnel turbulence and its effect on the air resistance of spheres and airship models, measurements made possible by the hot wire anemometer and associated apparatus in its original form was described in Technical Report no. 320 and some modifications are presented in an appendix to the present paper. One important result of the investigation is a curve by means of which measurements of the air resistance of spheres can be interpreted to give the turbulence quantitatively. Another is the definite proof that the discrepancies in the results on the N. P. L. Standard airship models are due mainly to differences in the turbulences of the wind tunnels in which the tests were made.

The investigation described in this report was conducted for the purpose of comparing an oleo-rubber-disk and a rubber-cord landing gear, built for use on an F6C-4 airplane. The investigation consisted of drop tests under various loading conditions and flight tests on an F6C-4 airplane. In the drop tests the total work done on each gear and the work done on each of the shock-absorbing units were determined. For both drop tests and flight tests the maximum loads and accelerations were determined. The comparative results showed that the oleo gear was slightly superior in reducing the ordinary landing shocks, that it had a greater capacity for work, and that it was very superior in the reduction of the rebound. The results further showed that for drops comparable to very severe landings, the rubber-cord gear was potentially more effective as a shock-reducing mechanism. However, due to the construction of this chassis, which limited the maximum elongation of the cords, this gear was incapable of withstanding as severe tests as the oleo gear. The action of the oleo gear was greatly inferior to the action of an ideal gear. The maximum accelerations encountered during the flight tests for severe landings were 3.64g for …

This report presents the results of an investigation to determine experimentally the instantaneous pressures at the discharge orifice of a common-rail fuel injection system in which the timing valve and cut-off valve were at some distance from the automatic fuel injection valve, and also to determine the methods by which the pressure fluctuations could be controlled. The results show that pressure wave phenomena occur between the high-pressure reservoir and the discharge orifice, but that these pressure waves can be controlled so as to be advantageous to the injection of the fuel. The results also give data applicable to the design of such an injection system for a high-speed compression-ignition engine.

This report presents the results of wind tunnel tests to determine the effect on the characteristics of a propeller of inclining the propeller axis at small angles to the relative wind. Tests were made of a full-scale propeller and fuselage combination at four angles of yaw (0 degree, +5 degrees, +10 degrees, +15 degrees), and of a model propeller, nacelle, and wing combination of five angles of pitch (-5 degrees, 0 degree, +5 degrees, +10 degrees and +15 degrees). The results of the full-scale tests of a propeller and fuselage, without a wing, show that the effect on the propeller performance is small. Similar results are shown by the model test data except that where the propeller is directly in front of the wing there is an appreciable decrease in effective thrust and propulsive efficiency with increase of angle of pitch.

An investigation of a large group of related airfoils was made in the NACA variable-density wind tunnel at a large value of the Reynolds number. The tests were made to provide data that may be directly employed for a rational choice of the most suitable airfoil section for a given application. The variation of the aerodynamic characteristics with variations in thickness and mean-line form were systematically studied. (author).

"The wall interference on an airfoil of finite span in an open-throat rectangular section has been treated theoretically and the result is presented in a convenient formula. Numerical results are given in tables and diagrams" (p. 355).

From Summary: "This report is the third of a series giving the results obtained in the 20-foot wind tunnel on the interference drag, and propulsive efficiency of nacelle-propeller-wing combinations. The first report gave the results of the tests of an NACA cowled air-cooled engine nacelle with tractor propeller located in 21 positions with reference to a thick wing. The second report gave the results for several engine cowlings and nacelles with tractor propeller located in four positions with reference to same wing. The present report gives results of tests of the same nacelles and cowlings in the same positions with reference to a smaller wing of Clark y section. The lift, drag, and propulsive efficiency were determined at several angles of attack for each cowling and in each nacelle location."

This report presents the results of wind tunnel tests to determine the effectiveness of various methods of reducing the high control forces of unbalanced upper-surface ailerons and of unbalanced split flaps. A balanced split flap was developed that required control forces about half those of the unbalanced split flap when the balanced split flap was deflected to give approximately the same maximum lift.

"The magnitudes of the yawing moments produced by various parts of an airplane during spins have previously been found to be of major importance in determining the nature of the spin. Discrepancies in resultant yawing moments determined from model and full-scale tests, however, have indicated the probable importance of scale effect on the model. In order to obtain data for a more detailed comparison between full-scale and model results, flight tests were made to determine the yawing moments contributed by various parts of an airplane in spins. The inertia moment was determined by the usual measurement of the spinning motion, and the aerodynamic yawing moments on the fuselage, fin, and rudder were determined by pressure-distribution measurements over these parts of the airplane" (p. 305).

This report presents the results of an analytical study of the lateral controllability of an airplane in which both the static rolling and yawing moments supplied by the controls and the reactions due to the inherent stability of the airplane have been taken into account. The investigation was undertaken partly for the purpose of coordinating the results of a long series of wind-tunnel investigations with phenomena observed in flight tests; for this reason a hypothetical average airplane, embodying the essential characteristics of both wind-tunnel models and the full-size test airplanes, was assumed for the study.

The cooling of a single-row radial air-cooled engine using several cowling arrangements has been studied in the NACA 20-foot wind tunnel. The results show the effect of the propeller and several cowling arrangements on cooling for various values of the indicated horsepower in the climb condition. A table giving comparative performance of the various cowling arrangements is presented. The dependence of temperature on indicated horsepower and pressure drop across the baffles is shown by charts. Other charts show the limiting indicated horsepower against the pressure drop across the engine and the heat dissipated at various values of the indicated horsepower.

"An analysis of the principal results of recent NACA lateral control research is made by utilizing the experience and progress gained during the course of the investigation. Two things are considered of primary importance in judging the effectiveness of different control devices: the (calculated) banking and yawing motion of a typical small airplane caused by a deflection of the control, and the stick force required to produce this deflection. The report includes a table in which a number of different lateral control devices are compared on these bases" (p. 1).

"The problem of the skin-stringer combinations used as axially loaded panels or as covers for box beams is considered from the point of view of the practical stress analyst. By a simple substitution the problem is reduced to the problem of the single-stringer structure, which has been treated in NACA Report no. 608. The method of making this substitution is essentially empirical; in order to justify it, comparisons are shown between calculations and strain-gage tests of three beams tested by the author and of one compression panel and three beams tested and reported elsewhere" (p. 469).

"Factors are obtained from semiempirical equations for correcting engine-cylinder temperatures for variation in important engine and cooling conditions. The variation of engine temperatures with atmospheric temperature is treated in detail, and correction factors are obtained for various flight and test conditions, such as climb at constant indicated air speed, level flight, ground running, take-off, constant speed of cooling air, and constant mass flow of cooling air. Seven conventional air-cooled engine cylinders enclosed in jackets and cooled by a blower were tested to determine the effect of cooling-air temperature and carburetor-air temperature on cylinder temperatures" (p. 49).

"Results of flight tests of the performance and cooling characteristics of three NACA D cowlings and of a conventional NACA D cowling on the XP-42 airplane are summarized and compared. The D cowling is, in general, characterized by the use of an annular inlet and diffuser section for the engine-cooling air. The D cowlings tested were a long-nose high-inlet-velocity cowling, a short-nose high-inlet-velocity cowling, and a short-nose low inlet-velocity cowling" (p. 371).

The effects of mass distribution on lateral stability and control characteristics of an airplane have been determined by flight tests of a model in the NACA free-flight tunnel. In the investigation, the rolling and yawing moments of inertia were increased from normal values to values up to five times normal. For each moment-of-inertia condition, combinations of dihedral and vertical-tail area representing a variety of airplane configurations were tested. The results of the flight tests of the model were correlated with calculated stability and control characteristics and, in general, good agreement was obtained.

Charts are presented that permit the estimation of F-3 and F-4 knock-limited performance ratings for certain ternary and quaternary fuel blends. Ratings for various ternary and quaternary blends estimated from these charts compare favorably with experimental F-3 and F-4 ratings. Because of the unusual behavior of some of the aromatic blends in the F-3 engine, the charts for aromatic-paraffinic blends are probably less accurate than the charts for purely paraffinic blends.

From Summary: "An analysis of available theory on seaplane impact and a proposed modification thereto are presented. In previous methods the overall momentum of the float and virtual mass has been assumed to remain constant during the impact but the present analysis shows that this assumption is rigorously correct only when the resultant velocity of the float is normal to the keel."

"A method is presented for calculating wing characteristics by lifting-line theory using nonlinear section lift data. Material from various sources is combined with some original work into the single complete method described. Multhopp's systems of multipliers are employed to obtain the induced angle of attack directly from the spanwise lift distribution. Equations are developed for obtaining these multipliers for any even number of spanwise stations, and values are tabulated for 10 stations along the semispan for asymmetrical, symmetrical, and antisymmetrical lift distributions" (p. 1).

Empirical design curves are presented for the critical stress of thin-wall cylinders loaded in axial compression. These curves are plotted in terms of the nondimensional parameters of small-deflection theory and are compared with theoretical curves derived for the buckling of cylinders with simply supported and clamped edges. An empirical equation is given for the buckling of cylinders having a length-radius ratio greater than about 0.75.