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Comparison of Three Exit-Area Control Devices on an N.A.C.A. Cowling, Special Report

Description: Adjustable cowling flaps, an adjustable-length cowling skirt, and a bottom opening with adjustable flap were tested as means of controlling the rate of cooling-air flow through an air-cooled radial-engine cowling. The devices were tested in the NACA 20-foot tunnel on a model wing-nacelle-propeller combination, through an airspeed range of 20 to 80 miles per hour, and with the propeller blade angle set 23 degrees at 0.75 of the tip radius. The resistance of the engine to air flow through the cowling was simulated by a perforated plate. The results indicated that the adjustable cowling flap and the bottom opening with adjustable flap were about equally effective on the basis of pressure drop obtainable and that both were more effective means of increasing the pressure drop through the cowling than the adjustable-length skirt. At conditions of equal cooling-air flow, the net efficiency obtained with the adjustable cowling flaps and the adjustable-length cowling skirt was about 1% greater than the net efficiency obtained with the bottom opening with adjustable flap.
Date: May 1, 1940
Creator: McHugh, James G.

The flow of a compressible fluid past a sphere

Description: The flow of a compressible fluid past a sphere fixed in a uniform stream is calculated to the third order of approximation by means of the Janzen-Rayleigh method. The velocity and the pressure distribution over the surface of the sphere are computed and the terms involving the fourth power of the Mach number, neglected in Rayleigh's calculation, are shown to be of considerable importance as the local velocity of sound is approached on the sphere. The critical Mach number, that is, the value of the Mach number at which the maximum velocity of the fluid past the sphere is just equal to the local velocity of sound, is calculated for both the second and the third approximation and is found to be, respectively, Mcr=0.587 and Mcr=0.573.
Date: May 1, 1940
Creator: Kaplan, Carl

On the theory of unsteady planing and the motion of a wing with vortex separation

Description: The disturbance imparted to water by a planing body give rise to a wave form of motion on the free surface, the length of the waves increasing indefinitely with increase in the Froude number and being directly proportional to the latter in the case of the plane or two-dimensional problem. At large Froude numbers the effect of the weight shows up to any appreciable extent only at some distance from the body, so that the flow near the body can be considered as part of a flow of an infinitely extending weightless fluid. This paper is a consideration of these characteristics as well as a formulation of the planing problem and its relation to the problem of a thin wing.
Date: May 1, 1940
Creator: Sedov, L

Pressure-distribution investigation of an NACA 0009 airfoil with an 80-percent-chord plain flap and three tabs

Description: Pressure-distribution tests of an NACA 0009 airfoil with an 80-percent-chord plain flap and three plain tabs, having chord of 10, 20, and 30 percent of the flap chord, were made. Section data suitable for application to the design of horizontal and vertical tail surfaces were obtained. Resultant-pressure diagrams for the airfoil with the flap and the 20-percent-chord tab are presented. Plots are also given of increments of normal-force and hinge-moment coefficients for the airfoil, the flap, and the three tabs. A comparison of some characteristic slopes for the 30-, the 50-, and the 80-percent-chord flaps, tested in the general investigation of plain flaps for control surfaces, is included. Section aerodynamic and load data have been made available for a wide range of flap and a tab chords to be used on an NACA 0009 airfoil or on other conventional sections.
Date: May 1, 1940
Creator: Ames, Milton B , Jr & Sears, Richard I

Pressure-distribution investigation on an NACA 0009 airfoil with a 30-percent-chord plain flap and three tabs

Description: Pressure-distribution tests of an NACA 0009 airfoil with a 30-percent-chord plain flap and three plain tabs, having chords 10, 20, and 30 percent of the flap chord, were made. The purpose of these tests was to continue an investigation to supply structural and aerodynamic section data that may be applied to the design of horizontal and vertical tail surfaces. The results are presented as diagrams of resultant pressures and of resultant-pressure increments for the airfoil with the flap and the 20-percent-chord tab. Increments of normal-force and hinge-moment coefficients for the airfoil, the flap, and the three tabs are also given. At all unstalled flap and tab deflections, the experimental distributions agree well with those calculated by an analytical method. The agreement is poor, however, then the stalled or the unstalled condition of the flap or tab deflected alone was changed to an unstalled or stalled condition by the simultaneous deflection of both the flap and the tab.
Date: May 1, 1940
Creator: Ames, Milton B & Sears, Richard I

The ryegrasses.

Description: Describes different kinds of ryegrass, the best climate and soil for its growth, and the steps a farmer should take for successful hay and pasture growth.
Date: May 1940
Creator: Schoth, H. A. (Harry August), b. 1891. & Hein, M. A. (Mason August), b. 1894.

Some data on the static longitudinal stability and control of airplanes : design of control surfaces

Description: In the solution of a number of problems on the stability and controllability of airplanes, there arises the necessity for knowing the characteristics of the tail surfaces of the types in common use today. Of those characteristics, the most important are the effectiveness and hinge moments of the tail surfaces. As has been shown in the present paper, there exists the possibility of determining these characteristics by the formulas obtained with a degree of accuracy sufficient for the purposes of preliminary computation. These formulas take into account a number of fundamental tail characteristics such as tail cut-outs on the control surface and the form of the control surface leading edge.
Date: May 1, 1940
Creator: Martinov, A & Kolosov, E

Wind-tunnel investigation of two airfoils with 25-percent-chord Gwinn and plain flaps

Description: Aerodynamic force tests of an NACA 23018 airfoil with a Gwinn flap having a chord 25 percent of the overall chord and of an NACA 23015 airfoil with a plain flap having a 25-percent chord were conducted to determine the relative merits of the Gwinn and the plain flaps. The tests indicated that, based on speed-range ratios, the plain flap was more effective than the Gwinn flap. At small flap deflections, the plain flap had lower drag coefficients at lift-coefficient values less than 0.70. For lift coefficients greater than 0.70, however, the Gwinn flap at all downward flap deflections had the lower drag coefficients.
Date: May 1, 1940
Creator: Ames, Milton B , Jr