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Some effects of nonlinear variation in the directional-stability and damping-in-yawing derivatives on the lateral stability of an airplane

Description: A theoretical investigation has been made to determine the effect of nonlinear stability derivatives on the lateral stability of an airplane. Motions were calculated on the assumption that the directional-stability and the damping-in-yawing derivatives are functions of the angle of sideslip. The application of the Laplace transform to the calculation of an airplane motion when certain types of nonlinear derivatives are present is described in detail. The types of nonlinearities assumed correspond to the condition in which the values of the directional-stability and damping-in-yawing derivatives are zero for small angle of sideslip.
Date: January 1, 1951
Creator: Sternfield, Leonard
Item Type: Report
Partner: UNT Libraries Government Documents Department

Some theoretical low-speed span loading characteristics of swept wings in roll and sideslip

Description: The Weissinger method for determining additional span loading for incompressible flow is used to find the damping in roll, the lateral center of pressure of the rolling for wing plan forms of various aspect ratios, taper ratios, and sweep angles. In addition, the applicability of the method to the determination of certain other aerodynamic derivatives is investigated, and corrections for the first-order effects of compressibility are indicated. The agreement obtained between experimentally and theoretically determined values for the aerodynamic coefficients indicates that the method of Weissinger is well suited to the calculation of such resulting aerodynamic derivatives of wings as do not involve considerations of tip suction.
Date: January 1, 1950
Creator: Bird, John D
Item Type: Report
Partner: UNT Libraries Government Documents Department

Sound-level measurements of a light airplane modified to reduce noise reaching the ground

Description: An Army liaison-type airplane, representative of personal airplanes in the 150 to 200 horsepower class, has been modified to reduce propeller and engine noise according to known principles of airplane-noise reduction. Noise-level measurements demonstrate that, with reference to an observer on the ground, a noisy airplane of this class can be made quiet -- perhaps more quiet than necessary. In order to avoid extreme and unnecessary modifications, acceptable noise levels must be determined.
Date: January 1, 1949
Creator: Vogeley, A W
Item Type: Report
Partner: UNT Libraries Government Documents Department

Sound from a two-blade propeller at supersonic tip speeds

Description: Report presents the results of sound measurements at static conditions made for a two-blade 47-inch-diameter propeller in the tip Mach number range 0.75 to 1.30. For comparison, spectrums have been obtained at both subsonic and supersonic tip speeds. In addition, the measured data are compared with calculations by the theory of Gutin which has previously been found adequate for predicting the sound at subsonic tip speeds. Curves are presented from which the maximum over-all noise levels in free space may be estimated if the power, tip Mach number, and distance are known.
Date: January 1, 1952
Creator: Hubbard, Harvey H & Lassiter, Leslie W
Item Type: Report
Partner: UNT Libraries Government Documents Department

Stalling of helicopter blades

Description: Theoretical studies have predicted that operation of helicopter rotor beyond certain combinations of thrust, forward speed, and rotational speed might be prevented by rapidly increasing stalling of the retreating blade. The same studies also indicate that the efficiency of the rotor will increase until these limits are reached or closely approached, so that it is desirable to design helicopter rotors for operation close to the limits imposed by blade stalling. Inasmuch as the theoretical predictions of blade stalling involve numerous approximations and assumptions, an experimental investigation was needed to determine whether, in actual practice, the stall did occur and spread as predicted and to establish the amount of stalling that could be present without severe vibration or control difficulties being introduced. This report presents the results of such an investigation.
Date: January 1, 1946
Creator: Gustafson, F B & Myers, G C , Jr
Item Type: Report
Partner: UNT Libraries Government Documents Department

The influence of lateral stability on disturbed motions of an airplane with special reference to the motions produced by gusts

Description: Distributed lateral motions have been calculated for a hypothetical small airplane with various modifications of fin area and dihedral setting. Special combinations of disturbing factors to simulate gusts are considered and the influence of lateral stability on the motions is discussed. Fin area and wing dihedral were found to be of primary importance in side gusts. It was found that the rolling action of the wing with as much as 5 degrees dihedral was distinctly unfavorable, especially when the weathercock stability was small. It is pointed out that the greatest susceptibility to lateral disturbances lies in the inherent damping and coupling moments developed by the wing.
Date: January 1, 1938
Creator: Jones, Robert T
Item Type: Report
Partner: UNT Libraries Government Documents Department

Initial results of instrument-flying trials conducted in a single-rotor helicopter

Description: Instrument-flying trials have been conducted in a single-rotor helicopter, the maneuver stability of which could be changed from satisfactory to unsatisfactory. The results indicated that existing longitudinal flying-qualities requirements based on contact flight were adequate for instrument flight at speeds above that for minimum power. However, lateral-directional problems were encountered at low speeds and during precision maneuvers. The adequacy, for helicopter use, of standard airplane instruments was also investigated, and the conclusion was reached that special instruments would be desirable under all conditions, and necessary for sustained low-speed instrument flight.
Date: January 1, 1953
Creator: Crim, Almer D; Reeder, John P & Whitten, James B
Item Type: Report
Partner: UNT Libraries Government Documents Department

The interference between struts in various combinations

Description: This report presents the results of wind tunnel tests made to determine the interference drag arising from various arrangements of streamline struts and round struts, or cylinders. Determinations were made of the interference drag of struts spaced side by side, struts in tandem, tandem struts encased in a single fairing, a strut intersecting a plane, and struts intersecting to form a v. Three sizes of struts were used for most of the tests. These tests show that the interference drag arising from struts in close proximity may be of considerable magnitude, in some instances amounting to more than the drag of the struts themselves.
Date: January 1, 1934
Creator: Biermann, David & Herrnstein, William H , Jr
Item Type: Report
Partner: UNT Libraries Government Documents Department

Interference method for obtaining the potential flow past an arbitrary cascade of airfoils

Description: A procedure is presented for obtaining the pressure distribution on an arbitrary airfoil section in cascade in a two-dimensional, incompressible, and nonviscous flow. The method considers directly the influence on a given airfoil of the rest of the cascade and evaluates this interference by an iterative process, which appeared to converge rapidly in the cases tried (about unit solidity, stagger angles of 0 degree and 45 degrees). Two variations of the basic interference calculations are described. One, which is accurate enough for most purposes, involves the substitution of sources, sinks, and vortices for the interfering airfoils; the other, which may be desirable for the final approximation, involves a contour integration. The computations are simplified by the use of a chart presented by Betz in a related paper. Illustrated examples are included.
Date: January 1, 1947
Creator: Katzoff, S; Finn, Robert S & Laurence, James C
Item Type: Report
Partner: UNT Libraries Government Documents Department

Interference of Tail Surfaces and Wing and Fuselage from Tests of 17 Combinations in the N.A.C.A. Variable-Density Tunnel

Description: An investigation of the interference associated with tail surfaces added to wing-fuselage combinations was included in the interference program in progress in the NACA variable-density tunnel. The results indicate that, in aerodynamically clean combinations, the increment of the high-speed drag can be estimated from section characteristics within useful limits of accuracy. The interference appears mainly as effects on the downwash angle and as losses in the tail effectiveness and varies with the geometry of the combination. An interference burble, which markedly increases the glide-path angle and the stability in pitch before the actual stall, may be considered a means of obtaining satisfactory stalling characteristics for complete combination.
Date: January 1, 1939
Creator: Sherman, Albert
Item Type: Report
Partner: UNT Libraries Government Documents Department

Interference of wing and fuselage from tests of 28 combinations in the NACA variable-density tunnel

Description: Report presents the results of tests conducted on 28 wing-fuselage combinations made in the variable-density wind tunnel as a part of the wing-fuselage interference program being conducted therein and in addition to the 209 combinations previously reported in NACA-TR-540. These tests practically complete the study of combinations with a rectangular fuselage and continue the study of combinations with a round fuselage and a tapered wing.
Date: January 1, 1937
Creator: Sherman, Albert
Item Type: Report
Partner: UNT Libraries Government Documents Department

Interference on an airfoil of finite span in an open wind tunnel

Description: 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.
Date: January 1, 1934
Creator: Theodorsen, Theodore
Item Type: Report
Partner: UNT Libraries Government Documents Department

Internal-flow systems for aircraft

Description: An investigation has been made to determine efficient arrangements for an internal-flow system of an aircraft when such a system operates by itself or in combination with other flow systems. The investigation included a theoretical treatment of the problem and tests in the NACA 5-foot vertical wind tunnel of inlet and outlet openings in a flat plate and in a wing.
Date: January 1, 1941
Creator: Rogallo, F M
Item Type: Report
Partner: UNT Libraries Government Documents Department

Investigation of a systematic group of NACA 1-series cowlings with and without spinners

Description: Report presents the results of an investigation conducted in the Langley propeller research tunnel to study cowling-spinner combinations based on the NACA 1-series nose inlets and to obtain systematic design data for one family of approximately ellipsoidal spinners. In the main part of the investigation, 11 of the related spinners were tested in various combinations with 9 NACA open-nose cowlings, which were also tested without spinners. The effects of location and shape of the spinner, shape of the inner surface of the cowling lip, and operation of a propeller having approximately oval shanks were investigated briefly. In addition, a study was conducted to determine the correct procedure for extrapolating design conditions determined from the low-speed test data to the design conditions at the actual flight Mach number.
Date: January 1, 1949
Creator: Nichols, Mark R & Keith, Arvid L , Jr
Item Type: Report
Partner: UNT Libraries Government Documents Department

An investigation of four wings of square plan form at a Mach number of 6.9 in the Langley 11-inch hypersonic tunnel

Description: The results of pressure-distribution and force tests of four wings at a Mach number of about 6.9 and a Reynolds number of 0.98 x 10(6) in the Langley 11-inch hypersonic tunnel are presented. The wings had a square plan form, a 5-percent-chord maximum thickness, and diamond, half-diamond, wedge, and half-circular sections.
Date: January 1, 1957
Creator: Mclellan, Charles H; Bertram, Mitchel H & Moore, John A
Item Type: Report
Partner: UNT Libraries Government Documents Department

Summary of measurements in Langley full-scale tunnel of maximum lift coefficients and stalling characteristics of airplanes

Description: The results of measurements in the Langley full-scale tunnel of the maximum lift coefficients and stalling characteristics of airplanes have been collected. The data have been analyzed to show the nature of the effects on maximum lift and stall of wing geometry, fuselages and nacelles, propeller slipstream, surface roughness, and wing leading-edge appendages such as ducts, armaments, tip slats, and airspeed heads. Comparisons of full-scale-tunnel and flight measurements of maximum lift and stall are included in some cases, and the effects of the different testing techniques on the maximum-lift measurements are also given.
Date: January 1, 1945
Creator: Sweberg, Harold H & Dingeldein, Richard C
Item Type: Report
Partner: UNT Libraries Government Documents Department

Summary of lateral-control research

Description: A summary has been made of the available information on lateral control. A discussion is given of the criterions used in lateral-control specifications, of the factors involved in obtaining satisfactory lateral control, and of the methods employed in making lateral-control investigations in flight and in wind tunnels. The available data on conventional flap-type ailerons having various types of aerodynamic balance are presented in a form convenient for use in design. The characteristics of spoiler devices and booster mechanisms are discussed. The effects of Mach number, boundary layer, and distortion of the wing or of the lateral-control system are considered insofar as the available information permits. An example is included to illustrate the use of the design data. The limitations of the available information and some of the lateral-control problems that remain to be solved are indicated.
Date: January 1, 1947
Creator: Toll, Thomas A
Item Type: Report
Partner: UNT Libraries Government Documents Department

Summary of methods for calculating dynamic lateral stability and response and for estimating aerodynamic stability derivatives

Description: A summary of methods for making dynamic lateral stability and response calculations and for estimating the aerodynamic stability derivatives required for use in these calculations is presented. The processes of performing calculations of the time histories of lateral motions, of the period and damping of these motions, and of the lateral stability boundaries are presented as a series of simple straightforward steps. Existing methods for estimating the stability derivatives are summarized and, in some cases, simple new empirical formulas are presented. Detailed estimation methods are presented for low-subsonic-speed conditions but only a brief discussion and a list of references are given for transonic and supersonic speed conditions.
Date: January 1, 1952
Creator: Campbell, John P & Mckinney, Marion O
Item Type: Report
Partner: UNT Libraries Government Documents Department

High-Speed Tests of a Model Twin-Engine Low-Wing Transport Airplane

Description: Report presents the results of force tests made of a 1/8-scale model of a twin-engine low-wing transport airplane in the NACA 8-foot high-speed tunnel to investigate compressibility and interference effects of speeds up to 450 miles per hour. In addition to tests of the standard arrangement of the model, tests were made with several modifications designed to reduce the drag and to increase the critical speed.
Date: January 1, 1942
Creator: Becker, John V & LEONARD LLOYD H
Item Type: Report
Partner: UNT Libraries Government Documents Department

High-Speed Tests of Conventional Radial-Engine Cowlings

Description: The drag characteristics of eight radial-engine cowlings have been determined over a wide speed range in the NACA 8-foot high-speed wind tunnel. The pressure distribution over all cowlings was measured, to and above the speed of the compressibility burble, as an aid in interpreting the force tests. One-fifth-scale models of radial-engine cowlings on a wing-nacelle combination were used in the tests.
Date: January 1, 1942
Creator: Robinson, Russell G & Becker, John V
Item Type: Report
Partner: UNT Libraries Government Documents Department

Ice prevention on aircraft by means of engine exhaust heat and a technical study of heat transmission from a Clark y airfoil

Description: This investigation was conducted to study the practicability of employing heat as a means of preventing the formation of ice on airplane wings. The report relates essentially to technical problems regarding the extraction of heat from the exhaust gases and its proper distribution over the exposed surfaces. In this connection a separate study has been made to determine the variation of the coefficient of heat transmission along the chord of a Clark Y airfoil. Experiments on ice prevention both in the laboratory and in flight show conclusively that it is necessary to heat only the front portion of the wing surface to effect complete prevention. Experiments in flight show that a vapor-heating system which extracts heat from the exhaust and distributes it to the wings is an entirely practical and efficient method for preventing ice formation.
Date: January 1, 1933
Creator: Clay, William C & Theodorsen, Theodore
Item Type: Report
Partner: UNT Libraries Government Documents Department

Improved airplane windshields to provide vision in stormy weather

Description: This report presents the results of wind tunnel tests to determine possible improvements in the design of airplane windshields, particularly with respect to the pilot's vision from the cabin in stormy weather.
Date: January 1, 1935
Creator: Clay, William C
Item Type: Report
Partner: UNT Libraries Government Documents Department