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National Advisory Committee For Aeronautics Research Abstracts NO.48 SEPTEMBER 8, 1953 CURRENT NACA REPORTS NACA TN 2965 AN ANALYSIS OF NORMAL-ACCELERATION AND AIRSPEED DATA FROM A FOUR-ENGINE TYPE OF TRANSPORT AIRPLANE IN COMMERCIAL OPERA- TION ON AN EASTERN UNITED STATES ROUTE FROM NOVEMBER 1947 TO FEBRUARY 1950. Thomas L. Coleman and Paul W. J. Schumacher. August 1953. 27p. diagrs., 5 tabs. (NACA TN 2965) Normal acceleration and airspeed data covering about 50, 000 hours of flight of one type of four- engine transport airplane flown in commercial oper- ations at altitudes to 20,000 feet on a north-south route in the eastern United States are analyzed to de- termine the gusts encountered and the accelerations experienced. Comparisons are made between the present results and the results previously obtained from other operations. Effects of airpseed and of seasons on the gusts and accelerations are indicated. NACA TN 2984 STUDIES OF THE LATERAL-DIRECTIONAL FLY- ING QUALITIES OF A TANDEM HELICOPTER IN FORWARD FLIGHT. Kenneth B. Amer and Robert J. Tapscott. August 1953. 42p. diagrs., photos., tab. (NACA TN 2984) Results of flight measurements and pilots' opinions of the forward-flight lateral-directional flying qualities of a tandem helicopter in several different configura- tions are compared and analyzed. The conclusions are presented in the form of desirable flying-qualities goals applicable to all types of helicopters. Compari- son between theoretical analyses and experimental results indicates theory to be a useful tool for study- ing means of achieving these goals. On the basis of theoretical analyses, possible practical methods of achieving these goals in the tandem helicopter are suggested. NACA TN 2986 EFFECT OF BLADE-THICKNESS TAPER ON AXIAL-VELOCITY DISTRIBUTION AT THE LEADING EDGE OF AN ENTRANCE ROTOR-BLADE ROW WITH AXIAL INLET, AND THE INFLUENCE OF THIS DISTRIBUTION ON ALINEMENT OF THE ROTOR BLADE FOR ZERO ANGLE OF ATTACK John D. Stanitz. August 1953. 33p. diagrs (NACA TN 2986) A method is developed for estimating the effect of blade-thickness taper on the inlet axial-velocity dis- tribution of an entrance rotor-blade row with axial inlet, and the influence of this velocity distribution on the alinement of the rotor blade for zero effective angle of attack (that is, zero blade loading at the nose). This alinement of the blade requires a devia- tion between the angle of the blade camber line di- rection at the inlet and the upstream relative flow direction. The method is developed for compress- ible and incompressible nonviscous fluids, and re- sults are presented for incompressible flow into a plane, two-dimensional cascade and for compress- ible flow into an entrance rotor-blade row with tapered blades. It is e for the en- trance rotor-blade r iil 4; 'tbade taper has a large effect on t In deviatiloh fe; whereas compressibility h small effect, eapbi perhaps at the hub, and the ream relative flow aeclion also has a small eff 9 NACA TN 2987 \ CHARTS RELATIN HIE % IESSPOE BUCKLING STRESS OF LONGIT LLY SUPPORTED PLATES TO THE EFFECTIVE DEFLECTIONAL AND ROTATIONAL STIFFNESS OF THE SUPPORTS. Roger A. Anderson and Joseph W. Semonian. August 1953. 53p. diagrs., 4 labs. INACA TN 2987) The stability of a plate under edge compressive stress is analyzed in terms of the deflectional and rotational stdffnesses of one or more longitudinal lines of support between the plate side edges. The results are presented in the form of charts which make possible the determination of the compressive buckling stress of plates supported by members whose stiffness may or may not be defined by ele- mentary beam bending and twisting theory but yet whose effective restraint is amenable to evaluation. The deflectional and rotational restraint provided by longitudinal stiffeners and full-depth webs is dis- cussed, and numerical examples illustrate the application of the charts to the design of wing struc- tures NACA TN 2990 FLIGHT MEASUREMENTS AND ANALYSIS OF HEL- ICOPTER NORMAL LOAD FACTORS IN MANEU- VERS F. B Gustafson and Almer D. Crim. August 1953 29p diagrs photos., 2 tabs (NACA TN 2990) Flight tests have been conducted in two single-rotor helicopters to determine the load factors due to var- ious maneuvers. A simple theoretical method of es- timating for new designs the maximum load factor that can be attained for any given flight condition is also presented, and the results compared with those obtained from the flight tests. * AVAILABLE ON LOAN ONLY. ADDRESS REQUESTS FOR DOCUMENTS TO NACA, 1724 F ST, NW, WASHINGTON 5,. D C, CITING CODE NUMBER ABOVE EACH TITLE; THE REPORT TITLE AND AUTHOR 6 29. /30.Z ttS^\- NACA 2 RESEARCH ABSTRACTS NO.48 NACA TN 2991 ACCELERATIONS AND PASSENGER HARNESS LOADS MEASURED IN FULL-SCALE LIGHT- AIRPLANE CRASHES. A. Martin Elband, Scott H. Simpkinson and Dugald 0. Black. August 1953. 67p. diagrs., photos. (NACA TN 2991) Full-scale light-airplane crashes simulating stall- spin accidents were conducted to determine the de- celerations to which occupants are exposed and the resulting harness forces encountered in this type of accident. Crashes at impact speeds from 42 to 60 miles per hour were studied. The airplanes used were of the familiar steel-tube, fabric-covered, tan- dem, two-seat type. In crashes up to an impact speed of 60 miles per hour, crumpling of the forward fuselage structure prevented the maximum decelera- tion at the rear-seat location from exceeding 26 to 33g. This maximum g value appeared independent of the impact speed. Restraining forces in the seat- belt shoulder-harness combination reached 5800 pounds. The rear-seat occupant can survive crashes of the type studied at impact speeds up to 60 miles per hour, if body movement is restrained by an adequate seat-belt shoulder-harness combina- tion, so as to prevent injurious contact with obsta- cles normally present in the cabin. Inwardly collapsing cabin structure, however, is a potential hazard in the higher-speed crashes. NACA TN 3000 STUDIES OF THE USE OF FREON-12 AS A WIND- TUNNEL TESTING MEDIUM. Albert E. von Doenhoff, Albert L. Braslow and Milton A. Schwartzberg. August 1953. 57p. diagrs. (NACA TN 3000) A number of studies relating to the use of Freon-12 as a substitute medium for air in aerodynamic testing have been made. The use of Freon-12 in- stead of air makes possible large savings in wind- tunnel drive power. Because of the fact that the ratio of specific heats is approximately 1. 13 for Freon-12 as compared with 1. 4 for air, some differ- ences exist between data obtained in Freon-12 and in air. Methods for predicting aerodynamic character- istics of bodies in air from data obtained in Freon- 12, however, have been developed, which provide substantial agreement in all cases for which compar- ative data are available. The Freon charging and recovery system used for the Langley low- turbulence pressure tunnel is described. NACA RM E53F19 MEASUREMENT AND ANALYSIS OF TURBULENT FLOW CONTAINING PERIODIC FLOW FLUCTUA- TIONS. William R. Mickelsen and James C. Laurence. August 1953. 45p. diagrs. (NACA RM E53F19) Techniques are presented for the measurement of the energy spectrum of flow fluctuations in both axial and lateral flow directions. A simple spectrum analysis is presented by which quantitative distinction may be made between turbulence and the flow disturbances associated with sound waves in ducts. Experimental data are presented which indicate that the energy spectrum of the turbulence is not affected by periodic and random sound disturbances outside the frequency ranges containing the disturbances. Preliminary measurements are presented that illustrate the effect of combustion on the approach-stream velocity- fluctuation spectra in a ram-jet combustor. \ NACA RM L53F16 SOME INFORMATION ON THE STRENGTH OF THICK-SKIN WINGS WITH MULTIWEB AND MULTI- POST STABILIZATION. Roger A. Anderson, Richard A. Pride and Aldie E. Johnson, Jr. August 1953. 19p. diagrs., 3 tabs. (NACA RM L53F16) The preliminary results of strength tests on thick- skin wing structures are described. Some of the factors which have a major influence on the buckling behavior and strength of multiweb and multipost stiffened construction are illustrated by the data pre- sented, and the conditions under which a combination of multiweb and multipost construction may be used are discussed. Also given are the results of bending tests on hollow circular-are airfoils. NACA TM 1335 MOTION OF A CYLINDER UNDER THE SURFACE OF A HEAVY FLUID. (Dvizhenie tsilindra pod poverkhnostyu tyazheloi zhidkosti). L. N. Sretensky. August 1953. 36p. (NACA TM 1335. Trans. from Central Aero-Hydrodynamical Institute. Transactions, Rept.346, 1938, p.3-27). General equations are derived for the approximate solution of the flow of a heavy infinite depth about a submerged circular cylinder where the center of the cylinder is submerged 1.5 diameter or greater. Then by replacing the cylinder by a dipole of a cer- tain strength an equation is derived for the wave re- sistance of a circular cylinder moving in a fluid of finite depth. BRITISH REPORTS N-26059* Aeronautical Research Council (Gt. Brit.) THEORETICAL CONSIDERATIONS ON FREE CON- VECTION IN TUBES. M. J. Lighthill. July 21, 1952. 44p. diagrs. (ARC 15,074; FM 1758) Methods are developed for predicting the flow and heat transfer due to free convection in heated verti- cal tubes, closed at the bottom and opening into a reservoir of cool fluid at the top. These include methods of predicting whether the flow is laminar or turbulent, and whether the boundary layer of heated fluid fills or does not fill the tube, or fills it with a stagnant region near the closed end. The theory is extended to apply to a tube closed at both ends, part heated and part cooled. There is some discussion of a mechanical engineering application in which the ex- ternal force is not gravity but centrifugal. NACA RESEARCH ABSTRACTS NO. 48 N-26063, Aeronautical Research Council (Gt. Brit.) THE DESIGN OF THIN FINITE WINGS IN INCOM- PRESSIBLE FLOW. G. J. Hancock. September 2, 1952. 17p. diagrs. (ARC 15,185; FM 1788) A method is developed for designing thin finite wings with prescribed lift distributions. Particular attention is given to wings which, at a certain opti- mum angle of incidence. have zero loading along the whole leading edge. It is suggested that such a wing will have greater range of lift coefficeint for low drag than other wings with the same plan form. On the basis of the linearized theory a formula, re- lating the wing surface to the pressure distribution over the surface, is deduced which differs from the usual potential relationship by avoiding the difficulty of the nonuniform convergence with respect to the normal distance away from the wing surface singularities. The surface integral which is de- veloped includes a regular singularity and a definite limiting process. Three examples have been worked out in which the condition of smooth flow at the leading edee is satisfied. N-26068' Aeronautical Research Council (Gt. Brit.) ON BOUNDARY LAYERS AND UPSTREAM IN- FLUENCE. U SUPERSONIC FLOW WITHOUT SEPARATION. M. J. Lighthill. October 23, 1952. 38p. diagrs., tab. (ARC 15, 298; FM 1805a) This report is concerned with interactions between a boundary layer and a supersonic main stream which take place without separation. These arise either from expansive disturbances, or from relatively weak compressive disturbances to a turbulent layer. The analysis may also have value for the study of the flow upst reanm of separation in interactions with laminar separation. N-26070* Aeronautical Research Council (Gt. Brit.) ON EDGE TONES AND ASSOCIATED PHENOMENA. Alan Powell. October 7, 1952. 17p. diagr., photos., tab. (ARC 15,333; FM 1809) The edge-tone phenomena occurring at high jet speeds have been photographed by the Schlieren method and the sound waves produced are clearly visible. They are of opposite phase on each side of the stream, and microphone traverses have shown this to be the case at low speeds also. This obser- vation makes possible an explanation of the mechan- ism by virtue of the "sensitivity" of the jet, which is particularly susceptible to this form of acoustic disturbance whereby the sound waves give rise to stream disturbances at the jet orifice. Two basic relationships are given, one connecting the relative phases of the motion and the other dealing with the effect e efficiencies of each of the component pro- cesses. 3 N-26300* Royal Aircraft Establilshment tGt. Brit.) SOME REMARKS ON THE CHOICE AND PRESEN- TATION OF FORMULAE FOR TURBULENT SKIN FRICTION IN COMPRESSIBLE FLOW. R. J. Monaghan. May 1953. 13p. (RAE Tech. Note Aero 2246) A review of the various formulas which have been developed for estimating turbulent skin friction in compressible flow has already been given and is mainly concerned with the theoretical aspects of the problem. The object of the present note is to ex- amine briefly the practical application of the re- sults obtained. It is suggested that there is now sufficient evidence to justify changing the com- pressibility parameter frori Mach number to the ratio (surface temperature)/(local ambient temper- ature). The merits of various formulas are dis- cussed and some brief remarks are made on the ef- fects of pressure gradients and on the present state of knowledge concerning transition. N-26301* Royal Aircraft Establishment (Gt. Brit.) AN ELECTRO-HYDRAULIC POWERED FLYING CONTROL SYSTEM WITH AUTOMATIC SAFE- GUARDS AND VARIABLE CONTROL CHARACTER- ISTICS. C. D. Watson. March 1953. 17p. photos., diagrs. (RAE Tech. Note Mech. Eng. 77) A standard Lincoln aircraft was fitted with an auto- pilot and powered flying controls to investigate the stability conditions of two series connected servo- mechanisms in an aircraft control system. This note describes the design and installation of the electrohydraulic power control units, and the vari- ous automatic and safety provisions. In addition, details are given of a variable rate spring feel system, semiautomatic feel trimming and variable servocontrol characteristics. To introduce power- ful threshold damping should sustained oscillations arise in flight, a divided reset mechanism is in- corporated, which is also described. Stability curves show the effect of tuning this mechanism. N-26302 * National Gas Turbine Establishment (Gt. Brit.) THE MEASUREMENT OF TRUE MEAN PRESSURES AND MACH NUMBERS IN OSCILLATORY FLOW. M. V. Nesbitt. March 1953. 37p. diagrs. (NGTE Memo. M. 180) In this paper, the problem of measuring mean pressures and Mach numbers under regular oscillat- ing flow conditions is considered. Firstly, a pa- rameter is developed which enables the damping or- ifice and instrument volume to be designed to give any required variation in pressure in the measur- ing section. Next the relationship between the measured mean pressure and true mean pressure is determined for rectangular, sine, and sawtooth wave forms and finally the relation between true mean Mach numbers and Mach numbers as computed from true mean pressures is determined for rec- tangular, sine and sawtooth waves :raveling up and downstream. UNIVERSITY OF FLORIDA 3 1262 08153 284 7 N-26303* Aeroplane and Armament Experimental Establish- ment (Gt. Brit.) THE FORWARD TAKE-OFF OF A HELICOPTER. F. O'Hara. June 26, 1953. 21p. diagrs. ,AAEE Res 276) A theoretical analysis is given of the accelerated motion of a single rotor helicopter for estimation of the forward take-off performance. The motion is considered in stages during which either the disk attitude to the horizontal or the flight speed is con- stant. Equations are derived for the motion along and normal to the flight path and solutions are given assuming constant mean values for the aerodynamic forces on the rotor and fuselage. The equations of motion for constant disk attitude have a simple solu- tion for motion from rest (and for special initial conditions) giving a straight flight paih. and a gen- eral solution giving a curved flight path. The per- formance at constant speed is considered for a gen- eral climb away case and also for climb away approaching steady flight conditions with the thrust approximately equal to the aircraft weight. For application of the theory, charts of the various so- lutions are given covering a representative range of the variables. N-26335 * Royal Aircraft Establishment (Gt. Brit.) DESIGN CRITERION FOR FATIGUE OF WINGS. P. B. Walker. May 1953. 16p. diagr., tab. (RAE Structures 146) Design criteria for wings are postulated from a study of past and present knowledge of aircraft structural fatigue. Earlier criteria are considered first, and are then followed by new criteria that are believed to be more appropriated to modern condi- tions. The main general conclusions are, first, that design must be based on a fatigue test of critical components and, secondly, that the conditions for this test must be derived from a typical gust case specially devised for fatigue life, followed by sug- gested adjustments when statistical information is available concerning the particular operational conditions. MISCELLANEOUS NACA TM 1317 Errata No. 2 on "A SIMPLE NUMERICAL METHOD FOR THE CALCULATION OF THE LAMINAR BOUNDARY LAYER." K. Schr5der. April 1952. NACA RESEARCH ABSTRACTS NO. 48 UNPUBLISHED PAPERS "I N-19474* Cornell U. Graduate School of Aeronautical Engi- neering. ON THE LONGITUDINAL STRESS PRO- PAGATION IN THE PLASTIC RANGE. Kuang-Tao Hsu, Cornell University. September 1950. vi, 67p. diagrs., photos. (Cornell U. Graduate School of Aeronautical Engineering) This report presents a graphical method to solve the problem of longitudinal wave propagation in the plastic range and a short summary of the theories developed by others. The problem of a semi- infinite plastic bar struck by a rigid mass and that of a constant force impact on the bar with the mass attached at its end are investigated. A short inves- tigation of the experimental method of photoelasticity applied to impact test is given. N-24814 Gas Turbine Lab., Mass Inst. of Tech. LAMINAR AND TURBULENT BOUNDARY LAYERS IN A ROTATING PIPE. A PRELIMINARY THEO- RETICAL AND EXPERIMENTAL INVESTIGATION. Joel S. Isenberg and Alan H. Stenrung. June 1952. vi, 67p. diagrs., photos. (Gas Turbine Lab., Mass. Inst. of Tech) An analysis is made of the boundary layer which forms in a straight rotating pipe through wluch a un- iform incompressible stream of fluid is flowing in the cases when this layer is entirely laminar or en- tirely turbulent. The analogous problem of a ro- tating flow entering a fixed pipe is also analyzed. NACA-Langley 9-8-53 -4000 |
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