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A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System (open access)

A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System

"The relation between the elevator hinge moment parameters and the control forces for changes in forward speed and in maneuvers is shown for several values of static stability and elevator mass balance. The stability of the short period oscillations is shown as a series of boundaries giving the limits of the stable regions in terms of the elevator hinge moment parameters. The effects of static stability, elevator moment of inertia, elevator mass unbalance, and airplane density are also considered" (p. 1).
Date: 1944
Creator: Greenberg, Harry & Sternfield, Leonard
System: The UNT Digital Library
Performance of NACA eight-stage axial-flow compressor designed on the basis of airfoil theory (open access)

Performance of NACA eight-stage axial-flow compressor designed on the basis of airfoil theory

"The NACA has conducted an investigation to determine the performance that can be obtained from a multistage axial-flow compressor based on airfoil research. A theory was developed; an eight-stage axial-flow compressor was designed, constructed, and tested. The performance of the compressor was determined for speeds from 5000 to 14,000 r.p.m with varying air flow at each speed" (p. 81).
Date: August 1, 1944
Creator: Sinnette, John T., Jr.; Schey, Oscar W. & King, J. Austin
System: The UNT Digital Library
The Theory of Propellers 2: Method for Calculating the Axial Interference Velocity (open access)

The Theory of Propellers 2: Method for Calculating the Axial Interference Velocity

"A technical method is given for calculating the axial interference velocity of a propeller. The method involves the use of certain weight functions P, Q, and F. Numerical values for the weight functions are given for two-blade, three-blade, and six-blade propellers" (p. 1).
Date: 1944
Creator: Theodorsen, Theodore
System: The UNT Digital Library
The Theory of Propellers 3: The Slipstream Contraction With Numerical Values for Two-Blade and Four-Blade Propellers (open access)

The Theory of Propellers 3: The Slipstream Contraction With Numerical Values for Two-Blade and Four-Blade Propellers

"As the conditions of the ultimate wake are concerned both theoretically and practically, the magnitude of the slipstream contraction has been calculated. It will be noted that the contraction in a representative case is of the order of only 1 percent of the propeller diameter. In consequence, all calculations need involve only first-order effects. Curves and tables are given for the contraction coefficient of two-blade and four-blade propellers for various values of the advance ratio; the contraction coefficient is defined as the contraction in the diameter of the wake helix in terms of the wake diameter at infinity" (p. 1).
Date: 1944
Creator: Theodorsen, Theodore
System: The UNT Digital Library
The Theory of Propellers 4: Thrust, Energy, and Efficiency Formulas for Single and Dual Rotating Propellers With Ideal Circulation Distribution (open access)

The Theory of Propellers 4: Thrust, Energy, and Efficiency Formulas for Single and Dual Rotating Propellers With Ideal Circulation Distribution

"Simple and exact expressions are given for the efficiency of single and dual rotating propellers with ideal circulation distribution as given by the Goldstein functions for single-rotating propellers and by the new functions for dual-rotating propellers from part I of the present series. The efficiency is shown to depend primarily on a defined load factor and, to a very small extent, on an axial loss factor. Tables and charts are included for practical use of the results. The present paper is the fourth in a series on the theory of propellers" (p. 99).
Date: October 12, 1944
Creator: Theodorsen, Theodore
System: The UNT Digital Library
The Effect of Increased Cooling Surface on Performance of Aircraft-Engine Cylinders as Shown by Tests of the NACA Cylinder (open access)

The Effect of Increased Cooling Surface on Performance of Aircraft-Engine Cylinders as Shown by Tests of the NACA Cylinder

A method of constructing fins of nearly optimum proportions has been developed by the NACA to the point where a cylinder has been manufactured and tested. Data were obtained on cylinder temperature for a wide range of inlet-manifold pressures, engine speeds, and cooling-pressure differences. The results indicate that an improvement of 40 percent in the outside-wall heat-transfer coefficient could be realized on the present NACA cylinder by providing a thermal bond equivalent to that of an integral fin-cylinder wall combination between the preformed fins and the cast cylinder wall" (p. 107).
Date: July 1, 1944
Creator: Schey, Oscar W.; Rollin, Vern G. & Ellerbrock, Herman H., Jr.
System: The UNT Digital Library
Compressible potential flow with circulation about a circular cylinder (open access)

Compressible potential flow with circulation about a circular cylinder

"The potential function for flow, with circulation, of a compressible fluid about a circular cylinder is obtained in series form including terms of the orders of m(4) where m is the Mach number of the free stream. The resulting equations are used to obtain pressure coefficients as a function of Mach number at a point on the surface of the cylinder for different values of circulation. The coefficients derived are compared with the Glauert-Prandtl and Karman-Tsien approximations which are functions of the pressure coefficients of an incompressible fluid" (p. 129).
Date: 1944
Creator: Heaslet, Max A.
System: The UNT Digital Library
Wind-tunnel procedure for determination of critical stability and control characteristics of airplanes (open access)

Wind-tunnel procedure for determination of critical stability and control characteristics of airplanes

This report outlines the flight conditions that are usually critical in determining the design of components of an airplane which affect its stability and control characteristics. The wind-tunnel tests necessary to determine the pertinent data for these conditions are indicated, and the methods of computation used to translate these data into characteristics which define the flying qualities of the airplane are illustrated.
Date: 1944
Creator: Goett, Harry J.; Jackson, Roy P. & Belsley, Steven E.
System: The UNT Digital Library
Wall interference in a two-dimensional-flow wind tunnel, with consideration of the effect of compressibility (open access)

Wall interference in a two-dimensional-flow wind tunnel, with consideration of the effect of compressibility

From Summary: "Theoretical tunnel-wall corrections are derived for an airfoil of finite thickness and camber in a two-dimensional-flow wind tunnel. The theory takes account of the effects of the wake of the airfoil and of the compressibility of the fluid, and is based upon the assumption that the chord of the airfoil is small in comparison with the height of the tunnel. Consideration is given to the phenomenon of choking at high speeds and its relation to the tunnel-wall corrections. The theoretical results are compared with the small amount of low-speed experimental data available and the agreement is seen to be satisfactory, even for relatively large values of the chord-height ratio."
Date: 1944
Creator: Allen, H. Julian & Vincenti, Walter G.
System: The UNT Digital Library
Compressibility and Heating Effects on Pressure Loss and Cooling of a Baffled Cylinder Barrel (open access)

Compressibility and Heating Effects on Pressure Loss and Cooling of a Baffled Cylinder Barrel

"Theoretical investigations have shown that, because air is compressible, the pressure-drop requirements for cooling an air-cooled engine will be much greater at high altitudes and high speeds than at sea level and low speeds. Tests were conducted by the NACA to obtain some experimental confirmation of the effect of air compressibility on cooling and pressure loss of a baffled cylinder barrel and to evaluate various methods of analysis. The results reported in the present paper are regarded as preliminary to tests on single-cylinder and multicylinder engines. Tests were conducted over a wide range of air flows and density altitudes" (p. 1).
Date: July 1, 1944
Creator: Goldstein, Arthur W. & Ellerbrock, Herman H., Jr.
System: The UNT Digital Library
Intercooler cooling-air weight flow and pressure drop for minimum drag loss (open access)

Intercooler cooling-air weight flow and pressure drop for minimum drag loss

An analysis has been made of the drag losses in airplane flight of cross-flow plate and tubular intercoolers to determine the cooling-air weight flow and pressure drop that give a minimum drag loss for any given cooling effectiveness and, thus, a maximum power-plant net gain due to charge-air cooling. The drag losses considered in this analysis are those due to (1) the extra drag imposed on the airplane by the weight of the intercooler, its duct, and its supports and (2) the drag sustained by the cooling air in flowing through the intercooler and its duct. The investigation covers a range of conditions of altitude, airspeed, lift-drag ratio, supercharger-pressure ratio, and supercharger adiabatic efficiency. The optimum values of cooling air pressure drop and weight flow ratio are tabulated. Curves are presented to illustrate the results of the analysis.
Date: February 25, 1944
Creator: Reuter, J. George & Valerino, Michael F.
System: The UNT Digital Library
Preknock vibrations in a spark-ignition engine cylinder as revealed by high-speed photography (open access)

Preknock vibrations in a spark-ignition engine cylinder as revealed by high-speed photography

"The high-speed photographic investigation of the mechanics of spark-ignition engine knock recorded in three previous reports has been extended with use of the NACA high-speed camera and combustion apparatus with a piezoelectric pressure pickup in the combustion chamber. The motion pictures of knocking combustion were taken at the rate of 40,000 frames per second. Existence of the preknock vibrations in the engine cylinder suggested in Technical Report no.727 has been definitely proved and the vibrations have been analyzed both in the high-speed motion pictures and the pressure traces" (p. 223).
Date: September 11, 1944
Creator: Miller, Cearcy D. & Logan, Walter O., Jr.
System: The UNT Digital Library
Performance of Blowdown Turbine Driven by Exhaust Gas of Nine-Cylinder Radial Engine (open access)

Performance of Blowdown Turbine Driven by Exhaust Gas of Nine-Cylinder Radial Engine

"An investigation was made of an exhaust-gas turbine having four separate nozzle boxes each covering a 90 degree arc of the nozzle diaphragm and each connected to a pair of adjacent cylinders of a nine-cylinder radial engine. This type of turbine has been called a "blowdown" turbine because it recovers the kinetic energy developed in the exhaust stacks during the blowdown period, that is the first part of the exhaust process when the piston of the reciprocating engine is nearly stationary. The purpose of the investigation was to determine whether the blow turbine could develop appreciable power without imposing any large loss in engine power arising from restriction of the engine exhaust by the turbine" (p. 243).
Date: 1944
Creator: Turner, L. Richard & Desmon, Leland G.
System: The UNT Digital Library
On the flow of a compressible fluid by the hodograph method 2: fundamental set of particular flow solutions of the Chaplygin differential equation (open access)

On the flow of a compressible fluid by the hodograph method 2: fundamental set of particular flow solutions of the Chaplygin differential equation

From Summary: "The differential equation of Chaplygin's jet problem is utilized to give a systematic development of particular solutions of the hodograph flow equations, which extends the treatment of Chaplygin into the supersonic range and completes the set of particular solutions. The particular solutions serve to place on a reasonable basis the use of velocity correction formulas for the comparison of incompressible and compressible flows. It is shown that the geometric-mean type of velocity correction formula introduced in part I has significance as an over-all type of approximation in the subsonic range."
Date: September 29, 1944
Creator: Garrick, I. E. & Kaplan, Carl
System: The UNT Digital Library
Flight Studies of the Horizontal-Tail Loads Experienced by a Fighter Airplane in Abrupt Maneuvers (open access)

Flight Studies of the Horizontal-Tail Loads Experienced by a Fighter Airplane in Abrupt Maneuvers

Field measurements were made on a fighter airplane to determine the approximate magnitude of the horizontal tail loads in accelerated flight. In these flight measurements, pressures at a few points were used as an index of the tail loads by correlating these pressures with complete pressure-distribution data obtained in the NACA full-scale tunnel. In addition, strain gages and motion pictures of tail deflections were used to explore the general nature and order of magnitude of fluctuating tail loads in accelerated stalls.
Date: May 8, 1944
Creator: Flight Research Maneuvers Section
System: The UNT Digital Library
The Flow of a Compressible Fluid Past a Circular Arc Profile (open access)

The Flow of a Compressible Fluid Past a Circular Arc Profile

"The Ackeret iteration process is utilized to obtain higher approximations than that of Prandtl and Glauert for the flow of a compressible fluid past a circular arc profile. The procedure is to expand the velocity potential in a power series of the camber coefficient. The first two terms of the development correspond to the Prandtl-Glauert approximation and yield the well-known correction to the circulation about the profile" (p. 385).
Date: July 15, 1944
Creator: Kaplan, Carl
System: The UNT Digital Library
Preignition-limited performance of several fuels (open access)

Preignition-limited performance of several fuels

Preignition-limited performance data were obtained on a supercharged CFR engine at two sets of operating conditions over a wide range of fuel-air ratios to determine the preignition characteristics for the following five fuels: s-3 reference fuel, s-3 plus 4 ml. tel per gallon, afd-33(140-p), benzene, and diisobutylene. Maximum thermal-plug temperatures at constant intake-air pressures were also determined to correlate the preignition characteristics of each fuel with its ability to increase general engine-temperature levels. Additional runs were made to compare the preignition-limited performance of triptane, triptane plus 4 ml. tel per gallon, and an-f-28r fuel.
Date: October 1, 1944
Creator: Male, Donald W. & Evvard, John C.
System: The UNT Digital Library
Knock-limited performance of several internal coolants (open access)

Knock-limited performance of several internal coolants

The effect of internal cooling on the knock-limited performance of an-f-28 fuel was investigated in a CFR engine, and the following internal coolants were used: (1) water, (2), methyl alcohol-water mixture, (3) ammonia-methyl alcohol-water mixture, (4) monomethylamine-water mixture, (5) dimethylamine-water mixture, and (6) trimethylamine-water mixture. Tests were run at inlet-air temperatures of 150 degrees and 250 degrees F. to indicate the temperature sensitivity of the internal-coolant solutions.
Date: February 1, 1944
Creator: Bellman, Donald R. & Evvard, John C.
System: The UNT Digital Library
Nitrited-Steel Piston Rings for Engines of High Specific Power (open access)

Nitrited-Steel Piston Rings for Engines of High Specific Power

"Several designs of nitrided-steel piston rings were performance-tested under variable conditions of output. The necessity of good surface finish and conformity of the ring to the bore was indicated in the preliminary tests. Nitrided-steel rings of the same dimensions as cast-iron rings operating on the original piston were unsatisfactory, and the final design was a lighter, rectangular, thin-face-width ring used on a piston having a maximum cross-head area and a revised skirt shape. Results were obtained from single-cylinder and multicylinder engine runs" (p. 1).
Date: April 1, 1944
Creator: Collins, John H., Jr.; Bisson, Edmond E. & Schmiedlin, Ralph F.
System: The UNT Digital Library
The NACA Impact Basin and Water Landing Tests of a Float Model at Various Velocities and Weights (open access)

The NACA Impact Basin and Water Landing Tests of a Float Model at Various Velocities and Weights

"The first data obtained in the United States under the controlled testing conditions necessary for establishing relationships among the numerous parameters involved when a float having both horizontal and vertical velocity contacts a water surface are presented. The data were obtained at the NACA impact basin. The report is confined to a presentation of the relationship between resultant velocity and impact normal acceleration for various float weights when all other parameters are constant" (p. 411).
Date: 1944
Creator: Batterson, Sidney A.
System: The UNT Digital Library
An Interim Report on the Stability and Control of Tailless Airplanes (open access)

An Interim Report on the Stability and Control of Tailless Airplanes

Problems relating to the stability and control of tailless airplanes are discussed in consideration of contemporary experience and practice.
Date: August 19, 1944
Creator: Donlan, Charles J.
System: The UNT Digital Library
Application of Spring Tabs to Elevator Controls (open access)

Application of Spring Tabs to Elevator Controls

Equations are presented for calculating the stick-force characteristics obtained with a spring-tab type of elevator control. The main problems encountered in the design of a satisfactory elevator spring tab are to provide stick forces in the desired range, to maintain the force per g sufficiently constant throughout the speed range, to avoid undesirable "feel" of the control in ground handling or in flight at low airspeeds, and to prevent flutter. Examples are presented to show the design features of spring tabs required to solve these problems for airplanes of various sizes.
Date: November 24, 1944
Creator: Phillips, William H.
System: The UNT Digital Library
Effect of hinge-moment parameters on elevator stick forces in rapid maneuvers (open access)

Effect of hinge-moment parameters on elevator stick forces in rapid maneuvers

"The importance of the stick force per unit normal acceleration as a criterion of longitudinal stability and the critical dependence of this gradient on elevator hinge-moment parameters have been shown in previous reports. The present report continues the investigation with special reference to transient effects for maneuvers of short duration" (p. 449).
Date: October 12, 1944
Creator: Jones, Robert T. & Greenberg, Harry
System: The UNT Digital Library
Charts for the Determination of Wing Torsional Stiffness Required for Specified Rolling Characteristics or Aileron Reversal Speed (open access)

Charts for the Determination of Wing Torsional Stiffness Required for Specified Rolling Characteristics or Aileron Reversal Speed

From Summary :"A series of charts are presented by which the wing torsional stiffness required to meet a given standard of rolling effectiveness may be quickly determined. The charts may also be used to obtain quickly the aileron reversal speed and the variation of the loss in rolling effectiveness with airspeed. The charts apply to linearly tapered wings and elliptical wings of tubular-shell construction having various aspect ratios with aileron span and location of ailerons as variables. In the derivation of the charts, induced lift effects have been taken into account and the form of the wing-torsional-stiffness curve has been assumed."
Date: November 9, 1944
Creator: Pearson, Henry A. & Aiken, William S., Jr.
System: The UNT Digital Library