Note presenting a method for studying the transient behavior of the flapping motion, as well as for calculating the steady-state flapping amplitudes, of free-to-cone and seesaw rotors operating at extreme flight conditions. The method is general and can be applied to blades of any airfoil section, mass distribution, twist, plan-form taper, root cutout, and flapping-hinge geometry.

Report presenting an investigation of the blades of an experimental two-blade jet-driven helicopter when subject to a condition of near resonance between the frequencies of the first elastic bending mode of the blades and third harmonic component of the aerodynamic loading that results in high bending strains in normal flight conditions. Various changes in design configuration on the blade bending strains were explored. Results regarding the preliminary studies, effects of variation in flight conditions and blade configuration, and harmonic analysis are provided.

Report presenting turbulent-heat-transfer measurements obtained through the use of an axially symmetric annual nozzle consisting of an inner shaped center body and an outer cylindrical sleeve at Mach number 2.06. Results regarding the variation of wall temperature with longitudinal distance, variation of local Nusselt number with local Reynolds number, and variation of local temperature-recovery factor with local Reynolds number are provided.

Report presenting the nonlinear characteristic differential equations applicable to a quasi-one-dimensional unsteady channel flow with friction and heat transfer, which are linearized and integrated in functional form for the particular study of small perturbations from ideal shock-tube flows.

Note presenting a study of the effects of variation in microstructure on the fatigue properties of 24S-T4 aluminum-alloy notched specimens tested in both longitudinal and transverse directions. The results show that a definite anisotrophy exists in the fatigue strength of this alloy in tests. However, the results also indicate that a sample size of 10 specimens does not give statistically reproducible results in all cases.

Note presenting an experimental investigation of the heat-loss characteristics of heated fine wires suitable for use as anemometers in turbulence research. The effects of each of the several variables on the heat-loss characteristics of both normally oriented and swept wires were measured. The temperature-loading effects were found to cause large sensitivity differences between constant-temperature and constant-current operation.

Report presenting testing of several configurations of rotor blades in order to evaluate the effect of variations in the blade-pitch-control stiffness and forward speed on the flutter speed.

Report regarding the measurement of velocity distribution and persistence of the trailing vortices of a propeller-driven fighter-type airplane. Vortex strength did not decrease appreciably up to 35 seconds after the vortices had been shed. When flying in the trailing wake of another airplane, the pilot reported that it was difficult to maintain a precise course and that the disturbance was similar to severe turbulence.

"This report presents results of a research and engineering program performed during the first half of 1950 that resulted in an acoustical treatment for the 8- by 6-foot supersonic wind tunnel at the Lewis Flight Propulsion Laboratory" (p. 1).

A graphical method is described by which the enthalpy, entropy, and compressibility factor for the equilibrium mixture of atoms and diatomic molecules for pure gaseous elements may be obtained and shown for any dissociating element for which the necessary data exist. Results are given for hydrogen, oxygen, and nitrogen. The effect of dissociation on the heat capacity is discussed briefly.

Report presenting external wave drag of bodies of revolution moving at supersonic speeds, which can be expressed either in terms of the geometry of the body or in terms of the body-simulating axial source distribution. The second of the methods is found to be more tractable.

From Introduction: "This report presents the results of an analytical study made to determine the accuracy with which several commonly used averaging or weighting methods reproduce the real flow properties."

Note presenting extensive data relating properties of wrought N-155 alloy under static, combined static and dynamic, and completed reversed dynamic stress conditions. Time periods for fracture ranged from 50 to 500 hours at room temperatrue, 1000, 1200, 1350, and 1500 degrees Fahrenheit. Results regarding the rupture and fatigue strengths, fatigue strengths based on cycles to failure, influence of superimposed fatigue loads on creep, influence on superimposed fatigue stress on elongation in the rupture test, stress-strain characteristics under fatigue loading, damping effects, influence of cyclic speed on fatigue properties, influence of notches on fatigue, surface finish, and limitations of findings are provided.

Note presenting several recent advances in plane subsonic flow theory combined into a unified second-order theory for airfoils of arbitrary shape. The solution is reached in three steps. Solutions for a number of airfoils are given and are compared with the results of other theories and of the experiment.

Report presenting a study of the lubrication of steel by a series of stable fluorine- and chlorine-substituted methane and ethane derivatives. Several compounds containing fluorine and two or more chlorine atoms per molecule functioned as boundary lubricants to reduce friction and to prevent surface welding and metal transfer.

Report presenting experimental measurements of average skin friction of the turbulent boundary layer on free-flying, hollow-cylinder models at four Mach numbers at conditions of high rates of heat transfer. The data of the investigation indicates that increasing skin-friction ratio with increasing heat-transfer rates will persist up to Mach numbers as high as 7. Results regarding skin-friction ratio and the T' method for evaluating skin friction are provided.

Note presenting some methods of estimating the induced drag of low-aspect-ratio wings, which are discussed and compared with experiments. The profile drag due to lift is also discussed and a method is developed which relates the effect of aspect ratio on the profile drag due to lift to an "effective" two-dimensional lift coefficient.

Report presenting an investigation using rocket-propelled models in free flight to determine the external drag and pressure recovery of the NACA 1-40-250 nose inlet at zero angle of attack.

From Introduction: "References 1 and 2 indicate that the sea-level static thrust of a centrigual-flow-type turbojet engine may be increased about 25 percent by use of liquid injection. Reference 3 indicates that greater thrust augmentation is possible at a compressor pressure ratio of 11 than of 4."

Report presenting the description and characteristics of two small temperature recorders suitable for flight use. One recorder is an electro-mechanical followup, self-balancing potentiometer type and one obtains self-balance by using an electronic feedback amplifier.

Note applying Stewartson's transformation to the laminar compressible boundary-layer equations and the requirement of similarity, resulting in a set of ordinary nonlinear differential equations previously quoted by Stewartson, but unsolved. The requirements of the system are specified. It is then transformed to an integral system with the velocity ratio as the independent variable.

Report presenting an investigation in the supersonic wind tunnel to determine some of the base pressure characteristics of related bodies of revolution at zero angle of attack. Results regarding variation of pressure over the base, variation of base pressure with Reynolds number, effect of nose and afterbody shapes, variation of base pressure with Mach number, and correlation of base pressure data are provided.

Report presenting an approximate method for the calculation of the compressible laminar boundary layer with heat transfer and arbitrary pressure gradient, based on Thwaites' correlation concept. The method results from the application of Stewartson's transformation to Prandtl's equations, which yields a nonlinear set of two first-order differential equations. Calculations of an example show that the method is reliable when compared with the perturbation method over the same range of Mach number, pressure gradient, and heat transfer.

Note presenting wind-tunnel tests to ascertain the total-pressure recovery of a circular nose inlet utilizing various shapes of inlet lips. The tests were conducted at a free-stream Mach number of 0.237 with inlet flows ranging from low values to choking and at angles of attack from 0 to 25 degrees.