The theory of characteristics will be presented generally for quasilinear differential equations of the second order in two variables. This is necessary because of the manifold requirements to be demanded from the theory of characteristics.

This paper includes the following topics: 1) Characteristic differential equations; 2) Treatment of practical examples; 3) First example: Diffuser; and 4) Second Example: Nozzle.

"So far, very careful investigations have been made regarding the flight properties, in particular the static and dynamic stability, of engine-propelled aircraft and of untowed gliders. In contrast, almost no investigations exist regarding the stability of airplanes towed by a towline. Thus, the following report will aim at investigating the directional stability of the towed airplane and, particularly, at determining what parameters of the flight attitude and what configuration properties affect the stability" (p. 1).

Contents include the following: Characteristic differential equations - initial and boundary conditions. Integration of the second characteristic differential equations. Direct application of Meyer's characteristic hodograph table for construction of two-dimensional potential flows. Prandtl-Busemann method. Development of the pressure variation for small deflection angles. Numerical table: relation between deflection, pressure, velocity, mach number and mach angle for isentropic changes of state according to Prandtl-Meyer for air (k = 1.405). References.

In an attempt to follow the time rate of change of the processes in turbulent flows by quantitative measurements the measurement of the pressure is often beset with insuperable difficulties for the reason that the speeds and hence the pressures to be measured are often very small. On the other hand, the measurement of very small pressures requires, at least, considerable time, so that the follow-up of periodically varying processes is as goad as impossible. In order to obviate these difficulties a method, suggested by Prof. Prandtl, has been developed by which the pressure distribution is simply determined from the photographic flow picture.

We have set ourselves the problem of calculating the laminar flow on a body of revolution in an axial flow which simultaneously rotates about its axis. The problem mentioned above, the flow about a rotating disk in a flow, which we solved some time ago, represents the first step in the calculation of the flow on the rotating body of revolution in a flow insofar as, in the case of a round nose, a small region about the front stagnation point of the body of revolution may be replaced by its tangential plane. In our problem regarding the rotating body of revolution in a flow, for laminar flow, one of the limiting cases is known: that of the body which is in an axial approach flow but does not rotate.

Report presenting an investigation using a 4600 pound-thrust turbojet engine as part of a program to determine the comparative performance of fuels conforming to specifications AN-F-58 and AN-F-32. Results regarding the altitude performance, altitude low-speed blow-out limits, idling limits of fuel-metering control, altitude windmilling starts, carbon-deposition rates, and iron oxide contamination are provided.

Memorandum presenting a preliminary investigation to determine the effects of alpha-particle bombardment on the creep rate of aluminum wire at 400 degrees Fahrenheit. The alpha radiation from an 85-millicurie polonium source appeared to decrease slightly the creep rate of the aluminum.

Report presenting a flight investigation to determine the comparative performance of AN-F-58 and AN-F-32 fuels in a 4000-pound-thrust turbojet engine. The fuels were equivalent over the range of conditions investigated. Results regarding corrected net thrust, corrected jet-fuel consumption, variation of corrected tail-pipe temperature, combustor blow-out speeds, and visual observations of the jet exhaust are provided.

Report presenting results obtained with quiescent fuel-air mixtures and with small diffusion flames, which indicate that combustion efficiencies close to 100 percent were obtained at pressure much lower than those found in turbojet combustors at altitudes of 60,000 feet.

"A method is described by which the total temperature of the gases at the combustion-chamber outlet of a ram-jet engine may be determined from the loss in total pressure measured across the combustion chamber. A working chart is presented by means of which the ratio of the total temperature of the gases at the combustion-chamber outlet to the total temperature of the gases at the combustion-chamber inlet may be determined from the measured loss of total pressure across the combustion chamber and the known values of air flow, total pressure, and total temperature at the combustion-chamber inlet. Values of total-temperature ratio across the combustion chamber of a 20-inch ram jet were obtained in the Cleveland altitude wind tunnel over a range of pressure altitudes from 6000 to 15,000 feet" (p. 1).

Report discussing testing on a series of tapered swept wings under conditions simulating rolling flight. The lift, longitudinal-force, and pitching-moment characteristics for three swept wings are provided. The results indicated that a decrease in taper ratio on a swept wing caused a small decrease in damping in roll at low and moderate lift coefficients.

Report presenting an investigation of a 45 degree sweptback-wing model with interchangeable round and sharp leading edges to determine the effect of leading-edge separation on the loads experienced by the models in gusts. Leading-edge separation was found to increase the gust load, which appeared to vary based on the gust-gradient distance and velocity.

"It is shown that for velocities slightly in excess of sonic, the position of detached shock wave located in front of a given body at zero angle of attack may be estimated theoretically to a reasonable degree of accuracy. In case of bodies of revolution the result was simple, but for two-dimensional bodies, pressure coefficient varies with Mach number, and slight difficulty appears. Theory developed compares favorably with available experimental data" (p. 1).

Report presenting a wind tunnel investigation to determine the downwash angles, dynamic pressure loss, and wake width behind wings with sweep angles of 45, 30, and 0 degrees. Results indicated that the spanwise distribution of downwash was affected by sweep in a manner similar to span loading, increased toward the root by sweepforward and toward the tip by sweepback.

Report presenting a correlation of carbon deposition of 19 fuels in a turbojet combustor as a function of the boiling point and of the flame height at the sooting point of the fuels in a simple wick lamp for a particular combustor operating at a single set of conditions. Two similar investigations with different combustors, operating conditions, and nine different fuels yielded similar correlations on the same graph.

Report presenting an investigation to determine the lift, drag, and pitching-moment characteristics of the NACA 0010 and 0010-64 airfoil sections at Mach numbers up to 0.91 and for a range of Reynolds numbers.

From Summary: "An all-internal conical compression inlet with annular bleed at the throat was investigated at Mach 5.0 and zero angle of attack. The minimum contraction ratio of the supersonic diffuser, coincident with a mass-flow ratio of 1.0, was determined to be 0.084 as compared with the isentropic contraction ratio of 0.04 at Mach 5.0. The over-all inlet performance was very sensitive to the amount of annular bleed at the throat because of the extensive boundary layer."

"The wave drag of a combination of slender bodies of revolution at zero angle of attack is studied with a view to determining the arrangements for which the total drag is a minimum. Linearized theory is used to calculate the pressure distribution in the field surrounding the bodies. The interference drag coefficient is computed for different arrangements" (p. 1).

Note presenting a study of the factors that affect the survival of human beings in airplane accidents followed by fire by conducting full-scale crashes of transport- and cargo-type airplanes. Some of the factors studied include thermal injury, toxic gases, missiles, and structural destruction of occupied compartments are provided.

From Introduction: "Analyses that provide a basis for comparing the centrifugal-stress distributions inherent in jet-engine turbine blades of several designs currently in use were therefore made and are presented."

Report presenting an experimental investigation to determine the vibration characteristics of loosely mounted turbine blades during service operation of a turbojet engine. High-temperature strain gages were used to measure turbine-blade vibrations. Results regarding oscillograph records, critical speeds and frequencies, vibratory-stress levels, and effect of tightening the blade mount are provided.

Report presenting an investigation in the stability tunnel to determine the effect of airfoil profile on symmetrical sections on the static- and yawing-stability derivatives of three untapered wings of 45 degrees sweepback. All of the wings had an aspect ratio of 2.61. Results regarding the characteristics in straight flow, yawing flow, and drag index are provided.

Report presenting a wind-tunnel investigation to determine the effects of a section modification on the aerodynamic characteristics of a wing with 35 degrees of sweepback. The wing was modified by increasing the leading-edge radius of the NACA 64A010 section and adding a small amount of camber to the forward portion of the chord. Lift, drag, pitching-moment, and trailing-edge-flap hinge-moment characteristics of the modified wing are compared with results from the original wing.