This report presents the results of a flight investigation to determine the effect on the performance of a turbosupercharged engine of an exhaust-gas-to-air heat exchanger installed between the engine-exhaust collector ring and the turbosupercharger. The background, results, and discussion of the investigation are described.

Report presenting a summary of a series of reports regarding heat exchangers, and in particular, the design of exhaust gas and air heat exchangers. The four parts included are a summary of heat transfer equations, single pass heat exchangers, heater performance in flight, and appendicies with additional aerodynamic information.

Report discussing an open box joined to a closed box subjected to torsional loading. A stiff bulkhead and a flexible bulkhead were tested at the discontinuity and the results were compared to a previously published theory. Stress distribution was found to not be sensitive to bulkhead stiffness when the stiffness is large, but the calculations became sensitive to errors in estimating when the stiffness was small.

Report presenting wind-tunnel testing in two-dimensional and three-dimensional flow to investigate the aerodynamic characteristics of spoilers on tail surfaces for low-speed flight. Test results indicated that spoilers on tail surfaces showed little possibility of replacing conventional control surfaces. Results regarding a flap alone, rear spoiler alone, forward spoiler alone, forward spoiler and flap, and a combination of forward and rear spoilers on upper and lower surfaces in both types of flow are provided.

Report discusses the results of testing on a linked differential flap system upon the effective-dihedral characteristics of an airplane scale model. The negative dihedral changes caused by power can be materially reduced or eliminated by use of a differential flap system. The static directional stability also increased with differential flap action.

Report presenting tests in a seal test chamber to determine the hinge moments contributed by the fabric seal in an internal-balance arrangement employing a thin-plate overhang. The tests were performed with various widths of fabric sealing various widths of flap-nose gap, with a horizontal, a vertical, and a circular type of wing structure forward of the balance, and with various heights of balance chamber. Results regarding seal-profile photographs, desired seal-moment characteristics, experimental seal-moment characteristics, effect of the balance configuration on the seal-moment characteristics, comparison of analytical and experimental seal-moment characteristics, computation of seal-moment characteristics by the approximate method, and application of the data are provided.

Report presenting the results of a theoretical analysis of the hinge-moment characteristics of various sealed-internal-balance arrangements for control surfaces. The results of the investigation indicated that the most nearly linear control-surface hinge-moment characteristics can probably be obtained from a flexible seal over a narrow gap, which is so installed that the motion of the seal is restricted to a region behind the point of attachment of the seal to the wing structure.

An experimental investigation is being conducted to determine the effect of varying the rivet diameter and pitch on the compressive strength of 24S-T aluminum-alloy panels with longitudinal Z-section stiffeners. The average stress at failing load for each rivet diameter, depth of countersink, and pitch of rivet is provided

Report presenting power-off tests made in the 6- by 6-foot test section of the stability tunnel to determine the variation of the static lateral stability characteristics with vertical-tail area, fuselage length, and wing dihedral. The results are presented as curves showing the variation of the static-lateral-stability slopes with angle of attack, and the rolling-moment, yawing-moment, and lateral-force coefficients with angle of yaw.

Report discuss the results of force tests, yaw-trim tests, and power-off tests to compare the stability and control characteristics of a powered airplane model in the erect and inverted flight attitudes. Due to the violent and uncontrollable maneuvers that sometimes occur after flight in the inverted attitude, more information was requested about stability and control characteristics in this position. Testing found that with the power on, a serious reduction in longitudinal and directional stability occurred in inverted flight.

Report presenting design charts for 24S-T aluminum-alloy flat compression panels with longitudinal Z-section stiffeners. It was found that maximum possible structural efficiency with these panels requires closer stiffener spacings than those now in common use.

Report discusses data obtained from measuring sideslip characteristics via the continuous-record method and the steady-record method. The situations in which each recording method is preferred are presented.

From Introduction: "The tests reported herein, conducted during the early part of 1945, were made to determine the inherent charge-air distribution characteristics of the engine-stage supercharger of the double-row radial engine."

Report on the NACA test-rig installation, measurements, instrumentation, test procedure, methods of calculation, and presentation of data for rating and testing centrifugal superchargers. Special precautions for certain portions of testing are also provided.

Report presenting testing to determine the stresses and bending moments required to break pieces 1 inch or less in length from the ends of cast-iron, keystone, compression piston rings. Strain gages were used to determine the stress pattern for various modes of vibration. The maximum-stress points of vibrating piston rings were at the antinodes or points of maximum deflection.

Report on the NACA recommended method for comparing the performance of centrifugal compressors. The most important indices of compressor performance are the adiabatic temperature rise ratio or adiabatic efficiency, the adiabatic shaft efficiency, and the pressure ratio, which incorporate many other parameters. Recommendations for reporting on compressor effectiveness and characteristics are provided.

Report presenting an investigation to develop methods and equipment for the measurement of operating stresses in aircraft-engine crankshafts and connecting rods. The results indicate that the measurement of stresses in connecting rods is feasible. Results regarding stresses in the crankshaft and stresses in the master connecting rod are provided.

Report presenting an analysis of the contact stresses in a damper installation of an aircraft engine that indicated that galling could be eliminated by increasing the diameters of damper pins and holes. Torsional-vibration pendulum dampers have been successful in minimizing vibrations at critical speeds in aircraft engines, but serious wearing problems are often encountered when using them. The damper used in this experiment did not suffer any type of damage after many hours of use.

"Air-consumption data from calibrations of two radial aircraft engines were analyzed to show the relation of engine air consumption to its primary influencing factors: intake-manifold pressure, exhaust back pressure, intake-manifold temperature, and engine speed. The analysis of the test data from these two engines led to the establishment of a relation of variables upon which the design of automatic metering controls can be based. The data obtained from one engine indicate that the air-consumption correlation obtained for this engine is accurate within 2 percent except under certain conditions that are well outside current engine-operation limits" (p. 1).

Report presenting charts relating helicopter aerodynamic design variables to performance in steady powered flight. The flight conditions covered are hovering, climb, and horizontal flight. The use of the charts is illustrated by numerical examples in order that computations can be made for particular problems.

Report presenting several methods of computing bending moments in helicopter rotor blades in the plane of flapping, and the results of a numerical example analyzed by four different methods are compared. The effect of computed bending moments of the tip-loss correction introduced by Wheatley is also considered.

Report discusses testing performed to determine the fatigue strength of various types of riveted and spot-welded joints in the following aluminum alloys: Alclad 24S-T, 24S-RT, 758-T, 24S-T81, and 24S-T86. Details of the experiment, tensile properties, and information about failure are provided.

"The lateral- and directional-stability and -control characteristics of a twin-engine patrol airplane as predicted from the results of wind-tunnel tests of a powered model and as measured in flight are compared in this report. The predictions from wind-tunnel-test data were in good agreement with the flight-test results. The results show that such predicted flying-qualities characteristics are sufficiently accurate to indicate the unsatisfactory lateral- and directional-stability and -control characteristics of airplanes in the preliminary design stage" (p. 1).

Report presenting an investigation by lifting-surface theory of a thin elliptic wing of aspect ratio 6 in a steady roll by means of the electromagnetic-analogy method. The results obtained by lifting-surface theory indicate that the damping in roll for a wing of aspect ratio of 6 is 13 percent less than that give by lifting-line theory and 5 percent less than that given by lifting-line theory with the edge-velocity correction derived by Robert T. Jones applied. Simple practical methods of applying the results of the investigation to wings of other plan forms are given.