Report presenting the results of a series of flight tests of the maximum speed and cooling characteristics in high-speed level flight and in climb of the XP-42 airplane equipped with a long-nose high-inlet-velocity cowling. The results indicated that a maximum speed of 338 miles per hour at 870 horsepower at 17,000 feet was achievable, which is above the engine critical altitude. Pressure measurements in the entrances in the cylinder baffles showed a uniform distribution of pressure on the front of the engine in high-speed level flight and a fairly uniform distribution in full-power climb.

"Tank tests were made of a flying-boat model having various types of fairing with and without ventilation ducts behind the main step to investigate the hydrodynamic characteristics of the model. All the types were designed to reduce significantly the air drag chargeable to the main step. The configuration that combined the best stability with a good aerodynamic form consisted of a shallow step and an adjoining ventilation aperture having an area about 7 percent of the square of the beam" (p. 1).

Report presenting tests to study the effectiveness of small pressure differences in removing the dust boundary layer through slots in the duct wall of airplane ducts and reducing separation losses. Two-dimensional diffusers of 15 and 30 degrees included angles and some 90 degree bends were tested. The 30 degree diffuser was tested with and without an intercooler.

Report presenting an analysis of the thermopile radiometer as used in the measurement of irradiation and radiant power interchange is given. The theory of the instrument when used to measure irradiation and net radiant power interchange is developed, and the precautions to be observed when using it for these measurements are presented.

Report presenting data on the thermal performance and static and total pressure drop characteristics of a fluted-type exhaust gas and air heat exchanger. Results regarding heat transfer, pressure drop, and non-isothermal pressure drop are provided.

Report presenting results of tests of the thermal performance and the static pressure drop characteristics of a flat-plate type exhaust gas and air heat exchanger. The ventilating air shroud built into the heat exchanger gives characteristics of cross flow and parallel flow.

Report presenting data on the thermal performance and static pressure drop of a finned-type cast-aluminum exhaust gas and air heat exchanger. Results regarding heat transfer, isothermal pressure drop, and heater surface temperature are provided.

Report presenting data on the thermal performance and the static pressure drop characteristics of a flattened-tube type crossflow exhaust gas and air heat exchanger. The measured thermal outputs and static pressure drops are compared with predicted magnitudes.

Report presenting the thermal and pressure drop performance data of a slotted-fin Stewart-Warner exhaust gas and ventilating air heat exchanger. Three different crossflow air shrouds were used in testing. The rate of heat transfer was about the same for each shroud, but the static pressure drops varied greatly.

Report presenting pressure-distribution measurements made on the right wing of a P-39N-1 airplane at values of Mach number up to 0.80. A considerable portion of the lift was carried by components of the airplane other than the wings, and the proportion carried by the wing varies considerably with Mach number. Results regarding the variation of wing loads and moments with Mach number, internal wing pressure, and airplane lift-curve slope are provided.

Report presenting testing of several designs of nitrided-steel piston rings under variable conditions of output. Testing indicated the importance of good surface finish and conformity of the ring to the bore. Results regarding temperature tests, single-cylinder-engine tests, and multicylinder-engine tests are provided.

Report presenting a practical and relatively rapid method of compensating for shear lag in box-beam analysis with accuracy sufficient for design purposes. Effectiveness curves for box beam elements are derived for an ideal, symmetrical structure. Tabular computation forms for rapid, accurate calculations of axial stresses, shear center, and shear stresses for beam with shear lag are induced.

"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" (p. 1).

Report discusses pressure-distribution tests of a plain flap with interchangeable beveled trailing edges on an NACA 0009 airfoil. The flap chord was 30 percent of the airfoil chord and the bevel chords were 15 and 20 percent of the flap chord. The purpose of these tests was to supply pressure-distribution data that may be used for structural and aerodynamic design of horizontal and vertical tail surfaces.

Report describing power-off tests 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. Two NACA 23012 rectangular wings with rounded tips and dihedral angles of 0 and 5 degrees were tested alone and in combination with three circular fuselages of different lengths. Results regarding the interference effects, effect of horizontal tail, effect of changes in fuselage length, effect of changes in vertical-tail area, effect of changes with constant tail volume, effect of changes in dihedral, and a comparison of data from 7- by 10-foot and stability tunnels are provided.

Flat-plate flaps with no wing cutouts and flaps having Clark Y sections with corresponding cutouts made in wing were tested for various flap deflections, chord-wise locations, and gaps between flaps and airfoil contour. The drag was slightly lower for wing with airfoil section flaps. Satisfactory aileron effectiveness was obtained with flap gap of 20% wing chord and flap-nose location of 80 percent wing chord behind leading edge. Airflow was smooth and buffeting negligible.

"Three Franz-type temperature probes and a pitot-static tube for use in supercharger passages have been calibrated in the NACA 24-inch high-speed wind tunnel. These instruments were designed for use in supercharger investigations" (p. 1).

Report presenting a method for showing, by means of three curves, the locations of points of tangency to the envelope of the main-spray blisters generated by flying boat hull models obtained from general testing. Three equations are applied to data from general spray testing on seven models.

Report presenting an investigation of a method of studying the longitudinal dynamic stability of flying-boat-hull models, as instability may be encountered when flying a flying boat on the water at high speeds and high trim angles, especially upper-limit porpoising and skipping. A method is described for carrying out generalized experimental studies of the longitudinal dynamic stability of flying-boat-hull models.

Report presenting knock-limited performance data obtained with several small-scale engines for blends containing nine aromatic hydrocarbons blended individually in various concentrations with selected base fuels.

Report presenting knock-limited small-scale-engine testing of several different types of aromatics mixed with selected base fuels. Data was obtained to determine the blending sensitivity, lead susceptibility, and the sensitivity of the blends to inlet-air temperature.

"A method for the estimation of the maximum stresses around a small rectangular cut-out in a sheet-stringer panel loaded in pure shear is presented; this method is based on a simplified application of the shear-lag theory. Comparisons indicate that the experimental maximum stringer and shear stresses agree reasonably well with the predictions, provided that neither the length nor the width of the cut-out is greater than the half-width of the panel" (p. 1).

Report presenting the development of a method of evaluating the epsilon-integral occurring in the arbitrary airfoil theory of Theodorsen by retaining higher order terms in the Taylor expansion and by use of Simpson's rule. Formulas are given for routine calculation of the epsilon-integral and for the necessary computational coefficients.

Report presenting an investigation in the NACA 15-foot free-spinning tunnel to determine the effect of wing leading-edge slots on spin and recovery characteristics. The results indicate that recovery will generally be slower with the slots open than with them closed and the spin will be flatter and at a lower rate of descent.