Report details the methods of determining the heat-transfer rate, pressure drop, and drag power of high-altitude radiators. Performance charts are provided for a wide range of design variables.

In open box beams subjected to torsion, secondary stresses arise owing to lateral bending of the spar caps. The present paper outlines a simple method for estimating the magnitude of these stresses and gives the results of tests of an open box beam in the neighborhood of a discontinuity where the cover changed from the top to the bottom of the box.

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 discusses an investigation to determine the aerodynamic section characteristics of an NACA 23021 airfoil with a double slotted flap with a chord 32 percent of the airfoil chord with the flaps at various positions. The maximum section lift coefficient, profile-drag coefficient, flap positioning, and effects of deflecting or removing the lower lip are described.

Report presenting a method for predicting from basic airplane characteristics the elevator deflection required to maintain optimum landing attitude. Charts for evaluating the components of the equation for elevator deflection and a comparison of computed and measured values for 15 airplanes are included. The computed deflection is considered the minimum value required to maintain landing attitude due to variations in piloting technique.

Report presenting testing in the stability tunnel of two types of spring tab used as balances on a partial-span plain aileron. The tabs were connected to a spring located in the control system so that tab deflection was dependent on the control force.

Report re-examining known procedures for handling general resistance testing on flying-boat hull models, with particular attention paid to saving test time and improving the usefulness of the results to designers. While specific testing will likely always be needed, the procedures given in the report for condensing resistance data should make data analysis easier to apply to design.

Report presenting a method of graphical analysis that allows for the prediction of the thermal and aerodynamic performance of a ram-operated heater and duct system, for cabin heating or wing de-icing, at any altitude and airplane speed. Performance can be predicted from the isothermal total pressure drop across the components of the duct system at several ventilating air rates and the thermal output of the heater at various air and exhaust gas rates.

Report describing the behavior of the heat meter when it is used in thermal circuits which are under the influence of transient potentials. Three scenarios are considered: a heat meter suddenly placed on a hot surface, a heat meter mounted on the interior surface of the cabin wall of an uninsulated airplane climbing through air of decreasing temperature, and a heat meter mounted on the interior surface of the composite cabin wall of an airplane climbing through air of decreasing temperature.

Report presenting a determination of the mean effective emissivity as a function of temperature for the surfaces of several metals and insulating materials. A description and discussion of the measuring technique is presented. The results are plotted on a variety of graphs.

Report presenting data on the thermal performance and the static pressure drop characteristics of two finned-type exhaust gas and air heat exchangers. One heater was constructed of copper and stainless steel while the other was constructed from aluminum alloy. The measured thermal outputs and static pressure drops are compared with predicted magnitudes.

Report presenting an investigation which found that the absolute viscosity of exhaust gases from a gasoline engine was measured at a range of temperatures and compositions. Results regarding preliminary runs, calibration runs at room temperature, check runs at medium temperatures, and exhaust gas measurements are provided.

Correlation is established between aerodynamic characteristics of control surfaces in two-dimensional and three-dimensional flow. Slope of lift curve was affected little by overhang and balance-nose shape, but increased by sealing flap-nose gap. Effectiveness of balancing tab was same for sealed plain flap and unsealed overhang flap. Changes in hinge-moment coefficient were diminished by sealing gap. Values measured by three-dimensional flow disagreed with two-dimensional flow values until aspect ratio corrections were made.

Report discussing an investigation of the aerodynamic effects of horn balances with various plan forms and of guards on a horizontal tail surface. Rounding the adjacent horn and stabilizer edges causes negligible changes to aerodynamic effects except for the area moment of the horn. A solid horn guard mounted on the end of the stabilizer was found to increase the rate of change of lift with angle of attack and elevator deflection.

Report presenting measurements in the full-scale tunnel of the pressure distribution over the horizontal tail surface of a typical pursuit airplane in order to determine the effects of propeller operation and angle of yaw on the tail load distribution. Most of the tests were made with the propeller operating to simulate climb conditions, high-speed dives, and pull-ups to various normal accelerations for a range of angles of yaw. Results regarding chordwise pressure distributions, spanwise distributions of normal-force coefficient, airflow measurements, and tail-load asymmetry are provided.

Report discusses an analysis of the stability of an airplane with ailerons free, with particular attention to the motions when the ailerons have a tendency to float against the wind. Information about the aerodynamic balance of the plane and oscillations that may be encountered are included. The effects of friction in the control system is also explored.

"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" (p. 1). Factors affecting stability positively and negatively are presented and potential modifications to the elevator control system are provided. The amount of solid friction present was found to be one of the greatest predictors of instability.

Report presenting compression testing on several series of flat panels with Z-section stiffeners with varying relative dimensions. The data presented show the effect of dimension ratio on the buckling stress for the sheet and on average stress at maximum load.

"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 determination of the effects of static margin and rotational damping in pitch on the longitudinal stability characteristics of an airplane by flight tests of a model in the NACA free-flight tunnel. The rotational damping in pitch was varied over a wide range by using horizontal tails that varied in area from 0 to 24 percent of the wing area. Results regarding the effect of variation of static margin and effect of variation of rotational damping are provided.

Report presenting charts and formulas in convenient form for use in the computation of the effects of propellers on stability. Formulas are given for the contributions of the direct propeller forces to the airplane pitching moment, yawing moment, and shift in neutral point due to power.

Report presenting some principles for designing the optimum hull for a large long-range flying boat in order to suit the requirements of minimum drag, seaworthiness, and ability to take off and land at all operational gross weights. The principles include the use of moderate gross-load coefficients, ample forebody lengths, and deep steps and the close adherence of the form to that of a streamline body of revolution with a moderate fineness ratio.

An investigation was conducted to determine and compare the tensile strength of NACA and conventional machine-countersunk flush rivets of several rivet-head angles and varying countersunk depth. The results of the investigation are presented in the form of curves that show the variation of the tensile strength of the rivet with the ratio of the sheet thickness to the rivet diameter. For the same rivet-head angle and for a given angle of c/d, the NACA rivets developed higher tensile strength than the conventional rivets.

Report presenting an investigation to determine any injurious effects of knock on engine parts. Endurance tests were run on a single-cylinder engine to compare the conditions of cylinders operated with and without knock. Results regarding the history of the tests, conditions of pistons and cylinders, absence of surface ignition, and effect of knock on cylinder temperatures are provided.