Report presenting elementary basic solutions of the equations of motion of a compressible fluid in the hodograph variables are developed and used to provide a basis for comparison in the form of velocity correction formulas, of corresponding compressible and incompressible flows.

Report discusses the results of testing on the pressure distribution at several longitudinal sections of the vertical tail surface of the Curtiss P-40K airplane at various angles of attack and angles of yaw and with the propeller removed and propeller operating. Results regarding the chordwise pressure distributions, effects of propeller operation on the spanwise distribution of normal-force coefficient, total normal-force coefficients, and effect of propeller operation on the variation of vertical-tail normal-force coefficients are presented.

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.

Results of subject tests indicate the difficulty of obtaining closely balanced rudder surfaces for most tail assemblies with shielded horns and maintaining a near zero rate-of-change of hinge-moment coefficient without an additional balancing device. A comparison is made between shielded and unshielded horn test results. Pressure distribution and tuft tests of flow over different shaped horns showed higher critical speed for medium-taper nosed horn. The trim tab nose shape had little effect on tab test results.

Report discusses the results of an investigation into the tightness, shear strength, tensile strength, and life under pulsating loads of hollow, hydraulically expanded rivets made of 17S-T aluminum alloy. The countersunk-head rivets with inserts had a much higher maximum load in shear than the modified-roundhead rivets, which did not have inserts.

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.

Report presenting a study to determine the effect on the knock-limited permissible power output on the indicated specific fuel consumption and on the cylinder temperatures of exhaust-gas dilution of the inlet-air charge, inlet-air temperature without exhaust-gas dilation, and of compressible ratio.

Report presenting an investigation conducted with the propeller cuffs and spinner removed to determine their effect in flight on the pressure recovery of the cooling-air flow. Curves are presented to compare the pressure and temperature distribution over the front row of cylinders for flights with and without cuffs and spinner.

Report presenting a study of nitrided-steel piston rings in nitrided-steel cylinder barrels, which showed material of high reflectivity on their running faces. The structure of the material could not be resolved at a magnification of 1500 diameters. Results regarding the occurrence of coating, thickness of coating, height of coating above the nominal surface, chemical characteristics, physical characteristics, metallurgical change, and additional tests are provided.

Report presenting a consideration of the performance of sliding surfaces, such as piston rings, cylinders, journals, and bearings in aircraft engines with reference to the surface characteristics that they possess before and after running-in, prior to service operation. The phenomena accompanying the running-in process are analyzed.

Report presenting an investigation of the flying qualities of a Curtiss SB2C-1 airplane. Tests were made to determine the effect of a bobweight in the elevator system and the effect of seals in the aileron gaps. Results regarding longitudinal stability and control, requirements for lateral stability and control, and stalling characteristics are provided.

Report discusses the maximum lift coefficients for conventional and tailless airplanes in the gliding and landing conditions. Three areas are used to calculate the coefficients: wing area alone, wing area plus horizontal-tail area, and wing area plus horizontal- and vertical-tail areas.

Report describes exploratory testing to determine the feasibility of using a hydrofoil with a type of flying boat afterbody called a planing tail. Several hydrofoil locations were examined, including no hydrofoil, and the effects of resistance characteristics were charted. The researchers concluded that it is possible to add a single hydrofoil to that type of afterbody to provide additional hydrodynamic lift without introducing instability.

Report presenting an investigation of thirteen exhaust-gas-to-air heat exchangers to determine the practicability of the use of such heat exchangers in the thermal ice-prevention systems on aircraft. The results show that the exchangers constitute an excellent source of heated air for aircraft ice prevention and can be constructed to resist thermal and vibrational stresses.

Report discusses methods of determining the iron contamination of used lubricating oil in order to study wear rates of piston rings and cylinder barrels of aircraft engines. Two methods of separating iron from used lubricating oil are presented. The results of the analyses of the oil are presented and the methods are evaluated.

Report describes a balanced-diaphragm device for measuring dynamometer torque of single-cylinder or multicylinder engines that was developed for laboratory use. Design variables are described, included desired torque-measuring device characteristics, diaphragm design, pilot valve, the torque-indicating instrument, the capacity range, ability of reversed operation, and double-acting operation. The accuracy is described as satisfactory and effects of other variables are negligible.

Report presenting the results of a study of the rupture-test characteristics of 13 wrought and 4 cast alloys which were considered to have promise for service in exhaust gas turbines. The results are given in the forms of a table of information and data, a page of curves, and a page of photomicrographs.

Tests were undertaken to determine the relationships for estimating the maximum amount of a water-soluble gasoline additive that will diffuse from the gasoline to the water when fuel is stored over the water and to determine from the relationships the amount of xylidines that will diffuse from the gasoline to the water in an overwater-storage system.

Report presenting an exploration of the electrical effects that glider tows operating in or near a thunderstorm may experience. The three primary hazards are a direct lightning strike, a lightning strike that passes to some intermediate point on the towline, and an electrical current of appreciable magnitude flowing in the towline the whole time that the tow is within a few miles of the thunderstorm.

Report presenting information regarding the development of a type GB-5 controllable glide bomb equipped with a target-seeking device. The model was tested on the six-component balance in order to measure the stability and control characteristics of the bomb in its original condition and with various modifications. Results regarding the effect of end plates on dihedral parameter, effect of vertical-tail arrangement on directional stability, aileron tests, and glide-path control are provided.