Propellers with trailing-edge extensions were studied to determine aerodynamic characteristics. Trailing-edge extension increased power absorbed by propeller with little loss in efficiency. Power coefficient for maximum efficiency was greater for 20% camber type extension than for 20% straight type extension over range of advance ratio of 1.0 to 2.5 although camber type was less efficient. Efficiency was about the same for cruising and high-speed at a high power coefficient for propeller with extension.

Report discussing tests to determine the performance of an aircraft engine cylinder using nitrous oxide to provide additional supercharging. The test results of injecting it as a gas and calculated results of injecting it as a liquid are described.

An investigation was conducted to compare the performance of two 25-ft-diam rotors which had identical dimensions and were similar in construction but different in blade airfoil-sections. Tests were conducted at indicated blade pitch angles from 3 degrees to 11.5 degrees and rotor speeds of 200, 290, and 371 rpm. The 23012.6 rotor required 2 percent less power to hover than the 0012.6. At thrust coefficients above design, the performance of the 23012.6 became better than the 0012.6 rotor.

Report discussing the effects of supercharging on the take-off thrust and useful load for a typical helicopter. Performance of the engine with the supercharger and on the rotor thrust is detailed.

Investigations were made to determine the cowling and cooling characteristics of the Ranger V-770-8 engine installation in an observation seaplane. Final cowl configurations possessed ample engine and oil-cooler pressure drops for cooling in the critical normal-power climb condition with any of the three baffle configurations tested. The indicated critical Mach number of the cowling was found to be 0.70 as determined by the pressure on the lower lip of the inlet.

"A continuous 50-hour test was conducted to determine the effect of maximum cruise-power operation at ultra-lean fuel-air mixture and increased spark advance on the mechanical conditions of cylinder components. The test was conducted on a nine-cylinder air-cooled radial engine at the following conditions:brake horsepower, 750; engine speed, 1900 rpm; brake mean effective pressure, 172 pounds per square inch; fuel-air ratio, 0.052; spark advance, 30 deg B.T.C.; and maximum rear-spark-plug-bushing temperature, 400 F. In addition to the data on corrosion and wear, data are presented and briefly discussed on the effect of engine operation at the conditions of this test on economy, knock, preignition, and mixture distribution" (p. 1).

Report presenting tests conducted on a steel cylinder barrel with aluminum fins in order to determine the heat-transfer coefficients of the cylinder and the excellence of the bond between the steel barrel and the aluminum fins. Results regarding the heat-transfer tests and physical tests are provided.

"Tests were conducted to develop a slip-ring and brush system that will perform satisfactorily in aircraft-engine, dynamic-strain-measuring applications where resistance-wire strain gages are the means of measuring the strain and to correlate the data obtained from tests in order to provide a basis for predicting the performance of similar slip-ring and brush systems operating under conditions similar to those imposed by these tests." 24 combinations of materials were tested dry and 8 were tested in oil. The five most predictable systems were identified.

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.

"A preliminary analysis has been made of the conditions of stability of free oscillations of a hinged rotor in hovering flight. The case analyzed is a rotor with hinges allowing freedom in flapping and lagging and having a completely reversible cyclic pitch-control system, so that a twisting moment on a blade moves the control stick without hindrance from spring or friction constraint. The principal results of this study are presented in the form of a stability chart" (p. 1).

Report discussing tests of a Sikorsky YR-4B helicopter, including photography of a rotor blade in forward-flight conditions at several azimuth angles for several tip-speed ratios. Fabric deformation in the form of sagging and bulging was noted. A reversal in the bending curve near the blade tip was also noted, which was hypothesized to come from losses of lift and high centrifugal force.

Report presenting testing of a steel cylinder barrel with aluminum fins of the optimum spacing of 0.090 inch. The primary purpose is to determine the excellence of the thermal bonds between the aluminum fins and the aluminum base and between the aluminum base and the steel and to compare the heat transfer of the barrel with that of barrels with a fin space of 0.052 inch.

Report presenting testing of a steel cylinder barrel with aluminum fins in order to evaluate the effect of using preformed aluminum fins on a steel barrel or aluminum barrel. Results regarding the heat-transfer tests and physical tests are provided.

Report presenting testing of two engine cylinder barrels with aluminum fins. The primary purpose was to determine the heat-transfer coefficients and the excellence of the bonds between the aluminum fins and the aluminum base and between the aluminum base and the steel of the two barrels when manufactured by a large-volume production method.

"Tests were conducted to determine the effect of engine-operating variables and internal coolants on spark-advance requirements of a single cylinder from a 12-cylinder liquid-cooled engine for maximum take-off power and maximum cruise economy. The effects of fuel-air ratio, engine speed, air flow (charge density), mixture temperature, and internal coolants on peak-power (optimum) spark advance were investigated. In addition, tests were conducted to determine the effect of spark advance on the knock-limited engine performance at several mixture temperatures for conditions simulating take-off, high-power cruise, and low-power cruise" (p. 1).

Report discussing a series of single-cylinder engine tests to determine the effect of special surface coatings in porous chrome-plated cylinder barrels on oil consumption and ring wear. The coating materials were selected for their bearing and lubrication properties and on their applicability to processing. The surface coatings tested were lead overplates, silver overplates, and colloidal graphite base paint.

Report discussing the effect of valve clearance on valve-lift diagrams, knock-limited performance, and engine cooling. The performance of single-cylinder and multicylinder engines was also compared across these variables.

"Results of performance measurements made in level fight with the HNS-1 (Army YR-4B) helicopter are presented. These data include torquemeter measurements of shaft power for both the main rotor and the tail rotor. The power data, in conjunction with full-scale-tunnel date on the lift and drag of the fuselage, are used to calculate the drag-lift ratio for the main rotor" (p. 1).

Report discussing icing and de-icing of the carburetor and supercharger inlet of typical aircraft engine induction systems. A description of the systems used to control and simulate different conditions is provided.

Report presenting a study of the effect of aftercooling on the brake horsepower, weight, and weight-power ratio of a power plant consisting of a 2000-horsepower air-cooled engine, an intercooler, and two stages of supercharging. Three cases are considered: inadequate supercharging, supercharging to constant manifold pressure, and supercharging to detonation-limited manifold pressure.

"A relatively simple equation has been found to express with fair accuracy, variation in manifold-charge temperature with charge in engine operating conditions. This equation and associated curves have been checked by multi cylinder-engine data, both test stand and flight, over a wide range of operating conditions. Average mixture temperatures, predicted by the equations of this report, agree reasonably well with results within the same range of carburetor-air temperatures from laboratories and test stands other than the NACA" (p. 1).

Report discussing an investigation to determine whether the crank angle for maximum rate of pressure rise can be used to indicate maximum-economy spark advance. Information about spark-advance tests at constant inlet-air pressure and fuel-air-ratio test results are provided.

"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 discussing basic performance data obtained on the PV-2 helicopter rotor. Blade motion, rotor forces, and power were measured for static-thrust condition and a limited range of forward-flight conditions. Recommendations are provided for further testing to obtain blade-motion data and force-test data in order to develop a more detailed analysis.