Report presenting the reasons for the existence of bending stresses due to torsion and the theoretical formulas applying to rectangular boxes with finite bulkhead spacing. Tests are described which were made to verify the theory, strains being measured on a rectangular torsion box with four bulkhead spacings. Results regarding normal stresses are provided.

"Tests were made of riveted double-angle columns to determine the total rivet strength that is required to make these built-up columns develop the strength predicted by the standard column formulas. Results of the tests led to the conclusion that the required rivet strength may be calculated by the beam method of design" (p. 1).

Report presenting an investigation of the force characteristics of single hydrofoils in order to help with preliminary hydrofoil design.

Report discusses the results of two tests: "1) aerodynamic tests to determine the effect of the slipstream and thrust from the powered propellers on the lift and trimming-moment characteristics, and 2) hydrodynamic tests to determine the effect of the powered propellers on the range of stable locations of the center of gravity (from Introduction)." Large differences in the stable range between half-thrust and full-thrust conditions were observed. Three effects of power were also involved in the location of the stable range of the center of gravity.

Report presenting an investigation of the transition of the boundary layer from the laminar to the turbulent region on a flat plate, on the concave and convex side of a plate with a 20-foot radius of curvature, and on the convex side of a plate with a 30-inch radius of curvature.

"The effect on static-pressure measurements of locating a pitot-static tube 0.55 chord ahead of an airfoil section has been investigated. The tests were conducted in the NACA 24-inch high-speed tunnel on airfoil sections of various thickness ratios over a large range of Mach number. The results show that for a wing having a thickness ratio of 0.15 the measured Mach number, determined from a pitot-static-tube reading, is approximately 0.01 too low at a stream Mach number of 0.4 and approximately 0.03 too low at a Mach number of 0.8" (p. 1).

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 results of testing on the suitability of six aromatic amines as fuel additives. Antiknock effectiveness, availability, physical properties, and chemical properties for knock tests were explored. The six aromatic amines were xylidines, cumidines, N-methylxylidines, N-methylcumidines, N-methylaniline, and N-methyltoluidine in 28-R aviation fuel.

Report presenting an experimental investigation of rectangular exhaust-gas ejector pump to provide data that would serve as a guide to the design of ejector applications for aircraft engines with marginal cooling. With a decrease in the quantity of air pumped and an increase in the length of an ejector, the ejector pressure rise increases to optimum values. Results regarding straight ejectors, diffuser ejectors, curved ejectors, ejector aspect ratio, divided ejectors, multistage ejectors, and nozzle-exit effects are provided.

Report presenting tests conducted to determine the performance of two pressurized shunt-type cooling systems for liquid-cooled aircraft engines using a mixture of 30 percent AN-E-2 ethylene glycol and 70 percent water as the coolant. Results regarding effect of engine speed on coolant-flow rate, effect of expansion-tank pressure on coolant-flow rate, relation between pump-inlet pressure and expansion-tank pressure, variation of coolant-flow rate with pump-inlet pressure, flow rate through the shunt lines, effect of coolant-flow rate on pressure drop, effect of venturi on performance of the cooling system, and the system operating experience are provided.

From Summary: "The results of an analytical investigation to determine the qualitative effects of elevator-fabric distortion on the stick-force characteristics of an airplane are presented. These results indicate that serious alteration of intended stick-force characteristics can be produced by elevator-fabric distortion."

"A rain-repellent lacquer was submitted to the National Advisory Committee for Aeronautics by Captain K.H. Kalberer, of Lorr Laboratories, and preliminary tests and observations have been made to determine its value in improving the vision through an airplane windshield during rain. The tests and observations were carried out at Ames Aeronautical Laboratory, Moffett Field, California, over a period of about a week. The results are reported herein" (p. 2).

Tests show that at inlet-air temperatures of 250 deg F and 100 deg F the knock-limited performance of the base fuel of blends, leaded with 4 ml TEL per gallon and containing 20 percent spiropentane, was reduced at fuel/air ratios below 0.085. The 20 percent methylenecyclobutane reduced the knock-limited power of the base fuel at fuel/air ratios below 0.112. Di-tert-butyl ether, methyl-tert-butyl ether, and triptane increased the knock-limited power of the base fuel at all fuel/air ratios and at both temperatures.

"The design of curved sheet panels to resist shear involves a consideration of several factors: the buckling resistance of the sheet, the stress at which buckling becomes permanent, and the strength which may be developed beyond the buckling limit by tension-field action. Although some experimental as well as theoretical work has been done on the buckling and tension-field phases of this problem, neither of these types of action appears to be very well understood. This report presents the results of the first series of torsion tests of stiffened circular cylinders to be completed in connection with this study at Aluminum Research Laboratories" (p. 1).

"The effects of changes in aileron rigging between 2 deg up and 2 deg down on the stick forces were determined from wind-tunnel data for a finite-span wing model. These effects were investigated for ailerons deflecting equally in both directions and linearly with stick deflection. Data were analyzed for a Frise, a sealed internally balanced, and a beveled-trailing-edge aileron" (p. 1).

Bulletin presenting a short investigation in the 19-foot pressure tunnel to determine the aerodynamic characteristics of a rectangular wing model constructed to NACA 0012 airfoil sections. Tests were run with the air in the tunnel at 2 different pressures: atmospheric and 35 pounds per square inch absolute.

"A method is developed for calculating the performance of a dual-rotating propeller from the section characteristics of the blade elements. The method is applied to an eight-blade dual-rotating propeller and the computed results are compared with low-speed wind-tunnel tests of the same propeller in both the tractor and pusher positions. The computations are found to agree within the experimental accuracy of the measurements" (p. 1).

Summary: The effective change in the velocity of flow past a wing section, caused by the presence of wind-tunnel walls, is known for potential flow. This theory is extended by investigation of the two-dimensional compressible flow past a thin Rankine Oval. It is shown that for a symmetrical section at zero angle of attack the velocity increment due to the tunnel walls in the incompressible case must be multiplied by the factor 1/1-M^2 to take account of compressibility effects. The Mach number, M, corresponds to conditions in the wind-tunnel test section with the model removed (p. 1.).

Report presenting an investigation to obtain force-test data on a wing design suitable for high-speed guided missiles, especially data on rolling moments produced in yawed and pitched attitudes. Force tests were conducted on two models of a wing design of low aspect ratio and 20 degree triangular plan form. Results regarding the application of results, four-unit wing design, and six-unit wing design are provided.

Report presenting a series of tests made in the 15-foot free-spinning tunnel to study the spin characteristics of a model of a hypothetical canard airplane, which was designed to be about the same size and have the same general aerodynamic characteristics as a Boeing B-247 airplane. The model spun normally and had excellent recovery characteristics.

"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 presenting a flight investigation to check the results of a theoretical analysis of longitudinal stability of an airplane with free controls. Tests used a Fairchild XR2K-1 airplane on which the weight moment and the aerodynamic balance of the elevator were varied to bring it into a condition where unstable short-period oscillations were encountered.

"A study was made of the performance of a jet-propulsion system composed of an engine-driven blower, a combustion chamber, and a discharge nozzle. A simplified analysis is made of this system for the purpose of showing in concise form the effect of the important design variables and operating conditions on jet thrust, thrust horsepower, and fuel consumption. Curves are presented that permit a rapid evaluation of the performance of this system for a range of operating conditions" (p. 1).

Report presenting testing to determine the boundary layer characteristics and profile drag of the NACA 35-215 airfoil section at high Reynolds numbers. The results indicated that a forward movement of the transition point occurred at about 3 percent of the chord due to operation of the engines and propellers.