Report discusses the results of an investigation to determine the effect of a collector ring on exhaust-gas sampling. The results of tests to determine the percentage by volume of exhaust gas from the collector ring are presented for several engine powers and speeds. The danger of air dilution from the breathing action of the engine is almost entirely eliminated by the use of a collector ring.

Report discussing the knock-limited performance of blends of 2,3-dimethylpentane and 23-R fuel in an F-4 engine at three sets of conditions and three compression ratios. The knock-limited performance of 2,3-dimethylpentane has about the same sensitivity to compression ratio and inlet-air temperature as 28-R fuel.

Report presenting tests in the propeller research tunnel to determine the characteristics at low blade angles of propellers for which high blade angles are already available.

"Strength tests were made on two sets of beams having webs with large circular lightening holes. The main conclusion drawn from the tests is that allowable web stressed derived from pure shear tests and allowable flange stresses derived from compression tests cannot be applied in the design of beams without making corrections for interaction" (p. 1). Pure shear tests and beam tests were performed and the circumstances of failure were investigated.

Report discussing testing to determine the effect of ethylene dibromide on the knock-limited performance of S reference fuel. An increase in ethylene-dibromide content did appear to decrease the knock-limited performance of the fuel up to a certain point and at all but the extremes of fuel-air mixtures.

Report presenting an investigation of the antiknock effectiveness of N-methyl-aniline and xylidines as fuel additives under severe engine operating conditions. 5-percent concentrations by weight were blended with an alkylate blending agent and a virgin-base gasoline.

"In order to determine the lead susceptibility of several fuels, leaded and unleaded fuels from the same stock were blended and tested in a full-scale air-cooled aircraft-engine cylinder. The fuels were S-4 reference fuel, virgin-base stock, aviation alkylate, neohexane, and blends of 25-percent benzene with 75-percent virgin-base stock and 25-percent toluene with 75-percent virgin-base stock" (p. 1).

Report presenting an investigation of the transition of the boundary layer from the laminar to the turbulent regime on the concave side of a plate with a radius of curvature of 8.5 feet. Results regarding the mean speed distribution, effect of curvature on the position of the transition point, effect of the pressure gradient on transition, and effect of free stream turbulence on transition are provided.

From Summary: "The results of the analysis showed that the combined efficiency, which is unacceptably low at speeds less than 300 miles per hour, becomes nearly equal to that of conventional power plants of current design at 500 miles per hour. It was also shown that the efficiency will be increased considerably as the physical limitations on cycle temperature and blower speed are raised and as the efficiencies of the system components are improved."

Report presenting testing to determine the influence of propeller rotation and vertical-tail design on the trim characteristics of a model of a twin-engine airplane with one engine inoperative. The tests showed that the effect of mode of propeller rotation on the directional trim characteristics of the model operating with asymmetric power was considerable. Results regarding the effect of mode of propeller rotation and effect of vertical-tail design are provided.

From Summary: "Results are presented of measurement of the pressure drop in ducts produced by two equal 90 degree elbows arranged at three different angular positions to each other, placed adjacent to each other, or separated by straight ducts of various lengths. The measured pressure drops have been analyzed and correlated, and the results are summarized in the form of curves adapted for design computations of pressure drop in compound-duct bends."

Report presenting corrections to the velocities near a cowling-flap tip in order to determine jet-boundary corrections to cowling-flap-outlet pressures. The presence of the low-energy air leaving the flap opening was taken into account by so shaping the nacelle model that its outer surface represented the stream surface leaving the flap tip. Copper was found unsatisfactory for use as electrode material.

Report presenting an investigation to determine the properties of diffuser-resistance combinations. The work applies to the design of airplane cooling ducts in which air is expanded in front of resistances, such as radiators, oil coolers, intercoolers, or the cylinders of an air-cooled engine.

Report presenting a method utilizing the Doppler effect on radio signals for determining the speed and distance traveled of an airplane. The method is called the NACA radio ground-speed system and uses the standard radio transmitter already found in most aircraft. Flight tests were made in which the method was used and the results were consisted with calibrated airspeed indications and stop-watch measurements.

Report describes an electrical-relay circuit that uses cylinder thermocouples for indicating preignition or misfiring in an aircraft engine. The potential dangers of preignition and the importance of an easy-to-use, practical preignition indicator are provided. The operating principles of the indicator and a description of its functioning, calibration, and installation procedures are also included.

Report discusses calibration testing performed on a Kollsman type G-1 and an NAF No. 1 pitot tube at several Mach numbers and angles of attack. The effect of drain holes on the flow within the pitot tube was analyzed and the ability to estimate the error in the total pressure was created. The accuracy of the extrapolated and estimated values were found to be within reasonable limits.

From Introduction: "The purpose of this report is to summarize, without extended proofs, the results of a study of a simplified model of nonadiabiatic, compressible fluid flow, both subsonic and supersonic, and to state these results in a form that will make them immediately useful in providing a theoretical background for current technical problems of high-speed combustion.

Report presenting performance tests of the thermal ice-prevention equipment developed for the B-17F airplane at the NACA Ice Research Project. Temperatures of the heated surfaces, structure, and circulating air and the air-flow rate and quantity of heat through the system were obtained during flights in dry air and in natural icing conditions. Results regarding the wing outer panel, wing tip, wing inner panel, carburetor and intercooler inlets, horizontal stabilizer, vertical stabilizer, windshield, windows, and engine cowls are provided.

"An investigation was conducted to determine the knock-limited blending characteristics of leaded fuels containing selected aromatic fuel components (benzene, toluene, mixed xylenes, and cumene). Each of the aromatics was blended with an alkylate blending agent and with a virgin base stock. The blending characteristics of the resulting fuels were determined in a full-scale aircraft-engine cylinder" (p. 1).

Report presenting the calculated performance of four-, six-, and eight-blade single-rotating propellers compared with experimental results for blade angles ranging from 25 to 65 degrees. The data were obtained on propellers mounted in front of a streamline body with a spinner housing the hub.

Report presenting an extension of tables of stiffness and carry-over factor to include the stiffness of a member with the far end subjected to a moment equal and opposite to the moment applied at the near end. The formulas used in calculation to determine the values are also provided.

Report presenting an investigation made to determine the effectiveness of various oxides and oxide mixtures in oxidizing at room temperature the exhaust gases from an internal-combustion engine for the determination of fuel-air ratio. The oxides of silver, copper, manganese, cobalt, nickel, iron, cerium, lead, bismuth, and mercury were tested individually and in various combinations.

Report presenting an investigation conducted with alcohol used in conjunction with a windshield wiper as a means of affording protection against ice formation on the windshields of aircraft when operating in inclement weather. Flight tests established the most economical flow rate of isopropyl alcohol to provide adequate ice prevention. The optimum location and size of the alcohol-distribution tube and orifices were determined for the specific installation investigated.

"Tests were conducted in the Langley 24-inch highspeed tunnel to ascertain the static-pressure and total-pressure losses through screens ranging in mesh from 3 to 12 wires per inch and in wire diameter from 0.023 to 0.041 inch. Data were obtained from a Mach number of approximately 0.20 up to the maximum (choking) Mach number obtainable for each screen. The results of this investigation indicate that the pressure losses increase with increasing Mach number until the choking Mach number, which can be computed, is reached" (p. 1).