Report presenting an investigation of the knock-limited performance of leaded blends of 12 pure aromatic hydrocarbons in a full-scale aircraft-engine cylinder at CRC simulated cruise and take-off conditions to determine the antiknock effectiveness of additions of pure compounds to aviation fuels. Results indicated that all of the hydrocarbons increased the knock limit of the base fuel except for 2 of them.

From Summary: "An investigation has been conducted to determine the possible extent of effects of wind-tunnel constriction at high speeds for airfoils of various thickness-to-chord ratios at or near zero lift. The results indicate that a limiting test Mach number exists which is principally a function of the ratio of model thickness to tunnel height. At high Mach numbers serious constriction effects occur; these effects are of such a nature that the standard calibration methods given speeds much lower than the actual test speeds."

Report presenting testing in the two-dimensional low-turbulence tunnels on a 24-inch-chord model of the NACA 66(215)-116 a = 0.6 airfoil with a 0.25-chord slotted flap. The optimum flap pivot positions were found for three different conditions. The conditions were determined from a consideration of the landing, take-off, and strafing requirements of the airplane.

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.

"Strain measurements were made on the compression side of two box beams with corrugated aluminum-alloy covers loaded to failure. Angles formed from sheet were used for corner flanges in beam 1; whereas extruded angles were used in beam 2. Failure in each beam occurred in the corner angle at a stress that was above the compressive yield stress for the material" (p. 1).

Report discusses the results of strength tests of several curved-sheet 24S-T aluminum alloy specimens stiffened longitudinally and transversely and loaded in shear. Curved-web beams and cylindrical shells were both examined in the tests. Results provided include the load at which the sheet began to show shear buckles, where the buckles occurred, and whether or not the failures involved rupture of the sheet.

Report discusses a method of replica creation and testing of the surface-finish variation of aircraft engine parts subject to wear. In this report, a positive replica is created, the surface is treated, the replica is tested to make sure the fidelity is high enough, and a series of ring-sticking tests are conducted on the replicas. A summary of the results of the testing is also included.

Report presenting pressure distribution tests of six NACA 16-series propeller sections with 1-foot chords in the 8-foot high-speed tunnel to determine the compressibility effects on peak section pitching-moment coefficients. Data is presented as curves of peak section pitching-moment coefficient against Mach number, thickness ratio, and camber. The peak pitching-moment coefficients were found to occur in the regions of positive and negative stall.

Report presenting flight measurements of the pressures on the horizontal tail surfaces of a typical propeller-driven pursuit airplane during stalled pull-outs at high Mach number. Unit loads measured on the stabilizer at safe maneuvering limits were not only considerably in excess of the design unit loads, but also occurred in a direction opposite to the design loads. Revision of the tail-load design requirements and manner of specifying safe maneuverability limits to pilots appears necessary.

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.

Report presenting testing of several designs of nitrided-steel piston rings under variable conditions of output. Testing indicated the importance of good surface finish and conformity of the ring to the bore. Results regarding temperature tests, single-cylinder-engine tests, and multicylinder-engine tests are provided.

Report presenting a study to determine the effect of several methods of increasing the knock-limited power on critical cylinder temperatures. The knock-limited indicated horsepower and cylinder temperatures were determined for a Wright R-2600-8 cylinder under specified operating conditions. The most satisfactory method of increasing knock limited power was found to be internal cooling with water and the least satisfacotry was increasing the engine speed.

Report presenting an investigation of the flow downstream from a two-dimensional grid formed of parallel rods. The nature of the flow was determined primarily by means of total-head measurements. Preliminary tests were made in both the closed-duct and open, two-dimensional configurations, but it was found that the same phenomenon occurred in both cases.

An investigation was made of the cooling characteristics of a P and W R-2800 engine with NACA short-nose high inlet-velocity cowling. The internal aerodynamics of the cowling were studied for ranges of propeller-advance ratio and inlet-velocity ratio obtained by deflection of cowling flaps. Tests included variations of engine power, fuel/air ratio and cooling-air pressure drop. Engine cooling data are presented in the form of cooling correlation curves, and an example for calculation of cooling requirements in flight is included.

From Introduction: "The purpose of this report is to show that it is practical to apply a least-squares method to the correlation of engine-cooling data."

Report presenting an equation based on simple blade-element theory and the assumption of a fixed wake pattern is derived and fitted to available data to show the first-order relation between the parameters of propeller operation and intensity of wake-excited periodic force acting on the blades of a pusher propeller. The derived equation indicates that the effect of power coefficient on the intensity of the wake-excited periodic force is small. Limited data also indicates that the wake-excited vibratory stress in a propeller increases with the drag of the body producing the wake.

From Introduction: "As a part of the general lateral-control investigation by the NACA, the large amount of two- and three-dimensional data on the rolling effectiveness of ailerons without exposed overhang balance is collected and analyzed in the present paper."

Report presenting a series of tests on the Brewster XSBA-1 airplane to determine the effects of various tail modifications. Some of the modifications include variations of the chord of the elevator and rudder while the span and total area of the surfaces are kept constant and variations of the total area of the vertical tail surface. Results regarding the longitudinal stability and control and lateral stability and control are provided.

Report discussing testing of the Douglas A-26B to determine the longitudinal stability and control characteristics. Information about the elevator, stick-fixed and stick-free stability, center of gravity, and flap effects are described.

Report presenting an investigation in the 7- by 10-foot wind tunnel of the effects of various modifications to the profile of a 0.20-chord plain sealed aileron and a 0.15-chord plain sealed aileron on an NACA 66,2-216 airfoil. Thickening of the aileron was found to reduce the aileron effectiveness, reduce the slope of the wing section lift curve, and reduce the hinge-moment coefficients. Results regarding the section data, aileron effectiveness, aileron hinge moments, lift, pitching moment, drag, and Reynolds number are provided.

Report presenting an investigation in the 7- by 10-foot wind tunnel of the effects of modifications to the trailing edge of a 0.20-chord plain sealed aileron on an NACA 66,2-216 airfoil. The modifications considered consisted of various amounts of symmetrical thickening and beveling of the aileron trailing edge. Results regarding aileron effectiveness, aileron hinge moments, aileron control forces, lift, pitching moment, drag, and Reynolds number are provided.

"The results of a series of tests to determine the effect of internal pressure on the buckling load of a thin cylinder under an applied torque indicated that internal pressure raises the shear buckling stress. The experimental results were analyzed with the aid of previously developed theory and a simple interaction formula was derived" (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 a description of a short method of estimating propeller efficiency for a given operating condition. The efficiency is determined for any design condition by evaluating separately from charts the induced losses and the profile-drag losses. The report covers single-rotating propellers of two, three, four, six, and eight blades and includes charts showing the rotational-energy loss for the given operating condition.