A report in two parts: one is a brief review of methods available to helicopter designers for obtaining desired stability characteristics by modifying airframe design and the other is a review of some of the methods of predicting rotor stability derivatives.

From Summary: "Data from ditching investigations conducted at the Langley Aeronautical Laboratory with dynamic scale models of various airplanes are presented in the form of tables. The effects of design parameters on the ditching characteristics of airplanes, based on scale-model investigations and on reports of full-scale ditchings, are discussed. Various ditching aids are also discussed as a means of improving ditching behavior."

Note presenting a qualitative approach to the problem of the effect of frequency and temperature on fatigue, as the theoretical and experimental results do not always seem to match. The fatigue problem is examined from the viewpoint of a two-component system.

Note presenting a study of Stokes' stream function for subsonic or supersonic flow past axisymmetric bodies of small slope. The first-order equation is found to be nonlinear. It can be linearized if one seeks only the formal order of accuracy of the slender-body approximation.

The test method presented shows that the "toss energy" contributed by the apparatus for brittle materials is negligible. The total toss energy is considered to consist of two components: (a) recovered stored elastic energy and (b) kinetic energy contributed directly by the apparatus. The results were verified by high-speed motion pictures of the test in operation.

Report presenting that the usual assumption of a uniform vortex cylinder for the wake vortex structure of a uniformly loaded, lifting rotor operating in the hovering or low-speed vertical-ascent flight conditions does not yield useful results for induced velocities in the region about the periphery of the rotor.

"The carpet-plotting technique is presented in this paper as a more useful and concise method of summarizing cascade data on the NACA 65-series compressor blades given in NACA Technical Note 3916. Carpet plots included permit the selection of the blade camber and the design angle of attack required to fulfill a design vector diagram. Other carpet plots provide means for the prediction of off-design turning angles" (p. 1).

Report presenting an investigation of the aerodynamic characteristics of a wing equipped with a 50-percent-chord sliding flap and a 30-percent-chord slotted flap operating in the slipstreams of two large-diameter propellers in the 300 mph 7- by 10-foot tunnel. Large tunnel-wall effects for which there are no known correction methods were encountered in the tests. Stalling was found to occur in conditions approaching steady level flight at high-power conditions,but a leading-edge slat effectively delayed the stall.

From Summary: "Experimental studies of panel flutter using thin metal plates were conducted at a Mach number of 1.3 to verify its existence and to study the effects of some structural parameters on the flutter characteristics. The effects of tensile forces and buckling were studied on panels clamped front and rear, in addition to initially buckled panels clamped on all four edges. Panel flutter was obtained under controlled laboratory conditions and it was found that tensile forces, shortening the panels, and increasing the bending stiffness were effective means for eliminating flutter. Buckled panels were more susceptible to flutter than unbuckled panels. No apparent systematic trends in the flutter modes or frequencies could be observed."

A two-dimensional low-speed porous-wall cascade tunnel investigation has been conducted to establish the performance of the NACA 65-series compressor blade sections over the useful range of inlet angle, solidity, and section camber. Design points for optimum high-speed operation are presented. The loading limitation is determined for some conditions. Trends of section operating range with increasing section camber are determined for the four inlet angles tested.

Equations and charts have been presented for the conical part of the sidewash above and below swept wings at small angles of attack. This flow-field component is necessary in making calculations of the wing-induced forces and moments on stores, missiles, and pylons. All supersonic Mach numbers and wing leading-edge sweep angles have been considered.

Note presenting an investigation of three narrow-beam models of concave-convex transverse shape and having, respectively, a straight keel, a curved bow, and a curved stern tested at the Langley impact basin as part of a larger study of hydrodynamic impact loads on chine-immersed bodies of heavy beam loading. Testing occurred over a wide range of trim and initial-flight-path angles. Results regarding the transverse curvature, longitudinal curvature, rough water, and observations on the constant-force-type bottom.

The rolling-contact fatigue spin rig was used to test balls of a bearing steel at maximum Hertz stresses of 600,000 to 750,000 psi. The effect of fiber orientation was observed with the ball track restricted to passing directly over the poles, coincident with the equator, or randomly around the ball. The polar areas were found to be weaker in fatigue than the nonpolar areas. This resulted in a much greater portion of the failures occurring in the polar areas than would be expected from a homogeneous material. The early failures are discussed.

Note presenting the use of the Janzen-Rayleigh method of expansion in powers of the stream Mach number to calculate the velocity potential for steady subsonic flow past a paraboloid of revolution. Only the first two terms of the expansion are calculated.

Note presenting tables containing 69,000 values of a set of characteristic functions which first arose in problems of supersonic wing-body interference. The tables are useful in problems of supersonic flow involving aerodynamic shapes which are wholly or in part quasi-cylinders or nearly circular cross sections.

Specimens of a nickel-bonded titanium carbide cermet were given the following surface treatments: (1) grinding, (2) lapping, (3) blast cleaning, (4) acid roughening, (5) oxidizing, and (6) oxidizing and refinishing. Room-temperature modulus-of-rupture and impact strength varied with the different surface treatments. Considerable strength losses resulted from the following treatments: (1) oxidation at 1600 F for 100 hours, (2) acid roughening, and (3) severe grinding with 60-grit silicon carbide abrasive. The strength loss after oxidation was partially recovered by grit blasting or diamond grinding.

Report presenting a system of general equations for computing the burning rates of small particles burning as diffusion flames. Two types of solutions are carried out: a complex numerical integration and a less complicated and rigorous analytical solution involving stepwise iteration across the temperature profile.

Report presenting vibrations of rotary-wing aircraft, which may derive their energy from the rotation of the rotor rather than from the air forces. The theory includes the effects of unequal stiffness of the pylon for deflections in different directions and the effect of damping in the hinges and in the pylon. Some areas of further investigation include polar symmetry and two blade cases.

Results are presented of free-jet tests of a 1.1-inch-diameter hydrogen-burning ram-jet engine over a Mach number range from 1.42 to 2.28 and a Reynolds number range from 6.01 times 10 to the 6th power to 15.78 times 10 to the 6th power. Tests demonstrated the reliability and wide operating range of the engine and showed its suitability for installation on wind-tunnel models of airplane and missile configurations. A comparison of engine operation with combustion-chamber lengths of 3.33 and 1.51 engine diameters was made at a Mach number of 2.06. A maximum test thrust coefficient of 0.905 was obtained at fuel-air ratio of 0.034 and a Mach number of 2.06 for the engine with the 3.33-diameter combustion chamber.

The vertical force-deflection characteristics were experimentally determined for a pair of 56-inch-diameter tires under static and drop-test conditions with and without prerotation. For increasing force, the tires were found to be least stiff for static tests, almost the same as for the static case for prerotation drop tests as long as the tires remain rotating, and appreciably stiffer for drop tests without prerotation.

Carpet plots included permit the selection of the blade camber and the design angle of attack required to fulfill a design vector diagram. Other carpet plots provide means for the prediction of off-design turning angles.