Report presenting an investigation in the two-dimensional low-turbulence pressure tunnel to determine the aerodynamic characteristics of the NACA 8-H-12 airfoil section at four Reynolds numbers. The section lift, drag, and pitching-moment characteristics are presented for smooth and rough surface conditions. Generally, no unusual scale effects are present for either condition.

From Summary: "The purpose of this investigation was to determine whether such airplanes could be made to fly uncontrolled for an indefinite period of time without getting into dangerous attitudes and for a reasonable period of time (one to three minutes) without deviating excessively from their original course. The results of this analysis indicated that the uncontrolled motions of a personal airplane could be made safe as regards spiral tendencies and could be greatly improved as regards maintenance of course without resort to an autopilot."

Report presenting an investigation of the flutter of a small one-blade wooden propeller with a Clark Y section. The highest flutter speeds were found in the vicinity of the angle of zero aerodynamic moment, with flutter speed increasing in this region with decreasing pressure.

Note presenting an investigation to derive the implications of a previously derived equation for rotating beams.

Report presenting the condition for plastic buckling of a long flat plate under combined shear and longitudinal compression is obtained by using the theory of plastic buckling developed for simple loading, provided the ratio of shear to longitudinal compression is assumed constant during the loading process. A detailed calculation for a number of simply supported plates made of a typical aluminum alloy shows that an approximate algebraic relationship provided in the paper will suffice for determination of buckling stress.

Report presenting a theoretical solution for the buckling of Alclad plates on the basis of plasticity theory. Both the differential equation of equilibrium of the buckled plate and energy expression are provided. Results regarding the buckling of long simply supported plates under longitudinal compression and under shear and for a plate column are provided.

From Summary: "Included in the report are the results of total-pressure surveys made at downstream ends of the mixing tubes."

Note presenting pressure distribution measurements made on the wing of a fighter-type airplane to determine the span loading and to compare center-of-pressure results with those obtained by strain-gage measurements on the same airplane during a previous flight investigation. Flight tests were all made at a pressure altitude of about 30,000 feet and covered a Mach number range from approximately 0.35 to 0.81. Results regarding additional air load, spanwise center of pressure of additional air load, basic air load distribution, and span loading during a stall and buffeting are provided.

"The experimental results are presented for the second part of an investigation of the compressive strength of 75S-T6 aluminum-alloy flat panels with longitudinal extruded Z-section stiffeners. This part of the investigation is particularly concerned with panels in which the ratio of the thickness of the stiffener material to the skin material is small and the ratio of stiffener spacing to skin thickness is large" (p. 1).

Note presenting an investigation with the aim of achieving improved hydrodynamic qualities for flying boats, which involved determining the combined effect of a warped forebody and extended afterbody on the hydrodynamic characteristics of a full having a basic length-beam ratio of 15. Results regarding longitudinal stability, landing stability, spray characteristics, and landings in waves are provided.

Report presenting testing to determine the force developed in a shock strut as a function of the flexibility of the attached wing structure. Both the experiment and analysis indicated that wing flexibility had some effect on the shape and peak value of the force-time curve in a shock strut.

"In order to provide engineers interested in rotating-wing aircraft but with no specialized training in stability theory some understanding of the factors that influence the flying qualities of the helicopter, an explanation is made of both the static stability and the stick-fixed oscillation in hovering and forward flight in terms of fundamental physical qualities. Three significant stability factors - static stability with angle of attack, static stability with speed, and damping due to a pitching or rolling velocity - are explained in detail" (p. 1).

Report presenting flight-test measurements and corresponding pilot's opinions of the forward-flight longitudinal flying qualities characteristics of several single-rotor helicopters. The most important consideration for satisfactory characteristics appears to be the prevention of prolonged stick-fixed divergent tendencies. Results regarding the characteristics appreciated, theoretical analysis of pull-up characteristics, and practical requirements are provided.

"Available information on gust structure, airplane reactions, and pertinent operating statistics has been examined. This paper attempts to coordinate this information with reference to the prediction of gust loads on airplanes. The material covered represents research up to October 1947" (p. 1).

Report presenting an investigation of the two-dimensional aerodynamic characteristics of 15 NACA airfoils at four Reynolds numbers. The results indicate that the drag coefficient at the design lift coefficient and the maximum lift coefficient are the most important aerodynamic characteristics and are most affected by Reynolds number changes.

"A theoretical solution is given for the critical shear stress of a simply supported curved rectangular plate stiffened by a central stiffener offering no torsional restraint which lies in either the axial or circumferential direction. Results are obtained by means of the Galerkin method and are presented in the form of computed curves and tables" (p. 1).

Note presenting the compressive buckling stress of outstanding flanges reinforced by bulbs, which was computed by the strain-energy method for flanges with 10 shapes and a range of lengths. The results were checked for some cases by computations based on a differential-equation method. The results were analyzed to determine which shape of flange gave the greatest support to the structure to which it was attached.

Note presenting experimental investigations of boundary-layer suction through slots as a means of increasing the extent of laminar flow on airfoil sections. The results show that, with the use of suitable slots, substantial increases in the extent of laminar flow can be achieved by boundary-layer control with only a small expenditure of power. Results regarding slot geometry and arrangement, suction slots in an unfavorable pressure gradient, suction slots in a favorable pressure gradient, and determinations of the relations controlling the distribution of suction slots are provided.

Report presenting an experimental investigation of boundary-layer suction through slots as a means of increasing the extent of laminar flow on airfoil sections. Results regarding slot geometry and arrangement, suction slots in an unfavorable pressure gradients, suction slots in a favorable pressure gradient, and a determination of the relations controlling the distribution of suction slots are provided.

From Summary: "The theory of plastic buckling, originally derived for individual plates, has been extended to apply to combinations of plates such as H- and Z-sections. The theory has been applied specifically to extruded H-sections of 75S-T6 aluminum alloy; the calculated buckling stresses agree satisfactorily with the stresses obtained experimentally."

Report presenting a strain-energy theory established for the calculation of the buckling load in pure bending of reinforced monocoque cylinders which have a symmetric cutout on the compression side and buckle according to general-instability patterns. The difference between this theory and other theories is the use of the axial wave length as an additional parameter whose value was determined from a minimum condition.

Report presenting information for the determination of the theoretical lift, damping-in-roll, and center-of-pressure characteristics for a group of plan forms at supersonic speeds. The information is presented in three forms: equations, figures presenting generalized curves, and figures presenting curves for representative groups of configurations. Several observations are made in regards to the effect of taper ratio, angle of sweep, and aspect ratio on the values of the derivatives.

From Summary: "The spanwise lift distributions of wings of low aspect ratio but of arbitrary plan form and angle-of-attack distribution have been analyzed by two well-established concepts: the virtual-mass concept and the Weissinger method. Both concepts have been found to yield the same simple integral expression for the spanwise lift distribution in terms of the spanwise angle-of-attack distribution. Tables and figures of lit distributions of low-aspect-ratio wings have been presented."

Report presenting an analysis of two matrix methods for calculating responses of linear systems for given forcing functions and indicial responses in order to find a method suitable for solving the inverse problem of calculating forcing functions from known responses. The results of both methods are compared with exact solutions for both the direct and the inverse problems.