This paper presents a continuation of the work published in Technical Report no. 496. The results of that paper have been extended to include the effect of aerodynamic balance and the effect of a tab added to the aileron. The aerodynamic coefficients are presented in a form convenient for application to the flutter problem.

"The study of combustion in a spark-ignition engine given in Technical Report no. 704 has been continued. The investigation was made with the NACA high-speed motion-picture camera and the NACA optical engine indicator. The camera operates at the rate of 40,000 photographs a second and makes possible the study of phenomena occurring in time intervals as short as 0.000025 second. Photographs are presented of combustion without knock and with both light and heavy knocks, the end zone of combustion being within the field of view" (p. 15).

"A study is presented of ground effect as applied to the lifting airscrew of the type used in modern gyroplanes and helicopters. The mathematical analysis of the problem has been verified by tests made of three rotor models in the presence of a large circular "ground plane." The results of the study are presented in the form of convenient charts" (p. 1).

"Span load distributions of swept-back wings have been calculated. The method used was to replace the wing with a bound vortex at the quarter-chord line and to calculate the downwash due to the system of bound and trailing vortices to conform at the three-quarter-chord line to the slope of the flat-plate wing surface. Results are given for constant-chord and 5:1 tapered plan forms, for sweep-back angles of 0 degrees, 30 degrees, and 45 degrees, and for aspect ratios of 3, 6, and 9" (p. 1).

"The present report describes a device for ascertaining the bending and buckling effect in stress measurements on shell structures accessible from one side only. Beginning with a discussion of the relationship between flexural strain and certain parameters, the respective errors of the test method for great or variable skin curvature within the test range are analyzed and illustrated by specimen example" (p. 1).

"Flight tests were made of a type of internally balanced sealed ailerons installed on a Ryan ST airplane. Aileron effectiveness and stick forces were measured at various airspeeds under NACA recording instruments. For comparison, the aileron characteristics were also determined without the internal balance and seals" (p. 1).

From Summary: "A 1/10-size model of the hull of the French flying boat Latecoere 521 was tested in the NACA tank. This model is one of a series of models of the hulls of actual flying boats of both foreign and domestic type that are being tested in the NACA tank to provide information regarding the water characteristics of a variety of forms of hull and to illustrate the development of present-day types of flying boat. The lines and the offsets of the hull were obtained from the manufacturer through the Paris office of the NACA."

From earlier measurements and the mathematical examples, it can be gathered that the inertia of dynamic pressure arrays can be computed with sufficient accuracy and the proper size of tubing established, provided that certain requirements are made on the inertia. A new mathematical term, the pneumatic time constant, depends only on the dimensions of the tubing and of the indicator and enables the comparison of different dynamic pressure arrays.

Report presenting the performance of several internally finned radiators and a comparison with more conventional honeycomb radiators. In a typical case, the new radiator can be designed with 55 percent less volume and 18 percent less power expenditure while dissipating the same amount of heat.

Report presenting a wooden model equipped with a slotted flap that was tested in the two-dimensional tunnel. It represented a wing section of the Curtiss-Wright P-60A airplane and the NACA 66,2-118 section. Results regarding lift characteristics, drag coefficients, and flap deflection characteristics are provided.

Report presenting lift and drag tests made in the two-dimensional tunnel of three airfoil models. The models represented intermediate sections on alternative wings of the XB-32 airplane and were equipped with 0.30 Fowler flaps. Results regarding the Davis model, the C.A.C. model, and low-drag model are provided.

"Problems involved in the stability and control of tailless airplanes are discussed. Such factors as the location of the aerodynamic center and its effect on the longitudinal stability, longitudinal trim with high-lift devices, the effects of various changes in the shape of the wing on lateral stability, and the effects of nacelles are covered. It appears that sufficient stability and controllability can be secured without sweepback" (p. 1).

"The following preliminary drag results obtained in flight on the low-drag wing of the Curtiss XP-60 airplane are given herewith in compliance with the request of the Army Air Corps" (p. 1).

"Pressure-distribution measurements were made at the request of the Materiel Division, U.S. Army Air Corps, on a 24-inch-chord wooden model equipped with a slotted flap and submitted by the Curtiss-Wright Corporation. The tests were made in the Langley two-dimensional tunnel at a Reynolds number of about 5,600,000" (p. 1).

Report presenting a pressure-distribution investigation conducted in the 4- by 6-foot vertical wind tunnel to determine the air loads on an airfoil with a 22.1-percent-chord balanced split flap. Results regarding section pressure distribution and aerodynamic section coefficients are provided.

This technical report details the production of fluorocarbon by reactions between fluorine and silicon carbide. The report contains two figures depicting aspects of the process.

"The stresses in circular frames of constant bending stiffnesses, as encountered in thin-wall shells, are investigated from the point of view of finite depth of sectional area of frame. The solution is carried out for four fundamental load conditions. The method is illustrated on a worked out example" (p. 1).

Report presenting an investigation of the influence of running propellers on the hydrodynamic characteristics of a model of a seaplane in the tank to evaluate the importance of power in tests of dynamically similar models. The powered propellers were found to have a large effect on the aerodynamic characteristics of the model and consequently on the hydrodynamic stability, which depends to a certain extent on these characteristics. Generally, the magnitude of the effects of a given increment of power in such tests decreases as the power is increased.

From Summary: "The present report deals with temperature measurements on cylinders of 0.2 to 3 millimeters diameter in longitudinal and transverse air flow at speeds of 100 to 300 meters per second. Within the explored test range, that is, the probable laminar boundary layer region, the temperature of the cylinders in axial flow is practically independent of the speed and in good agreement with Pohlhausen's theoretical values; Whereas, in transverse flow, cylinders of certain diameter manifest a close relationship with speed, the ratio of the temperature above the air of the body to the adiabatic stagnation temperature decreases with rising speed and then rises again from a Mach number of 0.6. The importance of this "specific temperature" of the body for heat-transfer studies at high speed is discussed."

"Tests were made on 18 shear panels of 24S-T aluminum alloy to verify the dependence of the ultimate stress on the degree of development of the diagonal-tension field. Tests were made on two thicknesses of sheet with the sheet either clamped between the flange angle or riveted to the outside of the angles" (p. 1).

Report presenting an investigation of several modifications of 20-percent-chord plain and Frise ailerons on an NACA 23012 airfoil in the 7- by 10-foot wind tunnel. Static rolling, yawing, and hinge moments were determined for several angles of attack.

Report presenting an investigation of a spoiler-slot aileron on an NACA 23012 airfoil with a full-span 30-percent-chord Fowler flap. The static rolling, yawing, and hinge moments were determined for several angles of attack and flap deflections. The ineffective region could be eliminated by a provision in the aileron linkage that would automatically uprig the ailerons as the flap is deflected.

Report discusses the results of an investigation to determine the effect of the split flaps on the aerodynamic characteristics of the tapered wing. The results indicated that values of maximum lift coefficient obtained from the NACA low-drag sections are comparable to values obtained on tapered wings with conventional sections. The addition of split flaps did not appreciably alter the pattern of the stall.

Report issued by the U.S. Bureau of Mines discussing the annual report over the research and technology of coal during 1941. As stated in the foreword, "these investigations increase our fund of exact knowledge on the properties and composition of American coals and lead to better methods in mining, preparing, storing, and utilizing coal" (p. 4). This report includes tables, illustrations, photographs, and a map.