"Rules and methods for insuring safe structural strength of racing airplanes used in the major air meets in this country have recently been considered. Acceleration records made in racing airplanes during actual air races were therefore considered desirable, and the NACA undertook the measurement of acceleration of loads on airplanes during all conditions of flight. Accelerations were measured on four airplanes at the Miami All-American Races in January 1934 and January 1935" (p. 1).

The results of a general tank test model 11-C, a conventional pointed afterbody type of flying-boat hull, are given in tables and curves. These results are compared with the results of tests on model 11-A, from which model 11-C was derived, and it is found that the resistance of model 11-C is somewhat greater. The effect of changing the plan form of the step on model 11-C is shown from the results of tests made with three swallow-tail and three pointed steps formed by altering the original step of the model. These results show only minor differences from the results obtained with the original model.

The total-head meter is essentially a venturi, housing a pitot tube for obtaining the total head. In yaw the flow within the nozzle is deflected, depending upon the degree of yaw, to a greater or lesser extent into the axial direction of the nozzle. After experimenting with several nozzle forms as to their suitability, the best design was finally adopted. When, with the chosen nozzle form, the total head is 0.5 entrance section diameter downstream, the instrument supplies the genuine total head at low Reynolds Numbers up to 43 degrees yaw.

The analysis of the stresses in the sheet and stiffeners is predicated upon the direction of the wrinkles, particularly the tensile stresses (principal stresses). This analysis and the calculation of stresses after buckling form the subject of the present article. It includes: 1) metal cylinders with closely spaced longitudinal stiffeners; 2) metal cylinders with closely spaced transverse rings.

The present report collects the investigations of the past years which, while not as yet intended for use in construction, show different possibilities for the building of a suction-type wing and at the same time present some basic explanations concerning the problem of suction. Experiments and results with a thick wing profile are detailed as well as boundary layer removal by suction and sink action. Experiments with flap profiles are also included.

"The National Advisory Committee for Aeronautics is testing the effectiveness of a method to prevent the formation of ice on airplanes. The system makes use of a leather cover that is attached to the leading edge of the wing. A small tube, attached to the inner surface of the leather, distributes to the leading edge a solution that permeates throughout the leather and inhibits the formation of ice on the surface. About 25 pounds of the liquid per hour would be sufficient to prevent ice from forming on a wing of 50-foot span" (p. 1).

"Fuel injected into a spherical bomb filled with air at a desired density and temperature could be ignited with a spark a few thousandths of a second after injection, an interval comparable with the ignition lag in fuel-injection engines. The effect of several variables on the extent and rate of combustion was investigated: time intervals between injection and ignition of fuel of 0.003 to 0.06 second and one of 5 minutes; initial air temperatures of 100 degrees C. to 250 degrees C.; initial air densities equivalent to 5, 10, and 15 absolute atmospheres pressure at 100 degrees C.; and air-fuel ratios of 5 to 25" (p. 107).

"High-speed motion pictures were taken at the rate of 2,500 frames per second of the fuel spray and flame formation in the combustion chamber of the NACA combustion apparatus. The compression ratio was 13.2 and the speed 1,500 revolutions per minute. An optical indicator was used to record the time-pressure relationship in the combustion chamber. The air-fuel ratio was varied from 10.4 to 365. The results showed that as the air-fuel ratio was increased definite stratification of the charge occurred in the combustion chamber even though moderate air flow existed. The results also showed the rate of vapor diffusion to be relatively slow" (p. 119).

This report presents the results of wind tunnel tests to determine the effect of wing-tip shape and dihedral on some of the aerodynamic characteristics of Clark Y wings that affect the performance and lateral stability of airplanes. Force tests at several angles of yaw and rotation tests at zero yaw were made. From these tests the rates of change of rolling moment, yawing moment, and cross-wind force coefficients with angle of yaw and the rate of change of rolling moment coefficient with rolling were determined.

This report presents the results of wind tunnel tests to determine the effectiveness of various methods of reducing the high control forces of unbalanced upper-surface ailerons and of unbalanced split flaps. A balanced split flap was developed that required control forces about half those of the unbalanced split flap when the balanced split flap was deflected to give approximately the same maximum lift.

"This paper presents the results of wind-tunnel tests of several airfoils of low aspect ratio. The airfoils included three circular Clark Y airfoils with different amounts of dihedral, two Clark Y airfoils with slots in their portions, and three flat-plate airfoils. Lift, drag, and pitching-moment characteristics of the slotted airfoils with slots open and closed; pitching moment characteristics of one of the slotted airfoils with slots open and closed; and lift characteristics of the flat-plate airfoils are included" (p. 1).

Report discussing the 6-foot-4-inch wind tunnel and its auxiliary equipment has proven itself capable of continuous and reliable output of data. The real value of the tunnel will increase as experience is gained in checking the observed tunnel performance against full-scale performance. Such has been the case of the 8- by 8-foot tunnel, and for that reason the comparison in the calibration tests have been presented.