Report presenting force-test measurements in two-dimensional flow in the 4- by 6-foot vertical tunnel of the characteristics of an NACA 0015 airfoil equipped with a plain flap with a chord 30 percent of the airfoil chord and a plain tab with a chord 20 percent of the flap chord. Results regarding lift, hinge moment of flap, pitching moment, drag, and tab characteristics are provided.

Report presenting a summary of published information on braking friction coefficients. Analysis indicates that the magnitude of the friction coefficient available will affect the technique required for obtaining the shortest ground run only under extreme conditions.

Report presenting the results of nearly 200 tests made on the strength of shear webs of 24S-T aluminum alloy, with and without lightening holes. The tests were made in a jig of the single-specimen type, in which the specimen is free to collapse completely without developing diagonal tension. Results regarding the strength of the shear webs, stiffness of shear webs, and permanent-set tests are provided.

"The calculation of the stresses around cut-outs is discussed on the basis of a simplified application of the shear-lag theory previously published. Experimental stringer strains were measured around a systematic series of cut-outs. The test results indicate that the proposed method of calculating the stringer stresses is acceptable as a basis for stress analysis" (p. 1).

Report presenting an investigation in the 20-foot propeller-research tunnel to determine the effect of variations in angle of pitch on the aerodynamic characteristics of several propeller combinations. The combinations investigated included two-, three-, four-, and six-blade single-rotating propellers and a six-blade dual-rotating propeller on a nacelle with four angles of thrust axis. The propulsive efficiency was found to decrease as the angle of pitch increased.

Report presenting an analysis of the failure of adhesive bonds and its relation to boundary stress concentrations. A variety of material combinations, including metals and plastics, were examined and stress tested. The method of computing the thermal coefficients is applied to mixtures and especially to reinforced plastics.

Report presenting tests conducted with an air-cooled cylinder on two fuels rated at approximately 100-octane number by the C.F.R. aviation method with and without a 40-percent addition of an aromatic mixture. The aromatic mixture consisted of 50 percent toluene, 37.5 percent xylene, and 12.5 percent benzene. Results regarding engine performance and engine temperature are provided.

Two airfoil plans were used for propeller blades. One is modified Clark Y section designed for structural reliability and the second an NACA 16 airfoil section designed to produce minimum aerodynamic losses. At low air speeds, the propeller designed for aerodynamic effects showed a gain of from 1.5 to 4.0 percent in propulsive efficiency over the conventional type depending on the pitch. Because of the numerous variables involved, the effect of each one on the aerodynamic characteristics of the propellers could not be isolated.