An investigation has been conducted to determine the effects of vertical-tail location and size on the subsonic aerodynamic characteristics of a model having a triangular wing. The wing had an aspect ratio of 3, an NACA 0003.5-63 section in the streamwise direction, and plain, trailing-edge ailerons. The wing was attached to the fuselage in either a mid or high position and an unswept horizontal tail was located on the fuselage center line. Two vertical tails were tested which had areas of 26.7 or 20.3 percent of the wing area. Each vertical tail was equipped with a rudder and had a geometric aspect ratio of 1.5, a taper ratio of 0.16, and 54 degrees of sweepback of the leading edge. Each vertical tail was tested at two different tail lengths. The wind-tunnel tests were conducted at a Reynolds number of 2.5 milMon at Mach numbers from 0.25 to 0.95.

A general theory of solid-state diffusion in strained systems is developed on a molecular-kinetic basis. The theory predicts that for simple strains the diffusion coefficient is an exponential function of the lattice parameter and that the rate of change of the diffusion coefficient with strain is linearly related to the interatomic forces. It has also been shown that for plastic flow the diffusion coefficient is a linear function of strain rate. All the conclusions are confirmed by the data available in the literature.