Book excerpt: The coefficients of damping in roll and rolling effectiveness (with differential incidence of the horizontal surfaces) are determined for a slender, equal-span, cruciform wing. It is found that the coefficient of damping in ar roll is 62 percent greater than for a plane slender wing of equal aspect ratio, and that the rolling effectiveness is 53 percent less than for a plane slender wing of equal aspect ratio. The analysis can be used in the estimation of the characteristics of a slender, equal-span, cruciform wing having any specified distribution of normal velocity components on the horizontal and vertical surfaces.