Off-axis coupling of a helicopter exhibits the opposite sign in flight test
s as compared to simulations. It has been shown that this effect may be att
ributable to the bending of the wake during a pitching maneuver, which intr
oduces a fore-to-aft gradient in induced How that can reverse the predicted
sign of roll coupling. It has been shown that this result can also be obta
ined with momentum and vortex theory. In the present work, a generalized mo
del for wake curvature in hover is developed using the exact relation deriv
ed from vortex tube theory. This model is coupled with a flap model to inve
stigate the influence on dynamic coupling.