  We study stability of isothermal two-component radiatively driven stellar
winds against one-dimensional perturbations larger than the Sobolev length, and
radiative-acoustic waves in such stellar winds. We perform linear perturbation
analysis in comoving fluid-frames of individual components and obtain
dispersion relation in the common fluid-frame. For high density winds the
velocity difference between velocities of both components is relatively small
and the wind is stable for radiative-acoustic waves discovered originally by
Abbott, in accordance with the previous studies of the one-component wind.
However, for such high density winds we found new types of waves including a
special case of "frozen-in" wavy patterns. On the other hand, if the velocity
difference between wind components is sufficiently large (for low density
winds) then the multicomponent stellar wind is unstable even for large scale
perturbations and ion runaway occurs. Thus, isothermal two-component stationary
solutions of the radiatively line driven stellar wind with an abrupt lowering
of the velocity gradient are unstable.
