  Diffusion vibrational modes are studied in superfluid $He^3-A$ in zero
magnetic fields for different angles between the orbital axis and the wave
vector. The dispersion relation for these modes is found to depend on the wave
polarization. It is shown that in addition to the normal component velocity,
the superfluid component velocity also oscillates in the diffusion modes of
$He^3-A$. The frictional forces due to viscous waves in $He^3-A$, exerted in
the plane surface which is in contact with a superfluid liquid layer of finite
thickness and performs a simple harmonic oscillatory motion, are calculated. We
also consider, volume of $He^3-A$ restricted by two parallel infinite surfaces,
when the lower surface accomplishes simple harmonic oscillation and we
calculate the frictional forces exerted on surfaces. It is found that the
frictional force has not only parallel, but also a perpendicular component
relative to the direction of oscillations.
