  We consider the possibility that a mass of ~10^{-5}-10^{-3} Msun flows back
from the dense shell of planetary nebulae and is accreted by the central star
during the planetary nebula phase. This backflowing mass is expected to have a
significant specific angular momentum even in (rare) spherical planetary
nebulae, such that a transient accretion disk might be formed. This mass might
influence the occurrence and properties of a very late thermal pulse (VLTP),
and might even trigger it. For example, the rapidly rotating outer layer, and
the disk if still exist, might lead to axisymmetrical mass ejection by the
VLTP. Unstable burning of accreted hydrogen might result in a mild flash of the
hydrogen shell, also accompanied by axisymmetrical ejection.
