  In search for deviations from homologous expansion in planetary nebulae we
present a 3D morphokinematical model of NGC 7009. The model has been
constructed with {\em Shape} based on PV diagrams from the literature and HST
images. We find that the data are consistent with a radial velocity field with
increased gradient at high latitudes compared to the equatorial region (Model
1). In a second model we assume a linearly increasing radial velocity component
with an added poloidal component of order 10 km/s at latitudes around
$70^\circ$. The true velocity field is likely to be in between these two
limiting cases. We also find that the expansion of the ansae is non-radial with
reference to the central star. Their velocity field is focused near the
apparent exit points from the main shell. We predict the proper motion pattern
for the model with a non-zero poloidal velocity component.
