  I discuss three-dimensional SPH simulations of neutron star black hole
encounters. The calculations are performed using a nuclear equation of state
and a multi-flavor neutrino treatment, general relativistic effects are
mimicked using the Paczynski-Wiita pseudo-potential and gravitational radiation
reaction forces. Most of the explored mass range (14 to 20 \msun) has not been
considered before in numerical simulations. The neutron star is always
disrupted during the first approach after most of its mass has been transferred
directly into the hole. In none of the analyzed cases episodic mass transfer is
found. If an accretion disk forms at all, it is relatively cold ($T < 2.5$
MeV), of only moderate density ($\rho \sim 10^{10}$ g/ccm) and substantially
consumed by the hole on the simulation time scale of a few milliseconds. None
of the investigated systems of this study yields conditions that are promising
to launch a GRB. While we cannot completely exclude that a subset of neutron
star black hole binaries, maybe black holes with low masses and very large
initial spins, can produce a GRB, this seems to happen -if at all- only in a
restricted region of the available parameter space. I argue that the difficulty
to form promising disks together with the absence of any observed neutron star
black hole binary may mean that they are insignificant as central engines of
the observed, short-hard GRBs and that the vast majority of the latter ones is
caused by double neutron star coalescences.
