  Using the Dyson-Schwinger approach we investigate Landau gauge QCD with a
relatively large number of chiral quark flavours. A self-consistent treatment
on the propagator level enables us to study unquenching effects via the quark
loop diagram in the gluon equation. Above the critical number of fermion
flavours the non-perturbative running coupling develops a plateau over a wide
momentum range. Correspondingly, the propagators follow a power law behaviour
in this momentum range indicating conformal behaviour. Our value
$N_f^{crit}=4.5$ is strongly sensitive to the details of the quark-gluon vertex
calling for more detailed investigations in future studies.
