  Let $Q$ be a connected quiver with no oriented cycles, $k$ the field of
complex numbers and $P$ a projective representation of $Q$. We study the
adjoint action of the automorphism group $\Aut_{kQ} P$ on the space of radical
endomorphisms $\radE_{kQ}P$. Using generic equivalence, we show that the quiver
$Q$ has the property that there exists a dense open $\Aut_{kQ} P$-orbit in
$\radE_{kQ} P$, for all projective representations $P$, if and only if $Q$ is a
Dynkin quiver. This gives a new characterisation of Dynkin quivers.
