  We present experimental results for dissociative electron attachment to
acetylene near the 3 eV $^2\Pi_g$ resonance. In particular, we use an
ion-momentum imaging technique to investigate the dissociation channel leading
to C$_2$H$^-$ fragments. From our measured ion-momentum results we extract
fragment kinetic energy and angular distributions. We directly observe a
significant dissociation bending dynamic associated with the formation of the
transitory negative ion. In modeling this bending dynamic with \emph{ab initio}
electronic structure and fixed-nuclei scattering calculations we obtain good
agreement with the experiment.
