The pilot reported that during his second flight, following the installation of a new autopilot, he noticed on short final that the mixture was set too lean. He further reported that "with a gloved hand" he pushed the mixture in to a richer setting; and accidently turned on the autopilot, which was located directly above the mixture control. The autopilot was set to navigation mode, heading mode, and altitude mode from a previous flight. The pilot reported that he was "fighting the auto pilot" and the airplane aerodynamically stalled, resulting in a hard landing.

The airplane sustained substantial damage to the firewall.

The pilot reported there were no pre-accident mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.