N505TJBell Textron Canada 429

The pilot reported that he decided to perform a practice approach to the runway using night vision goggles. He set up the approach and activated the autopilot. About 200 ft above the ground, the helicopter inadvertently entered a fog bank and the pilot lost visual reference to the runway. He attempted to perform a climbing right turn but forgot to deactivate the autopilot. The autopilot initiated a descent into the fog, the pilot maintained a level attitude, and shortly thereafter the helicopter impacted the ground and bounced. The pilot attempted to initiate a climb; however, the helicopter impacted the ground a second time, which resulted in substantial damage to the fuselage. The pilot reported no preimpact mechanical malfunctions or failures with the helicopter that would have precluded normal operation.