Cessna 414 pilot reported that electrical failure caused the landing gear to not lock in down position. During landing attempt; the landing gear retracted; so pilot did a go around; extended gear manually; and returned to a safe landing with minor aircraft damage.

Narrative

During cruise phase of flight; at first; I started experiencing sporadic radio problem. This was communicated with approach control. Shortly after; I requested approach control to divert. As I started the descend; the aircraft started having intermittent electrical power failure. I decided to extend the landing gear early; thinking it's better to extend the landing gear before having complete electrical power failure. The nose gear appear to be down and locked and maingear was not visible from the cockpit or cabin. By the time I divided my attention looking at the three green gear down lights; the aircraft had full electric power failure. When the aircraft was on extended base leg; only the radios came back momentarily and I was able to make request with approach control to perform a low flyby approach and have ZZZ tower visually confirm landing gear down. Then again; I had complete electrical power out. During a go-around from the flyby; the radios came back one last time and approach control relayed the message saying to ZZZ tower it appear that the landing gear are in normal down condition. This was the only indication that I had that the gear are in down position for a safe landing. During the first attempt of landing; the landing gear retracted back into the belly and main landing gear door made contact with the runway surface. At that moment a go-round was safely executed. Due to having electrical power issues; landing gear failed to extend and in down lock position with the normal gear extension. At some point in patter at ZZZ; alternate manual gear extension check list was completed. Then final landing check was completed; decision was then made to continue with landing. After a successful landing; aircraft was in a safe taxi condition and aircraft was then taxied to hard stand for shutdown. The aircraft's both landing gear door suffer minor scraping damage.