ACFT LANDED GEAR UP.

Narrative

SMA HAD VERY RECENTLY COME OUT OF EXTENSIVE ANNUAL; BUT HAD A PROBLEM WITH LNDG GEAR HYD PUMP BREAKER POPPING. RPTED TO FBO AND WE DECIDED TO MAINTAIN CLOSE WATCH TO DETERMINE IF IT WAS RECURRING AS I HAD ONLY FLOWN IT ONCE SINCE ANNUAL. THIS WAS THE SECOND FLT THEREFORE; AND BREAKER POPPED AFTER TKOF. WAS RESET PRIOR TO FIRST LNDG; POPPED AGAIN AFTER SECOND TKOF AFTER XCOUNTRY FLT; RESET AGAIN FOR SECOND LNDG IN XCOUNTRY FLT. ON THIRD AND FINAL LNDG AT HOME BASE IN SMO; CHKLIST WAS USED FOR CRUISE DSCNT; APCH AND DOWNWIND LEGS. GEAR WAS NOT EXTENDED ABEAM TWR AS WE WERE #4 IN LINE; AND WOULD HAVE TO FLY AN EXTENDED NORTHERN DOWNWIND. AFTER TURNING BASE AND FINAL; WE WERE STILL ON 2 MI FINAL AND I WENT THROUGH CHKLIST AGAIN; AS NORMAL; EXTENDED GEAR DOWN HANDLE BUT DID NOT PHYSICALLY CHK 'GEAR DOWN' POS EITHER BY REF TO LIGHT INDICATORS; OR GLANCING OUT OF PLT'S WINDOW! THE BREAKER HAD MEANWHILE POPPED AGAIN AND; WHILE THE GEAR DOORS HAD OPENED; THE GEAR REMAINED STOWED. IT WAS DISCOVERED WHEN THE PROP TIPS CONTACTED THE RWY; AND THE ACFT SETTLED DOWN IN A BELLY LNDG; GEAR UP. ABOUT 5 SECONDS PRIOR TO THIS; THE TWR ADVISED US TO GAR BUT IT WAS NOT SOON ENOUGH. BREAKER POPPING AS DESCRIBED ABOVE; BUT THIS SHOULD HAVE ADDED AWARENESS TO POSSIBLE LNDG GEAR PROBLEMS. THEREFORE EVEN THOUGH THE CHKLIST HAD BEEN UTILIZED CORRECTLY THROUGHOUT THE DSCNT; APCH; AND FINAL LEGS; THE ONE MAIN FACT OF VISUALLY CONFIRMING 'GEAR DOWN AND LOCKED' HAD NOT BEEN MADE.