BE55 SUFFERS PARTIAL GEAR COLLAPSE ON LNDG ROLLOUT.

Narrative

I WENT TO DO A COUPLE TKOFS AND LNDGS. AFTER THE INITIAL PREFLT WALKAROUND; I STARTED THE ENGS; ANNOUNCED ON CTAF TAXIING FOR TKOF ON RWY 16. AT THE HOLD POINT ON RWY 16; I DID THE PRE TKOF RUN-UP; ANNOUNCED MY INTENTIONS; AND TOOK THE RWY. AFTER CLRING THE RWY; THE GEAR WAS RAISED AND I TURNED L XWIND TO RWY 16; FOLLOWED BY THE DOWNWIND LEG. ABEAM THE THRESHOLD OF RWY 16; I LOWERED 20 DEGS OF FLAPS; DID THE GUMP CHK LOWERING THE GEAR; AND CALLED FOR L BASE 16. AFTER ANNOUNCING FINAL TO FULL STOP; I LINED UP WITH RWY 16 AND LOWERED TO FULL FLAPS; AGAIN PERFORMING THE GUMP CHK. JUST PAST THE NUMBERS; I MADE A SMOOTH LNDG; ROLLED APPROX 1000 FT; AND AS I APCHED THE INTXN OF RWY 16 AND RWY 20; I RAISED THE FLAPS AND BEGAN TO APPLY BRAKING. SUDDENLY; THE NOSE STARTED DOWN AND THE PROPS BEGAN STRIKING THE ASPHALT. WITHIN A COUPLE OF SECONDS; THE ACFT HEADED L; OFF THE RWY; WHERE I CAME TO REST IN THE GRASS FACING THE OPPOSITE DIRECTION. THE R MAIN WAS DOWN AND LOCKED; THE L MAIN HAD FOLDED TO ABOUT 20 DEGS; AND THE NOSE GEAR WAS FOLDED INTO ITS BAY. IMMEDIATELY; I TURNED OFF THE MAGNETOS; ALTERNATORS AND BATTERY SWITCHES; EXITED THE ACFT; AND CALLED FOR ASSISTANCE. THERE WAS NO FIRE; AND NO INJURIES. THE FOLLOWING MORNING; THE ACFT WAS RECOVERED BY A LCL A&P; WHOSE TEM RAISED THE ACFT BY THE L ENG MOUNTS AND MANAGED TO GET THE L MAIN AND NOSE GEAR DOWN.