LNDG GEAR COLLAPSES DURING LNDG ROLL.

Narrative

IMMEDIATELY BEFORE FLT; THE RETRACTABLE GEAR CIRCUIT BREAKER WAS OBSERVED TO BE DEFECTIVE AND WAS REPLACED. FLT WAS CONDUCTED TO RID WHERE TOUCH AND GO LNDGS WERE MADE. AFTER THE SECOND OR THIRD TKOF; THE LNDG GEAR CIRCUIT BREAKER DISENGAGED. IT WAS PUSHED OR RE-ENGAGED AND THE LNDG GEAR CYCLED PROPERLY. DURING THE LAST LNDG; THE ACFT CONTACTED THE RWY UNSUPPORTED BY THE LNDG GEAR. INVOLVEMENT OF THE LNDG GEAR MECHANISM IN THIS INCIDENT IS POSSIBLE. IT IS MORE PROBABLE THAT THE COLLAPSE OF THE LNDG GEAR WAS CAUSED BY AN INADVERTENT LNDG GEAR RETRACTION BY THE PLT INTENDING TO RETRACT THE FLAPS. THIS TYPE AND MODEL OF ACFT HAS THE GEAR AND FLAP SWITCHES IN A REVERSE POS FROM ALL OTHER RETRACTABLE GEAR ACFT PREVIOUSLY FLOWN BY THE PLT. ALTHOUGH THE PLT'S RECOLLECTION IS THAT THE LNDG GEAR COLLAPSED ON ROLLOUT FOLLOWING THE LNDG; THE PHYSICAL EVIDENCE SEEMS TO SUGGEST THAT THE LNDG GEAR WAS NOT EXTENDED PRIOR TO LNDG. HOWEVER; FINAL APCH WAS MADE AT A VERY LOW PWR SETTING AND NO WARNING HORN SOUNDED. STANDARDIZED PLACEMENT OF THE LNDG GEAR SWITCH COULD HELP PREVENT THIS TYPE INCIDENT.