CE414 PILOT REPORTS LANDING GEAR COLLAPSE AS THE ACFT IS TAXIING ONTO THE RWY FOR TKOF.

Narrative

AFTER A NORMAL PREFLT AND RUN-UP I TAXIED TO RWY 24 FOR DEP. AFTER BEING CLRED FOR TKOF; I BEGAN TO TAXI ONTO THE RWY; AT WHICH TIME THE L LNDG GEAR COLLAPSED AND THE L WING OF THE ACFT STRUCK THE GND; AS DID THE L PROP. AFTER THE GEAR COLLAPSED; ALL 3 LNDG GEAR INDICATORS WERE INDICATING THAT THE GEAR WERE STILL DOWN AND LOCKED; SUGGESTING SOME KIND OF MECHANICAL FAILURE OF THE LNDG GEAR SYS. I NOTIFIED THE CTL TWR WHO CONTACTED THE FAA AND MASSACHUSETTS AERONAUTICS COMMISSION; AS WELL AS LCL EMER PERSONNEL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CE414 LANDING GEAR IS HYDRAULICALLY ACTUATED WITH THE PUMP RUNNING WHEN THE GEAR IS SELECTED DOWN. THE PUMP STOPS RUNNING WHEN A MICRO SWITCH; ON EACH GEAR; CLOSES AS THE GEAR LOCKS DOWN. ONE SWITCH HAD FAILED CLOSED ON THE LAST LANDING; ALLOWING THE PUMP TO STOP RUNNING PRIOR TO THAT GEAR REACHING THE LOCKED POSITION. THE GEAR HELD AS LONG AS NO SIDE LOADS WERE IMPOSED ON THAT GEAR. SIDE LOADS WERE IMPOSED AS THE ACFT WAS TAXIED INTO POSITION. POST FLIGHT REVEALED THAT BOTH MAIN LANDING GEAR ACTUATORS HAD SIGNIFICANT QUANTITIES OF WATER IN THEM AND WAS RESPONSIBLE FOR THE MICRO SWITCH FAILURE. THE RIGHT ACTUATOR WAS SO CORRODED AS TO BE NOT REPAIRABLE.