PA34 INSTRUCTOR AND STUDENT EXPERIENCED A NOSE GEAR COLLAPSE ON LNDG.

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MY INSTRUCTOR AND I HAD BEEN PRACTICING SHORT FIELD TKOFS AND LNDGS. ON OUR 6TH TIME AROUND THE PATTERN (REMAINING IN L TFC FOR RWY 30L AT IWA) ON DOWNWIND; I BEGAN MY NORMAL BACK COURSE GUMP PROC. THE GEAR CYCLED THROUGH TRANSITION AND SHOWED ALL 3 GREEN ACTIVE LIGHTS ILLUMINATED. PLUS; THIS SPECIFIC SENECA HAS A MIRROR MOUNTED ON THE ENG SO THE PLT (ME) COULD CHK TO VISUALLY SEE THE NOSE GEAR IN THE DOWN POS. WITH UNDER 20 HRS IN A COMPLEX; BELIEVE ME; I AM CHKING 2 AND 3 TIMES. WE TOUCHED DOWN RIGHT AFTER THE THRESHOLD ON THE MAINS FIRST. PROCEEDED TO LET THE ACFT REST ON ITS NOSE GEAR FOR 1 OR 2 SECONDS; AND WITHOUT WARNING THE NOSE GEAR COLLAPSED CAUSING THE PLANE TO SKID ON ITS NOSE FOR APPROX 1100 FT WHILE BOTH PROPS STRUCK THE GND. MY INSTRUCTOR AND I WORKED TOGETHER TO GET THE ACFT TURNED OFF; ENGS SECURED; WHILE MAINTAINING DIRECTIONAL CTL OF THE ACFT. WHILE THE PLANE WAS SKIDDING TO A STOP; MY INSTRUCTOR INFORMED THE TWR OF WHAT WAS HAPPENING; AND WE EVACUATED IMMEDIATELY AFTER THE SENECA CEASED TO MOVE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT A MAINT CHK REVEALED THE NOSE LNDG GEAR 'OVER CTR LOCK' DID NOT OPERATE PROPERLY; ALLOWING THE NOSE LNDG GEAR TO COLLAPSE. IT WAS ALSO RPTED THAT ON 2 PREVIOUS OCCASIONS THIS ACFT EXPERIENCED THE SAME FATE. CALLBACK REVEALED THAT: THE REPORTER STATED THAT A MAINTENANCE CHECK REVEALED THE NOSE LANDING GEAR 'OVER CENTER LOCK' DID NOT OPERATE PROPERLY; ALOWING THE NOSE LANDING GEAR TO COLLAPSE. IT WAS ALSO REPORTED THAT ON TWO PREVIOUS OCCASIONS THIS ACFT EXPERIENCED THE SAME FATE.