ACFT EQUIP PROB. CABIN DOOR OPENED INFLT.

Narrative

ON JUL/XX/95; I HAD A TRIP FROM REPUBLIC ARPT TO ATLANTIC CITY IN A PIPER NAVAJO. I LOADED 6 PAX AND MY COPLT CLOSED AND LATCHED THE CABIN DOOR EXTINGUISHING THE CABIN DOOR LIGHT. AFTER TKOF ON CLBOUT; I HEARD A POPPING SOUND; THE CABIN DOOR LIGHT CAME ON; AND THE PAX YELLED UP TO ME THAT THE CABIN DOOR WAS OPEN. I TURNED AROUND AND NOTICED THAT THE DOOR WAS NOT COMPLETELY OPENED BUT THE REAR PAX WAS PULLING ON THE DOOR. I TOLD ATC THAT WE HAD A COMPANY DISCREPANCY THAT WE NEEDED TO TAKE CARE OF AND NEEDED TO RETURN TO REPUBLIC ARPT. WE WERE #1 FOR THE ILS. OUR APCH AND LNDG WAS UNEVENTFUL. AFTER DEPLANING THE PAX THE REAR PAX HAD A CUT ON HIS HAND WHICH I TOLD HIM I WOULD TEND TO BUT HE REFUSED ANY MEDICAL ATTN. 30 MINS LATER I WAS QUESTIONED BY THE FAA AT THE TERMINAL ON MY ACTIONS; OF WHAT HAPPENED; WHY DIDN'T I DECLARE AN EMER; OR WHY I DIDN'T WANT THE TRUCKS ON THE RWY. THEY ALSO SAID THAT THE REAR PAX COMPLAINED OF BEING HURT AND THAT I DID NOT TEND TO HIM WHICH IS FALSE. SOME PAX TOLD THE FAA THAT I DEPARTED WITH THE CABIN DOOR LIGHT ON WHICH IS ALSO FALSE. I BELIEVE THE CABIN DOOR WAS PROPERLY CLOSED AND LATCHED BUT THE LATCH MIGHT HAVE BEEN WORN CAUSING IT TO CRACK OPEN. I BELIEVE A ROUTINE CHK BY MAINT OF THE DOOR MIGHT PREVENT THIS FROM HAPPENING AGAIN. AS FAR AS THE FLT IN GENERAL; I FOLLOWED COMPANY PROCS; TOOK CORRECTIVE ACTION; AND LANDED WITHOUT ANY UNDUE DELAY.