DIAMOND DA40 PAX DOOR OPENED DURING TKOF ROLL. PLT REJECTED TKOF.

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CARGO/PAX DOOR OPENING DURING TKOF ROLL DUE TO FAILURE OF DOOR LATCH SYS. DOOR WAS CLOSED AND LATCHED PRIOR TO TKOF. TKOF SAFELY ABORTED AT 52 MPH PRIOR TO ROLLOUT. NO PAX IN REAR SEATS. PLT; AND PLT/CFI; ON BOARD. DOOR DAMAGED DURING OPENING DURING TKOF ROLL. TECHNICAL ASSISTANCE CONTACTED. DOOR REPAIRED BY MECHS AS RECOMMENDED BY TECHNICAL ASSISTANCE. DOOR NOT STRUCTURAL COMPONENT OF ACFT PER TECHNICAL ASSISTANCE. FLT CONTINUED WITHOUT INCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THAT THE DOOR IS A CLAMSHELL TYPE DOOR. THE LATCHING MECHANISM DRIVES PINS FORE AND AFT INTO THE DOOR FRAME. WHEN OPEN; THE HANDLES PROTRUDE INSIDE AND OUT BY APPROXIMATELY 3 INCHES. A SECONDARY LATCH IS ALSO INCORPORATED INTO THE DOOR; SIMILAR TO THE SECONDARY HOOD LATCH ON A CAR. THE FWD HINGE AND THE DOOR WERE DAMAGED WHEN THE DOOR OPENED ON THE REPORTER'S ACFT. THE REPORTER IS CERTAIN THAT THE DOOR WAS CLOSED PRIOR TO TKOF; BUT IS NOT CONVINCED; IN RETROSPECT; THAT THE DOOR HANDLES WERE CONFIRMED TO BE SECURED. WHEN THE MANUFACTURER WAS LATER CONTACTED; IT WAS DISCOVERED THAT A CHRONIC PROBLEM DOES EXIST WITH THE DOOR. IT MAY BE RELATIVELY EASY TO OVERLOOK AN UNLATCHED OR PARTIALLY LATCHED DOOR; PARTICULARLY WHEN THE BACK SEATS ARE UNOCCUPIED. IF THE DOOR IS NOT PROPERLY SECURED; AERODYNAMICS WILL PULL THE DOOR OPEN.