DA42 PLT REPORTS LOSS OF IMPROPERLY SECURED AFT CARGO DOOR ON TKOF ROLL.

Narrative

REAR (PLT SIDE) BAGGAGE DOOR BROKE AWAY DURING TKOF ROLL WELL BEFORE FLYING SPD. TKOF WAS PROMPTLY ABORTED. DURING PRE-FLT BAGGAGE; 1 PAX (FRONT SEAT) AND 1 DOG (REAR SEATS) WERE LOADED INTO THE ACFT. THE REAR BAGGAGE DOOR WAS CLOSED AFTER LOADING THE DOG. THE AUDIBLE DOOR ALARM WAS SUPPRESSED DURING PREFLT SINCE THE CANOPY DOOR WAS PUT IN THE 'COOLING' POS. SOMETIME DURING THE TAXI OR BACK-TAXI; THE REAR DOOR POPPED OPEN. IT IS POSSIBLE THAT A BLANKET FOR THE DOG PREVENTED THE DOOR FROM LATCHING PROPERLY. OR; THE DOOR WAS SIMPLY NOT FULLY LATCHED. OR; THERE WAS A FAILURE IN THE LATCHING MECHANISM. NEITHER THE PLT NOR THE PAX NOTICE AN ALARM (AUDIBLE OR OTHERWISE) OR THE OPEN DOOR DURING THE TAXI OR RUN-UP. NOISE CANCELLATION HEADSETS WERE IN USE BY THE PLT AND PAX. DURING THE PREFLT THE ACFT WAS REPOSITIONED TWICE FOR TFC. THIS MAY HAVE BEEN A CONTRIBUTING FACTOR SINCE IT INTERRUPTED THE ORDERLY FLOW OF THE CHKLIST. THE DOOR LOCKING MECHANISM APPEARED TO BE FULLY FUNCTIONAL WHEN THE DOOR WAS PLACED BACK ON THE AIR FRAME. THE DOOR WAS SCRATCHED; SOME COMPOSITE MATERIAL WAS CRACKED AND THE HINGES WERE SHEARED (PER DESIGN ACCORDING TO DIAMOND ACFT REPRESENTATIVE). THE DOOR WILL BE REPLACED BY A NEW DOOR.