BE58 PROP STRIKE AFTER COCKPIT DOOR OPENS ON TKOF ROTATION AT MIA; FL.

Narrative

UPON NORMAL ACCELERATION AND TKOF ON RWY 8L AT MIA; THE ACFT ATTAINED POSITIVE RATE OF CLB INDICATION; THE GEAR LEVER WAS PLACED INTO THE RETRACT POS AND THE R FORWARD (CO-PLT) DOOR CAME OPEN. THE ACFT SETTLED TOWARD THE GND AND AMID THE GREATLY INCREASED NOISE AND DEBRIS MOVING AROUND THE CABIN COMBINED WITH THE INCREASED DRAG DUE TO THE DOOR BEING OPEN; THE ACFT LOST SOME ALT. FULL THROTTLE WAS MAINTAINED AND THE ACFT CLBED OUT NORMALLY. I INFORMED TWR OF THE OPEN DOOR AND THAT WE WOULD LIKE TO RETURN FOR LNDG. THE ACFT WAS CLRED FOR L DOWNWIND TO LAND AGAIN ON RWY 8L. I DECLINED PRIORITY TO LAND BEFORE AN APCHING ACR ON ADJACENT RWY 8R AND FOLLOWED THE HVY IN SEQUENCE. A NORMAL APCH AND LNDG; INCLUDING USE OF CHKLIST; WAS CONDUCTED. SUBSEQUENT TO LNDG TO SECURE THE DOOR; THE ACFT WAS INSPECTED ON THE GND FOR SECURITY OF THE DOOR AND IT WAS DISCOVERED THAT THE PROP TIPS HAD STRUCK THE PAVEMENT DURING THE CLBOUT. PART OF THE NORMAL PREP-TKOF CHKLIST INCLUDES A CHK OF THE DOOR FOR SECURITY. THIS WAS PERFORMED BOTH BY ME AND BY THE MULTI-ENG INST RATED PLT-PAX SITTING IN THE COPLT SEAT. THE DOOR APPEARED TO BE SECURED AND THE HANDLE WAS DEFINITELY IN THE LOCKED POS. STANDARD PROCS WERE FOLLOWED DURING THE OPEN DOOR SIT WHICH INCLUDED A STANDARD CHKLIST FOR LNDG ON THE RETURN TO RWY 8L. I AM UNCERTAIN AS TO ACTIONS; EITHER DIRECT OR INDIRECT; WHICH COULD HAVE BEEN TAKEN TO PREVENT THE PROP TIP STRIKE.