NTSB Probable Cause

THE OBSTRUCTION (PROTRUDING DOOR SUPPORT BRACKET) IN THE DOORWAY OF THE AIRCRAFT; FAILURE OF THE COMPANY/OPERATOR PERSONNEL, THE PILOT, AND THE SKYDIVERS TO ASSURE THAT THE DOORWAY WAS CLEAR OF OBSTRUCTIONS; AND SUBSEQUENT SNAGGING OF THE D-RING, WHICH RESULTED IN INADVERTENT DEPLOYMENT OF THE PASSENGER'S (SKYDIVER'S) RESERVE PARACHUTE.