Abstract: AT THE TIME OF THE ACCIDENT A DRILL BIT ON AN OIL DRILLING RIG WAS BEING CHANGED. EIGHT EMPLOYEES FROM TWO DIFFERENT CREWS WERE ON OR NEAR THE DRILL FLOOR WHERE THE BIT WAS BEING INSTALLED. A LIFTING SUB HAD BEEN SCREWED INTO THE TOP OF A DRILL COLLAR AND WAS PICKED UP BY THE RIG ELEVATORS. A BELL SUB WAS THEN SCREWED INTO THE BOTTOM OF THE COLLAR, AND THE ASSEMBLY WAS PLACED ON TOP OF THE BIT. THE ELEVATORS WERE LOWERED SLIGHTLY, TRANSFERRING THE COLLAR'S WEIGHT ONTO THE BIT. A CHAIN TONG WAS PLACED ONTO THE BELL SUB AND WAS MANUALLY SCREWED ONTO THE BIT. AT THE SAME TIME THE DRILL COLLAR UNSCREWED FROM THE LIFTING SUB AND FELL OUT THE OPEN SIDE OF THE DERRICK, STRIKING EMPLOYEE #1. NO ONE LOOKED UP TO CHECK THE CONDITION OF THE LIFTING SUB. ALSO, IT IS PROBABLE THAT NOT ENOUGH WEIGHT WAS TAKEN OFF THE ELEVATORS.