A fatal incident occurred recently on a PDO Rig while removing the Bell Nipple Assembly (BNA) from the top of the Blowout Preventer (BOP) stack. Three men at ground level were pulling on a rope attached to the BNA base the airwinch was worked up and down. During the operation the bell nipple became stuck. A Floorman was sent to guide the BNA. During the attempts to pull the BNA sideways off the top of the BOP the bell nipple came free slid off the top of the annular and dropped approximately 60 cm. In the process the Floorman was struck by the drip tray of the bell nipple causing fatal internal injuries. He then dropped a distance of 4 4 m before his fall was arrested by his safety line (Lanyard).