Abstract
On board a turbine ship equipped with a ducted propeller going ahead at a diminishing speed following crash stop astern operation, big noise occurred at its final reduction gear box. It was caused by collision of the bull gear with the final pinions of the high pressure turbine shafting, while no one had clarified the reason why they so randomly as well as violently collide at the speed range. The author describes some of the given data and his reasoning in the past.
