As passengers are being flown home from an cancelled cruise on the Carnival Dream, another Carnival Cruise ship, the Carnival Legend, is limping to port with a damaged Azipod. Unlike more conventional designs where the ship’s propeller is connected to a ship’s engine by a shaft through the hull, the Azipod contains an electric motor in a rotating pod connected to the propeller. Because the pod can rotates it serves as both the ship’s propulsion and its rudder. The Carnival Legend has two Azipods and one is apparently broken.
The pod propulsion system is said to be roughly 10% more efficient than a conventional shaft driven propeller and considerable maneuverability, which is important to cruise ships which not generally use tugs for docking. The big problem with pod propulsion is that the loads on the rotating bearing where the pod joins the hull are significant and have been prone to failure. Azipod is a design by ABB. Rolls Royce has been marketing the Mermaid pod, a similar design. In 2010, Royal Caribbean was awarded $65 million in a lawsuit over Mermaid pod failures with Rolls Royce. A year later, Carnival settled a $24 million lawsuit with Rolls Royce over the failure of Mermaid pods. While the Azipods have a better operating history, this is not the first time that Carnival has had failures in their Azipod ships. Thanks to Phil Leon for contributing to the post.