Training in the handling of pod-propelled ships

Sogreah’s shiphandling training centre at Port Revel has just commissioned a ship equipped with a "pod" propulsion system.
An Afcan member reports back on a visit to the centre in response to a kind invitation from its Director.

Background to the project to develop a pod-propelled model ship

Pods are becoming increasingly widely used for propelling large, high-value vessels, since they vastly improve manoeuvrability. Numerous cruise liners have been fitted with them including the Queen Mary II and, more recently, the French Navy’s projection and command vessels MISTRAL and TONNERRE. With the benefits of specific training becoming increasingly obvious, the study initially focused on creating a 1:25 scale model of the Queen Mary II. The air draught (nearly 2 m) of a model ship of this type was beyond the capacity of the existing facilities. The excessive cost of building this model ship and its environment resulted in changes to the specifications, made easier by the fact that the main requirement was manoeuvring with pods rather than with a specific ship.

The choice then shifted towards modifying an existing model ship, CGM NORMANDIE, which has a large windage of 2369 TEU on 5 deck levels and dimensions of 275 m x 37 m, fairly similar to those of large cruise liners.

Building the pod-propelled model ship

A control unit was fitted at the bow, followed by a bench enabling two students to be on-board at the same time as is the case with the other model ships. This arrangement is specific to cruise liners, and makes it easy to change the configuration from that of a large container carrier to that of a cruise liner fitted with pods. It takes an hour to transform the model ship:

the model ship is placed in the boat hoist and partially lifted out of the water (1)
the rudder is removed (2)
the propeller is removed from the shaft (3)
the two pods are fitted (4)
the model ship is placed back in the water
the bow control unit cover is removed
the observer’s unit cover is removed and the bench is fitted

      The pods were made to a scale of 1:25. They are controlled in the same way as those of real ships, with all the real automatic power limitations, notably depending on orientation.

      They can be controlled using the corresponding lever, or coupled and controlled by the port or starboard lever.

      The stern thruster, now redundant, is automatically disabled.

However the model ship is configured, its position is given to within a centimetre by a differential GPS/GLONASS receiver, and transmitted to a base with all the manoeuvre parameters (course, speed, rudder angle or pod orientation, number of propeller rotations, wind direction and strength).

All this information is compiled by computer, enabling the instructors to assess precisely the trajectories followed, as well as any shiphandling errors and corrective measures required.

The captain’s point of view

       I started by getting back to grips with the Normandie configured as a container carrier. Even though I had spent several years back on land, I soon recognised a ship that I used to know well, since I captained her big sister for a while. This model ship is astonishingly realistic, especially the bank effect in the reproduction of the south entrance to the Suez Canal.

       Because of a timely change in the centre’s schedule, I was there when the model ship was converted for pod propulsion.

       After a few minutes of essential explanations on how to handle the controls, I operated the newly-transformed model of the NORMANDIE during the tests to make sure the propulsion system was functioning correctly.

       The pods are a bit difficult to control at first, but you simply have to remember to push the lever in the direction required and you soon acquire the right reflexes. The lack of a rudder did not bother me in the least, and stability of motion is perfect provided that the number of rotations is set correctly.

       Whereas a bow thruster or stern thruster in its tunnel soon loses power at speeds over 5 knots, the pod leaves it standing at all speeds, both in terms of its flexibility of use and its power output. But you need a certain level of skill to be able to use all its possibilities to the full which, for that matter, is why this course came into being.

       The steering controls are accurate and easy to adjust. On the other hand, the central needle of the control unit indicating the number of propeller rotations moves along a graduated scale, and does not give much indication of power output. It is better to read the number of propeller rotations, which is a much better indicator in my view. Lastly, the model ship has two large truck rear-view mirrors fitted on the outside so you can see what is happening astern. I must say, without a doubt, that the change from a bridge right at the stern to a bridge right at the bow is the most confusing aspect of this transformation.

Conclusion

       The pod propulsion system is efficient but expensive, although it will probably come into general use, as did the controlled-pitch propeller in the second half of the 20th century.
       In harbour manoeuvres, it can only conceivably be used directly by one person at a time, because the orders that must be given are complex and can cause delays or misunderstandings. The Captain must master the technique perfectly, in order to control the manoeuvres properly. The owner of a large pod-propelled cruise liner who is keen to ensure that his captain is fully qualified should certainly invest in a training course, especially in emergency manoeuvring.

pods used for crash-stop

       When it was first created the Port Revel lake was designed to represent the main shiphandling difficulties encountered throughout the world, and its general appearance has remained relatively unchanged ever since. However, several special facilities have been added in order to meet users’ specific needs.

       Both the technologies and the resources used have been substantially improved, and this is set to continue as a result of current development projects. This is why the realistic simulations and high-quality training offered at Port Revel are world-famous and have always been highly appreciated. I have asked pilots on several occasions if they have been to Port Revel, because of the way they handle ships. They have always said yes, and then added that they have fond memories of the hotel and restaurant where the students stay.

       The Port Revel training centre is described in detail in the "dossier technique" section under the heading "Le centre d'entraînement de Port Revel"

Capt F.X. Pizon

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