Free-manoeuvring model experiments are being conducted by the Centre of Marine Technology at QinetiQ Haslar (UK). The five-metre model being tested is of a generic frigate form, driven and directionally controlled by twin tractor pods of limited azimuthing capability. The purpose of the tests is to examine the directional stability and manoeuvrability of such a vessel within a full-scale equivalent speed range of 15kts to 28kts, and pod azimuth angles of between 10deg to 25deg.

Manoeuvres specifically associated with the special capabilities of pod azimuthing will be performed, in addition to traditional turning circles, pullouts and zigzags. Measurements will be made to allow the forces on the pod to be related to propeller thrust and torque, shaft bending and blade stress for the different manoeuvres. These measurements are additional to the traditional manoeuvring parameters obtained.
The work continues the model hydrodynamic assessment of an integrated hull-pod frigate, for which optimum pod orientation and powering performance have already been evaluated in the period 2000-2001. This builds on much earlier work, conducted between 1989 and 1995, that model tested a Leander Class frigate with fixed twin tractor pods directionally controlled by flap-rudders integral with the pod struts. These model hydrodynamic experiments comprised wake survey and cavitation viewing, resistance and propulsion, as well as manoeuvring and directional stability tests. The experiments also included seakeeping.