Anschütz autopilots are known for offering both excellent, precise course keeping and economical steering control. Since the introduction of the adaptivity (so-called ECO mode) over 15 years ago, Anschütz autopilots have shown their positive effect on the reduction of fuel consumption and, therefore, of costs and emissions. The new generation of Anschütz autopilots builds on this knowledge.

The NautoPilot 5000 NX series autopilots continue to use Anschütz's proven control algorithms, which enable high-precision steering control even at low speeds whenever necessary. In addition, the autopilots offer the widest range of fuel-saving functions for professional commercial shipping.

It is not easy to seriously qualify the influence of the functions on fuel consumption for a specific vessel. Weather, sea and loading conditions as well as draft and speed are just some of the factors that affect the steering performance and fuel consumption. But as a rule of thumb, the frequency of rudder movements and rudder angles are key factors that have a direct impact on fuel consumption. Another aspect specific to twin-rudder vessels is the interaction of the two propellers and the two rudders which can increase fuel consumption.

Toe Angle function for twin-rudder vessels

This is where the NautoPilot 5000 NX comes in. On twin-rudder vessels, the autopilot can dynamically control individual rudder angles depending on the vessel's speed, load status or draft.

While functions such as ECO mode and course control mode aim to reduce rudder movements in different ways, the “Toe Angle” function works on twin-rudder vessels by optimising rudder angles to reduce the resistance of the rudders in the wake field.

Research, including field tests and a computational fluid dynamics analysis, has shown that the rudder angles set by the autopilot can significantly reduce the power required at the same speed. The savings were even more significant when speed and draft deviated from the standard values defined in the ship's design.

Quantifiable results were also obtained from field tests. A fleet of five 85,000 dwt crude oil tankers, mainly operating in North America, served as test vessels. Different voyages were measured with and without the Toe Angle function activated under otherwise controlled conditions. A number of different angles were tested with promising results based on previous experience.

As a result, every possible combination of trim, draft and speed tested resulted in fuel savings. The maximum saving was 4.7%, with an average saving of just under 2% across all variants tested.

It is important to note that this adjustment is made directly by the autopilot and only when the autopilot is engaged. The manoeuvrability of the vessel under manual control is not affected.

Comprehensive set of fuel-saving features

The savings achieved by the Toe Angle function complement the automatic optimisations that the NautoPilot 5000 NX can provide by functions such as ECO mode or course control.

The actual benefits of the automation of rudder movements and steering performance need to be verified by navigators. However, assessing the actual steering performance is usually very complex for the navigator on the bridge. To simplify this, Anschütz autopilots offer an integrated heading and rudder plot as a graphical and intuitive display of steering performance. A reduction in rudder movement is immediately apparent, indicating that the autopilot is steering efficiently. At this point, good parameter settings are a prerequisite for realising fuel savings. For this reason, the autopilot parameters of Anschütz autopilots can be changed at the touch of a button from the course and rudder plot, and the effect can be observed directly. Up to five parameter sets can be saved to get the best setting for any situation.

All in all, the combination of automated functions and the intuitive assessment of the actual steering performance is important for achieving optimum efficiency in terms of fuel consumption and emissions in the long term.

If you add the Toe Angle function to twin-rudder ships, considerable fuel savings are possible. Autopilots are, therefore, rightly cited by classes and the IMO as a means of increasing ship efficiency and reducing emissions and can help ship owners to improve their Carbon Intensity Indicator (CII) rating.