Furuno NAVpilot NAVpilot-500 - Manual (Page 8)

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1. PRINCIPLE OF THE AUTOPILOT
Principle of Autopilot
Autopilot is an automatic device for steering a vessel maintaining its heading in
an intended direction. Anyone can appreciate the advantages of the autopilot –
being free to carry out navigational checks, trim adjustments or simply to relax
and enjoy.
The autopilot utilizes a proportional rate system to steer the boat. The
proportional rate system is similar to the highly accurate and reliable system
used on aircraft, missiles and space vehicles. The proportional rate autopilot
provides the necessary course correction to the steering gears in proportion to
the speed and amount the boat moves off course.
With the removal of the dead band, the autopilot no longer wanders within a
dead band but now steers a prescribed course, taking action within the presence
of even a minute course error. The amount of action depends on the course
error detected; that is, when the course error rate is small a very low helm
correction rate is applied.
Because the wandering is eliminated, the proportional rate autopilot has the
advantages of low power consumption and low wear and tear on the autopilot
and the steering system. Off-course correction is smooth, not jerking back and
forth at full speed.