SYSTEM OPERATION – Power Up
Page 45 of 80
Unsecured stations will not have a LOCKED OUT indicator and may take
steering control from any other station at any time.
3.3 STEERING MODES
3.3.1 Standby / Manual Mode
In the STANDBY/MANUAL mode none of the power steering input devices
are active and the directional solenoid outputs are turned off. In this mode
the digital helm manifold solenoids will also be turned off which will give
the operator manual control of the steering gear through the use of the
manual helm pump if provided.
3.3.2 NFU
NFU steering control is an open loop, time dependent mode of steering
control. The steering system will move the rudder in the port or starboard
direction as long as the NFU input device is activated to port or starboard.
When the NFU input device is released the rudder movement is stopped.
When NFU mode is selected the NFU input device connected to the MCP
will provide the port and starboard directional solenoid commands. The
NFU input device includes momentary port and starboard micro-switches.
A jog lever is a NFU input device with port and starboard micro-switches
operated by a spring centered lever.
Systems including a NFU input device and a Digital FFU input device can
be configured through the DSC setup program to operate these two
modes of steering control in a seamless transfer arrangement. This
means that the operator can use either the NFU jog lever or the Digital
Helm without the having to expressly select the mode using an input
selector button.
A NFU input device can also be configured through the DSC setup
program to provide a “dodge” function while the system is operating under
autopilot control. Under autopilot control, operation of the NFU input
device will momentarily move the rudder from the position commanded by
the autopilot system. Once the NFU device is released control of the
rudder position will be returned to the autopilot.
NFU steering will normally only provide on-off (also known as ‘bang-bang’)
control of the rudder even when a proportional directional valve is used.
The DSC, in this case, has the ability to provide a certain amount of
acceleration and deceleration of a proportional rudder control system even
in NFU steering mode. This will ensure that a proportional system is used
to its full advantage.
Doc No.: MAN01504, 20-02-06 DSC 100 & MCP 100 Manual
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