Figure 5-42.--Steering gear functional block diagram.
Modes of Steering
Movement of the ram moves the rudders and drives a
feedback mechanism to the differential control to cancel
out the rudder angle order (RAO) input signal when the
There are four means of controlling the operation of
rudder reaches the ordered angle, taking the pump off
the steering gear. Three modes (autopilot, hand electric,
and emergency) control the movement of the rams by
using electric power to position valves to allow
Power for each steering gear is provided by one of
hydraulic fluid under pressure from the power units to
two hydraulic pumps. The steering control system
position the rudders. The fourth mode (manual) is
provides rudder command inputs to mechanical
totally manually driven.
differentials. Differentials then provide a mechanical
rudder position command input to each hydraulic
A U T O P I L O T M O D E . -- Steering (rudder
deflection) commands are generated by the autopilot
(part of the SCC) during automatic steering modes.
The rudders have a maximum working angle of 35"
These electrical commands are proportional to the
right and 35° left from the midships at rest position.
difference between the actual ship heading, as
These angles are set by an adjustment in the electronic
determined by the ships gyrocompass, and the desired
limit circuit. If there are uncontrolled surges within the
or selected ship's heading.
hydraulic system severe enough to cause ram
overtravel, there are copper crush stops to mechanically
Before the automatic steering mode is selected, the
ship must be steered manually (hand electric) to the
engage the tie rod at 37° of rudder angle and steel stops
desired course to prevent uncontrolled turning rates,
that are engaged at 38° of rudder angle.