thrusters to the position ordered by the operator. When
that detect yoke movement and send electrical signals
the yoke is turned, it positions a potentiometer and sends
through the CSEP to the hydraulic operating
an electrical signal to a mode and bias amplifier in the
mechanism.
CSEP. The signal then goes to the bow thruster drive
Like the rudder control system, the bow thruster
mechanism to position the bow thruster. The bow
control system uses hydraulic power to turn the bow
thruster turns, positioning a feedback potentiometer, and
thrusters. A system of pumps, flow control valves, and
sends a feedback signal to the CSEP. When the feedback
piping supplies hydraulic power to the bow thruster
signal equals the command signal, the bow thruster is in
wheel units and lift fan cushion vanes. When the
the desired position.
operator turns the yoke, electrical signals are generated
BOW THRUSTER TURNING VANES.-- T h e
and routed through the CSEP to the bow thruster
purpose of the turning vanes is to direct airflow toward
actuators. The basic components of the bow thruster
and out of the bow thrusters. Figure 7-8 shows the
control system are the steering yoke, forward/reverse
configuration of the bow thruster turning vanes. Notice
switch, bow thruster drive mechanism, turning vanes,
how the fixed vanes are attached into the air duct of the
channel selector switch, and indicators.
lift fan module and into the bow thruster volute. This
STEERING YOKE.-- The relative location of the
design allows the airflow to reach the bow thrusters with
steering yoke in the operator control station is shown in
a minimum of turbulence inside the volute and air duct.
figure 7-3. The components and controls of the steering
BOW THRUSTER CHANNEL SELECTOR
yoke are shown in greater detail in figure 7-7. The
SWITCH.-- The bow thruster channel selector switch is
operator at the steering control station uses the steering
located on the C&C keyboard at the engineer station.
yoke to control the direction of the bow thrusters. The
This switch, labeled BOW THRUSTER A/B, allows the
steering yoke will turn 45 in either direction.
operator to choose between channels of the CSEP in
FORWARD/REVERSE SWITCH.-- This switch
case of an emergency or system fault.
allows the operator to select the direction in which the
BOW THRUSTER INDICATORS.-- The function
bow thrusters apply thrust. The switch is located on the
of the bow thruster control system indicators is to inform
steering yoke. (See fig. 7-7.) The switch allows an
the operator of existing operating conditions and alarm
electrical signal to pass through the CSEP to the bow
conditions concerning the following areas:
thruster drive mechanism to position the bow thruster as
ordered.
Bow thruster control failure
BOW THRUSTER DRIVE MECHANISM.-- The
Port and starboard hydraulic reservoir low
bow thruster drive mechanism works to move the bow
Port and starboard hydraulic pressure low
Now that you have read about the most important
components of the steering control system, let's take a
look at an associated system that is supplied by the same
hydraulic power sourcethe propeller pitch control
system.
PROPELLER PITCH CONTROL SYSTEM
The purpose of the propeller pitch control system is
to allow the operator to control the speed and direction
of the LCAC by changing propeller pitch. The LCAC
propeller assembly is capable of both forward and
reverse pitch. The greater the angle of pitch, the faster
the craft will move.
The propeller pitch control system is composed of
the yoke assembly, propeller pitch indicator, a control
Figure 7-7.--Steering yoke and controls.
amplifiers. The control station operator controls the
7-6