The FBCS senses the manual inputs from the
Nevertheless, you should be aware of this possibility
helmsman (pilothouse) as well as those monitored by
whenever you are troubleshooting the ACS.
the ACS, such as roll, pitch angle, yaw rate, vertical
water, and other measurements associated with the
motion, direction, and weight of the ship and the sea
In troubleshooting the FBCS, the best method you
conditions. The FBCS then converts these inputs to the
can use to perform fault isolation techniques is to use
a p p r o p r i a t e control-surface deflections to provide
deductive reasoning, experience, instructions, panel
continuous dynamic control of the ship.
indications, and the BITE. You should use the following
procedures for troubleshooting the FBCS:
I n general, foilborne control is accomplished
through operator and control system inputs, causing the
Identify the trouble symptom.
FBCS to position the control surfaces, such as the
2 Locate the trouble symptom in the system fault
trailing edge flaps on the forward and aft foils, and to
swivel the forward strut. Each control surface and the
forward strut are controlled by separate electrohydraulic
Note the probable causes of failure.
actuators. For example, the port and starboard flap
Perform the specified corrective procedures.
segments on each hydrofoil will operate simultaneously.
Heed all precautions and warnings.
The flaps on the forward and aft foils will move up and
down differentially to give pitch and foil depth control.
W h e n a specified procedure recommends
Differential movement of the flaps on the two aft foils
component replacement as a corrective action,
will allow the craft to accomplish roll control (banking).
refer to the removal/installation section of the
For example, port flaps up and starboard flaps down will
appropriate technical manual.
counter a ship roll to starboard. Along with roll control
You have just read about the foilborne propulsion
capability (banking), steering of the forward strut will
system and how it provides for speed, handling, and
provide the craft with directional heading control.
propulsion of the PHM. In the following paragraphs, we
will take a look at the other PHM main propulsion
TROUBLESHOOTING THE FOILBORNE
system, the hullborne system.
In troubleshooting the foilborne propulsion system,
MAIN PROPULSION (HULLBORNE)
you will be mostly concerned with isolating faults
within the control systems. Let's look at some of the
The hullborne propulsion system provides the PHM
procedures you may be required to use when you are
with the capability of steering, reversing, docking, and
troubleshooting the different FBCSs.
other operations requiring close-in maneuvering. The
hullborne propulsion system consists of both a port and
We mentioned earlier that the foilborne ACS was
The principles of operation for the hullborne system
equipped with self-tests. All ACS troubleshooting
are very similar to those of the foilborne system. In each
procedures are derived from test failures of the ACS
hullborne propulsion unit, the rotational speed of the
operational self-tests. The BITE will enable you to fault
diesel engine is reduced by the gearbox and transmitted
isolate a high percentage of ACS failures within a high
to the propulsor assembly. Working together, both port
and starboard hullborne propulsion units can propel the
craft in the hullborne mode at speeds up to 11 knots.
Regarding ACS troubleshooting procedures, you
should be especially aware of the ACS power supply and
any special conditions you may encounter. For example,
if another ACS component fails so that its power input
is shorted, the microbuses for that specific power in the
Each of the two hullborne plants is made up of three
ACS power supply will be blown. This condition will
major components: (1) a diesel engine, (2) a speed
result in a failure of the ACS power supply. Your use of
reduction gearbox, and (3) a water jet pump that acts as
the correct fault isolation procedures will likely prevent
the propulsor assembly. Let's take a brief look at the
the possibility of a random double failure of this type.
most important design features of these components.