if another ACS component fails so that its power input
stabilize and propel the craft forward. Basically,
is shorted, the microfuses for that specific power in the
foilborne propulsion is achieved through the interaction
of hydrodynamic forces similar to the aerodynamic
ACS power supply will be blown. his condition will
forces in flying. To understand the interaction of
result in a failure of the ACS power supply. Your use of
hydrodynamic forces involved in the propulsion of the
the correct fault isolation procedures will likely prevent
PHM, let's take a look at some normal events.
the possibility of a random double failure of this type.
Nevertheless, you should be aware of this possibility
The FBCS senses the manual inputs from the
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
appropriate 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
In general, foil borne control is accomplished
procedures for troubleshooting the FBCS:
through operator and control system inputs, causing the
1. Identify the trouble symptom.
FBCS to position the control surfaces, such as the
trailing edge flaps on the forward and aft foils, and to
2. Locate the trouble symptom in the system fault
swivel the forward strut. Each control surface and the
forward strut are controlled by separate electrohydraulic
3. Note the probable causes of failure.
actuators. For example, the port and starboard flap
segments on each hydrofoil will operate simultaneously.
4. Perform the specified corrective procedures.
The flaps on the forward and aft foils will move up and
5. Heed all precautions and warnings.
down differentially to give pitch and foil depth control.
Differential movement of the flaps on the two aft foils
6. When a specified procedure recommends
will allow the craft to accomplish roll control (banking).
component replacement as a corrective action,
For example, port flaps up and starboard flaps down will
refer to the removal/installation section of the
counter a ship roll to starboard. Along with roll control
appropriate technical manual.
capability (banking), steering of the forward strut will
You have just read about the foilborne propulsion
provide the craft with directional heading control.
system and how it provides for speed, handling, and
TROUBLESHOOTING THE FOILBORNE
propulsion of the PHM. In the following paragraphs, we
will take a look at the other PHM main propulsion
system, the hullborne system.
In troubleshooting the foilborne propulsion system,
you will be mostly concerned with isolating faults
within the control systems. Let's look at some of the
HULLBORNE PROPULSION SYSTEM
procedures you may be required to use when you are
The hullborne propulsion system provides the PHM
troubleshooting the different FBCSs.
with the capability of steering, reversing, docking, and
other operations requiring close-in maneuvering. The
hullborne propulsion system consists of both a port and
We mentioned earlier that the foilborne ACS was
equipped with self-tests. All ACS troubleshooting
The principles of operation for the hullborne system
procedures are derived from test failures of the ACS
operational self-tests. The BITE will enable you to fault
are very similar to those of the foilborne system. In each
isolate a high percentage of ACS failures within a high
hullborne propulsion unit, the rotational speed of the
diesel engine is reduced by the gearbox and transmitted
to the propulsor assembly. Working together, both port
Regarding ACS troubleshooting procedures, you
and starboard hullborne propulsion units can propel the
should be especially aware of the ACS power supply and
craft in the hullborne mode at speeds up to 11 knots.
any special conditions you may encounter. For example,