transducer excitation and output coils. The rotating
electronics cylinder rectifies the rotary transformer
excitation to 24 V dc for powering the hub-mounted
transducer and receives the transducer output. The
rotating electronics cylinder is attached to the prairie air
tube extension at the end of the OD box. The cylinder
electronically regulates the transducer output to- 3 kHz
for the rotary transformer. For a more detailed
description of this systems operation, consult the
DDG-51 propulsion plant manual or the DDG-51 CPP
system technical manual.
P for the online strainers and
If the electronic pitch control system becomes
inoperative, you must instruct your personnel to shift to
manual control at the OD box. Manual operation is
accomplished by shifting the two changeover valve
levers on the manifold block assembly from AUTO to
MANUAL. The propeller will remain at the pitch set
initiated at the time of the change. You can change the
pitch by operating the control valve lever and observing
the local pitch indicator.
Once the problem with the electronic controls has
been corrected, shift back to automatic operation.
Before initiating the change from MANUAL to AUTO,
be sure the pitch command signal from the controlling
remote station matches the actual pitch setting at the
time the mode change (manual to auto) is initiated. Shift
the two changeover levers simultaneously to the AUTO
position. If the command signal and actual pitch
settings do not match, the pitch will automatically
change to the commanded pitch upon completion of the
If the local manual mode is inoperative, shift the
changeover valves to the OFF position, secure the
hydraulic oil power module (HOPM), and set
emergency pitch according to engineering operational
sequence system (EOSS) procedures.
When operating in the emergency ahead mode,
the OD box temperature must be monitored
continuously. You may have to apply cooling water
to the OD box housing to maintain the temperature
below 160°F. Remember, the most effective and
preferred method to maintain OD box temperatures
is the use of prairie air.
CRP/CPP SYSTEM INSPECTIONS
The following is a list of routine checks and services
that should be made to the CRP/CPP system while
Check the OD box temperature, 160ºF
maximum (150°F DDG-51 class).
Check the hydraulic system oil pressures;
ensure all comply with EOSS.
Check the prairie air rotoseal for leaks.
Check the D
2. Each watch
a. Check the hydraulic oil level in the sump and
b. Inspect the hydraulic system for leaks and
3. Before entering port or any restricted
a. Verify the control system response by
decreasing pitch slightly and noting
b. Verify the pump (attached or electric)
operation depending on ship class.
4. When the system is secured
Check the oil level in the head tank. If the
head tank oil level is low, replenish oil as
necessary by operating the system until the
oil level returns to normal.
Inspect the oil for water contamination
CRP/CPP TROUBLESHOOTING AND
Even though the CRP/CPP systems installed on a
gas turbine-powered ship use the same types of pumps
and fluids as the MRG LO system, they are much more
Paying close attention to system
operating pressures is your most important step in
successfully troubleshooting any problem and making
the appropriate repairs. The following paragraphs will
describe some of the common problems associated with
system pressure and the methods you can use to identify
the component or components that might be causing the