Emergency Operation 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 mode change.

a. 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

b. sequence system (EOSS) procedures. 

NOTE 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 underway:

1. Hourly

a. Check the OD box temperature, 160 F maximum (150 F DDG-51 class).

b. Check the hydraulic system oil pressures; ensure all comply with EOSS.

c. Check the prairie air rotoseal for leaks.

d. Check the D falters.

2. Each watch

a. Check the hydraulic oil level in the sump and head tank.

b. Inspect the hydraulic system for leaks and vibration.

3. Before entering port or any restricted maneuvering situation

a. Verify the control system response by decreasing pitch slightly and noting response.

b. Verify the pump (attached or electric) operation depending on ship class.

4. When the system is secured

a. 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.

b. Inspect the oil for water contamination periodically.

CRP/ CPP TROUBLESHOOTING AND MAINTENANCE

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 sophisticated. 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 problems. The two most common casualties that you can identify just by noting variations in the system pressure are loss of pitch control and loss of hydraulic oil pressure.

Loss of Pitch Control A loss of pitch control can be caused by either a mechanical or an electrical failure. Mechanical failures tend to occur more frequently. You should be aware, however, that electrical problems can occur that will occasionally produce a loss of control. Normally, an electrical problem, such as a broken or loose cannon plug or loss of feedback position, will require the system to be shifted to manual control. In DDG-51 class ships, however, the CPP system has both a normal and an alternate system by which the pitch position can be monitored. If the normal system fails to provide command or feedback data, the CPP system can be shifted to the alternate system. When investigating a loss of pitch control on any gas turbine-powered ship, you must be aware of the components in the CRP/ CPP systems that are most likely to fail. The following are some of the components you will have to monitor most frequently.

ELECTROHYDRAULIC SERVO VALVE.- The most common component failure is the electrohydraulic servo valve. This valve is the primary component for remote operation and control. If this valve were not installed, all operations would require personnel to be stationed at the OD box at all times.

You can easily identify a faulty electrohydraulic servo valve. Any of the following symptoms should alert you as to the possible failure of this valve:

Pitch fails to respond to a desired integrated throttle control (ITC) change.

Pitch changes (fluctuations) occur without a pitch change command.

Hub servo pressure increases steadily without a change in system demands.

AUXILIARY RELIEF VALVE.- A faulty auxiliary relief valve also will cause a loss of pitch control. If the valve fails in the open position, all of the control oil will be ported back to the sump. Pitch cannot be changed without control oil to position the auxiliary servo piston in the OD box. In addition to the loss of pitch control, you should investigate any loss of pressure. You should be able to spot a pressure loss by checking the HOPM pressure gauges. This should be one of your first steps in checking the system.

REDUCING VALVE.- A faulty reducing valve is another cause for a loss of pitch control. If the reducing valve fails in the closed position, the flow of control oil will be cut off to the auxiliary servo piston, and pitch will fail to respond. Like the auxiliary relief valve, this loss of pressure will have to be viewed at the HOPM during the initial system investigation.

Loss of Hydraulic Oil Pressure Usually, a loss of hydraulic oil pressure will cause an alarm to be generated at the PACC/ PCC. The generation of this alarm, of course, will immediately alert the operator to a problem. The alarm will sound when casualties occur either to the main relief valve or to a sequencing valve. The alarm may or may not sound, however, when a major leak occurs. Look at the three main causes of hydraulic oil pressure loss and the resulting alarms.

MAIN RELIEF VALVE.- A faulty main relief valve can be identified by a low-pressure alarm at the console, but the actual answers can be found at the HOPM. This component failure can be easily identified by the operator. The operator simply looks at the HOPM pressure gauges and notes that all pressures are extremely low or nonexistent.

SEQUENCING VALVE.- You may suspect that a sequencing valve is faulty after a loss of pitch control as well as a loss of hydraulic oil pressure, depending on how the valve fails. For instance, if the valve fails in the open position, then all the oil would become high-pressure oil and the low-pressure alarm would not sound. In this case, the auxiliary servo supply (control oil) pressure would be drastically low and the system control would fade. On the other hand, if the sequencing valve fails in the closed position, a low-pressure alarm would sound and alert the operator. In this instance, the operator would also be able to see an extremely sluggish pitch response time.