The anchor-handling supply boat to which you are assigned is fitted with a totally pneumatic propulsion control system as shown in the illustration. If the astern clutch fails to engage from the engine room control station, but engages properly from all remote-control stations, which of the following system faults best accounts for these symptoms? Illustration MO-0168
• Trace the astern clutch engagement pilot air path from each control station on the MO-0168 diagram. • Compare what components are common to all stations vs. what is unique to the engine room control station. • Think about whether the described fault would affect only astern from the engine room or all stations / both directions.
• On the schematic, starting at the engine room control lever in the astern position, which valves and ports must the pilot air pass through before it reaches the clutch actuator 4-way valve? • Which of the listed faults would still allow proper astern engagement when the pilot air comes from the remote (pilothouse) station, but not when it comes from the local engine room lever? • For each choice, ask: would this fault interfere with ahead, astern, or both, and would it affect local only or both local and remote?
• Verify which components (lever ports, transfer valve, pilot air tubing, 4-way valve) are upstream only of the engine room station versus in the common downstream circuit. • Confirm from the diagram whether blocking the local port of the transfer valve would stop all engine room clutch signals (ahead and astern), not just astern. • Check whether a separation in the pilot air tubing at the clutch control panel or a problem in the 4-way valve exhaust port would affect signals from every station, not just the engine room station.
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