The OSV to which you are assigned is fitted...

The OSV to which you are assigned is fitted with a totally pneumatic propulsion control system as shown in the illustration. All propulsion controls function properly from all locations with the exception of the pneumatic remote control station. Here the propulsion engine will run only at idle and neither propulsion clutch will engage regardless of the throttle lever control position. Which of the following system faults best accounts for these symptoms? Illustration MO-0168

🔍 Key Concepts

• Trace how supply air and pilot air signals (speed and clutch engagement) flow from each control station to the clutch control panel in the MP-IC-12 diagram. • Compare what is controlled by an attendance valve versus a transfer valve in a pneumatic propulsion control system. • Think about what a blocked remote port would do to signals coming only from the pneumatic remote station, while leaving pilot house and engine room control unaffected.

💭 Think About

• From the symptoms (engine only at idle and no clutches from the remote station), what does that tell you about whether any pilot air signals from the remote station are actually reaching the clutch control panel? • If the pilot house and engine room controls both still work normally, which component faults would also have affected those stations, and which would affect only the pneumatic remote station? • Look at where the pilot air lines from the pneumatic remote station tie into the system: do they pass through the same valve section as the pilot house signals, or through a separate port? What happens if just that port is blocked?

✅ Before You Answer

• Verify which device in the diagram actually selects between pilot house vs. pneumatic remote for sending signals forward (look for a labeled transfer valve). • Check whether a blocked attendance valve outlet or a blocked speed signal port at the remote lever would prevent clutch engagement as well as speed control, or only one of those functions. • Confirm which transfer valve port, if blocked, would cause only the remote station to lose both speed and clutch control, while keeping pilot house and engine room fully operational.