🔍 Key Concepts

• Controllable-Pitch Propeller (CPP) basic function: changing blade angle without changing shaft rotation or RPM • Difference between high-pressure oil for mechanical movement and control oil for signaling/positioning in a hydraulic system • What systems normally handle stern tube sealing versus propeller pitch control

💭 Think About

• Think about what kind of oil pressure (high or low) is required to actually move heavy propeller blades against water force. • Consider whether the CPP hydraulic system is usually built to do more than one job (like stern tube sealing) or is mainly dedicated to pitch control. • Separate in your mind the oil that does the physical work on the blades from the oil that sends control signals or positions the pitch mechanism.

✅ Before You Answer

• Identify which function logically needs high-pressure oil: moving blades or simple sealing/control. • Decide if CPP hydraulic systems are primarily designed for blade actuation and pitch control only, or if they normally also manage stern tube seals. • Check that your chosen option correctly pairs the type of pressure (high or low) with the tasks that demand the most force.