Exam Question

Controllable Pitch Propellers (CPP)
(a) Servomotor Location
It is preferable to house the main servomotor for a controllable pitch propeller (CPP) in the propeller hub rather than in the shafting forward of the propeller shaft. This design, known as a hub servo system, is preferred over the external servo system, which uses a long push-pull rod extending from the engine room. The primary reason for this preference is that the long push-pull rod in an external servo system is prone to bending. This bending can occur due to the rod's length and the significant water pressure acting against the propeller blades, which can compromise the pitch control mechanism's reliability and precision. Housing the servomotor directly in the hub eliminates the need for this long rod, resulting in a more robust and reliable system.
(b) Regular Maintenance and Checks