What is a controllable pitch propeller (CPP)?
A controllable pitch propeller (CPP), a subset of variable pitch propellers (VPP), is a type of propeller that can be adjusted to optimize the blade angle (pitch) for different conditions; this allows the propeller to be more efficient at different speeds and under different loads. Globally, this propeller type accounts for ~35% of market share.
CPP In Operation
How a Controllable Pitch Propeller (CPP) Works
Most controllable pitch propellers use a hydraulic or electrical system to change the propeller blade pitch (angle of attack). CPPs are used on many ships, but are more commonly found on larger ships and vessels because they offer a number of advantages over fixed pitch propellers.
Hydraulically Actuated CPP
Controllable Pitch Propeller Advantages
One advantage of a controllable pitch propeller is that it can be fine-tuned to match the specific needs of the vessel. For example, a vessel that frequently operates in shallow water may need a propeller with a shallower blade angle to avoid damaging the underwater environment.
Another advantage is that controllable pitch propellers are more efficient than fixed pitch propellers because the blades can be angled to match the ideal angle of attack for the current conditions. This means that less energy is wasted in generating thrust.
Finally, controllable pitch propellers are easier to reverse than fixed pitch propellers because the angle of the blades can be quickly changed to act against the water in the opposite direction; this makes it easier to maneuver in tight spaces and to berth the vessel.
Additional Resources
https://cultofsea.com/ship-handling/basic-propeller-types/
http://generalcargoship.com/controllable-pitch-propellers.html