What does the constant speed propeller system primarily regulate?

The constant speed propeller system primarily regulates the pitch angle of the blades. This system is designed to automatically adjust the blade angle to maintain optimal RPM (revolutions per minute) of the engine, regardless of changes in airspeed or engine power.

When the propeller blades have a finer pitch, they allow the propeller to accelerate faster, which is useful during takeoff. Conversely, a coarser pitch is created to optimize engine performance at higher speeds and altitudes, ensuring that the engine operates efficiently without over-revving. This regulation of the blade pitch helps in maximizing thrust and fuel efficiency while providing a smoother flight experience.

The other options relate to aspects of aircraft performance but are not the main focus of what a constant speed propeller system does. For example, while the propeller's pitch affects thrust in flight, the primary function of the constant speed mechanism is to control the pitch, not directly the thrust itself. Similarly, weight distribution is not influenced by the propeller system, nor does it directly regulate the engine's RPM in the way that regulating blade pitch does.