Which component regulates oil pressure to ensure proper functioning of the pitch change mechanism?

The component that regulates oil pressure for the pitch change mechanism is the Propeller Interface Unit (PIU). The PIU plays a crucial role in controlling the pitch of the propeller blades by managing the hydraulic oil pressure supplied to the pitch change mechanism. It adjusts the oil pressure according to the power requirements of the engine and the desired propeller pitch angle. This regulation ensures that the propeller can efficiently change its blade angle to optimize performance and maintain engine efficiency based on various flight conditions.

The PIU interacts with various sensors and controls to monitor parameters like engine speed and power settings, making real-time adjustments to ensure the propeller operates within the desired range of pitch. This is vital not only for performance but also for protecting the engine and propeller from potential damage due to improper pitch settings.

Other components mentioned, such as the reduction gearbox and the propeller control unit, play significant roles in the overall propulsion system. However, they do not directly regulate the oil pressure related to the pitch change mechanism. The phase shift torque probe is focused on measuring torque rather than controlling oil pressure. Thus, the PIU is the specialized unit tasked with this function, making it the correct answer.