Which component reduces air pressure between a turbine-engine compressor and a hydraulic reservoir?

The component that effectively reduces air pressure between a turbine-engine compressor and a hydraulic reservoir is the air pressure regulator. This device plays a crucial role in managing and controlling air pressure within a hydraulic system.

Air pressure regulators maintain consistent output pressure levels regardless of variations in the input pressure from the compressor. By doing so, they protect the hydraulic components from receiving excessive pressure, which could lead to failures or malfunctions. The regulator ensures the hydraulic reservoir operates efficiently and safely by adjusting the air pressure to an appropriate level suitable for hydraulic system operation.

In contrast, a hydraulic pump is primarily responsible for increasing the flow and pressure of hydraulic fluid but does not specifically reduce air pressure. A pressure relief valve is designed to limit the maximum pressure in a system by allowing fluid to bypass or vent when the system pressure exceeds a set threshold, but it does not specifically reduce pressure from the compressor to the reservoir. An accumulator serves to store energy and mitigate pressure fluctuations within a hydraulic system but does not inherently reduce air pressure. Thus, the air pressure regulator is the correct choice for this function in the context of turbine-engine operation and hydraulic systems.