What occurs when the Pressure Reducing Valve is selected to Normal?

When the Pressure Reducing Valve is selected to Normal, it regulates bleed air pressure from the common feeder duct. This regulation is essential for maintaining optimal system performance, as it ensures that the correct pressure levels are supplied to various systems that rely on bleed air, such as cabin pressurization and engine starts.

In a typical jet engine or aircraft system, bleed air is extracted from the engine compressor and utilized for various functions, including environmental control and pneumatic starts. By regulating the bleed air pressure from the common feeder duct, the Pressure Reducing Valve helps maintain safety and efficiency by preventing overpressure conditions that could damage system components or lead to inefficiencies.

The other options do not align with the function of the Pressure Reducing Valve in this context, as it specifically focuses on managing bleed air pressures rather than altering hydraulic pressures or disabling systems.