Final answer:
The answer to the specified pressure setting of the #3 hydraulic priority valve in an aircraft is not provided in the reference material, and such settings can vary based on different aircraft designs.
Step-by-step explanation:
The question pertains to a hydraulic system used in aircraft and more specifically to a hydraulic priority valve. When the hydraulic #3 pressure decreases below a certain psi, the valve directs all hydraulic fluid to the primary flight controls, maintaining critical systems during a loss of pressure. The correct response to the pressure below which the #3 hydraulic priority valve directs fluid solely to the primary flight controls is not provided in the provided reference information. However, typically in aviation hydraulic systems, values like 2100 psi, 2200 psi, 2400 psi, or 2600 psi could indeed be set points at which a hydraulic priority valve might redirect flow, depending on the aircraft's specific design.