Which method is used to pressurize a hydraulic reservoir?

Using engine bleed air to pressurize a hydraulic reservoir is a common practice in aircraft systems. This method involves tapping air from the engine's compressor section to create sufficient pressure in the hydraulic reservoir. This pressurization is crucial because it helps to ensure that hydraulic fluid flows properly throughout the system, allowing for the effective operation of hydraulic components such as flight controls, landing gear, and brakes.

Engine bleed air is chosen because it provides a reliable and readily available source of pressurized air that can effectively maintain the necessary pressure in the reservoir, ensuring that there are no issues with fluid movement or aeration. This method helps maintain system integrity and operational safety.

The other methods listed, such as gravity feed, magnetic pressure, and vacuum-assisted pressure, do not typically apply to the pressurization of hydraulic reservoirs in most aircraft. Gravity feed relies on gravitational force rather than active pressurization, while magnetic pressure is not a recognized method in hydraulic systems. Vacuum-assisted pressure, which implies suction, would not facilitate the necessary flow of hydraulic fluid in the required manner.