How is the LO unloader operated?

• A. Hydraulically
• B. Electrically
• C. Pneumatically
• D. Mechanically

Answer: (A)

The LO unloader is operated hydraulically. In the lubrication system of a gas turbine, an unloader valve uses the engine’s own oil pressure to drive a hydraulic actuator—a piston or spool—that moves the unloader mechanism. This arrangement lets the lubrication system relieve or divert pressure quickly during start-up, reducing the load on rotating parts so the engine can accelerate more easily. As oil pressure builds during running, the unloader returns to normal, restoring full lubrication.

Why this method fits best is that hydraulic actuation can handle high pressures and provide fast, reliable responses using the same fluid being controlled, without needing separate power sources. Electric, pneumatic, or mechanical actuation would require additional systems or power and are less robust in the high-pressure, oil-filled environment typical of turbine lubrication.