What causes the L/R FUEL LEVEL LO annunciator to illuminate?

The illumination of the L/R FUEL LEVEL LO annunciator is specifically triggered when less than 200 pounds or 32 gallons remain in the wing tanks. This is a critical alert designed to inform the flight crew that fuel levels in the wing tanks are approaching a minimum threshold, which could jeopardize safe flight operations. Monitoring fuel levels is essential for ensuring that there is enough fuel for the journey, and the annunciator serves as an early warning mechanism to prompt the crew to take appropriate actions, such as re-evaluating the fuel status or preparing to land.

The other choices pertain to different situations: depleting fuel in mid tanks may not directly signal low fuel in the wings, operational fuel transfer pumps do not indicate low fuel, and a fault in the engine fuel system relates to different warnings and does not directly activate the fuel level low annunciator. Thus, the correct understanding of fuel management and indication systems emphasizes the significance of the threshold established for the wing tanks.