What action occurs when fuel level in a tank falls below the set threshold?

When the fuel level in a tank falls below a predetermined set threshold, the low fuel light is activated. This system serves as an important warning mechanism to inform the pilot that the fuel level has dropped to a point where it could impact the operation of the aircraft. The activation of the low fuel light provides an early alert, allowing the pilot to take necessary action, such as preparing for landing or refueling before the situation becomes critical.

In contrast, shutting down the fuel pump or the engine automatically, or venting the fuel lines, are not standard responses to a low fuel condition. Each of those scenarios addresses different operational issues or failure modes rather than simply indicating a low fuel state. The primary function of the low fuel light is to provide a simple and effective warning system for the pilot's situational awareness rather than initiating immediate shutdown procedures.