What does a [FUEL PX] annunciator indicate?

The indication provided by the [FUEL PX] annunciator pertains specifically to the pressure in the fuel supply line, which is a crucial factor in ensuring proper fuel delivery to the engines of an aircraft. When the annunciator illuminates, it signifies that the fuel pressure has dropped below a critical threshold, specifically less than 10 psi. This situation can lead to inadequate fuel flow to the engines, potentially causing engine performance issues or failure.

Monitoring fuel pressure is essential for flight safety, as the engines require a certain pressure level to operate effectively. Should this pressure fall too low, pilots may need to take specific actions to address the situation, such as checking fuel system components or considering an alternate fuel supply.

In contrast, the other options involve different aspects of fuel management. For instance, fuel probe failure relates to the functionality of sensors measuring fuel levels, while fuel imbalance refers to discrepancies in fuel quantities between tanks, which could affect aircraft balance and handling. Low fuel quantity detection concerns the overall amount of fuel remaining, which is distinctly separate from pressure issues highlighted by the [FUEL PX] alert.