What happens if both channels of the fuel quantity system fail?

If both channels of the fuel quantity system fail, the system is designed to alert the crew by illuminating the MASTER CAUTION light and displaying a FUEL QTY SYSTEM annunciation. This provides a clear and immediate indication of a critical issue regarding fuel quantity, ensuring that the pilots are aware of a potential problem that could affect the safe operation of the aircraft.

The MASTER CAUTION light serves as a general alert for various system malfunctions, while the accompanying FUEL QTY SYSTEM annunciation specifically informs the crew about the failure of the fuel quantity measurement system, signifying an issue that requires attention. This design enhances situational awareness and promotes a timely response to abnormal conditions, essential for flight safety and operational effectiveness.

In contrast, the other choices do not fully capture the nature of the alert system for a dual channel failure, nor do they provide the same level of awareness regarding the failure of the fuel quantity measurement.