If both WCCs fail or if the WAP fails, which light illuminates?

When both the Weight on Wheels Control Computers (WCCs) fail or if the Weight on Wheels Advisory Panel (WAP) fails, the WACS FAIL light illuminates. The purpose of the WACS FAIL light is to indicate that there is a failure in the systems that monitor or control weight on wheels, which are critical for safe operations related to the aircraft's weight and landing gear status.

The WACS (Weight on Wheels Advisory Control System) is designed to provide information and alerts essential for the safe operation of the aircraft, particularly during taxiing, takeoff, and landing. The illumination of the WACS FAIL light serves as a clear visual indication to the crew that a failure has occurred in the WCCs or WAP, prompting the necessary corrective actions and procedures.

Understanding the significance of the WACS FAIL light can help pilots make informed decisions regarding the aircraft's operational status and safety procedures in the event of system failures. In contrast, the MASTER WARNING light and MASTER CAUTION light have different functions related to other types of alerts and malfunctions, while the Head-Up Display is a tool for presenting flight information but does not serve as a failure indicator for WCCs or WAP.