Before caution messages can be manually scrolled, what must first be done?

To manually scroll caution messages on the C-17, acknowledging the caution alerts with the MASTER CAUTION light is a necessary first step. The MASTER CAUTION light serves to alert the crew to any existing caution messages that require attention.

Once this acknowledgment is made, it indicates to the system that the crew is aware of the caution condition and are ready to review the specific messages that are indicated on the displays. This ensures that the pilot is not overwhelmed with alerts and can focus on critical information that demands their attention. By performing this action, the pilot can then utilize the scrolling feature without unnecessary distractions from unacknowledged alerts.

It is important to note that pressing other buttons such as SCROLL or AURAL SILENCE would not allow scrolling until the caution messages are first acknowledged. This sequence is designed to ensure that the pilot is adequately informed and validates their understanding of the aircraft's status before assessing the details of specific alerts.