What is the first step for emergency ground egress according to the critical action table?

In an emergency situation where ground egress is required, the first step is to set the ISS (Intercom Switch Selector) mode selector to SOLO. This action ensures that the communications system is configured to isolate the individual crew member who is exiting the aircraft, reducing the risk of confusion or communication issues during the emergency phase. Setting the ISS to SOLO allows the pilot or crew member to gain control of the intercom system, ensuring clear communication with the ground crew or with other crew members if needed.

This procedure is crucial, as it lays the groundwork for a safe exit from the aircraft. The other options relate to different configurations or states of the ISS mode selector, which are not appropriate to initiate emergency ground egress. For instance, switching the ISS to DUAL might lead to confusion in communication, while OFF or MANUAL settings would not provide the necessary support for a clear and effective egress process during an emergency.