When might packs and recirc fans turn off?

When the DUMP button is pressed, it triggers a system reaction that is crucial for cabin pressure management. The DUMP button, when activated, is used primarily for rapid cabin depressurization and atmospheric safety. This button turns off the packs and recirculation fans to help facilitate a faster drop in cabin altitude. The deactivation of the packs prevents additional conditioned air from entering the cabin, further accelerating the depressurization process. This function is vital for ensuring the safety of passengers and crew if there is a cabin pressure issue.

In contrast, while cabin altitude exceeding 10,000 feet could affect the operation of the cabin pressure system, it would not automatically turn off the environmental control system components as pressing the DUMP button would. Similarly, during engine start, packs and recirculation fans typically remain operational to maintain environmental conditions in the cabin. Lastly, while certain operational phases such as descent may lead to adjustments in system management, they do not necessarily mean that packs and recirculation fans will be turned off.