FilterBOSS - Early Warning System (EWS) - Manual

The Early Warning System (EWS) was designed to allow the crew to monitor the filter condition while underway. When the primary filter starts to clog the engine driven lift pump will increase suction (vacuum) that can be measured by the vacuum gage, when the needle is in the yellow band the filter is starting to clog and should be changed. The remote Early Warning Panel (EWP) will also warn the crew when the vacuum reaches approximately 7" hg, the "check filter light" will illuminate on the EWP indicating that the filter is clogging. With the installation of a filter shutoff valve, the crew can check the system for
leaks and operation prior to departure.