Q How can power to the L and R wing tank Facet pumps automatically switch off when the wing tanks are dry? A. I have found that the facet pumps make quite a racket when the tanks are dry. In every instance I was alerted immediately and turned off the pump(s) within five seconds. This is while wearing the BOSE ANR headsets.. Otherwise you would have to install a float switch in each main tank and route that signal to a double pole double pole relay switch to break a ground circuit for the facet pumps. Perhaps, you might take some signal from your main tank fuel level system to use as a trip mechanism signal. Call your manufacturer of your fuel level system and get the stats on it when your tank is sensed as empty. Good luck Bob Smiley N94RJ