Something

refuel = func{

    brakesOn = getprop("/controls/gear/brake-parking");
    wow = getprop("/gear/gear/wow");
    fueltanks = props.globals.getNode("consumables/fuel").getChildren("tank");

    if (brakesOn and wow){
        foreach(tank; fueltanks) {
            level = tank.getNode("level-gal_us",0);
            remaining = level.getValue();
            interpolate(level,400, 30);
        }
    }
} # End function