How much time would it take to restart the engine. So fuel pump on, switch tanks, mixture rich throttle in some fuel, fuel pump off, mixture where needed, start?
That’s likely way too complicated. Remember that the prop is windmilling, and the throttle and mixture are already set.
In my plane, the procedure is:
1. Switch tanks
2. Boost pump on
3. Boost pump off after engine restarts.
Simple. Takes all of maybe 15-30 seconds or less.
As a side note, my plane has three tanks — 1 in each wing and an aux tank in the fuselage. When I’m flying on a long trip, I regularly run tanks dry. Take off on either the left or right wing tank, switch to the other wing tank after the tank is half full (about an hour into the flight). Switch to the aux tank after another hour and run it dry. Switch back to the first wing tank and run it dry, then switch back to the second wing tank. That way I know that all of my usable fuel and reserves are in the same tank, and I’m not counting on trying to draw any fuel from mostly empty tanks. Depending on altitude and mixture settings, I get about 4-4 1/2 hours of flight plus an hour to hour and a half of reserve with this method. Helps to have a fuel totalizer as well.
Of course, as the tank nears empty, I’m really paying attention so that I can make the switch quickly, and I always warn my passenger(s) (usually just my wife, sometimes my son and his girlfriend as well) when a tank is nearing empty. There have been a few times that ATC has called with a “have new clearance, advise ready to copy” just as the tank runs dry!
