Okay, I ran out of usable fuel and to this day can’t explain why I didn’t have at least 40 minutes fuel left in the mains, but I did learn several lessons. For instance,just because the systems on one B-17 work in a particular way, don’t count on the all working that way. Also,there are important bits of information in maintenance manuals that aren’t in the flight manuals. I already knew not to put much faith in fuel gauges, but I thought that at least one of them might be remotely accurate.