|
Francisco:
I'm not sure I understand the questions, but let me try to answer them.
If you run a main dry and go to the aux, you can't get flow. Turning the electric pump on doesn't help, because it's sucking from the dry main tank which anyway is no longer connected to the engine (the aux tank is). So the engine will windmill but produce no power.
If you're running good on the main and switch to the aux, uninterrupted flow occurs and the engine keeps running without even burping.
If you run a main dry and switch to the opposite main, you can get flow by turning on the electric pump for that side. (Careful: the pump will be forcing fuel from that main into both engines, so I prefer to put that side on its aux tank first before turning on the pump, to avoid any chance of flooding my working engine!); so if F engine sputters because L main is dry, my procedure is R engine to aux tank, wait several seconds to confirm good flow, F engine to cross-fed R main, turn R main electric pump on for a few seconds until the F engine re-starts, and then you can switch the F engine to the L aux without burping).
You should never land on aux tanks. First, because the book says so, second because there's no accurate way of knowing how much fuel is on that tank (remember it's draining at roughly twice the normal rate), and thirdly, I believe that the supply lines are smaller diameter and will not support the flow needed for full-power if you need to do a go-around (although I have not confirmed this last point, but I've heard it). Having said this, in an emergency -- like a leaking main tank that can't hold fuel -- I think you could do it safely. Generally, however, you should land on the main, even if its near empty: just run on the aux circling over the airport for an extra 5-10 minutes, and then when you're ready to get on the pattern switch to the main which will now have in it fuel that will last roughly however long you were on the aux tank -- incidentally, this is part of question #3 in the quiz at the end of my fuel management web page.
Ernie
|