Transferring fuel from aux to mains?

1. do you let pump run until aux tank is empty

or

2. leave a small amount of fuel in the aux tank and not run the
transfer pump dry

Thanks

As the gauges are not accurate and the pumps do not always pump at the quoted .4 gpm, it is difficult to know when you have pumped down to a gallon or so.
I run them till empty and know that point by rocking wings with aux button depressed. No needle movement = tank empty.

On my 180A Comet, I usually change from each tank on the half hour and wait until the main tanks are showing at least half empty, before pumping. That is usually two half hour cycles of flying on each tank or two hours flying all up.

I find that it takes about half an hour to pump the 50 litres (liters to you) from the Aux tanks. So whilst I am taking from left Main, I am pumping on the right. I always pump until the needle shows empty. This has proved to be pretty accurate so far, when I do my tank dip checks after the flight.

I ususally leave 1/4 tank in the auxillarys so that the pump never gets dry. Since checking for pump function is part of the preflight I like to make sure there's always a little fuel in the tank. Plus, that extra 7 or so gallons is a nice safety net to always have in the bank.

I pump them dry, and if I'm counting on that fuel, I pump them as soon as there is space in the main to accept the fuel. I don't want to be in a position that I have to have the fuel, because that's when Murphy will kick in and the pump won't work.

I agree with fuel transfer as soon as the mains can accept more fuel. My biggest problem is remembering to turn them off before I am pumping fuel out the overflow I start signt seeing and..... It isn't that I can use a clock, I just forget to look at it. Anyone have help for the memory challenged?

If my memory is working well I will test the transfer pumps before starting the engine so I can tell they are both working. I don't want to run out of fuel with 20 gallons left because a transfer pump failed (fear of Murphy as described above)

I too am suspicious of Murphy...typically run either the L or R main down for 30 mins or so and then begin transferring from the corresponding aux tank for the next 30 mins, then repeat for the opposite tanks...from that point I run the corresponding aux tank pump for the selected main, until the aux is dry.

Just because the pumps are running doesn't always mean you wll transfer fuel.
It's been mentioned before; but in my first month of ownership I kept getting a little water from the right aux when sumping, just a few globs and I kept at it hoping to get it all out eventually.
Murphy reared his ugly head on a cold long flight when voila! No transfering from the right aux. It takes a very small amount of ice in the line to stop the vibratory pumps.
So, like lots of folks have said; transfer early and confirm.

Kirk

I turn one on when main is down to half and switch tanks. when other tank is down to 3/4 i switch the other on. I usually turn them off when I notice they are still on when I do landing prechecks. (or when I park)