"Bass, Jerry" wrote:

Thanks for clearing that up. I do have two pumps in parallel, which pump
from the selected tank. No transfer pump however.  I plan to run the left
tank till half down, then switch  to the right tank. At low power settings,
the pump puts out more fuel than the engine uses, which goes to the left
tank.
Jerry Bass

I thought about this a bit more and it is not a good system.
If the tanks are 30 gallons per side the return flow at only 30 GPH
could empty the right tank starting from full in only 45 minutes counting the 
the ten gallons an hour the engine is using, possibly overflowing the left 
tank and pumping fuel overboard.

Imagine what would happen if you were down to five gallons in the right tank.
In that case the tank would empty in 7.5 minutes if my calculations are correct.
40 gallons an hour or .66 gallons a minute. You would expect a half an hour 
of fuel was left in that tank.

The fuel management workload rapidly becomes overwhelming. This is probably what
happened to Solly. If you are on short final and too low it could become disastrous
as you may not have the presence of mind to switch tanks immediately.

Over the years I have gotten into the habit of coming in high and slipping to 
land for last minute loss of power reasons. In a low wing airplane without a "both" 
tank selection slipping can become a problem as the in the tank fuel pickup can become 
uncovered.
 
Paul Lamar
 
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