Fuel tank balance

Roger (K8RI) writes:

Low wing aircraft generally have a set sequence or sequences of
drawing fuel from specific tanks to keep the plane balanced. If I
burn too much off one side (and it doesn't take a lot) the Deb will
get decidedly lop sided. A half hour to 45 minutes per side on the
mains is good. An hour on one side and the other wing will get heavy.
Were I to burn all the gas out of one wing tip tank while the other
was full I'd be in a heap of hurt and I'd want to get the major
portion out of the second tank before landing. The book says no more
than 5 gallons difference between the two.

That's what puzzles me: If you're not supposed to have a significant
difference between the two, why aren't the two tanks just connected so
that they always drain at the same rate on both sides? Why would you
_want_ one wing substantially heavier than the other?

I can see why one might want to change things for fore and aft tanks,
or between center tanks and wing tanks, but I don't see any utility to
having one wing heavier than the other, or to having wing tanks that
don't communicate with each other (provided there's a cutoff for
emergencies).

--
Transpose mxsmanic and gmail to reach me by e-mail.

"Mxsmanic" wrote in message
...

That's what puzzles me: If you're not supposed to have a significant
difference between the two, why aren't the two tanks just connected so
that they always drain at the same rate on both sides?

On a low win airplane, you need a fuel pump to get the fuel to the engine.
If you have one fuel pump connected to both tanks, and one tank runs dry,
the fuel pump will be sucking only air, and no fuel from the other tank.

If you put in two fuel pumps, and one tank runs dry, you will probably burn
out the fuel pump running it dry.

If you put in a way for the pump to shut down when it's dry, you run the
risk of a faulire that shuts down the pump when there is still fuel in the
tank.

The goal is relable and simple. One fuel pump (actually, mine has an engine
driven pump and an electric backup pump), and a valve to select tanks.


Why would you
_want_ one wing substantially heavier than the other?

When I fly alone, the left side of the plane is heavier. If I burn fuel from
the left tank, after about an hour the plane is more balanced.

"Steve Foley" wrote in message
...
"Mxsmanic" wrote in message
...

That's what puzzles me: If you're not supposed to have a significant
difference between the two, why aren't the two tanks just connected so
that they always drain at the same rate on both sides?

On a low wing airplane, you need a fuel pump to get the fuel to the engine.
If you have one fuel pump connected to both tanks, and one tank runs dry,
the fuel pump will be sucking only air, and no fuel from the other tank.

If you put in two fuel pumps, and one tank runs dry, you will probably burn
out the fuel pump running it dry.

If you put in a way for the pump to shut down when it's dry, you run the
risk of a faulire that shuts down the pump when there is still fuel in the
tank.

The goal is relable and simple. One fuel pump (actually, mine has an engine
driven pump and an electric backup pump), and a valve to select tanks.


Why would you
_want_ one wing substantially heavier than the other?

When I fly alone, the left side of the plane is heavier. If I burn fuel
from
the left tank, after about an hour the plane is more balanced.

Mxsmanic wrote:
why aren't the two tanks just connected so
that they always drain at the same rate on both sides?

Also keep in mind the need to isolate a fuel leak.