Why are center tanks not used?

When you say "filled" do you mean amount of fuel in the each tank compared
to each tank's capacity?

On a B727, there is a limitation which calls for tanks 1 and 3 to contain no
more than 2000 lbs than tank 2 (the center tank), prior to takeoff. So, if
you fill tanks 1 and 3 (about 12,000 lbs) you would have at least 10,000 lbs
in tank 2 (capacity of about 30,000 lbs.) to comply with this limitation.-
Tank 2 would be "partially filled" compared to its capacity, but hardly
"empty".
"Mxsmanic" wrote in message
...
Why does it seem that wing tanks are filled in commercial airliners in
preference to center tanks? What is the advantage to filling the wing
tanks while keeping the center tank empty or partially filled?
Wouldn't heavy wing tanks increase the inertia of the aircraft around
the roll axis?

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tom418 writes:

When you say "filled" do you mean amount of fuel in the each tank compared
to each tank's capacity?

I just meant that the wing tanks usually contain fuel and are filled
with equal amounts of fuel, up to and including all that is necessary
for the flight. The center tank apparently remains empty, unless its
extra capacity is needed, even to the point of not turning on the
center tank pumps (I think). And supposedly the manufacturer forbids
putting more than a small amount of fuel in the center tank (at least
in the 737) without adding at least as much to the wing tanks.

On a B727, there is a limitation which calls for tanks 1 and 3 to contain no
more than 2000 lbs than tank 2 (the center tank), prior to takeoff. So, if
you fill tanks 1 and 3 (about 12,000 lbs) you would have at least 10,000 lbs
in tank 2 (capacity of about 30,000 lbs.) to comply with this limitation.-
Tank 2 would be "partially filled" compared to its capacity, but hardly
"empty".

Hmm. Sounds quite different from the 737. I wonder why.

I've always read that the 727 is a great aircraft to fly. It
certainly made history. The 737 is now doing the same.

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But that's a 727, with three fuselage mounted jet engines. It's static
loading problem is completely different than an airplane with wing mounted
engines only.

The 727 is a weird airplane, like the Falcon 50 I fly.........as far a fuel
goes.

Karl



"tom418" wrote in message
news:cUaQg.18$Rp3.10@dukeread12...
When you say "filled" do you mean amount of fuel in the each tank compared
to each tank's capacity?

On a B727, there is a limitation which calls for tanks 1 and 3 to contain
no
more than 2000 lbs than tank 2 (the center tank), prior to takeoff. So,
if
you fill tanks 1 and 3 (about 12,000 lbs) you would have at least 10,000
lbs
in tank 2 (capacity of about 30,000 lbs.) to comply with this limitation.-
Tank 2 would be "partially filled" compared to its capacity, but hardly
"empty".
"Mxsmanic" wrote in message
...
Why does it seem that wing tanks are filled in commercial airliners in
preference to center tanks? What is the advantage to filling the wing
tanks while keeping the center tank empty or partially filled?
Wouldn't heavy wing tanks increase the inertia of the aircraft around
the roll axis?

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