747 weight distribution

On Sat, 18 Jun 2005 13:15:37 GMT, Brian Whatcott
wrote:

Hmmm...in case we dismiss Jack out of hand, better mention that
Concorde used tank redistribution of weight in flight and the KC135
which has been shunting fuel round the sky for a long, long time, can
place fuel between various tanks for CofG purposes.

I knew about the KC135 (that one was obvious because of it's special
mission) and the Concorde, but when the OP wrote about "most large
aircraft" having trim tanks I had to ask. I really don't consider the
Concorde a large (or normal!) aircraft.

Brian Whatcott

-Jack Davis
B737

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In article ,
says...

The Concorde used trim tanks. There's a fascinating explanation of it at
http://www.aircraft-info.net/aircraf...iale/concorde/.
Sounds like pumping fuel around to maintain proper CG during different
flight conditions was a full time job.

There's a double DVD from www.itvv.com - over 5 hours of Concorde flight
deck material from the Captain & Flight Engineer. Lots of explanation
of procedures; the 2nd DVD particularly covers a lot of the fuel
management. As an interested non-pilot, I found it fascinating.

T.

Jack Davis wrote:

On Sat, 18 Jun 2005 03:25:15 GMT, Gord Beaman
wrote:

Jack Davis wrote:

Huh? I've not flown a jet with a "small fuel tank in the tail". Am I
missing something?

-Jack Davis
B737

Only on larger a/c Jack...747 have them (some at least). What I
find interesting is how few people seem to know much about them,
is it that they aren't used much now?...

I see. Obviously you can count me among the many who didn't have a
clue, and I used to fly 747s (-100 and -200).

Thanks!

-Jack Davis
B737

Ok Jack...I haven't ever flown the 47 (not even as a pax) but
I've read a lot about this feature of large a/c. Perhaps it's
only certain marks of 747's that have it?...as I said before, I
find it very odd that so few have heard of it. That article about
the Concorde was interesting but wasn't what I meant, this
feature that I'm speaking of is solely an economy measure which
reduces drag for more efficient cruise.

It's only purpose is to replace aerodynamic tail down trim with
fuel weight therefore reducing drag. I don't know what the hell
it's called but it makes sense (to me at least)...frustrating
that not many know about it, even some 747 pilots/engineers.

Thanks for your courteous input Jack
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"

On Sat, 18 Jun 2005 08:07:11 -0400, Jack Davis
wrote:

On Sat, 18 Jun 2005 03:25:15 GMT, Gord Beaman
wrote:

Jack Davis wrote:

Huh? I've not flown a jet with a "small fuel tank in the tail". Am I
missing something?

-Jack Davis
B737

Only on larger a/c Jack...747 have them (some at least). What I
find interesting is how few people seem to know much about them,
is it that they aren't used much now?...

I see. Obviously you can count me among the many who didn't have a
clue, and I used to fly 747s (-100 and -200).

FWIW, the 400 has them. I believe the 777 and A300 are similarly
equipped. From what I understand they pump to the CWT and help keep
things in the trim envelope when you're near MTOW and high fuel loads.

Isn't there a 747 model with fuel inside the vertical stab? I seem
to recall reading of same...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Peter Clark wrote:

On Sat, 18 Jun 2005 08:07:11 -0400, Jack Davis
wrote:

On Sat, 18 Jun 2005 03:25:15 GMT, Gord Beaman
wrote:

Jack Davis wrote:

Huh? I've not flown a jet with a "small fuel tank in the tail". Am I
missing something?

-Jack Davis
B737

Only on larger a/c Jack...747 have them (some at least). What I
find interesting is how few people seem to know much about them,
is it that they aren't used much now?...

I see. Obviously you can count me among the many who didn't have a
clue, and I used to fly 747s (-100 and -200).

FWIW, the 400 has them. I believe the 777 and A300 are similarly
equipped. From what I understand they pump to the CWT and help keep
things in the trim envelope when you're near MTOW and high fuel loads.

Yes, I'm certain that some (at least) of the 747's do have them
but this reason isn't what I'm talking about...it seems that the
Concorde article in this regard is all to do with the critical
fore/aft balance and to keep the CG where they want it for
different phases of flight and this post from Peter sounds
similar BUT it's not what I'm referring to which is using fuel
weight INSTEAD of aerodynamic trim to reduce drag for more
economical cruise.
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"

On Mon, 20 Jun 2005 03:28:37 GMT, Gord Beaman
wrote:

Peter Clark wrote:

On Sat, 18 Jun 2005 08:07:11 -0400, Jack Davis
wrote:

On Sat, 18 Jun 2005 03:25:15 GMT, Gord Beaman
wrote:

Jack Davis wrote:

Huh? I've not flown a jet with a "small fuel tank in the tail". Am I
missing something?

-Jack Davis
B737

Only on larger a/c Jack...747 have them (some at least). What I
find interesting is how few people seem to know much about them,
is it that they aren't used much now?...

I see. Obviously you can count me among the many who didn't have a
clue, and I used to fly 747s (-100 and -200).

FWIW, the 400 has them. I believe the 777 and A300 are similarly
equipped. From what I understand they pump to the CWT and help keep
things in the trim envelope when you're near MTOW and high fuel loads.

Yes, I'm certain that some (at least) of the 747's do have them
but this reason isn't what I'm talking about...it seems that the
Concorde article in this regard is all to do with the critical
fore/aft balance and to keep the CG where they want it for
different phases of flight and this post from Peter sounds
similar BUT it's not what I'm referring to which is using fuel
weight INSTEAD of aerodynamic trim to reduce drag for more
economical cruise.


Hmmmm...maybe I'm missing something: trimming near aft CG limit is
aero drag favorable in sub sonic transports

Brian Whatcott

Brian Whatcott wrote:

On Mon, 20 Jun 2005 03:28:37 GMT, Gord Beaman
wrote:

Peter Clark wrote:

On Sat, 18 Jun 2005 08:07:11 -0400, Jack Davis
wrote:

On Sat, 18 Jun 2005 03:25:15 GMT, Gord Beaman
wrote:

Jack Davis wrote:

Huh? I've not flown a jet with a "small fuel tank in the tail". Am I
missing something?

-Jack Davis
B737

Only on larger a/c Jack...747 have them (some at least). What I
find interesting is how few people seem to know much about them,
is it that they aren't used much now?...

I see. Obviously you can count me among the many who didn't have a
clue, and I used to fly 747s (-100 and -200).

FWIW, the 400 has them. I believe the 777 and A300 are similarly
equipped. From what I understand they pump to the CWT and help keep
things in the trim envelope when you're near MTOW and high fuel loads.

Yes, I'm certain that some (at least) of the 747's do have them
but this reason isn't what I'm talking about...it seems that the
Concorde article in this regard is all to do with the critical
fore/aft balance and to keep the CG where they want it for
different phases of flight and this post from Peter sounds
similar BUT it's not what I'm referring to which is using fuel
weight INSTEAD of aerodynamic trim to reduce drag for more
economical cruise.


Hmmmm...maybe I'm missing something: trimming near aft CG limit is
aero drag favorable in sub sonic transports

Brian Whatcott

Yes it is IF it's done by transferring fuel aft. This has to be
done ONLY at stable cruise though because it drastically reduces
the fore/aft stability and requires operation of the
autopilot...I understand that some a/c are unmanageable without
an autopilot in this condition due to the reduced stability.

IIRC a Russian airliner became unmanageable and crashed when the
Captain's teenaged son wrestled control from the autopilot while
the a/c was trimmed like this.

Is this what you meant Brian?
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"

On Mon, 20 Jun 2005 20:42:54 GMT, Gord Beaman
wrote:

Brian Whatcott wrote:

On Mon, 20 Jun 2005 03:28:37 GMT, Gord Beaman
wrote:

Peter Clark wrote:

On Sat, 18 Jun 2005 08:07:11 -0400, Jack Davis
wrote:

On Sat, 18 Jun 2005 03:25:15 GMT, Gord Beaman
wrote:

Jack Davis wrote:

Huh? I've not flown a jet with a "small fuel tank in the tail". Am I
missing something?

-Jack Davis
B737

Only on larger a/c Jack...747 have them (some at least). What I
find interesting is how few people seem to know much about them,
is it that they aren't used much now?...

I see. Obviously you can count me among the many who didn't have a
clue, and I used to fly 747s (-100 and -200).

FWIW, the 400 has them. I believe the 777 and A300 are similarly
equipped. From what I understand they pump to the CWT and help keep
things in the trim envelope when you're near MTOW and high fuel loads.

Yes, I'm certain that some (at least) of the 747's do have them
but this reason isn't what I'm talking about...it seems that the
Concorde article in this regard is all to do with the critical
fore/aft balance and to keep the CG where they want it for
different phases of flight and this post from Peter sounds
similar BUT it's not what I'm referring to which is using fuel
weight INSTEAD of aerodynamic trim to reduce drag for more
economical cruise.


Hmmmm...maybe I'm missing something: trimming near aft CG limit is
aero drag favorable in sub sonic transports

Brian Whatcott

Yes it is IF it's done by transferring fuel aft. This has to be
done ONLY at stable cruise though because it drastically reduces
the fore/aft stability and requires operation of the
autopilot...I understand that some a/c are unmanageable without
an autopilot in this condition due to the reduced stability.

But that's not what I understand stab tanks are for. With MTOW and
lots of gas you are pretty heavy forward, and can be out of the
acceptable takeoff trim range, so having fuel in the back helps put
you back in the envelope (basically acting as ballast). As you fly
off the fuel in the main tanks, you replenish with the stab tanks by
pumping forward (range). They don't replace (or get used for)
elevator trim.

I believe the Concorde didn't have elevator trim due to the delta
wing, so the only way to make adjustments was to pump the fuel around
and physically shift the arm.

On Mon, 20 Jun 2005 20:42:54 GMT, Gord Beaman
wrote:

Brian Whatcott wrote:

On Mon, 20 Jun 2005 03:28:37 GMT, Gord Beaman
wrote:

Peter Clark wrote:

On Sat, 18 Jun 2005 08:07:11 -0400, Jack Davis
wrote:

On Sat, 18 Jun 2005 03:25:15 GMT, Gord Beaman
wrote:

Jack Davis wrote:

Huh? I've not flown a jet with a "small fuel tank in the tail". Am I
missing something?

-Jack Davis
B737

Only on larger a/c Jack...747 have them (some at least). What I
find interesting is how few people seem to know much about them,
is it that they aren't used much now?...

I see. Obviously you can count me among the many who didn't have a
clue, and I used to fly 747s (-100 and -200).

FWIW, the 400 has them. I believe the 777 and A300 are similarly
equipped. From what I understand they pump to the CWT and help keep
things in the trim envelope when you're near MTOW and high fuel loads.

Yes, I'm certain that some (at least) of the 747's do have them
but this reason isn't what I'm talking about...it seems that the
Concorde article in this regard is all to do with the critical
fore/aft balance and to keep the CG where they want it for
different phases of flight and this post from Peter sounds
similar BUT it's not what I'm referring to which is using fuel
weight INSTEAD of aerodynamic trim to reduce drag for more
economical cruise.


Hmmmm...maybe I'm missing something: trimming near aft CG limit is
aero drag favorable in sub sonic transports

Brian Whatcott

Yes it is IF it's done by transferring fuel aft. This has to be
done ONLY at stable cruise though because it drastically reduces
the fore/aft stability and requires operation of the
autopilot...I understand that some a/c are unmanageable without
an autopilot in this condition due to the reduced stability.

IIRC a Russian airliner became unmanageable and crashed when the
Captain's teenaged son wrestled control from the autopilot while
the a/c was trimmed like this.

Is this what you meant Brian?


Well...I also recall hearing crew asking passengers to move on
account of unexpected cargo distribution. That was pre-take-off.

Brian Whatcott