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#11
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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 ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#12
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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. |
#13
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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" |
#14
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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. |
#15
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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 |
#16
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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" |
#17
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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 |
#18
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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" |
#19
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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. |
#20
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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 |
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