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747 weight distribution
Hello, this is an odd question of curiosity from an amateur: Two days
ago I was flying from Dulles to LHR on a United 747-400. The aircraft taxied to the end of the runway, then the pilot announced there was a problem with the weight distribution on the aircraft wings, and we would have to move passengers to compensate. For the next half hour, cabin crew moved passengers around, apparently from economy to business, and then we took off. Is this normal? Can passengers body weight really make a difference on a huge aircraft like a 747? |
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Yes, it certainly does... nose to tail is where the weight distribution
matters. Sounds like you had too many people at the tail at not enough toward the nose... "Robin" wrote in message om... Hello, this is an odd question of curiosity from an amateur: Two days ago I was flying from Dulles to LHR on a United 747-400. The aircraft taxied to the end of the runway, then the pilot announced there was a problem with the weight distribution on the aircraft wings, and we would have to move passengers to compensate. For the next half hour, cabin crew moved passengers around, apparently from economy to business, and then we took off. Is this normal? Can passengers body weight really make a difference on a huge aircraft like a 747? |
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Brian Whatcott wrote:
loaders like to place the CofG near the aft limit. Fuel and cargo make huge invisible loads. Still, when someone gets it wrong, you can still shuffle passengers. I was under the impression that most big jets had a small fuel tank in the tail, and they could pump fuel back and forth to trim the CG. Am I mistaken? |
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On Wed, 30 Mar 2005 04:09:15 GMT, Gord Beaman
wrote: (Roy Smith) wrote: I was under the impression that most big jets had a small fuel tank in the tail, and they could pump fuel back and forth to trim the CG. Am I mistaken? No you're not but they use it for economy...most a/c are built to be quite nose heavy so they need quite a lot of nose up trim in level flight, this increases the 'fore and aft stability'. Huh? I've not flown a jet with a "small fuel tank in the tail". Am I missing something? -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 =---- |
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Jack Davis wrote:
On Wed, 30 Mar 2005 04:09:15 GMT, Gord Beaman wrote: (Roy Smith) wrote: I was under the impression that most big jets had a small fuel tank in the tail, and they could pump fuel back and forth to trim the CG. Am I mistaken? No you're not but they use it for economy...most a/c are built to be quite nose heavy so they need quite a lot of nose up trim in level flight, this increases the 'fore and aft stability'. 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?...that they've gone out of style?...that the risks of using them isn't worth the savings?...what?. They're called 'Trim Tanks' I believe and the theory is to replace the aerodynamically derived 'down force' of the tailplane with fuel weight at some expense of fore/aft stability which is compensated for by use of very capable autopilots. This system is only used in stable cruise. IIRC this system caused the crash of a large Russian airliner which was handled roughly while in this mode by the captain's son. -- -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" |
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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 ----== 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 =---- |
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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). Thanks! -Jack Davis B737 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. Brian Whatcott |
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Gord Beaman wrote:
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?...that they've gone out of style?...that the risks of using them isn't worth the savings?...what?. They're called 'Trim Tanks' I believe and the theory is to replace the aerodynamically derived 'down force' of the tailplane with fuel weight at some expense of fore/aft stability which is compensated for by use of very capable autopilots. 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. |
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