Baroque
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Post by Baroque on Jun 20, 2015 1:29:01 GMT 1
Thanks for the detailed explanations, although I'm still trying to work out the picture. In your opinion, Taliesin, what weights need improvements (and if you can deduce how much) to get a -1100 to fly a meaningful payload to the same range as the -1000?
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s543
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Post by s543 on Jun 20, 2015 12:11:46 GMT 1
Theoretically - You fill the tank completely and calculate what is left to MTOW and that is your payload ? Then you fly and finish with minimum allowable fuel reserve after the maximum range was flown. You can do that, it would give you the range at the intersection of section 2 and 3, but it's not an exercise commonly done. Usually, you want to take as much payload as you can and see where that gets you. If you can't make it to your destination, you exchange payload for fuel until you can. OK I thought we just theorize how far you can get - and what would be the payload there.... Of course real life situation is different - you have a route you have to fulfill, you have some partly given - people, partly optional -cargo - payload and there you economize how to do it the cheapest way. You have some plane (or selection of) and you have to use it. Just from the common sense - the stretch is always heavier - can not be different (!!!) i.e. needs more fuel to make the same route i.e. if you do not do "something" to help it you finish with shorter range. What stelthmanbob was getting at was this "something" being done.
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Taliesin
Final Assembly Line stage 1
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Post by Taliesin on Jun 20, 2015 12:42:42 GMT 1
Thanks for the detailed explanations, although I'm still trying to work out the picture. In your opinion, Taliesin, what weights need improvements (and if you can deduce how much) to get a -1100 to fly a meaningful payload to the same range as the -1000? That's very hard to say, because the numbers for the -1000 aren't fixed yet. Even for the -900, Airbus doesn't offer detailed payload range data in their newest Aircraft Data Sheet for the A350, so it's very hard to calculate weight specific fuel burn for the A350. The quoted figure for the A350-1000's MTOW is 308t. Let's bet generous and say Airbus can raise the MTOW by 20t. A 6m stretch plus modifications to wings and engines would probably come in at around 8t. Additional payload would probably come in around 6t, which leaves some 6t for additional fuel. Now these are all ball park figures, but if Airbus can pull it off, the -1100 might have the same range as the -1000. If Airbus can't significantly raise MTOW, the range will probably fall short of the -1000's by some 500nm. Just from the common sense - the stretch is always heavier - can not be different (!!!) i.e. needs more fuel to make the same route i.e. if you do not do "something" to help it you finish with shorter range. What stelthmanbob was getting at was this "something" being done. But even with a higher MTOW, the stretch typically has less range
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s543
in service - 2 years
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Post by s543 on Jun 20, 2015 14:38:18 GMT 1
Actually Taliesin you might enlighten us what steps are generally needed in order to increase the MTOW ?
I would assume: -certify the structural soundness for the MTOW i.e. body, wings, landing gear.... (and if needed apply some changes) -be sure the engines are able to push the thing at the increased weight - some changes....
We well know that the MTOW of let's say A330 was increased many times. Sometimes it was bureaucracy only sometimes real structural work was done and the final results are HUGE - to compare today's A330 with the first one - and the Empty weight is more-less the same - so the progress in the "soundness" of the construction is fantastic.
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Taliesin
Final Assembly Line stage 1
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Post by Taliesin on Jun 20, 2015 16:31:25 GMT 1
Actually Taliesin you might enlighten us what steps are generally needed in order to increase the MTOW ? I would assume: -certify the structural soundness for the MTOW i.e. body, wings, landing gear.... (and if needed apply some changes) -be sure the engines are able to push the thing at the increased weight - some changes.... I think that's more or less it. If your landing gear can handle the additional stresses, it comes down to the structure (wing and fuselage) and engines / field performance. We well know that the MTOW of let's say A330 was increased many times. Sometimes it was bureaucracy only sometimes real structural work was done and the final results are HUGE - to compare today's A330 with the first one - and the Empty weight is more-less the same - so the progress in the "soundness" of the construction is fantastic. I think the A330 is somewhat unusual. I'm not familiar enough with the A330 to say how exactly this additional capability came to be, but I would say that much of it, let's say the first 20t came from it simply being over-engineered, probably as a side effect of the development of the A340. Another effect could be that Airbus came to better understand the life cycles and fatigue of the airframe. If you know exactly where your weak points are, you can reinforce the airframe where it matters most, for relatively little added weight. I'm not an expert on the development of MTOW over time on other airframes, but I'd be willing to guess that an increase of 30t without significant changes to the structure or engines, without it being a new variant, must be some kind of record.
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s543
in service - 2 years
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Post by s543 on Jun 20, 2015 17:22:05 GMT 1
I believe there was a "significant" change to the structure over time - but of course what is "significant" ... ? I know the A330 is from this point of view unique - probably the most successful long time rise of MTOW - that was the reason I cited it.
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philidor
in service - 6 years
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Post by philidor on Jun 21, 2015 10:17:17 GMT 1
Don't forget software improvements are often part of the package required to make a higher MTOW version.
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Post by peter on Aug 4, 2015 21:32:16 GMT 1
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Post by stealthmanbob on Aug 4, 2015 23:30:09 GMT 1
I think teleportation will come before this AB Patent gets built.
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Baroque
in service - 2 years
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Post by Baroque on Aug 5, 2015 0:05:23 GMT 1
Just another patent. Can't see it happen unless, in the future, they find an extremely cheap source of fuel and durable construction materials. Perhaps I should draw designs for patenting in my spare time!
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