Taliesin
Final Assembly Line stage 1
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Post by Taliesin on Jun 19, 2015 14:33:30 GMT 1
It depends on the aircraft type/version. No it doesn't. There are 3 sections to every payload range chart. Section 1: You're not MTOW or fuel volume limited. If you want to go further, you tank more fuel Section 2: You're MTOW limited, if you want to go further, you unload payload and tank more fuel. Section 3: You're fuel volume limited, if you want to go further, unload payload or install additional fuel tanks. I remember this is the case of some A330 versions intended for short range (with a desactivated central fuel tank). Likewise, the A321neoLR uses up to three additional tanks. If you deactivate fuel tanks, the MTOW limit might not play a role and Section 2 of your payload range chart might disappear. Somehow, a fuel volume limitation due a deactivated center tank doesn't seem like much of an issue on an A330 intended for short range.Likewise, if you need to install additional fuel tanks on an A321NEO-LR, it means you are operating it on a route for which you need to unload payload in order to load more fuel. If that's the case, you're not doing it right in the first place and it's certainly not a typical route for that airplane. How commercially viable can a route be, for which you tank so much fuel that your fuel tanks are full, yet so little payload that you can afford to carry and fill extra fuel tanks? On an A321 no less? I admit I'm not familiar with the prospected payload range of the A321NEO-LR, but I can't imagine MTOW but be so high that this would be a viable option. You can convince me otherwise with some evidence But can we get back to the original point here and agree that stretching an airplane does not increase its range, but typically decreases it? You can't just magically tank more fuel just because your airplane gets bigger.
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Post by stealthmanbob on Jun 19, 2015 16:15:04 GMT 1
It depends on the aircraft type/version. No it doesn't. There are 3 sections to every payload range chart. Section 1: You're not MTOW or fuel volume limited. If you want to go further, you tank more fuel Section 2: You're MTOW limited, if you want to go further, you unload payload and tank more fuel. Section 3: You're MTOW and fuel volume limited, if you want to go further, unload payload or install additional fuel tanks. I remember this is the case of some A330 versions intended for short range (with a desactivated central fuel tank). Likewise, the A321neoLR uses up to three additional tanks. If you deactivate fuel tanks, the MTOW limit might not play a role and Section 2 of your payload range chart might disappear. Somehow, a fuel volume limitation due a deactivated center tank doesn't seem like much of an issue on an A330 intended for short range.Likewise, if you need to install additional fuel tanks on an A321NEO-LR, it means you are operating it on a route for which you need to unload payload in order to load more fuel. If that's the case, you're not doing it right in the first place and it's certainly not a typical route for that airplane. How commercially viable can a route be, for which you tank so much fuel that your fuel tanks are full, yet so little payload that you can afford to carry and fill extra fuel tanks? On an A321 no less? I admit I'm not familiar with the prospected payload range of the A321NEO-LR, but I can't imagine MTOW but be so high that this would be a viable option. You can convince me otherwise with some evidence But can we get back to the original point here and agree that stretching an airplane does not increase its range, but typically decreases it? You can't just magically tank more fuel just because your airplane gets bigger. I am sure I posted this before ? But I am sure the range of a B777-300 is longer than a B777-200 ?
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Post by stealthmanbob on Jun 19, 2015 16:37:01 GMT 1
I did not mean that fuel is not stored in the fuselage. The wings are the preferred storage of fuel in an aeroplane because of the weight distribution. Distributed weight in the wing works as a stress relief on the wing joint with the center box. Number two area is the center box, does not take volume from possible payload little influence on trim. If those two areas do not meet the volume need for fuel you add tanks in the belly. that's what I thought, you explained it better
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Taliesin
Final Assembly Line stage 1
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Posts: 228
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Post by Taliesin on Jun 19, 2015 19:09:10 GMT 1
I am sure I posted this before ? But I am sure the range of a B777-300 is longer than a B777-200 ? The ranges at MZFW are as follows: 777-200, MFZW of 254t: 3300nm 777-200ER, MFZW of 297t: 5800nm 777-300, MFZW of 299t: 3600nm At comparable weights, the shrink outranges the stretch by some 2200nm.
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s543
in service - 2 years
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Post by s543 on Jun 19, 2015 21:09:06 GMT 1
I am sure I posted this before ? But I am sure the range of a B777-300 is longer than a B777-200 ? The ranges at MZFW are as follows: 777-200, MFZW of 254t: 3300nm 777-200ER, MFZW of 297t: 5800nm 777-300, MFZW of 299t: 3600nm At comparable weights, the shrink outranges the stretch by some 2200nm. Well of course if the MFZW increase - there is more weight available for more fuel.... (and it must be placed somewhere where it would not take space for the payload.... But I am confused by your numbers. Looking at: en.wikipedia.org/?title=Boeing_777The weights are the same but the ranges are significantly bigger ? If we compare just 777-300 and 777-300ER i.e. the same plane only the second has way bigger MFZW + way more modern and powerful engines. According to Wiki link: the range increases 7825/6005 nmi MZFW 351/299 Fuel capacity 181283/171177 i.e. it makes something like 8t Empty weight 168/161 i.e. the usable payload increased by 351-299-8-7=37t !!!! and this with +1820nmi flown !!! Is there some mistake ? Here we agree that increase in MTOW provided the engines are powerful enough to handle it makes HUGE difference. It is about the same with 777-200 and 777-200ER - we should not compare and make comparison from a planes which are generation apart - and that is the case - 777-200ER is generation apart from 777-300. It is only logical that the stretch has bigger MTOW - if it does not the whole stretch is nonsense, since the gained space could not be utilized.
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Taliesin
Final Assembly Line stage 1
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Post by Taliesin on Jun 19, 2015 21:27:13 GMT 1
Well, I have my data from the original Boeing Aircraft Data Sheets.. maybe that explains the differences? Fuel capacity 181283/171177 i.e. it makes something like 8t Empty weight 168/161 i.e. the usable payload increased by 351-299-8-7=37t !!!! and this with +1820nmi flown !!! Is there some mistake ? Yea, you done goofed. A plane at MTOW can't fill its tanks to the brim, so I'm not sure what you're doing there. The difference between MTOW and MZFW will give you the amount of fuel you can tank at MZFW. The difference between MEW/OEW and MZFW will give you the maximum payload, although that is usually a seperately quoted figure, too. It is about the same with 777-200 and 777-200ER - we should not compare and make comparison from a planes which are generation apart - and that is the case - 777-200ER is generation apart from 777-300. It's hardly a generation apart, 8 years and PIP'd up engines does not a generation make. The comparison between 777-200ER and 777-300 is valid to demonstrate that a stretch usually has shorter range. It is only logical that the stretch has bigger MTOW - if it does not the whole stretch is nonsense, since the gained space could not be utilized. Actually, it's not logical at all. The wings need to be able to lift the additional weight and the engines need to be able to provide enough thrust. Airplanes don't always go out with full payload, because some are cargo space limited. If you can stretch an airplane, provide more cargo space, it may just free up the difference between usable payload and maximum structural payload. Thus, you carry more payload, but your MTOW limit means you have to carry less fuel, so you don't fly as far. Thus, you can carry more payload without raising your MTOW. Stretching an airplane makes a lot of sense, even without an increase of MTOW, if your performance is still ok.
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Post by stealthmanbob on Jun 19, 2015 22:11:47 GMT 1
I am sure I posted this before ? But I am sure the range of a B777-300 is longer than a B777-200 ? The ranges at MZFW are as follows: 777-200, MFZW of 254t: 3300nm 777-200ER, MFZW of 297t: 5800nm 777-300, MFZW of 299t: 3600nm At comparable weights, the shrink outranges the stretch by some 2200nm. So as I have said more than once the streched plane can fly further than the original ? The -300 flys further than the -200, forget the ER version cos that's got the extra tanks in the fuselage as I thought
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Taliesin
Final Assembly Line stage 1
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Post by Taliesin on Jun 19, 2015 22:16:24 GMT 1
So as I have said more than once the streched plane can fly further than the original ? The -300 flys further than the -200, forget the ER version cos that's got the extra tanks in the fuselage as I thought ***'** * ******* **** ** ******, ****'* ***? ******* ** ** ****** ****.
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s543
in service - 2 years
Posts: 3,957
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Post by s543 on Jun 19, 2015 22:19:59 GMT 1
OK - I understand - I stand corrected - thanks for explanation.
I still thought that all the real life stretches always had bigger MTOW. Checked true for A320 family, B737 orig, clasic, NG, B757, A330 - but I found one where it is not true - A340-500/A340-600 - where it is even opposite The stretch has lower MTOW. Empy 171/178 t. MTOW 372/368 !
One more thing. "A plane at MTOW can't fill its tanks to the brim"
Why ? 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. Of course we could tank less fuel, have bigger payload and do not flight as far - but that was theoretical exercise what the plane can do.....
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Taliesin
Final Assembly Line stage 1
In Thrust we trust
Posts: 228
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Post by Taliesin on Jun 19, 2015 23:07:56 GMT 1
I still thought that all the real life stretches always had bigger MTOW. Checked true for A320 family, B737 orig, clasic, NG, B757, A330 It makes sense, because it would give you back some of the range that got eaten up by higher structural weights and higher usable payload, but it's not always feasible. Even a higher MTOW should not translate to more range, though. It would be weird if it did. Higher structural weight and payload should still leave you with less fuel than the shrink. "A plane at MTOW can't fill its tanks to the brim" Oops, I meant MZFW. 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.
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