ferpe
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Airbus Reveals A350-1000 OEW

Thu Nov 03, 2011 4:08 pm

Airbus had this breifing to their investors at this years Paris airshow, they then publizied this chart together with the following figures:

http://www.google.com/url?sa=t&rct=j...AFQjCNFDqMQa94Ap-ysYpZEbnIe2XSclMA

Airbus 2011-06 A350-1000 payload-range chart


A350-1000 revised
MTOW 308t
MZFW 220t

Now if one adds a MSP of 67t gleaned from the chart to that one get the OEW at 153t. The MZFW went up 1,5t (218,5t to 220t) with the same MSP for the old and the new version so it cost them 1,5t to raise the MTOW from 298t to 308t. This is plausible as most of that MTOW increase was fuel (8,5t of the 10t hike). So now we have the complete data set:

A350-1000:
MTOW 308t
MLW 233t
MZFW 220t
OEW 153t

Range @MZFW 5600nm
Range @350 Pax 8400nm
Range @maxfuel 8600nm

[Edited 2011-11-03 09:10:46]
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autothrust
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RE: Airbus Reveals A350-1000 OEW

Fri Nov 04, 2011 8:57 am

Quoting ferpe (Thread starter):
A350-1000:
MTOW 308t
MLW 233t
MZFW 220t
OEW 153t

So the A350 OEW will be roughly 14tons lighter then 777-300ER OEW (167,800 kg) but 8 tons heavier the the 777-200LR.

Somehow i'm dissapointed. I expected more weight savings.
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ferpe
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RE: Airbus Reveals A350-1000 OEW

Fri Nov 04, 2011 12:18 pm

We have had the same reaction and discussion in the 787 threads. I think the CFRP influence is overestimated by us all, if one does a little math it becomes clearer:

1. The CFRP typically saves about 20% compared to an AL part.

2. The INCREASE of composites is from say 10 > 50% between the 777 and the 350-1000.

3. The 50% is 50% of the structure, not the OEW or even the MEW. Say the structure composes 70% of the MEW or 60% of the OEW, then we would have:

40% of 60% of the OEW would be 20% lighter = > the OEW decreases 4,8% i.e. 8t for a 777.

The additional 6t in the case of the 777 vs 35J would come from Engines demanding some 15-20% less fuel, ie you don't need the structure for the 35t extra fuel the 77W needs for a 8000nm mission vs the 35J and you carry some 15-20 pax less.

So the wonder of CFRP shall bring us about 5% weight advantage, once one digest this things get a little more leveled (I was also trapped in the CFRP maze before doing the math   ).

[Edited 2011-11-04 05:20:16]
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rheinwaldner
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RE: Airbus Reveals A350-1000 OEW

Fri Nov 04, 2011 12:34 pm

Quoting ferpe (Reply 2):
So the wonder of CFRP shall bring us about 5% weight advantage, once one digest this things get a little more leveled (I was also trapped in the CFRP maze before doing the math).

Although despite that 5% may look small this is in fact a "wonder". The related fuel tankage reduction has also to be accounted as a gain.

Bringing down overall weight by a comparable dimension is hardly possible by any other technology...
 
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RE: Airbus Reveals A350-1000 OEW

Fri Nov 04, 2011 2:16 pm

The 777-300ER has a Maximum Structural Payload of 70t, so the 67t MSP of the A350-1000 tracks with reports/claims/speculation that the 77W has the edge in raw lift. The 77W also has a slight edge in range at MZFW (150nm), but comes up about 350nm short at the 30t nominal (pax+bags) payload of the A350-1000.

[Edited 2011-11-04 07:27:35]
 
sf260
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RE: Airbus Reveals A350-1000 OEW

Fri Nov 04, 2011 11:45 pm

From the chart can also be derived (initial) cruise fuel burn is 5,5t/h. How does that compare to 787 or 77W?

Apart from longer fuselage, 6 wheel MLG and larger wing area, what are other major differences for the -1000?
 
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 05, 2011 2:51 am

Quoting rheinwaldner (Reply 3):

Although despite that 5% may look small this is in fact a "wonder". The related fuel tankage reduction has also to be accounted as a gain.

Bringing down overall weight by a comparable dimension is hardly possible by any other technology...
Quoting Autothrust (Reply 1):
So the A350 OEW will be roughly 14tons lighter then 777-300ER OEW (167,800 kg) but 8 tons heavier the the 777-200LR.

Somehow i'm dissapointed. I expected more weight savings.

From structural perspective, 777-300A is closer to the A350-1000 than the ER version. A350 is only about 7 tons lighter compared to the 300A.
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ferpe
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 05, 2011 11:52 am

Quoting sf260 (Reply 5):
From the chart can also be derived (initial) cruise fuel burn is 5,5t/h. How does that compare to 787 or 77W?

Can you explain how you reached this figure, here the ones that my calculation gives for their average fuel burn doing their respective spec range missions:

77W....8,1t/hr....@7930nm mission
788.....4,8t/hr....@7800nm mission
789.....5,2t/hr....@8200nm mission
358.....5,2t/hr....@8500nm mission
359.....5,5t/hr....@8100nm mission
35J.....6,3t/hr....@8400nm mission
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sf260
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 05, 2011 2:17 pm

Trading 4,5t of payload for fuel (the oblique line is MTOW limiting, but you know that already, don't you  ), gives you 400nm extra range. This translates in a fuel burn of 5,5t/hr at M0,85. This should be ± initial cruise fuel burn as the "extra fuel" is used first.

Of course It depends on the accuracy of the "400nm" figure Airbus provided. If it's only 350nm in reality, this would mean a 6,3t/hr fuel burn. That gets quite close to your number... (and seems more realistic to me)

A figure for the 77W I just found in another thread, 7,6t/hr avg.

Btw, how did you get your numbers? (Just out of curiosity)  
 
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 05, 2011 3:06 pm

Quoting sf260 (Reply 8):
This should be ± initial cruise fuel burn as the "extra fuel" is used first.

The extra fuel is there to run the last bit (the frame flies exactly the same profile until then, it only extends the last step climb leg with say 400nm, therefore you have to assume that this is the fuel for this extension). So your reasoning is correct IMO but this is the fuel burn at the end of the cruise.

Quoting sf260 (Reply 8):
Btw, how did you get your numbers?

It is quite simple, the framers gives you the MTOW, Payload (Pax+bags@210lb) and the ensuing spec range. The only thing you then need to calculate how much fuel they use for that mission is the OEW which we just got.

Now MTOW -payload -OEW = fuel including reserves. Reserves are 5% of the total trip consumption + 45 min holding + 200nm diversion, it makes an almost perfect 10% of trip fuel. So now you have trip fuel, divide with range and you have kg/nm, multiply with groundspeed and you have kg/hr.
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 05, 2011 3:36 pm

Quoting ferpe (Reply 9):

Now MTOW -payload -OEW = fuel including reserves. Reserves are 5% of the total trip consumption + 45 min holding + 200nm diversion, it makes an almost perfect 10% of trip fuel. So now you have trip fuel, divide with range and you have kg/nm, multiply with groundspeed and you have kg/hr.

Just out of curiosity what groundspeed are you using, as I am also not getting anywhere close to your numbers.

With your MTOW of 308, payload of 32t (estimated from chart), and OEW of 153t, I'm getting a fueling including reserves of 123t. Minus the 10% reserve fuel gives you 110.7t. Divide by 8400nm gives you 0.01318t/nm. Now this is where groundspeed comes into play. I have no clue what the A35J ground speed is, so I just used an estimated 0.85 mach, which is 562.25 knots (nm/hr). Multiplying that by 0.01318 is giving me 7.4t/hr. Better than the 77W, but no where near as much as you are saying. Where is my math going wrong?

I only checked the A35J by the way, I don't know if there are discrepancies with the other models.
 
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 05, 2011 5:34 pm

Quoting polot (Reply 10):
so I just used an estimated 0.85 mach, which is 562.25 knots (nm/hr)

here you go wrong, speed of sound depends on temperature, so M0.85 at -56.5ºC (ISA at cruise alt >11km) it is ± 487knots.

@ferpe, it isn't. Think about it the other way around, taking off with MTOW - 4,5t will get you 400nm less far away. That is basically on the chart.
Fuel that you need at the end of the flight needs to be carried, that's why your fuel burn in the beginning of the flight will be higher than at the end.
So it should be initial fuel burn, more or less.
 
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 05, 2011 6:38 pm

Quoting sf260 (Reply 11):
here you go wrong, speed of sound depends on temperature, so M0.85 at -56.5ºC (ISA at cruise alt >11km) it is ± 487knots.

I see, thank you. I completely forgot to take temperature into account.
 
ferpe
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 05, 2011 10:12 pm

Quoting sf260 (Reply 11):
@ferpe, it isn't. Think about it the other way around, taking off with MTOW - 4,5t will get you 400nm less far away. That is basically on the chart.
Fuel that you need at the end of the flight needs to be carried, that's why your fuel burn in the beginning of the flight will be higher than at the end.

I am with you there, I thought about that after my post. The induced drag (drag due to lift) will be higher when you start with a higher TOW basically all the way. But there you are comparing 2 different frames with different MTOW, you can't use this to conclude about the average fuel burn for an A/C, see my post how to get average fuel burn. Now the slope describes something else (IMO):


The slope of a payload-range graph after the max range @MZFW is the area where your trade x ton of payload swapped for the same weight amount of fuel. Reduce payload and fill her up to the same TOW and you fly longer time and therefore further (this is indeed the graph part for constant TOW, before and after you vary TOW, before you have constant payload but reduces fuel for less needed range and after this part you reduce payload with constant (full) fuel to fly further.

Say we swap 6t from payload to fuel, then you have the same TOW in both cases and the same induced drag for both flights until you in one flight can fly about 1 hour longer on the last cruise height. The negative slope of this diagram will be your weight vs nm swap ratio for the last cruise leg, i.e. your fuel burn for this range extension, you can express it in t/nm or as the groundspeed is reasonably constant as t/hr.

I think my reasoning makes sense but stand happily corrected otherwise.
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RE: Airbus Reveals A350-1000 OEW

Mon Nov 07, 2011 4:59 am

With the chart from As Paris briefing I could see that my extrapolations did not fit 100% @MZFW range, it turned out I did not treat the trip fuel contingency of 5% correctly when doing the average fuel burn estimations for the extrapolations. Here a more correct chart where the old, new 350-1000 and the 77W is compared:

Payload range 35J vs 35JN vs 77W


A few interesting things can be seen (the calculations I do are now pretty close to reality, have also checked my estimations with PianoX for the 787):

1. It is now more clear why the 77W is a better lifter as Stich said, it was better all the way to spec range for the original 35J and now it is better until say 7300nm. The 35JN is now closer matched to the 77W.

2. Look at the MTOW slopes, they show you the fuel burn per nm, the more vertical slope of the 77W (higher fuel burn) is obvious. The 35JN also burn 150kg/hr more then the 35J, this can also be gleaned from the chart.

3. The A Paris chart is simplified to emphasize the differences to an investor community, therefore the MTOW slopes are shown as identical (they are not) and the max fuel range has the same curve down to 0 payload. In reality they have burned 90% vs 97% of their max fuel at spec range, thus the 35J can fly that much further (9100nm) when one trades more fuel for less payload.

As can be seen you don't gain without losses, the 35JN can start with a higher MTOW. Therefore it needs more thrust, it pays with a 2,4% higher fuel burn then the original 35J.
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sf260
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RE: Airbus Reveals A350-1000 OEW

Mon Nov 07, 2011 9:30 pm

So you agree with me that the slope that first "vertical line" is fuel burn @ initial cruise?

(I gave it some thought yesterday, changed my mind twice and lost it somewhere, but now I think I was right in the beginning)  

Thanks for that updated diagram, btw!
 
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RE: Airbus Reveals A350-1000 OEW

Tue Nov 08, 2011 7:01 am

Quoting sf260 (Reply 15):
the slope that first "vertical line" is fuel burn @ initial cruise?

Final, not initial. Thought experiment: imagine the airplane carries a sealed vault that contains 5 tons of fuel or 5 tons of payload, except you don't know which one at departure. At the end of the flight, you open the vault and either descend if it's payload, or burn the fuel to fly further if it turned out to be fuel. The difference between these 2 cases determines the slope of the payload-range curve. Initial cruise fuel burn, when you didn't know what was in the vault, is irrelevant.
 
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RE: Airbus Reveals A350-1000 OEW

Tue Nov 08, 2011 9:56 am

That was indeed one of the thoughts I had, but I can't figure where I go wrong in the following: if you take off with previous MTOW (so new MTOW - 4.5t), you end up being 400nm closer.... Can anyone help please?  
 
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RE: Airbus Reveals A350-1000 OEW

Tue Nov 08, 2011 1:17 pm

Quoting WingedMigrator (Reply 16):
Final, not initial. Thought experiment: imagine the airplane carries a sealed vault that contains 5 tons of fuel or 5 tons of payload, except you don't know which one at departure. At the end of the flight, you open the vault and either descend if it's payload, or burn the fuel to fly further if it turned out to be fuel. The difference between these 2 cases determines the slope of the payload-range curve. Initial cruise fuel burn, when you didn't know what was in the vault, is irrelevant.

Nice explanation, but remind me not to fly with you over water, just in case your thirst for empiricism overtakes wisdom!  
 
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RE: Airbus Reveals A350-1000 OEW

Tue Nov 08, 2011 1:20 pm

Quoting sf260 (Reply 17):
Can anyone help please?

Airbus did increase the MZFW by a number of tons (probably to increase the maximum structural payload closer to the 777-300ER) and since that chart is at MZFW, it's possible that even with the MTOW increase, total fuel load (by weight) at MZFW has gone down, which would impact range.
 
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RE: Airbus Reveals A350-1000 OEW

Tue Nov 08, 2011 2:49 pm

Quoting WingedMigrator (Reply 16):
Final, not initial. Thought experiment: imagine the airplane carries a sealed vault that contains 5 tons of fuel or 5 tons of payload, except you don't know which one at departure. At the end of the flight, you open the vault and either descend if it's payload, or burn the fuel to fly further if it turned out to be fuel. The difference between these 2 cases determines the slope of the payload-range curve. Initial cruise fuel burn, when you didn't know what was in the vault, is irrelevant.

Are we going to have a cat and a geiger counter as well?

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RE: Airbus Reveals A350-1000 OEW

Tue Nov 08, 2011 3:29 pm

Quoting sf260 (Reply 17):
if you take off with previous MTOW (so new MTOW - 4.5t), you end up being 400nm closer.... Can anyone help please?

There is only one MTOW. If you take off 4.5 tons short of MTOW, your range performance will not fall on the line we are discussing.
 
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RE: Airbus Reveals A350-1000 OEW

Tue Nov 08, 2011 4:42 pm

Ok, I see now where I went wrong. Thanks all!  
 
ferpe
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RE: Airbus Reveals A350-1000 OEW

Tue Nov 08, 2011 4:43 pm

Quoting sf260 (Reply 17):
if you take off with previous MTOW (so new MTOW - 4.5t), you end up being 400nm closer

WingedMigrator said it, here another version of the same thing:

- When an OEM publicizes the payload-range chart in e.g. the ACAP (AirCraftAirportPlanning guide) they only give you one version, the one where you start as heavy as it gets = MTOW. The chart envelope then show the frames maximum performance all the way out until you fly with 0 payload and full fuel at some +10000 nm.

- You got mixed up because A put 2 charts on top of each other, one with the old 35J with a MTOW of 298t and the new with 308t. You can only use the 4,5t diff in payload capability at a given range >5600nm as a comparison between the two variants. The values 4,5t and 400nm also gives you the slope of the curve for the heavier frame and somewhat wrongly the lighter frame (they generalize quite freely in this slide, but what the heck it was financial analysts in the audience, don't confuse them with facts    ). You can use this slope to understand your fuel burn at that range.

-Stitch, the MZFW was increase with 1,5t to cover for the fact that the 35JNew has a higher MEW. They fool you into thinking +1.5t with the graph but they said to Flightglobal at Paris it was 2.4t in reality. So the MSP should have been lowered for 35JN with a ton in the graph. As said a generalized "investor" graph    .
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 12, 2011 5:31 am

I wonder how Airbus sees the A350-1000... as an ultra-long-haul aircraft or a big people mover on normal long-haul routes, like BKK-FRA or LAX-LHR. Or both?
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 12, 2011 6:47 am

Over in Civil, RR are saying that the bigger engine has the same SFC (must mean TSFC) as the smaller engine. Previously a 1% or so penalty had been assumed. Does this make any difference?
 
ferpe
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 12, 2011 7:34 am

Quoting Baroque (Reply 25):
Over in Civil, RR are saying that the bigger engine has the same SFC (must mean TSFC) as the smaller engine. Previously a 1% or so penalty had been assumed. Does this make any difference?

The old version of the engine was spinning faster with changes to IMO the fan and high turbine only, i.e. the IP, HP, IP, LP was indentical to the 84k version. As lightsaber writes at this thread this means the compressors and turbines work at suboptimal blade speeds/Mach numbers, presumably thus the 1% loss of TSFC.

For the 97k version all ambitions for commonality of modules are relaxed therefore all aerodynamics can be re-optimised for the 6% higher rotational speed of the engine, thus the kept TSFC. Now this does not stop the frame from consuming more lbf thus the 2,4% higher trip fuel at spec range.
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ferpe
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RE: Airbus Reveals A350-1000 OEW

Sat Nov 12, 2011 2:26 pm

Quoting Baroque (Reply 25):
The old version of the engine was spinning faster with changes to IMO the fan and high turbine only, i.e. the IP, HP, IP, LP was indentical to the 84k version.

This is of course a serious case of brain fade   , should read "IC, HC, IT and LT" or read out: intermediate compressor, high compressor, intermediate turbine and low turbine"   .

Quoting CRJ900 (Reply 24):
I wonder how Airbus sees the A350-1000... as an ultra-long-haul aircraft or a big people mover on normal long-haul routes, like BKK-FRA or LAX-LHR. Or both?

The 35J is having a ULH design point, there is however no really modern 350 pax hauler with a midrange or short range design point. Thus given it's very efficient engines it will give you good economics also on sectors below 12 hours. The alternative would really be a 333 for those shorter sectors (you miss 50 pax) or a 773 (you gain 15 pax or more if your are EK). The economics then comes down to fuel burn (35J 6,3t/hr average, 333 6,2t and 773 7,7t), capital cost (the 35J certainly would cost more but if you have it you have it) and maintenance costs (no idea who costs the most but would guess the 773 would not be the cheapest).
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baroque
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RE: Airbus Reveals A350-1000 OEW

Sun Nov 13, 2011 7:47 am

Quoting ferpe (Reply 27):
Quoting Baroque (Reply 25):
The old version of the engine was spinning faster with changes to IMO the fan and high turbine only, i.e. the IP, HP, IP, LP was identical to the 84k version.

This is of course a serious case of brain fade , should read "IC, HC, IT and LT" or read out: intermediate compressor, high compressor, intermediate turbine and low turbine"

Now I am totally confused.   

You were actually quoting yourself not me. And I am not that sure about the correction.

Do we actually know what they are changing? They keep the fan the same diameter, but I have not seen them promise to change the blade shapes. And I thought the core was being revised, as in a greater mass flow. How that was being done, I had not seen and those links did not spell it out, well for me they did not?

The question I did ask was does the later information that (T)SFC was unchanged from the smaller engine make any difference to your calculations? Previously it had been assumed the larger version would be a bit more thirsty. Now it seems this may not be the case.

Also, does the throwaway line about growth in the TXWB have any implications for the 35J?
 
ferpe
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RE: Airbus Reveals A350-1000 OEW

Sun Nov 13, 2011 8:25 am

Quoting Baroque (Reply 28):
The question I did ask was does the later information that (T)SFC was unchanged from the smaller engine make any difference to your calculations? Previously it had been assumed the larger version would be a bit more thirsty. Now it seems this may not be the case


Sorry Baroque, I made a fault with the reference, of course it was my part of the post I referenced, not yours. To your questions:

My calculations are not affected by any changes in the engine., they calculate the factual fuel used for the spec mission, i.e. it is based on the OEMs own calculations for spec range with the actual engines including any changes. The only source of any fault there (once you know their assumed OEW) is how they calculate the reserves. Now there is a well established standard there so that should be OK.

Re the TXWB, the original 93k version was identical to the 84k version except for a tweaking of the fan blade aero and small but important changes to the high pressure turbine. The idea was that these improvements could be waterfalled down to the 84k version as time passed. Important log lead-time items like castings etc were kept.

The 97k version increases the size of the fan by making the inner hub diameter smaller = longer blades, keeping the outer diameter and it introduces more thorough changes to the core for more mass flow. If they touch the core parts they might just as well re-optimise the core blades/vanes for the higher RPM, that was my point.

Also please note what RR said, the "SFC" is unchanged, i.e. the fuel used per pound of thrust is the same. This is clever of them as the unassuming audience equates that to no higher fuel consumption for the frame, but this is not what they said! The heavier 35JN uses more pounds of thrust to keep M0,85 at cruise as it has a higher drag due lift (it is heavier), i.e. it burns more trip fuel. It does this even with the same payload as it is 2,4t heavier in the MEW then the original version.

[Edited 2011-11-13 00:32:56]
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