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zeke
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Re: 787 vs A350 range

Tue Oct 30, 2018 4:34 pm

My guess is it the additional mass of the 787-9 is giving it a very different verticle profile in addition to the other items you addressed.

I think the 787-8 and A350-900 would climb straight to FL370 after takeoff with that payload, then the 787-9 maybe limited to FL330. Every change of 1000 could change that fuel burn by 1%.
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OldAeroGuy
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Re: 787 vs A350 range

Tue Oct 30, 2018 6:56 pm

If you do as I did and use the 788 landing weight with the 789 mission data, that will eliminate the weight effect on initial cruise altitude. In terms of landing weight, the mission profile doesn't differentiate between DOW, Payload and Reserve Fuel.

The 5% fuel burn difference between the 788 and 789 shown in the table has to be due to something else and the body stretch drag increment won't explain it all.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
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zeke
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Re: 787 vs A350 range

Tue Oct 30, 2018 11:45 pm

Initial altitude capability is a function of TOW not LDW, the charts at the moment have the additional OEW delta, and fuel delta at TOW.. I can look at changing this to be a function of TOW and vary LDW.
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thepinkmachine
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Re: 787 vs A350 range

Wed Oct 31, 2018 1:55 pm

In order to verify validity of our calculations, I decided to compare FCOM data against actual Computer Flight Plans from my recent flights on the 788 and 789. In case of the 789, I was also able to include the actual fuel burn on the flight. Below are the results with all the data required to cross-check the FCOM calculation, if Zeke (or anyone else) wishes to do so:

788 flight:

ESAD 3680 NM
LDW: 159430 kg
Fuel at landing: 7930 kg
Perf. deterioration factor 0.2%

CFP trip fuel: 37864 kg

FCOM trip fuel: 37500 kg

FCOM trip fuel adjusted for perf det. factor:37575 kg

789 flight:

ESAD 4257 NM
LDW: 173362 kg
Fuel at landing: 9762 kg
Perf. deterioration factor 0.5%

CFP trip fuel: 48119 kg

FCOM trip fuel: 47500 kg

FCOM trip fuel adjusted for perf det. factor:47738 kg

Actual burn: 47900 kg


So, our FCOM data and calculation method is accurate to within 300-400 kg, or slightly under 1%. Mind you, that the CFP plans were computed using a mix of ECON and Constant Mach segments (since major part of these flights was TATL), actual airspace constraints and non-standard temperature, whereas FCOM figures are based on LRC, ISA and 4000ft. Taking above into account, I consider our calculations pretty darn accurate... :)

P.S. regarding Initial FL of the 788 vs 789 - the latter cruises approx 2000ft lower than the former. The 788 normally starts at FL370-380, While the 789 at FL350-360. Of course close to MTOW or with higher temp deviation, initial levels might be lower.
 
abies111
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Re: 787 vs A350 range

Wed Oct 31, 2018 8:14 pm

Seeing the excellent provided graphs for the 787-9 and the A359 I fail to understand how the 787-10 is going to be a (substantially) more economical plane to operate than the second for the expected medium haul routes as it was previously reasoned
 
parapente
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Re: 787 vs A350 range

Thu Nov 01, 2018 3:51 pm

The 787-10 carries a load more passengers but still using the same engines so it will be highly efficient - as long as you have those pax and the reduced range is not a problem.Hence the BA order as an example.
Indeed BA is also a good example for the 787-8 when you don't have as many pax ( than the 9 or 10).A plane that they recently ordered more of.The presented fuel consumption figures if right show why.
 
kurtverbose
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Re: 787 vs A350 range

Fri Nov 02, 2018 10:58 am

But abies111's comparing the 787-10 with the A350-900, and the capacity of the A359 is very similar to the 787-10. Given how close the A359 is to the 789 in fuel burn, it must better the 787-10 and have the ability to fly considerably futher.
 
bbowma77
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Re: 787 vs A350 range

Sat Nov 03, 2018 12:32 am

Isnt the 787-10 bigger than the A350-900? Singapore has 3 versions of the A350-900, the ULR at 161 seats, a 253 seat version (i guess the standard long haul) and a 303 seat medium haul version at 303 seats. There new 787-10s are all 337 seaters, makes me think in similar configuration the 787-10 is a bit larger.
 
RJMAZ
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Re: 787 vs A350 range

Sat Nov 03, 2018 6:21 am

OldAeroGuy wrote:
I agree that using 8t of reserve fuel for all models is very conservative. It skews mission fuel burn at shorter ranges for all airplanes and disadvantages the modern airplanes (A350 & 787) relative to the older models.

Bingo!! Zeke's table is not accurate at all.

The 787-8 to 787-9 difference proves that a poor methodology used.

The reserve fuel should not be fixed at 8T but should scale to provide the same duration of flight. The 787-8 would have a lower reserve fuel weight than the 787-9.

The empty weight plays a big part. Zeke has used incorrect empty weights for the A350-900 previously. Weights must be apple to apple with a similar fitout, e.g seats and all fluids not including fuel. If you use an empty weight even 2T off it can chnge the fuel burn by multiple percent.
 
RJMAZ
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Re: 787 vs A350 range

Sat Nov 03, 2018 6:32 am

kurtverbose wrote:
But abies111's comparing the 787-10 with the A350-900, and the capacity of the A359 is very similar to the 787-10. Given how close the A359 is to the 789 in fuel burn, it must better the 787-10 and have the ability to fly considerably futher.

It annoys me when the answer to a question is a few comments up.
RJMAZ wrote:
The A350-900's cabin area is half way between the 787-9 and 787-10.
 
parapente
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Re: 787 vs A350 range

Sat Nov 03, 2018 9:13 am

Yup the 787-10 does have a larger seating capacity.A fairer example would be United's 3 class seating plan (inc premium) at 318.But it's still 20-30 seats larger in economy.And yes those seats are smaller,but.The real difference is range.The 359 is 8knm plus ( the ULR can fly for circa 17 hours I believe) the 7810 is about 6.5knm.Which makes it more of a regional machine.But in doing so it probably has the lowest seat mile costs of any machine flying.
Airbus were initially planning to do something very similar with their origonal dash 1000.A straight stretch trading range for capacity.Clearly some clients said this was not what they wanted,as such it became a much stronger beast with uprated everything including engines to get the range back up.
Boeing had no need to do this ( it wasn't technically possible anyway ) as they had the new 777x range coming out.
So range versus capacity/economics.Did Airbus or Boeing get it right ( or both?).Time will tell.
 
flipdewaf
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Re: 787 vs A350 range

Sat Nov 03, 2018 9:31 am

RJMAZ wrote:
OldAeroGuy wrote:
I agree that using 8t of reserve fuel for all models is very conservative. It skews mission fuel burn at shorter ranges for all airplanes and disadvantages the modern airplanes (A350 & 787) relative to the older models.

Bingo!! Zeke's table is not accurate at all.

The 787-8 to 787-9 difference proves that a poor methodology used.

The reserve fuel should not be fixed at 8T but should scale to provide the same duration of flight. The 787-8 would have a lower reserve fuel weight than the 787-9.

The empty weight plays a big part. Zeke has used incorrect empty weights for the A350-900 previously. Weights must be apple to apple with a similar fitout, e.g seats and all fluids not including fuel. If you use an empty weight even 2T off it can chnge the fuel burn by multiple percent.

Surely the 788-789 gap would be bigger with the methodology changed to show a lower amount of reserve fuel required in the smaller jet?

Fred


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RJMAZ
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Re: 787 vs A350 range

Sat Nov 03, 2018 12:01 pm

flipdewaf wrote:
Surely the 788-789 gap would be bigger with the methodology changed to show a lower amount of reserve fuel required in the smaller jet?

If the payload range charts show the aircraft took off with say 50T of fuel then using 8T reserve fuel means 42T of fuel is consumed on the trip.

If 7T of reserve fuel used used then that means 43T of fuel consumed. So using a lower reserve fuel on the 787-8 should increase the trip fuel burnt.
 
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zeke
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Re: 787 vs A350 range

Sat Nov 03, 2018 12:18 pm

flipdewaf wrote:
The reserve fuel should not be fixed at 8T but should scale to provide the same duration of flight. The 787-8 would have a lower reserve fuel weight than the 787-9.


They would be very close to being the same as we have been using the same landing weight and that reserve fuel is calculated at a max endurance speed hold at 1500 ft at that landing weight.

8 tonnes would be close to what is known as isolated airport or remote aerodrome reserve which is 2 hrs.
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thepinkmachine
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Re: 787 vs A350 range

Sat Nov 03, 2018 1:03 pm

@RJMAZ,

Reserve fuel is only used to obtain the landing weight, which in turn is required to get the fuel burn values.

The resulant fuel figures are only trip fuel figures, ie. fuel burnt from takeoff to landing.

If it makes you happy, we can assume eg. 6T of reserve fuel for the 788, but it will only change the results by 1%, or so...

Forget payload-range charts, FCOM data is way more accurate. To quote yourself:
It annoys me when the answer to a question is a few comments up.


Please se my posts #44 and #54, which discuss the accuracy of the methodology used and how small weight changes affect the results.

@Zeke, 7-8 Ton landing fuel is a realistic figure. For an islolated aerodrome, you’d see something like 12-13 T. Just to make sure we are on the same page: by “reserve fuel”, I meant expected fuel at landing, ie. final reserve fuel+ alternate fuel+unused contingency fuel. As I said before. 8-10 tons remaining at landing is quite typical, whether it’s a 788, or 789. What do you normally land with on the 350?
 
RJMAZ
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Re: 787 vs A350 range

Sat Nov 03, 2018 9:12 pm

thepinkmachine wrote:
As I said before. 8-10 tons remaining at landing is quite typical, whether it’s a 788, or 789. What do you normally land with on the 350?

So an A380 plotted on the graph would also have 8T fuel remaining after a typical landing? No chance..

A 787-8 with 8T of fuel can fly nearly 50% further than a 777-200ER with 8T of fuel. You have to scale reserve fuel.

You can fudge the reserve fuel and empty weights to get any answer you like.
 
thepinkmachine
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Re: 787 vs A350 range

Sat Nov 03, 2018 9:35 pm

A380 and 777 will probably have significantly different values of reserve fuel. So will A320 and 737.

However, A332, A333, A359, 788 and 789 all are airplanes of similar size and will have similar amount of fuel remaining after landing.

A ton, or two, of difference will have negligible effect on fuel burn...

What makes you think anyone is trying to fudge anything here? :banghead:
 
RJMAZ
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Re: 787 vs A350 range

Sun Nov 04, 2018 12:01 am

thepinkmachine wrote:
However, A332, A333, A359, 788 and 789 all are airplanes of similar size and will have similar amount of fuel remaining after landing.
thepinkmachine wrote:
The A350-900 has a 23% higher MTOW than the 787-8.

The A350-900 fuselage has a 22% greater wetted area than the 787-8. That is not similar.

thepinkmachine wrote:
What makes you think anyone is trying to fudge anything here? :banghead:

Zeke is an Airbus fanboy. He would definitely fudge the numbers.

You've conveniently got a difference source for the A350 data. The tables are more conservative. The least conservative data happens to be for A350.

It goes against all the fuel burn figures posted by UA pilots.
 
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zeke
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Re: 787 vs A350 range

Sun Nov 04, 2018 2:42 am

thepinkmachine wrote:
@Zeke, 7-8 Ton landing fuel is a realistic figure. For an islolated aerodrome, you’d see something like 12-13 T. Just to make sure we are on the same page: by “reserve fuel”, I meant expected fuel at landing, ie. final reserve fuel+ alternate fuel+unused contingency fuel. As I said before. 8-10 tons remaining at landing is quite typical, whether it’s a 788, or 789. What do you normally land with on the 350?


Final reserve on the A359 typically 2.2 for holding for 30 minutes at 1500 ft. Remote airport has a two hour holding fuel requirement, however that 2 hours is not required to be at 1500 ft. Typically we have that planned at FL180. That is where 8 tonnes will cover the 2 hours at the planning stage, only need to land with the normal fixed reserve of 30 minutes at 1500 ft. Normally I will land between 5-6 tonnes, min divert to an alternate (diversion fuel plus final reserve) which for my home port is normally around 4.4 tonnes (2.2 diversion plus 2.2. reserve), plus around 10-15 minutes, 1-1.2 tonnes, 5.5 tonnes is comfortable.

I looked at your numbers above for the 787-8 I got 36.37 for the 788 and 46.46 for the 789.

RJMAZ wrote:
Zeke is an Airbus fanboy. He would definitely fudge the numbers.

You've conveniently got a difference source for the A350 data. The tables are more conservative. The least conservative data happens to be for A350.

It goes against all the fuel burn figures posted by UA pilots.


You really need to sit up an apologize for the statement. I have sent via PM my calculations to both thepinkmachine and oldaeroguy who have both come out and said my numbers look good above in the thread. It is really embarrassing for you where my calculations have been via a peer review process.

You have three experienced people looking at published FCOM data. I havent fiddled or factored it at all, all I have done is some bi-linear interpolation in excel of the data published in the FCOM. For example FCOM may have numbers published for 4800 and 5200 nm and 220000 and 260000 lb , I used excel to gain numbers for 5000 nm and 130 tonnes. When plotted the data looks very reasonable.

Please go ahead and show us all where the United pilots have been publishing this data you are hanging you hat on. We have several hundred data points now so we can work back and tell you what it really means.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
RJMAZ
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Re: 787 vs A350 range

Sun Nov 04, 2018 4:52 am

thepinkmachine wrote:
A380 and 777 will probably have significantly different values of reserve fuel. So will A320 and 737.

However, A332, A333, A359, 788 and 789 all are airplanes of similar size and will have similar amount of fuel remaining after landing.

The A350-900 has a 23% higher MTOW than the 787-8.

The A350-900 fuselage has a 22% greater wetted area than the 787-8. That is not similar.

So you should definitely scale the reserve/left over fuel.

That is a similar percentage difference as between the 777 and A350. Or between the C series and A320. You cant use the same leftover fuel.
 
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zeke
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Re: 787 vs A350 range

Sun Nov 04, 2018 5:12 am

Does not matter what the published maximum takeoff weight is, what we are looking at here is the various airframes taking the same payload, over the same distance, landing with the same reserve.

This all cane about because of one of the other armatures on here saying thea350 burbs 10% more for the same payload which is false.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
armchairceonr1
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Re: 787 vs A350 range

Sun Nov 04, 2018 7:37 am

This topic is very fascinating, real world professionals share their knowledge and real world numbers to all of us. Everything not has to be A vs. B, even someone try to do also that. Thanks zeke, thepinkmachine and oldaeroguy&co.

PS. I hope we not have to see more personal attacks in this topic.
 
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ElroyJetson
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Re: 787 vs A350 range

Sun Nov 04, 2018 8:51 am

RJMAZ wrote:
thepinkmachine wrote:
However, A332, A333, A359, 788 and 789 all are airplanes of similar size and will have similar amount of fuel remaining after landing.
thepinkmachine wrote:
The A350-900 has a 23% higher MTOW than the 787-8.

The A350-900 fuselage has a 22% greater wetted area than the 787-8. That is not similar.


Zeke is an Airbus fanboy. He would definitely fudge the numbers.

You've conveniently got a difference source for the A350 data. The tables are more conservative. The least conservative data happens to be for A350.

It goes against all the fuel burn figures posted by UA pilots.



I trust the data regarding the A359 because even though Zeke is a massive Airbus fanboy it is the plane he flies.

However, I also trust the 789 pilots who commented on a thread i started several months ago. The burn is not close between the A359 and the 789. DL says their A359's burn 6600kg per hour on their TPAC routes. Some other carriers say 6400 kg per hour.

UA pilots said LAX-MEL the 789 burns 5600-5800kg per hour. That is a major difference.


Now you can jigger around the numbers any way you want, but those are real world from pilots and I trust what they are saying.

If Zeke's numbers are to be believed than the A359 and the 789 have virtually the identical fuel burn even though the 789 is smaller, lighter, and has less surface area. Sorry, I do not believe that because otherwise the 789 would never sell.

Both are excellent aircraft, but there's a real world penalty for the A359 being a l larger, heavier, and more capable frame. None of the numbers add up to 789 pilots have said or data that has been published.
707 717 727 72S 737 733 737-700 747 757 753 767-300 764 A319 A320 DC-9-10 DC-9-30 DC-9-50, MD-82 MD-88 MD-90 DC-10-10 DC-10-40 F-100
 
flipdewaf
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Re: 787 vs A350 range

Sun Nov 04, 2018 9:18 am

ElroyJetson wrote:
RJMAZ wrote:
thepinkmachine wrote:
However, A332, A333, A359, 788 and 789 all are airplanes of similar size and will have similar amount of fuel remaining after landing.

Zeke is an Airbus fanboy. He would definitely fudge the numbers.

You've conveniently got a difference source for the A350 data. The tables are more conservative. The least conservative data happens to be for A350.

It goes against all the fuel burn figures posted by UA pilots.



I trust the data regarding the A359 because even though Zeke is a massive Airbus fanboy it is the plane he flies.

However, I also trust the 789 pilots who commented on a thread i started several months ago. The burn is not close between the A359 and the 789. DL says their A359's burn 6600kg per hour on their TPAC routes. Some other carriers say 6400 kg per hour.

UA pilots said LAX-MEL the 789 burns 5600-5800kg per hour. That is a major difference.


Now you can jigger around the numbers any way you want, but those are real world from pilots and I trust what they are saying.

If Zeke's numbers are to be believed than the A359 and the 789 have virtually the identical fuel burn even though the 789 is smaller, lighter, and has less surface area. Sorry, I do not believe that because otherwise the 789 would never sell.

Both are excellent aircraft, but there's a real world penalty for the A359 being a l larger, heavier, and more capable frame. None of the numbers add up to 789 pilots have said or data that has been published.

Well we ‘know’ that the A359 burns about 5.85t/hr on the SIN-EWR flight with a very generous amount of fuel left over, the numbers have been made public. The LAX-MEL sector is a long flight and would not be landing at MZFW but likely leaving at MTOW to maximise cargo revenue. You say these have been shown to be 5600-5800kghr^-1. Which seems to ring true with exactly what has been said on this thread.

DL TPAC flights at 6400kghr^-1? I can believe that, but what are those flights and what were the loads? A flight that departs at MTOW and lands at MZFW will generate the highest average fuel flows, this does not however compare to a flight that is very long and goes well beyond MZFW range and will have a lower average fuel flow.

This thread moved away from here say and dealt with numbers that were directly comparable and had a basis in fact, you seem to want to move it back towards heresay.

Fred


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armchairceonr1
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Re: 787 vs A350 range

Sun Nov 04, 2018 9:39 am

ElroyJetson wrote:
I trust the data regarding the A359 because even though Zeke is a massive Airbus fanboy it is the plane he flies.

However, I also trust the 789 pilots who commented on a thread i started several months ago. The burn is not close between the A359 and the 789. DL says their A359's burn 6600kg per hour on their TPAC routes. Some other carriers say 6400 kg per hour.

UA pilots said LAX-MEL the 789 burns 5600-5800kg per hour. That is a major difference.


Now you can jigger around the numbers any way you want, but those are real world from pilots and I trust what they are saying.

If Zeke's numbers are to be believed than the A359 and the 789 have virtually the identical fuel burn even though the 789 is smaller, lighter, and has less surface area. Sorry, I do not believe that because otherwise the 789 would never sell.

Both are excellent aircraft, but there's a real world penalty for the A359 being a l larger, heavier, and more capable frame. None of the numbers add up to 789 pilots have said or data that has been published.

It seems that you miss the point of this comparision. It's made using real life numbers, when different aircrafts have same payload on same mission. Of course A359 should burn more fuel on it's typical mission, because it carry bigger payload than 789. Or otherwise operator bought wrong aircraft for it's needs.
 
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zeke
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Re: 787 vs A350 range

Sun Nov 04, 2018 10:47 am

ElroyJetson wrote:
The burn is not close between the A359 and the 789. DL says their A359's burn 6600kg per hour on their TPAC routes. Some other carriers say 6400 kg per hour.

UA pilots said LAX-MEL the 789 burns 5600-5800kg per hour. That is a major difference.


Where have DL and UA I said this ?

ElroyJetson wrote:
If Zeke's numbers are to be believed than the A359 and the 789 have virtually the identical fuel burn even though the 789 is smaller, lighter, and has less surface area. Sorry, I do not believe that because otherwise the 789 would never sell.

Both are excellent aircraft, but there's a real world penalty for the A359 being a l larger, heavier, and more capable frame. None of the numbers add up to 789 pilots have said or data that has been published.


As I explained earlier there are offsets that the A350 has, it climbs to higher flight levels which reduces drag and fuel burn.

The 787 is a lot heavier than a 767, lot more area, 77L bigger and heavier than a 77E, both burn less fuel than their siblings.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
WIederling
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Re: 787 vs A350 range

Sun Nov 04, 2018 3:42 pm

RJMAZ wrote:
flipdewaf wrote:
Surely the 788-789 gap would be bigger with the methodology changed to show a lower amount of reserve fuel required in the smaller jet?

If the payload range charts show the aircraft took off with say 50T of fuel then using 8T reserve fuel means 42T of fuel is consumed on the trip.

If 7T of reserve fuel used used then that means 43T of fuel consumed. So using a lower reserve fuel on the 787-8 should increase the trip fuel burnt.

This is more or less misstating the mechanics.
real fuel used builds on LDW, airplane characteristics and distance flown.
1t less LDW will thus result in less fuel used.
Murphy is an optimist
 
RJMAZ
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Re: 787 vs A350 range

Sun Nov 04, 2018 7:41 pm

ElroyJetson wrote:
If Zeke's numbers are to be believed than the A359 and the 789 have virtually the identical fuel burn even though the 789 is smaller, lighter, and has less surface area. Sorry, I do not believe that because otherwise the 789 would never sell.

Both are excellent aircraft, but there's a real world penalty for the A359 being a l larger, heavier, and more capable frame. None of the numbers add up to 789 pilots have said or data that has been published.

I couldn't agree more.

Airlines would be crazy to buy the 787-9 when you can buy a A350-900 that has equal fuel burn. The A350-900 brings greater range and a much larger cabin area. You are having your cake and eating it too.

We are seeing a compounding effect of cherry picking in the A350's favour.
1) High payload weight to favour the heavier frame.
2) Fuel data with conservative safety margins removed to favour the A350.
3) Fixed final reserve fuel weight to favour the heavier frame.
4) Fuel data from the latest aero tweaked A350 frames not one of the first 200 already in service.
5) Fuel data from a 5 year old non PIP'd 787-9 as displayed by the big difference between the 787-8 and 787-9.

Each one might add up to only 0.5% but add up all five and the 787-9 just gained 2.5%.

GIGO (garbage in, garbage out) is a concept common to computer science and mathematics: the quality of output is determined by the quality of the input.
 
flipdewaf
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Re: 787 vs A350 range

Sun Nov 04, 2018 7:58 pm

RJMAZ wrote:
ElroyJetson wrote:
If Zeke's numbers are to be believed than the A359 and the 789 have virtually the identical fuel burn even though the 789 is smaller, lighter, and has less surface area. Sorry, I do not believe that because otherwise the 789 would never sell.

Both are excellent aircraft, but there's a real world penalty for the A359 being a l larger, heavier, and more capable frame. None of the numbers add up to 789 pilots have said or data that has been published.

I couldn't agree more.

Airlines would be crazy to buy the 787-9 when you can buy a A350-900 that has equal fuel burn. The A350-900 brings greater range and a much larger cabin area. You are having your cake and eating it too.

We are seeing a compounding effect of cherry picking in the A350's favour.
1) High payload weight to favour the heavier frame.
2) Fuel data with conservative safety margins removed to favour the A350.
3) Fixed final reserve fuel weight to favour the heavier frame.
4) Fuel data from the latest aero tweaked A350 frames not one of the first 200 already in service.
5) Fuel data from a 5 year old non PIP'd 787-9 as displayed by the big difference between the 787-8 and 787-9.

Each one might add up to only 0.5% but add up all five and the 787-9 just gained 2.5%.

GIGO (garbage in, garbage out) is a concept common to computer science and mathematics: the quality of output is determined by the quality of the input.

Then enlighten us!


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armchairceonr1
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Re: 787 vs A350 range

Sun Nov 04, 2018 8:04 pm

RJMAZ wrote:
I couldn't agree more.

Airlines would be crazy to buy the 787-9 when you can buy a A350-900 that has equal fuel burn. The A350-900 brings greater range and a much larger cabin area. You are having your cake and eating it too.

We are seeing a compounding effect of cherry picking in the A350's favour.
1) High payload weight to favour the heavier frame.
2) Fuel data with conservative safety margins removed to favour the A350.
3) Fixed final reserve fuel weight to favour the heavier frame.
4) Fuel data from the latest aero tweaked A350 frames not one of the first 200 already in service.
5) Fuel data from a 5 year old non PIP'd 787-9 as displayed by the big difference between the 787-8 and 787-9.

Each one might add up to only 0.5% but add up all five and the 787-9 just gained 2.5%.

Let me remind you:
RJMAZ wrote:
The A350-900 definitely burns 10% more fuel than the 787-9 carrying the same load the same distance.

RJMAZ wrote:
GIGO (garbage in, garbage out).

Can't argue with that. ;)
 
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zeke
Posts: 12791
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Re: 787 vs A350 range

Mon Nov 05, 2018 3:49 am

RJMAZ wrote:
2) Fuel data with conservative safety margins removed to favour the A350.
3) Fixed final reserve fuel weight to favour the heavier frame.
4) Fuel data from the latest aero tweaked A350 frames not one of the first 200 already in service.
5) Fuel data from a 5 year old non PIP'd 787-9 as displayed by the big difference between the 787-8 and 787-9.


Let me dispel a few things, the numbers we have presented in this thread are for the same payload, and same reserve fuel for both the 787 and A350. What I have not presented is I have also extended this to the 77E, 77L, A343, A332. I provided my calculations to two other members for peer review, one a 787 pilot, the other a retired Boeing Engineer. Both said the looks ok.

The payload weight was not selected by me, it was suggested by thepinkmachine who is a current 787 pilot. With that payload and range the A350 is well below the MTOW, it has the performance to go to higher levels than the 787 initially after takeoff. The reason this was done is because YOU stated " A350-900 definitely burns 10% more fuel than the 787-9 carrying the same load the same distance". This has been proven to be false, the difference is less than 1%.

The final reserve does not have a lot difference in it, the actual holding rate for 30 minute at 1500 ft being around 2.2 tonnes for both the 787 and A350. For the purpose of this calculation we assumed all aircraft landed with 8 tonnes in the tanks. Up thread I mentioned to thepinkmachine I would operationally normally land with less at our home base, the reason for that is our main alternate is just 20 nm away.

The A350 data I used is not the latest or the greatest, it was the software I used during my initial course, which was before we had received a single aircraft. The electronic software and manuals installed on the aircraft reflects the actual performance for the actual tail number. I assume the 787-9 data used is current, as it comes from thepinkmachine who actually currently flying it.

Lots of accusations and finger pointing and little substance. We provided substance on this thread by using real FCOM data. I have been asking you to cite the UA and DL sources you have claimed, again no substance on your behalf.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
tommy1808
Posts: 9164
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Re: 787 vs A350 range

Mon Nov 05, 2018 7:17 pm

RJMAZ wrote:
Each one might add up to only 0.5% but add up all five and the 787-9 just gained 2.5%..


So 3.5% total, which is far, far, far of of 10%.

Q.e.d.

Best regards
Thomas
This Singature is a safe space......
 
Eyad89
Posts: 428
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Re: 787 vs A350 range

Mon Nov 05, 2018 8:40 pm

ElroyJetson wrote:



However, I also trust the 789 pilots who commented on a thread i started several months ago. The burn is not close between the A359 and the 789. DL says their A359's burn 6600kg per hour on their TPAC routes. Some other carriers say 6400 kg per hour.


DL never said that. You got this number from the Bureau of Transportation Statistics by dividing by fuel issued for DL's frames divided by hours flown. This does not only tell you nothing about the payload or sector length, it also is an improper way to compare fuel burn between different planes. The fact that this method shows UA's 763 burn 8% less than DL's 763 proves that you can't use this method to compare DL's A359 against UA's 789 based on that data.


You want A 359's real data fuel burn for a specific sector? Look at the published SQ's A359ULR fuel burn for the SIN-EWR. It had a TOW of 273t, flew for 17:22 hours, burned 101.4t of fuel for the whole trip, and landed with 10t of fuel left.

That means it burned 5.8 t/h on average for that flight. That's a real life data, not the ones you are referring to.

ElroyJetson wrote:
UA pilots said LAX-MEL the 789 burns 5600-5800kg per hour. That is a major difference.


Nope, not a major difference, that looks almost the same as what A359 would burn on a bit longer route.


ElroyJetson wrote:
If Zeke's numbers are to be believed than the A359 and the 789 have virtually the identical fuel burn even though the 789 is smaller, lighter, and has less surface area.


But the A359 has a lower induced drag and slightly better engines. That fact that it can achieve a slightly higher cruise altitude faster than 789 does means it can compensate a bit for the parasitic drag its larger size would generate. 789 has a lower parasitic drag, but the difference is smaller than the amount generated by their size difference since A359 flies a bit higher for a portion of a long flight.


ElroyJetson wrote:
Sorry, I do not believe that because otherwise the 789 would never sell.


There are many different reasons why a 789 would sell with those fuel burn numbers, to name a few:
- 789 is cheaper
- Some customers don't need the extra range or payload the A359 offers.
- Some customers prefer a GE engine over RR.
- Since 787 was launched earlier, some customers committed to 787 even before than A359 was launched, and they thought ordering A359 wouldn't add anything more but fleet complexity.
- Boing was able to deliver 787 much earlier than what Airbus could have. I mean, more than 500 787s were delivered even before A350 started ramping up.
- Fleet commonality with 777 made 787 a better option for many airlines.
- Let's not pretend that politics don't help both Airbus and Boeing get some orders. This is another reason why a certain airline would order 787 or A350 over the other.
- Well, 789 has a slightly better fuel per fuel per trip (but higher CASM).


Those are a few reasons that I can think of right now. Ordering a certain type does not only depend on fuel burn figures, especially if the fuel burn difference is such a small number
 
RJMAZ
Posts: 951
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Re: 787 vs A350 range

Mon Nov 05, 2018 10:13 pm

tommy1808 wrote:
RJMAZ wrote:
Each one might add up to only 0.5% but add up all five and the 787-9 just gained 2.5%..


So 3.5% total, which is far, far, far of of 10%.

Q.e.d.

Best regards
Thomas

Yes a 3.5% advantage in favour of the 787-9 on long haul sounds correct. But I am still right as I did not specify long haul. That would also now match the published payload range charts for both aircraft.

The advantage to the 787 continues to increase as the flight gets shorter. Zekes graph you can see the difference despite his methodology having a bigger effect on shorter ranges. 1T extra fuel on landing is only 1% extra fuel burn on an 100T fuel burn long haul flight. However on a short flight where 20T of fuel got burnt that 1T of extra fuel fudged the fuel burn figure by 5%. Lucky his graph started at 4000nm to minimise such errors with OEW and fuel weights.

However only a fraction of 787 flights are long haul. The 787 worldwide fleet has an average stage length of only 2500nm. Yes that is crazy short and that doesn't include the 787-10 which will keep that average down. Most 787 flights are going straight up to optimal cruising altitude so the argument that the A350 can climb higher is just cherry picking a scenario to make the A350 look superior. Members on this forum are obsessed with ultra long haul. On an average 787 flight the advantage will around 10% over the A350.

I'm sure when we look at the average flight length data in 10 years time the A350 will be flying much longer flights.
 
flipdewaf
Posts: 2261
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Re: 787 vs A350 range

Mon Nov 05, 2018 11:10 pm

RJMAZ wrote:

1T extra fuel on landing is only 1% extra fuel burn on an 100T fuel burn long haul flight. However on a short flight where 20T of fuel got burnt that 1T of extra fuel fudged the fuel burn figure by 5%.
I think you are confused, 1T extra after a 8000nm flight means that the fuel burn would increase more so than for 1 T carried for a 2000nm flight. A simple study of how the beefier range equation is derived will show you why thi is the case.

RJMAZ wrote:

However only a fraction of 787 flights are long haul. The 787 worldwide fleet has an average stage length of only 2500nm. Yes that is crazy short and that doesn't include the 787-10 which will keep that average down.
the reason why it seems crazy short is that it is a standard way of skewing the perception of data, ever heard the story about Bill Gates and the 10 hobos in a bar? On average they are all billionaires. What one should do is give a time weighted average to the average length of flight and the fuel burn is determined in usage per hour. So it is not the number that counts is not
“total flight distance”/“number of segments”

but:

“Sum ofTime x distance”/“distance/time”

You don’t want I know how many times your aircraft does long flights you want it know how long it spends doing them.

Fred



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MSPNWA
Posts: 2759
Joined: Thu Apr 23, 2009 2:48 am

Re: 787 vs A350 range

Tue Nov 06, 2018 2:18 am

Eyad89 wrote:
You want A 359's real data fuel burn for a specific sector? Look at the published SQ's A359ULR fuel burn for the SIN-EWR. It had a TOW of 273t, flew for 17:22 hours, burned 101.4t of fuel for the whole trip, and landed with 10t of fuel left.

That means it burned 5.8 t/h on average for that flight. That's a real life data, not the ones you are referring to.


That is real life data - data that can't be used for a meaningful comparison for the purpose of this thread. I'll give you a chance to find out why we can't use SQ's ULR for a fuel burn data comparison.

Ironically it confirms - if the UA 789 data is correct - that the average 787 has a significant fuel burn advantage over the larger, heavier frame, as it should.
 
tommy1808
Posts: 9164
Joined: Thu Nov 21, 2013 3:24 pm

Re: 787 vs A350 range

Tue Nov 06, 2018 6:03 am

MSPNWA wrote:
Ironically it confirms - if the UA 789 data is correct - that the average 787 has a significant fuel burn advantage over the larger, heavier frame, as it should.


The A350 has significantly more span, quite large raked winglets instead of just raked tips, and is a 5 years younger one at that. You´d expect the 777x fuel burn to best the 77W by more than the engines TSFC improvement, don´t you?
I don´t really see how an almost 10% longer wing won´t overcome 4-5% more weight on long haul, especially in the scenario considered here with a higher ICA. After all that is what the 10% longer 777x wing is supposed to accomplish vs. the 77W, despite the higher weight, on top of TSFC improvement.

best regards
Thomas.
This Singature is a safe space......
 
User avatar
zeke
Posts: 12791
Joined: Thu Dec 14, 2006 1:42 pm

Re: 787 vs A350 range

Tue Nov 06, 2018 7:00 am

MSPNWA wrote:

Ironically it confirms - if the UA 789 data is correct - that the average 787 has a significant fuel burn advantage over the larger, heavier frame, as it should.


Several times on this thread it has been stated that UA has published 789 furn burn data, I have asked for the reference time and again.

Why are people so afraid of making the source known and open to scrutiny ?

BTW I did not see significant fuel burn differences between numbers I have put on here for the A350 and flight plans, just like thepinkmachine did earlier. So there seems to be two schools of thought, those who fly imaginary planes on a flat earth, and those who do it in real life.

"QF9 FAST FACTS
229 passengers and crew
253.5 tonnes takeoff weight (half a tonne under MTOW)
100.6 tonnes of fuel
Approximate flight time of 17 hours 02 minutes
Departing Perth’s runway 21 at 1900 local time Saturday March 24
Landed London Heathrow at 0502 local time Sunday March 25"

from http://australianaviation.com.au/2018/0 ... in-london/

5883 kg/hr average

SQ22 101.4 tonnes, 17 hrs 22 minutes = 5838 kg/hr

https://twitter.com/FATIIIAviation/stat ... 1213747200
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
thepinkmachine
Posts: 280
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Re: 787 vs A350 range

Tue Nov 06, 2018 9:45 am

Zeke, small correction regarding QF9. According to my calculations, the Trip Fuel for this flight should be around ~95 tonnes, So average fuel flow would be around 5588 kg/hr.

100.6 tonnes quoted earlier is most likely the Block Fuel and that’s approximately a tonne short of the maximum tank capacity (unless QF birds have bigger than standard tanks, which I doubt).

Having said that, comparing average fuel flow quoted by some anonymous United Pilots (or whoever) against official FCOM flight planning data is pretty meaningless. Why did we even allow to get dragged into this? :banghead:

We have gathered some very accurate data, you have done great work putting it all together and posted it with genuine intents. Now it is up to the readers to believe it, or not...

Over and out,

PInk
 
kengo
Posts: 244
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Re: 787 vs A350 range

Tue Nov 06, 2018 9:54 am

Zeke, is that a fair comparison? One is flying westerly and the other is flying easterly with different wind conditions. Also, QF9 and SQ22 has a seat difference of around 60 seats, so I am not so sure if it is a fair comparison between the two types flying in a opposing routes. Would be interesting to see the return flight fuel burns for the two.
 
tommy1808
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Re: 787 vs A350 range

Tue Nov 06, 2018 10:09 am

kengo wrote:
Zeke, is that a fair comparison? One is flying westerly and the other is flying easterly with different wind conditions.


The comparison is via flight time, not distance, so wind doesn't play. The SQ flight is still longer, despite the A359 being a touch faster.

Also, QF9 and SQ22 has a seat difference of around 60 seats,.


SQ22 has a lot more heavy business and Y+ seats, making up some of the difference, the rest will maybe pan out to be 1T of fuel or so. The half an hour worth of fuel the 789 would need to carry on top to make the SQ flight would largely negate that, the ~5T more fuel, I.e. double, SQ22 had left in the tanks on touchdown easily make up the rest, as that alone is likely more than the payload/seat weight delta between the two flights.
It is as good a comparison as we can get.

Best regards
Thomas
This Singature is a safe space......
 
flipdewaf
Posts: 2261
Joined: Thu Jul 20, 2006 6:28 am

Re: 787 vs A350 range

Tue Nov 06, 2018 10:20 am

So the 787 burns about 250kg^hr less which works out I about a million a year fuel costs.

As ever, if you need the lift then you buy the lift you need. If you don’t need the lift then don’t buy the lift!

Are they close? Yes. Is there a gap? Yes!

Let’s keep this thread going though as it’s helping calibrate my models ;-)

Fred


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sadiqutp
Posts: 234
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Re: 787 vs A350 range

Tue Nov 06, 2018 11:45 am

Just wanted to appreciate and thank the data presentation by Zeke and thepinkmachine.. I always learn something new from such topics... It may seem frustrating when few fanboys make a lot of noise, but there are more of those who always enjoy and look forward to such discussions.
 
WIederling
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Re: 787 vs A350 range

Tue Nov 06, 2018 12:50 pm

thepinkmachine wrote:
100.6 tonnes quoted earlier is most likely the Block Fuel and that’s approximately a tonne short of the maximum tank capacity (unless QF birds have bigger than standard tanks, which I doubt).


I was just going to ask if the 100.6t represent loaded fuel or used fuel.
Murphy is an optimist
 
RJMAZ
Posts: 951
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Re: 787 vs A350 range

Tue Nov 06, 2018 12:50 pm

flipdewaf wrote:
So the 787 burns about 250kg^hr less which works out I about a million a year fuel costs.

250kg^hr is a 4.5% fuel burn advantage to the 787-9 on an ultra long haul flight.

Zeke's graph showed less than 1% which is clearly wrong. One thing the graph did display correctly is the 787 advantage grows as the flight becomes shorter. The 4.5% advantage grows and my original 10% is probably the closest estimate in this thead for an average sector length.

Though I should have been more clearer and just stated 10% less trip cost. Airport fees are strongly based around aircraft weight. As the 787-9 is lighter the trip cost of fuel plus fees would easily bring a 10% advantage.
 
RJMAZ
Posts: 951
Joined: Sat Jul 09, 2016 2:54 am

Re: 787 vs A350 range

Tue Nov 06, 2018 1:14 pm

WIederling wrote:
thepinkmachine wrote:
100.6 tonnes quoted earlier is most likely the Block Fuel and that’s approximately a tonne short of the maximum tank capacity (unless QF birds have bigger than standard tanks, which I doubt).


I was just going to ask if the 100.6t represent loaded fuel or used fuel.

Loaded fuel. Once you deduct the fuel it landed with it shows Zekes graph is wrong.

5588kg^hr for QF9 787-9
5838kg^hr for SQ22 A350-900

That is a 4.5% advantage to the 787-9.

sadiqutp wrote:
Just wanted to appreciate and thank the data presentation by Zeke and thepinkmachine.. I always learn something new from such topics... It may seem frustrating when few fanboys make a lot of noise, but there are more of those who always enjoy and look forward to such discussions.

I get a feeling this is directed at me. The last few posts just proved that Zeke's data presentation is wrong. You should be thanking me instead for pointing it out as incorrect.

Maybe next time I might not say anything and just let everyone reference false information for years.
 
armchairceonr1
Posts: 251
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Re: 787 vs A350 range

Tue Nov 06, 2018 2:33 pm

RJMAZ wrote:
Zeke's graph showed less than 1% which is clearly wrong. One thing the graph did display correctly is the 787 advantage grows as the flight becomes shorter. The 4.5% advantage grows and my original 10% is probably the closest estimate in this thead for an average sector length.

No, it wasn't wrong. zeke used 40 tons payload, instead of around 25 tons. I assume that light payload is advantage for 787 to every mission. Both 787 and A359 carry more payload 90% of flights. Your 10% estimate is just dreaming.
RJMAZ wrote:
Maybe next time I might not say anything .

Maybe not bad idea.
 
tommy1808
Posts: 9164
Joined: Thu Nov 21, 2013 3:24 pm

Re: 787 vs A350 range

Tue Nov 06, 2018 2:40 pm

RJMAZ wrote:
That is a 4.5% advantage to the 787-9..


on a ~2% shorter flight, with ~5T less fuel remaining and probably 2 tons or so less furniture in the cabin, which is a far cry from "10% more fuel burn for the same payload/range". It would appear you have proven yourself wrong once more...

It also says nothing about the validity of the fuel burn graph as it doesn´t cover flights beyond 7000 nm.....

best regards
Thomas
This Singature is a safe space......
 
smaragdz
Posts: 32
Joined: Fri Aug 03, 2007 9:48 pm

Re: 787 vs A350 range

Tue Nov 06, 2018 2:40 pm

RJMAZ wrote:
The last few posts just proved that Zeke's data presentation is wrong. You should be thanking me instead for pointing it out as incorrect.


Please post a detailed technical analysis, similar to Zeke's, showing us your 10% mismatch. Note that the other three posters have used actual FCOM data, so that the level of analysis you're going up against. If you have the numbers, then great -- we can have a discussion. But if you don't, then there's nothing really to discuss...
 
kengo
Posts: 244
Joined: Mon Apr 08, 2013 11:04 am

Re: 787 vs A350 range

Tue Nov 06, 2018 2:46 pm

tommy1808 wrote:
kengo wrote:
Zeke, is that a fair comparison? One is flying westerly and the other is flying easterly with different wind conditions.


The comparison is via flight time, not distance, so wind doesn't play. The SQ flight is still longer, despite the A359 being a touch faster.

Also, QF9 and SQ22 has a seat difference of around 60 seats,.


SQ22 has a lot more heavy business and Y+ seats, making up some of the difference, the rest will maybe pan out to be 1T of fuel or so. The half an hour worth of fuel the 789 would need to carry on top to make the SQ flight would largely negate that, the ~5T more fuel, I.e. double, SQ22 had left in the tanks on touchdown easily make up the rest, as that alone is likely more than the payload/seat weight delta between the two flights.
It is as good a comparison as we can get.

Best regards
Thomas


Thanks for the clarification.

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