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Sokes
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 12:51 am

What are the ranges of the different B777, B787 and A350 variants at MZFW?
What are the initial cruise altitudes and fuel burns at MTOW?
 
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zeke
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 12:57 am

Sokes wrote:
What are the ranges of the different B777, B787 and A350 variants at MZFW?
What are the initial cruise altitudes and fuel burns at MTOW?


You don’t ask for much do you ;)

Good luck
 
Sokes
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 1:56 am

zeke wrote:
Sokes wrote:
What are the ranges of the different B777, B787 and A350 variants at MZFW?
What are the initial cruise altitudes and fuel burns at MTOW?


You don’t ask for much do you ;)

Good luck

Different pilots fly different planes. You think we won't get the answers? :weightlifter:
Why don't you answer for the A350?
 
DylanHarvey
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 2:01 am

Sokes wrote:
What are the ranges of the different B777, B787 and A350 variants at MZFW?
What are the initial cruise altitudes and fuel burns at MTOW?

The A359 at 280t and 197.2t MZFW is probably around 6200-6300nm, the A35K is probably around 6000-6200nm, 77W is around 5700 I think. and the 787-9 is close to 5300, 787-10 is like 4200nm IIRC, 788 is around 5500nm I think, and the 77E is around 5900. Fuel burns I'd have no idea, cruise altitudes depend on so many things. 77E is probably 300-340, 77W, 280-3100, 359, 340-380, the 35K is around 300-330 IIRC. 788 is probably 350-370, 789 330-350, 78X around the same as the 9 I think. That’s the best I can give from an av-geek perspective lol.
 
Sokes
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 3:31 am

DylanHarvey wrote:
Sokes wrote:
What are the ranges of the different B777, B787 and A350 variants at MZFW?
What are the initial cruise altitudes and fuel burns at MTOW?

The A359 at 280t and 197.2t MZFW is probably around 6200-6300nm,
the A35K is probably around 6000-6200nm,
77W is around 5700 I think
77E is around 5900 and the
787-9 is close to 5300,
787-10 is like 4200nm IIRC,
788 is around 5500nm I think.

Fuel burns I'd have no idea, cruise altitudes depend on so many things.
77E is probably 300-340,
77W, 280-3100,
359, 340-380, the
35K is around 300-330 IIRC.
788 is probably 350-370,
789 330-350,
78X around the same as the 9 I think.

That’s the best I can give from an av-geek perspective lol.

Wow, that's a lot of info. I hope you don't mind I rearranged your quotation.

One of the reasons I was asking is because I wondered what an A350 would do with an engine update. From your initial cruise altitude I conclude that for the -1000 same payload, less MTOW with same range is required. Or even cut some range and make a lighter landing gear?

That low initial cruise altitude of the A350-1000 also makes me optimistic for the B777-9X.

Obviously the lower the capacity, the more a plane can profit from engine updates. In that sense the B787 should have the best future.
 
DylanHarvey
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 5:18 am

Sokes wrote:
DylanHarvey wrote:
Sokes wrote:
What are the ranges of the different B777, B787 and A350 variants at MZFW?
What are the initial cruise altitudes and fuel burns at MTOW?

The A359 at 280t and 197.2t MZFW is probably around 6200-6300nm,
the A35K is probably around 6000-6200nm,
77W is around 5700 I think
77E is around 5900 and the
787-9 is close to 5300,
787-10 is like 4200nm IIRC,
788 is around 5500nm I think.

Fuel burns I'd have no idea, cruise altitudes depend on so many things.
77E is probably 300-340,
77W, 280-3100,
359, 340-380, the
35K is around 300-330 IIRC.
788 is probably 350-370,
789 330-350,
78X around the same as the 9 I think.

That’s the best I can give from an av-geek perspective lol.

Wow, that's a lot of info. I hope you don't mind I rearranged your quotation.

One of the reasons I was asking is because I wondered what an A350 would do with an engine update. From your initial cruise altitude I conclude that for the -1000 same payload, less MTOW with same range is required. Or even cut some range and make a lighter landing gear?

That low initial cruise altitude of the A350-1000 also makes me optimistic for the B777-9X.

Obviously the lower the capacity, the more a plane can profit from engine updates. In that sense the B787 should have the best future.

I quoted a low initial altitude for the 35K because it is often being used out of hot climates. Unlike the 777 it all always end up at 400 or 410. Even at 316 tons you should be able to get 33 or 34 on a cool day. It is just there because of weight, do you takeoff performance is essentially equal to the 359 give or take a few hundred feet. And it also burns close to the same as the 359 at equal weight. more often than not you can get 35-36 because you won’t need 316 tons most of the time because of the efficiency(6.7-6.8t, but around 7.0t an hour on a hot DOH day)
 
DylanHarvey
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 5:23 am

Sokes wrote:
DylanHarvey wrote:
Sokes wrote:
What are the ranges of the different B777, B787 and A350 variants at MZFW?
What are the initial cruise altitudes and fuel burns at MTOW?

The A359 at 280t and 197.2t MZFW is probably around 6200-6300nm,
the A35K is probably around 6000-6200nm,
77W is around 5700 I think
77E is around 5900 and the
787-9 is close to 5300,
787-10 is like 4200nm IIRC,
788 is around 5500nm I think.

Fuel burns I'd have no idea, cruise altitudes depend on so many things.
77E is probably 300-340,
77W, 280-3100,
359, 340-380, the
35K is around 300-330 IIRC.
788 is probably 350-370,
789 330-350,
78X around the same as the 9 I think.

That’s the best I can give from an av-geek perspective lol.

Wow, that's a lot of info. I hope you don't mind I rearranged your quotation.

One of the reasons I was asking is because I wondered what an A350 would do with an engine update. From your initial cruise altitude I conclude that for the -1000 same payload, less MTOW with same range is required. Or even cut some range and make a lighter landing gear?

That low initial cruise altitude of the A350-1000 also makes me optimistic for the B777-9X.

Obviously the lower the capacity, the more a plane can profit from engine updates. In that sense the B787 should have the best future.

The thing you have to consider, the 35K at DOW(catering and stuff included) is 149-152t. The 779X is gonna be 170-175t. Also at most the 35K will be 32t lighter in 319 guise, the fuel burn advantage should be slightly in favor of the 35K, and range is not exactly close right now. The -8X is a different story, if that plane happens.
 
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zeke
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 6:12 am

DylanHarvey wrote:
The thing you have to consider, the 35K at DOW(catering and stuff included) is 149-152t. The 779X is gonna be 170-175t.


If you said 180-185 people would start believing you.
 
DylanHarvey
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 6:18 am

zeke wrote:
DylanHarvey wrote:
The thing you have to consider, the 35K at DOW(catering and stuff included) is 149-152t. The 779X is gonna be 170-175t.


If you said 180-185 people would start believing you.

It’s A.net people don’t even believe you as a pilot ;) I didn’t want to be accused of trying to favor Airbus lol. Most 77W’s are probably already close to 175+ and the 779X is heavier by a margin
Advantage to the 35K even more then, what a beast.
 
DylanHarvey
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 6:20 am

zeke wrote:
DylanHarvey wrote:
The thing you have to consider, the 35K at DOW(catering and stuff included) is 149-152t. The 779X is gonna be 170-175t.


If you said 180-185 people would start believing you.

180-185 it is. The engine and wing are ALOT heavier in the X. I also think 148-150 is a better estimate for the 35K. Also are there some 359’s floating around with 133-134t DOW now? I know most are around ~135 now
 
mmo
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 8:03 am

The X also has a different wing which will perform better than the ER/LR/77W even though it is heavier.

The OP wrote about an engine update that would allow better cruise altitude. That might not and probably not true. It is also a function of the wing and lift. My guess would be a redesigned wing would be a better option.
 
Sokes
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 8:33 am

mmo wrote:
The OP wrote about an engine update that would allow better cruise altitute.

Do you mean original post? I don't understand what you mean.
 
flipdewaf
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A350-1000 fuel burn

Wed Aug 05, 2020 10:43 am

mmo wrote:
The X also has a different wing which will perform better than the ER/LR/77W even though it is heavier.

The OP wrote about an engine update that would allow better cruise altitude. That might not and probably not true. It is also a function of the wing and lift. My guess would be a redesigned wing would be a better option.

At the risk of deletion from self promotion I posted a thread about a year ago where I analysed the performance of the 77w vs 77x wing viewtopic.php?t=1426609

My take away from the work was that the bulk of the efficiency came from the new engines but that there was ~3.5-3.8% L/D gain from the new wing. Leaving the standard wing would have given a much higher payload range.

I believe one of the relatively hidden benefits of the A351 is that wing having the trailing edge extension whilst being of slightly lower AR then the A359 and therefore needing higher thrust actually has a benefit in the cruise due to having a lower T/C helping manage high Mach effects at altitude. This allows the aircraft to better match the increased engine performance to the wing performance.

Fred

Sent from my iPhone using Tapatalk
 
mmo
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 12:38 pm

Sokes wrote:
One of the reasons I was asking is because I wondered what an A350 would do with an engine update.






Sokes wrote:
mmo wrote:
The OP wrote about an engine update that would allow better cruise altitute.

Do you mean original post? I don't understand what you mean.



Sorry, it was actually you!
 
Sokes
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Re: A350-1000 fuel burn

Wed Aug 05, 2020 4:39 pm

flipdewaf wrote:
At the risk of deletion from self promotion I posted a thread about a year ago where I analysed the performance of the 77w vs 77x wing viewtopic.php?t=1426609
Fred

Sent from my iPhone using Tapatalk

Thanks for the link. I learnt a lot from that discussion, but already had forgotten most.
Good to read it again.
 
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AECM
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Re: A350-1000 fuel burn

Mon Dec 28, 2020 5:42 pm

From social media today, A35K from Air Caraibes flying from ORY to PTP
Image
 
VSMUT
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Re: A350-1000 fuel burn

Mon Dec 28, 2020 6:12 pm

AECM wrote:
From social media today, A35K from Air Caraibes flying from ORY to PTP
Image


6.2 tons per hour over an 8 hour flight.
 
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SQ22
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Re: A350-1000 fuel burn

Mon Dec 28, 2020 6:16 pm

Pleasxe remember to provide a link to your source unless it is your own one and clearly marked accordingly when uploading images. Thanks.
 
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AECM
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Re: A350-1000 fuel burn

Mon Dec 28, 2020 6:24 pm

AECM wrote:
From social media today, A35K from Air Caraibes flying from ORY to PTP
Image
Source:
https://instagram.com/my_flying_life?ig ... 4rnmcnou58

Last "story"
 
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SQ22
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Re: A350-1000 fuel burn

Mon Dec 28, 2020 7:03 pm

AECM wrote:
Last "story"



Thanks
 
flipdewaf
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Re: A350-1000 fuel burn

Mon Dec 28, 2020 7:17 pm

AECM wrote:
From social media today, A35K from Air Caraibes flying from ORY to PTP
Image

Nice! So at 319t TOW it could do 16hrs with 415 pax...

Fred


Sent from my iPhone using Tapatalk
 
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zeke
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Re: A350-1000 fuel burn

Tue Dec 29, 2020 2:45 am

VSMUT wrote:
6.2 tons per hour over an 8 hour flight.


It will actually be lower than that, looks like they haven’t finished the setup completely. As you can see they are landing with 300 kg less than required.

Also ZFW of 197.5 tonnes, and 415 pax means their OEW is around 150 tonnes.
 
StTim
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Re: A350-1000 fuel burn

Tue Dec 29, 2020 1:02 pm

zeke wrote:
VSMUT wrote:
6.2 tons per hour over an 8 hour flight.


It will actually be lower than that, looks like they haven’t finished the setup completely. As you can see they are landing with 300 kg less than required.

Also ZFW of 197.5 tonnes, and 415 pax means their OEW is around 150 tonnes.


What changes would affect that deficit other than just adding more fuel?
 
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zeke
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Re: A350-1000 fuel burn

Tue Dec 29, 2020 1:16 pm

Enroute step altitudes, real temperature/wind profile. Could also be constraints on the SID/STAR.

If you look at the variable reserve that should also turn into 1.8 tonnes of spare fuel on arrival if not by burnt enroute.
Last edited by zeke on Tue Dec 29, 2020 1:43 pm, edited 2 times in total.
 
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Starlionblue
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Re: A350-1000 fuel burn

Tue Dec 29, 2020 1:24 pm

StTim wrote:
zeke wrote:
VSMUT wrote:
6.2 tons per hour over an 8 hour flight.


It will actually be lower than that, looks like they haven’t finished the setup completely. As you can see they are landing with 300 kg less than required.

Also ZFW of 197.5 tonnes, and 415 pax means their OEW is around 150 tonnes.


What changes would affect that deficit other than just adding more fuel?


You wouldn't add more fuel for a 300kg nominal deficit unless you'd exhausted all other options. It is practically a rounding error with 61.5 block fuel.

It could be that they haven't entered the step climbs in the flight plan yet. Once that is done you get a more accurate, lower total fuel burn figure.

I'd also be interested to see what happens if the Cost Index is decreased from 120, which is quite high, to somewhere under 50.

Other things you can do are enter accurate en-route winds/temps, and/or a more accurate destination to alternate routing than the default. If you expected a short taxi, you could even adjust the taxi fuel down.
Last edited by Starlionblue on Tue Dec 29, 2020 1:48 pm, edited 1 time in total.
 
VSMUT
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Re: A350-1000 fuel burn

Tue Dec 29, 2020 1:26 pm

Starlionblue wrote:
StTim wrote:
zeke wrote:

It will actually be lower than that, looks like they haven’t finished the setup completely. As you can see they are landing with 300 kg less than required.

Also ZFW of 197.5 tonnes, and 415 pax means their OEW is around 150 tonnes.


What changes would affect that deficit other than just adding more fuel?


You wouldn't add more fuel for a 300kg nominal deficit unless you'd exhausted all other options. It is practically a rounding error with 61.5 block fuel.

It could be that they haven't entered the step climbs in the flight plan yet. Once that is done you get a more accurate, lower total fuel burn figure.

I'd also be interested to see what happens if the Cost Index is decreased from 120, which is quite high, to somewhere under 50.

Other things you can do are enter accurate en-route winds/temps, a more accurate destination to alternate routing than the default. If you expected a short taxi, you could even adjust the taxi fuel down.


Cost index?
 
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zeke
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Re: A350-1000 fuel burn

Tue Dec 29, 2020 1:32 pm

The have a cost index of 120 that photo which is on the high side, probably around M0.86 cruise
 
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Starlionblue
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Re: A350-1000 fuel burn

Tue Dec 29, 2020 1:38 pm

VSMUT wrote:
Starlionblue wrote:
StTim wrote:

What changes would affect that deficit other than just adding more fuel?


You wouldn't add more fuel for a 300kg nominal deficit unless you'd exhausted all other options. It is practically a rounding error with 61.5 block fuel.

It could be that they haven't entered the step climbs in the flight plan yet. Once that is done you get a more accurate, lower total fuel burn figure.

I'd also be interested to see what happens if the Cost Index is decreased from 120, which is quite high, to somewhere under 50.

Other things you can do are enter accurate en-route winds/temps, a more accurate destination to alternate routing than the default. If you expected a short taxi, you could even adjust the taxi fuel down.


Cost index?


The Cost Index can be thought of as the tradeoff between fuel and all the other costs. A higher CI means higher fuel burn but lower sector time. Lower sector time gives lower engine hours, lower crew hours, etc. It isn't a linear relationship, though. Higher CI numbers give you significantly increased fuel burn but only marginally decreased sector time.

The CI is an input you get on the flight plan, as calculated by the planners given current fuel and other costs.

Within reason, pilots can adjust the cost index. You can use a higher cost index (get there faster but use more fuel) in order to make up for a late departure time, for example. Or you can use a lower cost index, say if you want to delay your arrival until a night curfew ends, or if you want to save fuel.
 
StTim
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Re: A350-1000 fuel burn

Tue Dec 29, 2020 1:50 pm

Thanks guys - always learning.
 
xwb565
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Re: A350-1000 fuel burn

Wed Dec 30, 2020 6:19 am

Some more data. Same route length, 40t payload, 15:05 for the 35k, 15:15 for the 77w, 350 with a more premium and heavier cabin, mtow for the 77w and well bellow for the 350. 99.3t trip fuel for the 35k and 777w 125.7t. Temps were on the colder side for both flights.
 
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zeke
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Re: A350-1000 fuel burn

Wed Dec 30, 2020 6:48 am

Something not right there with flight time. The A350 will be around 12 kts faster, it should be 20-30 minutes quicker over 15+ hrs.
 
xwb565
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Re: A350-1000 fuel burn

Wed Dec 30, 2020 7:25 am

My guess is more favourable winds at lower altitudes where the 77w tends to cruise.
 
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zeke
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Re: A350-1000 fuel burn

Wed Dec 30, 2020 7:50 am

xwb565 wrote:
My guess is more favourable winds at lower altitudes where the 77w tends to cruise.


My guess is they are not on the same routes. I have noticed this where I work that flights over the same city pairs maybe flying different routes, the flight plans are made for minimum cost, it maybe more cost effective to fly the A350 a little further to save on some enroute charges. I have noticed this for example EWR/JFK-HKG the 77W is sometimes sent polar and the A350 sent via Canada/Alaska/China avoiding expensive Russian airspace.
 
xwb565
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Re: A350-1000 fuel burn

Wed Dec 30, 2020 8:27 am

zeke wrote:
xwb565 wrote:
My guess is more favourable winds at lower altitudes where the 77w tends to cruise.


My guess is they are not on the same routes. I have noticed this where I work that flights over the same city pairs maybe flying different routes, the flight plans are made for minimum cost, it maybe more cost effective to fly the A350 a little further to save on some enroute charges. I have noticed this for example EWR/JFK-HKG the 77W is sometimes sent polar and the A350 sent via Canada/Alaska/China avoiding expensive Russian airspace.


The air miles flown in this particular case was very similar but I suppose even that probably may not mean identical tracks or winds. I do not have the detailed nav data.
 
SteelChair
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Re: A350-1000 fuel burn

Mon Jan 11, 2021 1:24 am

Hasn't Airbus advertised that the A350 has the lowest fuel burn per seat of any longhaul aircraft in the world? Thats a pretty bold claim, but in this case it appears to be true.

I personally feel like it is an outstanding aircraft. I hate the manual system though, it does not conform to the ATA 100, and there is no traditional QRH. The QRH is essentially a hierarchical computer program that doesn't have page numbers.
 
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Starlionblue
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Re: A350-1000 fuel burn

Mon Jan 11, 2021 3:06 am

SteelChair wrote:
Hasn't Airbus advertised that the A350 has the lowest fuel burn per seat of any longhaul aircraft in the world? Thats a pretty bold claim, but in this case it appears to be true.

I personally feel like it is an outstanding aircraft. I hate the manual system though, it does not conform to the ATA 100, and there is no traditional QRH. The QRH is essentially a hierarchical computer program that doesn't have page numbers.


I'm by no means an expert on ATA100 but I'm looking at the A350 FCOM and all the systems chapters are numbered as per ATA100.


As you say most of the QRH was moved into the non-sensed procedures menu in ECAM. We're left with the "pamphlet" QRH (so nicknamed because it is so thin).

There are no page numbers in the system itself, but the abnormal non-sensed procedures are all listed in the FCOM, at the start of each section, with the prefix [ABN]. (The QRH procedures are, as on the A330, prefixed [QRH]). So the procedures can still be referenced without access to the system.

It does take a bit of getting used to, but on the other hand, so does navigating the QRH on the A330.
 
x1234
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Re: A350-1000 fuel burn

Mon Jan 11, 2021 3:14 pm

If only UA had the A359 or A35K they'd launch SFO-BOM. I read on the UA thread that UA has the 789 to the limit on SFO-DEL with extra contingency fuel because they don't want the flight to divert to Iran, Afghanistan or any other unfriendly countries. This is different than all the other flights TPAC where they don't carry as much contingency fuel.
 
SteelChair
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Re: A350-1000 fuel burn

Mon Jan 11, 2021 4:33 pm

Starlionblue wrote:
SteelChair wrote:
Hasn't Airbus advertised that the A350 has the lowest fuel burn per seat of any longhaul aircraft in the world? Thats a pretty bold claim, but in this case it appears to be true.

I personally feel like it is an outstanding aircraft. I hate the manual system though, it does not conform to the ATA 100, and there is no traditional QRH. The QRH is essentially a hierarchical computer program that doesn't have page numbers.


I'm by no means an expert on ATA100 but I'm looking at the A350 FCOM and all the systems chapters are numbered as per ATA100.


As you say most of the QRH was moved into the non-sensed procedures menu in ECAM. We're left with the "pamphlet" QRH (so nicknamed because it is so thin).

There are no page numbers in the system itself, but the abnormal non-sensed procedures are all listed in the FCOM, at the start of each section, with the prefix [ABN]. (The QRH procedures are, as on the A330, prefixed [QRH]). So the procedures can still be referenced without access to the system.

It does take a bit of getting used to, but on the other hand, so does navigating the QRH on the A330.


Scenario: in flight abnormal occurs and the QRH procedure is run. After completion (Aviate-Navigate-Communicate), the crew calls Dispatch via radio or Satcomm and a discussion ensues. Maintenance may join the call. The crew explains what happened and what they did. Maintenance is looking at their telemetry from the airplane and also the history on the airplane. Dispatch is looking at enroute alternate weather and NOTAMS in case that option is needed. It's a very important conversation and it's a good practice for Dispatch and the crew to confirm that everyone is looking at the same page of the QRH. Ultimately, in the absence of an emergency, the PIC and Dispatcher need to agree to continue or divert.

The A350 doesn't have QRH pages, therefore that can't be verified (which procedure they ran). Most Euro-carriers don't require positive operational control with joint responsibility, so this scenario is not an issue to them, the course of action to be taken is on the pilot's alone. And Airbus is a European company, so I doubt they were thinking of the requirements of FAR 121.533 when they designed the system.
 
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zeke
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Re: A350-1000 fuel burn

Mon Jan 11, 2021 7:02 pm

SteelChair wrote:
Scenario: in flight abnormal occurs and the QRH procedure is run. After completion (Aviate-Navigate-Communicate), the crew calls Dispatch via radio or Satcomm and a discussion ensues. Maintenance may join the call. The crew explains what happened and what they did. Maintenance is looking at their telemetry from the airplane and also the history on the airplane. Dispatch is looking at enroute alternate weather and NOTAMS in case that option is needed. It's a very important conversation and it's a good practice for Dispatch and the crew to confirm that everyone is looking at the same page of the QRH. Ultimately, in the absence of an emergency, the PIC and Dispatcher need to agree to continue or divert.

The A350 doesn't have QRH pages, therefore that can't be verified (which procedure they ran). Most Euro-carriers don't require positive operational control with joint responsibility, so this scenario is not an issue to them, the course of action to be taken is on the pilot's alone. And Airbus is a European company, so I doubt they were thinking of the requirements of FAR 121.533 when they designed the system.


I don’t follow the point you are making at all, the A350 is not a 744, all the ECAMs are generally sensed procedures, if there is a decision to be made during an ECAM procedure, the exact same options are available on flysmart remotely either on a PC or tablet. Flysmart displays the level 1-3 information also.

Essentially the only procedures left in the QRH a dispatcher has no business getting involved with, they are time critical like smoke or fumes, emergency landing, emergency evacuation, and how to restart the EFB. The PIC would be negligent letting a dispatcher getting involved with any of those.
 
AvgWhiteGuy
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Re: A350-1000 fuel burn

Mon Jan 11, 2021 10:39 pm

Quote: "The A350 will be around 12 kts faster, it should be 20-30 minutes quicker over 15+ hrs."

From my knowledge, the 777-300ER's LRC is .84M (and verified by a good friend who flew them, saying, "LRC anywhere near optimum altitude was .84 and change.") So, if we accept that the speed of sound at FL350 and higher (ISA temp) is 573 kts, then 12kts faster is equal to .021M faster. So you're claiming the A350's LRC is .86+ ?
 
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Starlionblue
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Joined: Fri Feb 27, 2004 9:54 pm

Re: A350-1000 fuel burn

Tue Jan 12, 2021 12:08 am

SteelChair wrote:
Starlionblue wrote:
SteelChair wrote:
Hasn't Airbus advertised that the A350 has the lowest fuel burn per seat of any longhaul aircraft in the world? Thats a pretty bold claim, but in this case it appears to be true.

I personally feel like it is an outstanding aircraft. I hate the manual system though, it does not conform to the ATA 100, and there is no traditional QRH. The QRH is essentially a hierarchical computer program that doesn't have page numbers.


I'm by no means an expert on ATA100 but I'm looking at the A350 FCOM and all the systems chapters are numbered as per ATA100.


As you say most of the QRH was moved into the non-sensed procedures menu in ECAM. We're left with the "pamphlet" QRH (so nicknamed because it is so thin).

There are no page numbers in the system itself, but the abnormal non-sensed procedures are all listed in the FCOM, at the start of each section, with the prefix [ABN]. (The QRH procedures are, as on the A330, prefixed [QRH]). So the procedures can still be referenced without access to the system.

It does take a bit of getting used to, but on the other hand, so does navigating the QRH on the A330.


Scenario: in flight abnormal occurs and the QRH procedure is run. After completion (Aviate-Navigate-Communicate), the crew calls Dispatch via radio or Satcomm and a discussion ensues. Maintenance may join the call. The crew explains what happened and what they did. Maintenance is looking at their telemetry from the airplane and also the history on the airplane. Dispatch is looking at enroute alternate weather and NOTAMS in case that option is needed. It's a very important conversation and it's a good practice for Dispatch and the crew to confirm that everyone is looking at the same page of the QRH. Ultimately, in the absence of an emergency, the PIC and Dispatcher need to agree to continue or divert.

The A350 doesn't have QRH pages, therefore that can't be verified (which procedure they ran). Most Euro-carriers don't require positive operational control with joint responsibility, so this scenario is not an issue to them, the course of action to be taken is on the pilot's alone. And Airbus is a European company, so I doubt they were thinking of the requirements of FAR 121.533 when they designed the system.


Like any other procedures, the non-sensed procedures all have unique names that can be referenced in the FCOM. I don't see the problem since pilots, dispatchers and engineers can all easily find the relevant information.

Either way, does the dispatcher really need to know what procedure was run? Isn't he just interested in what systems are inop? In what sort of scenario does the dispatcher need to know exactly what the pilots did to address an issue after the fact?
 
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zeke
Posts: 16432
Joined: Thu Dec 14, 2006 1:42 pm

Re: A350-1000 fuel burn

Tue Jan 12, 2021 3:26 am

AvgWhiteGuy wrote:
Quote: "The A350 will be around 12 kts faster, it should be 20-30 minutes quicker over 15+ hrs."

From my knowledge, the 777-300ER's LRC is .84M (and verified by a good friend who flew them, saying, "LRC anywhere near optimum altitude was .84 and change.") So, if we accept that the speed of sound at FL350 and higher (ISA temp) is 573 kts, then 12kts faster is equal to .021M faster. So you're claiming the A350's LRC is .86+ ?


Who operates aircraft at LRC ?

Airlines operate off ECON speed based off a cost index. I had been in contact with the poster via PM, it turns out the flights were around 12 months apart, not on the same day. I was able to compare two flights on the same day operated by those types over that sort of distance, and it was exactly as I described, around 30 minutes in difference in flight time.

You can verify that for yourself on FR24 with the city pair JFK and HKG, you will find some days where a 77W and A35K have operated over the same city pair recently and the flight time difference is around 30 minutes.
 
xwb565
Posts: 208
Joined: Sun Dec 02, 2018 1:01 pm

Re: A350-1000 fuel burn

Tue Jan 12, 2021 4:41 am

A 777 at a low cost index is closer to mach.83 most of the time. That was incidentally the original design cruise speed.
 
AvgWhiteGuy
Posts: 35
Joined: Tue Jun 25, 2019 2:44 pm

Re: A350-1000 fuel burn

Tue Jan 12, 2021 2:21 pm

LRC is a reference standard, being 99% best range speed, as it applies evenly across all aircraft, so it doesn't matter if no carrier uses it or all carriers use it, it eliminates variables associated with cost index numbers. So the question stands, is your implication that the A350's LRC is .86+?

And the 777 was designed to cruise at .83M, but was found in testing to be .84. Again, it's LRC is .84, so that is the standard by which I choose to judge an aircraft's design speed, as normal CI numbers will have an airliner fly .005-.015 faster, but it is variable - LRC at optimum altitude (and no wind) is NOT variable.

***Question stands, what is A350's LRC at optimum altitude?
 
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zeke
Posts: 16432
Joined: Thu Dec 14, 2006 1:42 pm

Re: A350-1000 fuel burn

Tue Jan 12, 2021 10:09 pm

My implication is the 77W doesn’t get to FL360 until much later in a long haul flight. It’s not unusual for it to start off cruising at FL290 when on a 15 hr flight.

And yes cost index does matter, as the previous poster and myself were giving examples of real flights operated by real airlines where the difference is available for anyone to see on historical FR24 logs.

LRC on the A350 is not a fixed number, nor is optimum altitude, hence the reason asking for a single datapoint is useless.

If you want compare two flights over 15 hrs, compare two flights over 15 hrs, a single data point is irrelevant.
 
AvgWhiteGuy
Posts: 35
Joined: Tue Jun 25, 2019 2:44 pm

Re: A350-1000 fuel burn

Wed Jan 13, 2021 1:38 am

I never asked or commented on the 77W's cruise altitudes, which is well known to start low due to it's high wing loading, my inquiry is, and has been, solely the A350's LRC mach number at optimum altitude, which you now seem to be avoiding the answer to.
And no, cost index has zero effect on LRC - the only speed I have been talking about.
LRC, like MCrit and Force (drag) divergence mach number, does not change but .002 at the most at optimum altitude, no wind, regardless of weight. Do you think MCrit and FDmn change too?

So, if it makes you happy, give me two of the A350's LRC numbers off the FMC at two different weights (data points) that are convenient for you on your next trip. Maybe 260T and 230T for example. Or whatever you choose, but I know I could prove my point re LRC on the plane I fly in under a minute of invested time, to include taking a picture of the FMC and uploading it here. Seems much more simple than sidestepping my very direct question over and over and over.

Awaiting your pictures of the FMC when at or near optimum altitude, negligible wind, and LRC is selected....
 
majano
Posts: 370
Joined: Sun Oct 14, 2018 10:45 am

Re: A350-1000 fuel burn

Wed Jan 13, 2021 9:27 am

AvgWhiteGuy wrote:
I never asked or commented on the 77W's cruise altitudes, which is well known to start low due to it's high wing loading, my inquiry is, and has been, solely the A350's LRC mach number at optimum altitude, which you now seem to be avoiding the answer to.
And no, cost index has zero effect on LRC - the only speed I have been talking about.
LRC, like MCrit and Force (drag) divergence mach number, does not change but .002 at the most at optimum altitude, no wind, regardless of weight. Do you think MCrit and FDmn change too?

So, if it makes you happy, give me two of the A350's LRC numbers off the FMC at two different weights (data points) that are convenient for you on your next trip. Maybe 260T and 230T for example. Or whatever you choose, but I know I could prove my point re LRC on the plane I fly in under a minute of invested time, to include taking a picture of the FMC and uploading it here. Seems much more simple than sidestepping my very direct question over and over and over.

Awaiting your pictures of the FMC when at or near optimum altitude, negligible wind, and LRC is selected....

Is it not because your question is not really relevant? Why should a poster help to add more noise to what should be a focused discussion?
 
Okcflyer
Posts: 876
Joined: Sat May 23, 2015 11:10 pm

Re: A350-1000 fuel burn

Wed Jan 13, 2021 1:30 pm

The A35K's strongest competitor is the A359 (especially later builds). What would the trip fuel had been for the A359 for the above trip photo-documented?

Per several analysis, there is very little, if any, per-seat fuel burn advantage of the K over the 9. Without a unit cost advantage, the primary reason to buy the more expensive stretch (K model) is if the carrier's network needs additional capacity.

Further, how do engine maintenance costs vary between the 9 and K?

The sales data suggest the K's economic advantages over the 9 are usually not justified.
 
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enzo011
Posts: 1982
Joined: Tue Jun 21, 2011 8:12 am

Re: A350-1000 fuel burn

Wed Jan 13, 2021 7:04 pm

Okcflyer wrote:
The A35K's strongest competitor is the A359 (especially later builds). What would the trip fuel had been for the A359 for the above trip photo-documented?

Per several analysis, there is very little, if any, per-seat fuel burn advantage of the K over the 9. Without a unit cost advantage, the primary reason to buy the more expensive stretch (K model) is if the carrier's network needs additional capacity.

Further, how do engine maintenance costs vary between the 9 and K?

The sales data suggest the K's economic advantages over the 9 are usually not justified.



But isn't that true for all models? If you don't need the extra seats the A359 has over the 789 you should look at the 789 instead. Is this is not true for aviation as a whole?
 
Okcflyer
Posts: 876
Joined: Sat May 23, 2015 11:10 pm

Re: A350-1000 fuel burn

Wed Jan 13, 2021 8:36 pm

enzo011 wrote:
Okcflyer wrote:
The A35K's strongest competitor is the A359 (especially later builds). What would the trip fuel had been for the A359 for the above trip photo-documented?

Per several analysis, there is very little, if any, per-seat fuel burn advantage of the K over the 9. Without a unit cost advantage, the primary reason to buy the more expensive stretch (K model) is if the carrier's network needs additional capacity.

Further, how do engine maintenance costs vary between the 9 and K?

The sales data suggest the K's economic advantages over the 9 are usually not justified.



But isn't that true for all models? If you don't need the extra seats the A359 has over the 789 you should look at the 789 instead. Is this is not true for aviation as a whole?


Typically the larger airplanes have a lower CASM (cost per available seat mile).Basically, the cost per seat decreases as the capacity increases.

What’s very unique to the A359/A35K case is that the unit seat costs are effectively the same despite the A35K being larger and more expensive.

In the case of the 787, for any route the 78J can fly, the per-seat costs are materially less than the 789 on the same route. This increases profitability when those other seats are used.
This IS NOT the case for the A35K.

(Ignore revenue management for this ... that actually further helps the smaller airplanes).

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