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Re: 787 vs A350 range

Posted: Sun Sep 29, 2019 9:08 pm
by majano
Vladex wrote:
AECM wrote:
Eyad89 wrote:

And as he said, 6.2 tons is the fuel consumption of the full one hour flight, including take off, climb and cruise.
According to FR24 the recorded data from this "flight" starts at 13:31 UTC and goes until 15:00 UTC. If we account that the total fuel consumption from engine start to engine shutdow was 6,2 tons and that the engines were running for arround 1h30 the average fuel burn per hour is ~ 4,14 ton.


That would be world record and would allow it to fly more than 20 hours but he said before the takeoff that 1 hour burns 6.2 tonnes not the flight itself which is higher than reported here. However the flight was almost full of employees, no children

I am not sure what to make of this. Firstly you claimed that there were "about 250 persons onboard", yet the video states from 13:43 that "... every seat is filled" . The aircraft itself seats 324 passengers. Now you claim that "he said before the takeoff that 1 hour burns 6.2 tons, not the flight itself. The captain states from 7:32 of the video that"...it will take us one hour to reach Paris, with a fuel consumption of 6.2 tons of petrol, which is very low..... "

Please understand that I am not trying to defend the 4.14 calculation you are questioning. Just curious about the claims you made.

Re: 787 vs A350 range

Posted: Mon Sep 30, 2019 12:16 am
by Vladex
majano wrote:
Vladex wrote:
AECM wrote:
According to FR24 the recorded data from this "flight" starts at 13:31 UTC and goes until 15:00 UTC. If we account that the total fuel consumption from engine start to engine shutdow was 6,2 tons and that the engines were running for arround 1h30 the average fuel burn per hour is ~ 4,14 ton.


That would be world record and would allow it to fly more than 20 hours but he said before the takeoff that 1 hour burns 6.2 tonnes not the flight itself which is higher than reported here. However the flight was almost full of employees, no children

I am not sure what to make of this. Firstly you claimed that there were "about 250 persons onboard", yet the video states from 13:43 that "... every seat is filled" . The aircraft itself seats 324 passengers. Now you claim that "he said before the takeoff that 1 hour burns 6.2 tons, not the flight itself. The captain states from 7:32 of the video that"...it will take us one hour to reach Paris, with a fuel consumption of 6.2 tons of petrol, which is very low..... "

Please understand that I am not trying to defend the 4.14 calculation you are questioning. Just curious about the claims you made.


I think I heard earlier in the video that it was 250 passengers but it looks more than 300 . So considering it was almost full occupancy and a takeoff and climb , it makes sense that the fuel burn was little more than usual as stated here.

Re: 787 vs A350 range

Posted: Mon Sep 30, 2019 1:33 pm
by Stitch
Even with 300+ passengers, for a block time of under two hours the plane would have been going out at her Basic Weight plus ~30,000kg of payload (passengers only, likely, so no cargo) and fuel (combined). So I could very well see such a "low" trip fuel value.

Re: 787 vs A350 range

Posted: Tue Oct 01, 2019 1:54 am
by zeke
majano wrote:
I am not sure what to make of this. Firstly you claimed that there were "about 250 persons onboard", yet the video states from 13:43 that "... every seat is filled" . The aircraft itself seats 324 passengers. Now you claim that "he said before the takeoff that 1 hour burns 6.2 tons, not the flight itself. The captain states from 7:32 of the video that"...it will take us one hour to reach Paris, with a fuel consumption of 6.2 tons of petrol, which is very low..... "

Please understand that I am not trying to defend the 4.14 calculation you are questioning. Just curious about the claims you made.


The 6.2 tonne number makes sense.

I ran a plan from TLS to CDG at FL350 with ORY as an alternate. Routing LFBO14R FISTO5R FISTO UY156 FOUCO UT181 POI UT182 KEPER KEPER7W LFPG27L which is a ground distance of 413 nm, ISA deviation is +5, planned flight time 1:06.

The 6.2 tonnes makes total sense, 500 kg would be for taxi before departure, 3.3 tonnes to climb to FL350, 1.5 tonnes for cruise, and 900 kg for descent and landing.

Re: 787 vs A350 range

Posted: Tue Oct 01, 2019 2:40 pm
by majano
zeke wrote:
majano wrote:
I am not sure what to make of this. Firstly you claimed that there were "about 250 persons onboard", yet the video states from 13:43 that "... every seat is filled" . The aircraft itself seats 324 passengers. Now you claim that "he said before the takeoff that 1 hour burns 6.2 tons, not the flight itself. The captain states from 7:32 of the video that"...it will take us one hour to reach Paris, with a fuel consumption of 6.2 tons of petrol, which is very low..... "

Please understand that I am not trying to defend the 4.14 calculation you are questioning. Just curious about the claims you made.


The 6.2 tonne number makes sense.

I ran a plan from TLS to CDG at FL350 with ORY as an alternate. Routing LFBO14R FISTO5R FISTO UY156 FOUCO UT181 POI UT182 KEPER KEPER7W LFPG27L which is a ground distance of 413 nm, ISA deviation is +5, planned flight time 1:06.

The 6.2 tonnes makes total sense, 500 kg would be for taxi before departure, 3.3 tonnes to climb to FL350, 1.5 tonnes for cruise, and 900 kg for descent and landing.

Thanks. Because of the short flight duration, every kilogram makes a difference. If the discussion was an 18 hour flight, the 500 kg required for taxiing would not matter, but it matters greatly in this context.

Re: 787 vs A350 range

Posted: Wed Oct 02, 2019 4:46 am
by Starlionblue
Eyad89 wrote:
Vladex wrote:
According to the capetan, Air France A350-900 delivery flight with about 250 people on board burns 6.2 tonnes for one hour .
https://youtu.be/DqmViXCyVKA?t=433


And as he said, 6.2 tons is the fuel consumption of the full one hour flight, including take off, climb and cruise.


Don't forget taxi fuel, which could be half a ton.

Re: 787 vs A350 range

Posted: Wed Oct 02, 2019 7:40 am
by WIederling
Starlionblue wrote:
Don't forget taxi fuel, which could be half a ton.

To quote
zeke wrote:
I ran a plan from TLS to CDG at FL350 with ORY as an alternate. Routing LFBO14R FISTO5R FISTO UY156 FOUCO UT181 POI UT182 KEPER KEPER7W LFPG27L which is a ground distance of 413 nm, ISA deviation is +5, planned flight time 1:06.

The 6.2 tonnes makes total sense,
. 500 kg would be for taxi before departure,
3,300 kg tonnes to climb to FL350,
1,500 kg tonnes for cruise, and
. 900 kg for descent and landing.


:-)

Re: 787 vs A350 range

Posted: Sat Nov 02, 2019 4:04 pm
by lightsaber
IgorD wrote:
Thomas, I appreciate your critique! But let me explain some things where we differ.

First, FCOM is an official document. It provides datapoints on fuel burn at certain weights and altitudes. When I put these datapoints into a regression, it looks like x = ab + c, where x is fuel burn, a is a coefficient, b is weight and c is a constant. What I found is that a is around 1/38 and c can be set to 0 without a substantial increase in inaccuracy. The model gives R2 in excess of 0,99. In other words, there is a constant fuel burn to weight ratio, which is logical, given that L/D should be more or less constant for the optimal altitude and constant speed. I sufficiently trust these data: the hard work has been done by Boeing in providing the data points, my job was just to find a linear law behind them.

With Airbus it is more tricky, as I don't have access to a nice FCOM with data points. Those I collected from photos. I agree that these data are messier, where speed and temperature play a role (speed can be corrected, as 10 degrees above / below ISA lead to 3% extra or 3% less fuel burn respectively). But again, if one plots the data, there could found an simple law behind them. The deviation from the average of 1/38 to 1/39 is around 2,5%, not 5%, which is the difference between the extremes. I think the difference between specific airframes and engines within the same type can be even larger. This data driven approach is alternative to the engineering one you propose -- and of course I am interested in feedback on it, as my interest is in model validation and not in a discussion on which type is better (I know they are more or less equal, otherwise the market would kill one program over another :)) By the way, both 77W and A346 burn the same for a given weight, circa 1/35 per hour. We know why 77W won -- it is lighter and has some more capacity (deck floor space).

Concerning the argument on a larger wing of A350, I am considering that it is heavier and has more wetted area. So the overall impact on the fuel burn in less clear cut, otherwise the industry would go to the designs with very long wings, which has not happened yet (yes I am aware about gate space issue too :)).

Wings are always optimized for a mission shorter than average. Optimizing for long missions does more to dame short range economics as the climb penalty is huge. Only at cruise does one benefit.

The worst penalty is weight, that is why material changes are key. But with newer underside laminar flow, longer wingspans will happen.

There is a huge gate space cost for wingspan. Folding wingtips mitigate that cost. I could see a new A350 with folding wingtips.

Lightsaber

Re: 787 vs A350 range

Posted: Wed Nov 06, 2019 5:54 am
by Sokes
lightsaber wrote:

Wings are always optimized for a mission shorter than average. Optimizing for long missions does more to dame short range economics as the climb penalty is huge. Only at cruise does one benefit.
Lightsaber



Interesting. I always assumed longer is better beside really short flights. I guess that was my thought: Longer wings enable a plane for a given weight to fly slower. Turboprops are really light, but wingspan is not so little. So even if there is a climb penalty for 20 min, doesn't the rest of the flight compensate for this?
And doesn't the extra lift along the wing during climb help to "lift" the plane?
And why would the A330 NEO add wingspan? It's meant for medium range.

lightsaber wrote:

There is a huge gate space cost for wingspan. Folding wingtips mitigate that cost. I could see a new A350 with folding wingtips.
Lightsaber



We had this discussion earlier with narrowbodies.

7 m/ 64.8 m = 0,108. So the folding mechanism increases the span by 11%.
1.11 * 1.11 = 1.2321. Lift increases roughly 23%.
I thought folding wingtips are too complicated. But one really needs only a "tiny" extension for a lot more lift.
Maybe I should submit to your judgement.
I guess it's not yet out in the open how much extra weight the folding mechanism adds?

https://www.boeing.com/777x/reveal/vide ... g-Wingtip/

Re: 787 vs A350 range

Posted: Wed Nov 27, 2019 11:20 am
by xwb565
slide 40- SQ stating that the 787-10 has 26 % better fuel productivity vs a333 on medium haul and the a350 has 29% better fuel productivity vs the 772 on long haul.

https://www.singaporeair.com/saar5/pdf/ ... fy1920.pdf

Re: 787 vs A350 range

Posted: Fri Nov 29, 2019 3:26 pm
by majano
xwb565 wrote:
slide 40- SQ stating that the 787-10 has 26 % better fuel productivity vs a333 on medium haul and the a350 has 29% better fuel productivity vs the 772 on long haul.

https://www.singaporeair.com/saar5/pdf/ ... fy1920.pdf

Do you happen to know what the LTK / AG is? Or anyone else for that matter?

Re: 787 vs A350 range

Posted: Fri Nov 29, 2019 4:51 pm
by zeke
majano wrote:
Do you happen to know what the LTK / AG is? Or anyone else for that matter?


I posted this on another thread recently as people keep repeating the same junk without knowing what it means

viewtopic.php?t=1435781&p=21822077

“ Garbage in = garbage out. Those figures are based upon a little used LTG/AG basis.

They A333 is 285 seats, 78J 337 seats, 772 266 seats, and 359 medium haul 303 seats.

The Load Tonnes Kilometre (LTK) as computed as a product of network distance (based on Great Circle Distance) and payload, we don’t know what routes they are basing the figures over for each fleet. The seat disparity between types obviously makes up for a lot of the difference. Cargo payload is weighed, hence the weight is known. Passenger weight is the product of passenger numbers and nominal weight, for different classes (J,Y), they have different ratios between types. The American Gallon of fuel (AG) is obtained from fuel receipt as signed by Flight Crew, which is highly dependent of the routes being served.”

Re: 787 vs A350 range

Posted: Fri Nov 29, 2019 6:07 pm
by majano
zeke wrote:
majano wrote:
Do you happen to know what the LTK / AG is? Or anyone else for that matter?


I posted this on another thread recently as people keep repeating the same junk without knowing what it means

viewtopic.php?t=1435781&p=21822077

“ Garbage in = garbage out. Those figures are based upon a little used LTG/AG basis.

They A333 is 285 seats, 78J 337 seats, 772 266 seats, and 359 medium haul 303 seats.

The Load Tonnes Kilometre (LTK) as computed as a product of network distance (based on Great Circle Distance) and payload, we don’t know what routes they are basing the figures over for each fleet. The seat disparity between types obviously makes up for a lot of the difference. Cargo payload is weighed, hence the weight is known. Passenger weight is the product of passenger numbers and nominal weight, for different classes (J,Y), they have different ratios between types. The American Gallon of fuel (AG) is obtained from fuel receipt as signed by Flight Crew, which is highly dependent of the routes being served.”

Thank you very much.

Re: 787 vs A350 range

Posted: Sun Jan 12, 2020 2:57 pm
by xwb565
The a330-900 is proving a real fuel sipper... 40 t payload on 12 hour sectors at 5.3-5.4t per hour with different operators. That span increase is doing wonders. The big trent is not bad either.

Re: 787 vs A350 range

Posted: Sun Jan 12, 2020 4:13 pm
by thepinkmachine
xwb565 wrote:
The a330-900 is proving a real fuel sipper... 40 t payload on 12 hour sectors at 5.3-5.4t per hour with different operators. That span increase is doing wonders. The big trent is not bad either.


Cool. Do you have access to any flight plans or FCOM data? Would love to run a comparison with the 787...

Re: 787 vs A350 range

Posted: Mon Jan 13, 2020 12:53 am
by AECM
xwb565 wrote:
The a330-900 is proving a real fuel sipper... 40 t payload on 12 hour sectors at 5.3-5.4t per hour with different operators. That span increase is doing wonders. The big trent is not bad either.
These 40 ton on 12 hour sectors in a 242 ton A339 means that they are taking off at MTOW?

Re: 787 vs A350 range

Posted: Mon Jan 13, 2020 2:07 am
by xwb565
thepinkmachine wrote:
xwb565 wrote:
The a330-900 is proving a real fuel sipper... 40 t payload on 12 hour sectors at 5.3-5.4t per hour with different operators. That span increase is doing wonders. The big trent is not bad either.


Cool. Do you have access to any flight plans or FCOM data? Would love to run a comparison with the 787...


Unfortunately no...

Re: 787 vs A350 range

Posted: Mon Jan 13, 2020 2:07 am
by xwb565
AECM wrote:
xwb565 wrote:
The a330-900 is proving a real fuel sipper... 40 t payload on 12 hour sectors at 5.3-5.4t per hour with different operators. That span increase is doing wonders. The big trent is not bad either.
These 40 ton on 12 hour sectors in a 242 ton A339 means that they are taking off at MTOW?


No- its below.

Re: 787 vs A350 range

Posted: Mon Jan 13, 2020 12:35 pm
by AECM
xwb565 wrote:
AECM wrote:
xwb565 wrote:
The a330-900 is proving a real fuel sipper... 40 t payload on 12 hour sectors at 5.3-5.4t per hour with different operators. That span increase is doing wonders. The big trent is not bad either.
These 40 ton on 12 hour sectors in a 242 ton A339 means that they are taking off at MTOW?


No- its below.
So the new 251 ton version could possible be an 14 hour sector plane with 40 ton payload?

Re: 787 vs A350 range

Posted: Mon Jan 13, 2020 9:01 pm
by IgorD
Assuming DoW of 137 ton, 40 ton payload = ZFW of 177 ton. Adding 12 hours of 5,3 ton hourly average burn (63,6 ton) would give us 240,6 ton. Given 242 ton MTOW there is only 1,4 ton capacity available for the reserves. Which is less than 30 minutes of hold at 1500.

The only way to make it right is if DoW is much less than 137 ton.

Re: 787 vs A350 range

Posted: Mon Jan 13, 2020 10:23 pm
by xwb565
Dow is far far less than 137t....there are a350s that operate at lighter than that.

Re: 787 vs A350 range

Posted: Mon Jan 13, 2020 10:51 pm
by AECM
xwb565 wrote:
Dow is far far less than 137t....there are a350s that operate at lighter than that.
It's just a guess but I would say that a A339 with a typical C and Y layout and +/- 300 seats total may have a DOW +/- 130 ton

Re: 787 vs A350 range

Posted: Tue Jan 14, 2020 7:24 am
by IgorD
Wiki shows a 137 ton OEW for A339. I know it is not very reliable (and I was myself surprised by this number), but I did not see other data for the empty weight.

In case of a 130 ton DOW, there would be some 8 ton left for the reserves, which would be enough in the majority of cases. Nice.

Re: 787 vs A350 range

Posted: Tue Jan 14, 2020 7:39 am
by Mrakula
Czech airlines A333 has DOW (dry operating weight) 126t and it is almost 19 years old ship. A339 DOW(OEW) would be around 130t but it always depends on seat, galley, lavatory configuration. But still 5,3-5,4t fuel burn per hour with 40t payload on 12h routs sounds rather optimistic for me!

Re: 787 vs A350 range

Posted: Wed Jan 15, 2020 9:51 am
by tommy1808
IgorD wrote:
Wiki shows a 137 ton OEW for A339. I know it is not very reliable (and I was myself surprised by this number), but I did not see other data for the empty weight. .


oh, that is pretty reliable, as in having a proper source, i.e. a proposal to United from, iirc, before the Neo was even launched. So, not reliable for OEW today, and i think so far no one has worked out how much weight Airbus has taken out starting from the early +5t assumption. And 132t don´t seem absurd for a 57 first and business, 32 extra-legroom economy and 214 economy configuration, plus 5t and you have 137t.

Mrakula wrote:
But still 5,3-5,4t fuel burn per hour with 40t payload on 12h routs sounds rather optimistic for me!


Why? Its pretty much what the 787-9 will burn, and they do have the same engines, the Neo is a bit heavier, but has a higher aspect ratio wing to make up for it. I would expect both to burn about the same amount of fuel for the same mission.

best regards
Thomas

Re: 787 vs A350 range

Posted: Wed Jan 15, 2020 11:15 am
by IgorD
tommy1808 wrote:
IgorD wrote:
Wiki shows a 137 ton OEW for A339. I know it is not very reliable (and I was myself surprised by this number), but I did not see other data for the empty weight. .


oh, that is pretty reliable, as in having a proper source, i.e. a proposal to United from, iirc, before the Neo was even launched. So, not reliable for OEW today, and i think so far no one has worked out how much weight Airbus has taken out starting from the early +5t assumption. And 132t don´t seem absurd for a 57 first and business, 32 extra-legroom economy and 214 economy configuration, plus 5t and you have 137t.


I tend to agree -- I was surprised by this number. Given that recent builds of A333 have a DOW of 121-123 (Turkish Airlines), the A339 may be even in the range of 121-123 + 5 = circa 126-129 ton.
I am not surprised that it burns 1/38,5 of its weight per hour -- it is slightly better than A359 per hour (1/38) ceteris paribus, although A339 flies some 3-4% slower (it is still a .82 machine?).

Re: 787 vs A350 range

Posted: Wed Jan 15, 2020 11:42 am
by AECM
Hifly operates two A339 and according to their website:

CS-TKY - C18Y353 - DOW = 126 ton
9H-SZN - C32W21Y237 - DOW =132,505 ton

For comparison they also have a former Singapore A333 that is 6,5 years old

9H-TAJ - C30Y255 - DOW = 123,860 ton

Re: 787 vs A350 range

Posted: Wed Jan 15, 2020 12:00 pm
by IgorD
Cool that Hifly publish the data of their aircraft!
I would take these data with a pinch of salt though. For instance they say for one of their machines that the DOW is 126 ton and MZF is 177, while max payload is 45 ton. 177-126 =51 -- that should be their payload, or another explanation is that they confuse the DOW with OEW.

Re: 787 vs A350 range

Posted: Sun Jan 26, 2020 10:42 am
by zeke
IgorD wrote:
Cool that Hifly publish the data of their aircraft!
I would take these data with a pinch of salt though. For instance they say for one of their machines that the DOW is 126 ton and MZF is 177, while max payload is 45 ton. 177-126 =51 -- that should be their payload, or another explanation is that they confuse the DOW with OEW.



The maximum payload figure published is simply the sum of the cargo hold maximum values

22,861 + 18,507 + 3,468 = 44,836

Re: 787 vs A350 range

Posted: Sun Jan 26, 2020 1:52 pm
by xwb565
The a339 is not 5t heavier than the a333. Yesterday's 777x ff and the preceding media briefings saw some very tall claims of efficiency over the a35k. I don't put it past Boeing and G.E(in particular) to deliver on some of these claims. Boeing need not make any claims as the 9x deals with a different mission. However to give an idea of the enormity of what they are up against here are some numbers- 16hrs trip, 108t of fuel used and 50t of payload carried. This from an a35k with an extremely heavy configuration. Of course things vary with different conditions.

Re: 787 vs A350 range

Posted: Mon Jan 27, 2020 3:32 am
by Zkpilot
xwb565 wrote:
The a339 is not 5t heavier than the a333. Yesterday's 777x ff and the preceding media briefings saw some very tall claims of efficiency over the a35k. I don't put it past Boeing and G.E(in particular) to deliver on some of these claims. Boeing need not make any claims as the 9x deals with a different mission. However to give an idea of the enormity of what they are up against here are some numbers- 16hrs trip, 108t of fuel used and 50t of payload carried. This from an a35k with an extremely heavy configuration. Of course things vary with different conditions.

Yes I’d be very interested to hear how a 779 compares to A35K. Obviously the 779 is a much heavier bird, but then it’s also larger and does have bigger wings. So how much can it haul? How far can it haul? How much fuel does it use? Those are all going to be the big questions. For 90% of missions I think the A35K is going to be better suited for most, but we’ll see.

Re: 787 vs A350 range

Posted: Mon Jan 27, 2020 3:37 am
by LCDFlight
I would find trip fuel comparison of 77W versus 777-9 more interesting than 777-9 versus A35K. The latter two are not even in the same size class. The wording of "10% better cost per seat" is notoriously open to assumptions about seat configuration and capital cost. In other words, it has no meaning at all. Airbus will say A35K has 10% better seat mile cost versus 777-9. And there will be facts supporting both opposite statements.

Trip fuel burn is the real issue at end of day. What routes justify 777X's increased trip fuel burn versus A350 and which do not. That will determine the sales price of the 777X. If there are no routes then the 777X will be worth near zero. I expect it has a niche on the big end, namely replacing A380s.

What will be the difference in trip fuel burn for 777-9 versus A388, highly highly interesting question, but outside this thread.

Re: 787 vs A350 range

Posted: Mon Jan 27, 2020 7:08 am
by RJMAZ
The performance of an aircraft can be measured three ways.

1) Fuel burn per kg of payload.
2) Fuel burn per square metre of cabin area.
3) Total trip fuel burn.

It is a balance of all three. If an aircraft if superior in all three then it will easily sell 10:1 over the inferior aircraft.

A simple stretch like the 787-10 significantly improved fuel burn per square meter of cabin area. Fuel burn per kg and total trip fuel burn become slightly worse.

The 777-200LR is the opposite.

Airlines have a very slight bias towards total trip fuel burn which generally reflects a desire for smaller aircraft with increased frequency. The A380 for example has excellent fuel burn per kg of payload and square metre of cabin area but the total trip cost is very high.

This is why the 767 remained in service for so long. It has lower trip burn on medium haul even compared to the latest 787. But the 767 guzzled fuel in terms of payload weight and cabin area.

The smaller and lighter 787 family has an advantage over the A350 in this regard. Likewise the A350 has the same advantage over the 777X.

Re: 787 vs A350 range

Posted: Mon Jan 27, 2020 8:30 am
by SQ22
Please remember this thread is about B787 vs. A350 range. Feel free to open a separate thread if you want to discuss other topics. Thanks.