thepinkmachine wrote:

40 T payload is indeed on the high side for ULR flights. If anyone’s interested, here’s trip fuel burn data for [email protected] 25T payload, which is more or less what QF9/10 carries. Incidentally, 25T is also where the 789 becomes fuel volume limited. At higher ranges/lower payloads it will run out of fuel volume before it hits the MTOW. Assumptions for the numbers below are same as before.

4000NM - 41.5T
5200NM - 55.0T
6000NM - 64.6T
7200NM - 79.8T
8000NM - 90.5T
8400NM - 96.0T

The 280T A350 maxes out on fuel at about 32~35T payload and carries some 9T fuel more than the 789. This is offset by somewhat higher fuel consumption. I guess the A350 still has a slight edge, but at extreme distances and low payloads they come close to each other. How close would depend on how much more the 350 burns. Zeke?

Thanks for the data. My concern all along was the assumed 40t payload when comparing the 789 vs the A359. To me, a much more realistic payload comparison would be in the 30-35t range. This would generally include full pax and bags and a few tons of cargo.

On ULH sectors i would think cargo is much less a priority as cargo doesn't mind routing through a hub or layovers. I would be very interested to see a comparison of both frames at 30-35t of payload to see if that produces a meaningful difference.

Thanks again for the info.


Edit: On a provided payload range chart it looks like your 41.5t of fuel burn at 4000nm is exactly correct for the 789 with a 25t payload. The A359 under the exact same conditions appears to burn about 5t more fuel. This makes sense to me as the A359 is a heavier aircraft with a larger wetted area.

ElroyJetson wrote:

thepinkmachine wrote:

40 T payload is indeed on the high side for ULR flights. If anyone’s interested, here’s trip fuel burn data for [email protected] 25T payload, which is more or less what QF9/10 carries. Incidentally, 25T is also where the 789 becomes fuel volume limited. At higher ranges/lower payloads it will run out of fuel volume before it hits the MTOW. Assumptions for the numbers below are same as before.

4000NM - 41.5T
5200NM - 55.0T
6000NM - 64.6T
7200NM - 79.8T
8000NM - 90.5T
8400NM - 96.0T

The 280T A350 maxes out on fuel at about 32~35T payload and carries some 9T fuel more than the 789. This is offset by somewhat higher fuel consumption. I guess the A350 still has a slight edge, but at extreme distances and low payloads they come close to each other. How close would depend on how much more the 350 burns. Zeke?

Thanks for the data. My concern all along was the assumed 40t payload when comparing the 789 vs the A359. To me, a much more realistic payload comparison would be in the 30-35t range. This would generally include full pax and bags and a few tons of cargo.

On ULH sectors i would think cargo is much less a priority as cargo doesn't mind routing through a hub or layovers. I would be very interested to see a comparison of both frames at 30-35t of payload to see if that produces a meaningful difference.

Thanks again for the info.


Edit: On a provided payload range chart it looks like your 41.5t of fuel burn at 4000nm is exactly correct for the 789 with a 25t payload. The A359 under the exact same conditions appears to burn about 5t more fuel. This makes sense to me as the A359 is a heavier aircraft with a larger wetted area.

Could you reference the data for the A359 fuel burn with a load of 25T?

ElroyJetson wrote:

Thanks for the data. My concern all along was the assumed 40t payload when comparing the 789 vs the A359. To me, a much more realistic payload comparison would be in the 30-35t range. This would generally include full pax and bags and a few tons of cargo.

On ULH sectors i would think cargo is much less a priority as cargo doesn't mind routing through a hub or layovers. I would be very interested to see a comparison of both frames at 30-35t of payload to see if that produces a meaningful difference.

Thanks again for the info.


Edit: On a provided payload range chart it looks like your 41.5t of fuel burn at 4000nm is exactly correct for the 789 with a 25t payload. The A359 under the exact same conditions appears to burn about 5t more fuel. This makes sense to me as the A359 is a heavier aircraft with a larger wetted area.

The data I have is provided for weights in 20T increments. To obtain data 30-35T payload, a simple interpolation should do accurately enough. I must admit I’m being a bit lazy. I chose 25T payload because I could read it straight from the table . I’m pretty sure there are people on this forum who can do interpolations better than me

As for fuel burn difference of 5t between the 787 and A350 - that looks a bit steep. My guess it is due to different assumptions in the payload-range chart.

majano wrote:

Could you reference the data for the A359 fuel burn with a load of 25T?

Unfortunately I don’t have A359 data and AFAIK it doesn’t come in paper format anymore. Maybe Zeke could help.

majano wrote:

Could you reference the data for the A359 fuel burn with a load of 25T?

From two samples for the latest airframes(difficult to find more as the payload carried is usually much higher than 25t) - 5.6t/hr over 13.5 hours.

thepinkmachine wrote:

Unfortunately I don’t have A359 data and AFAIK it doesn’t come in paper format anymore. Maybe Zeke could help.

What you get from the ACAPS provided p/r chart is
second turning point should have loaded 101t fuel.
MTOW( 254t ) - max _useable_ fuel(101t) = 153t ( probably less due to "unuseable" fuel )
MZFW ( 181t ) - 153t = 28t below max payload

same payload brings you to 4100nm with 200t TOW resp. 48t fuel load ( not used )

P/R charts are payload referenced by Airbus but OEW+payload by Boeing.
With Airbus you can backtrack (assumed) OEW via MZFW - max struct. payload (given)
while Boeing does not really allow to separate OEW and payload.

xwb565 wrote:

majano wrote:

Could you reference the data for the A359 fuel burn with a load of 25T?

From two samples for the latest airframes(difficult to find more as the payload carried is usually much higher than 25t) - 5.6t/hr over 13.5 hours.

Thanks, this helps. With this information, I can only conclude that the 5T difference referred to by ElroyJetson above was a misreading of Wlederling's graph which showed 787-9 with a load of 25T whilst the A359 was still with 40T. As the Pinkmachine says, A 5T difference for a 4,000NM mission is a lot.

majano wrote:

I can only conclude that the 5T difference referred to by ElroyJetson above was a misreading of Wlederling's graph which showed 787-9 with a load of 25T whilst the A359 was still with 40T.

That "misreading" must have taken a real effort. The tagging was obvious enough afaics.

With the initial graph showing 789 and 359 overlaying tightly @40t payload
it is fantasy to expect the gap to widen with lower payloads to show a significant advantage.

We could compare the "zero payload" ranges
Actually the "payload derate per range increase" i.e. is a pretty telling metric.

majano wrote:

xwb565 wrote:

majano wrote:

Could you reference the data for the A359 fuel burn with a load of 25T?

From two samples for the latest airframes(difficult to find more as the payload carried is usually much higher than 25t) - 5.6t/hr over 13.5 hours.

Thanks, this helps. With this information, I can only conclude that the 5T difference referred to by ElroyJetson above was a misreading of Wlederling's graph which showed 787-9 with a load of 25T whilst the A359 was still with 40T. As the Pinkmachine says, A 5T difference for a 4,000NM mission is a lot.

You are correct. I thought both frames were carrying 25t payloads. I assumed this because the chart data exactly agreed with pink machines FCOM data.

ElroyJetson wrote:

You are correct. I thought both frames were carrying 25t payloads. I assumed this because the chart data exactly agreed with pink machines FCOM data.

"both 25t" :: Why should that have been the case?

The updated graph is the exact same one posted previously ( with *@40t data ) and overlayed by the [email protected] date kindly provided.
Anybody able to provide the complementary set for the [email protected] ? I'll add it in and post again.

WIederling wrote:

ElroyJetson wrote:

You are correct. I thought both frames were carrying 25t payloads. I assumed this because the chart data exactly agreed with pink machines FCOM data.

"both 25t" :: Why should that have been the case?

The updated graph is the exact same one posted previously ( with *@40t data ) and overlayed by the [email protected] date kindly provided.
Anybody able to provide the complementary set for the [email protected] ? I'll add it in and post again.

Do you think that is necessary? You indicated fuel burn differences between the two aircraft should basically stay the same regardless of payload.

andrej wrote:

Hey guys,
today I came across this video on the YouTube.
Ethiopian 602 flight from Addis Ababa to Dubai. Allow me to share with you fuel page screen shot and a link to the video.
Maybe you will find it useful and it may act as another real world data on the fuel consumption.



Source: https://youtu.be/KItuLnhdPXo?t=243

Thank you for this screenshot and your input. I am not technical at all coming form an accounting background, so my attempt may have plenty of errors which I am happy to be corrected on.

The fuel burn on the trip was 22.1T, being the TOW (take-off weight) of 217.4T less the LW (landing weight) of 195.3T. 217.4 – 195.3 = 22.1. As a cross-check, at the point of the trip when the screenshot was made, the GW (gross weight) was 197.1T, and FOB (fuel on board) 11.3T. To complete the trip, a further 1.9T was required. (217.4 – 197.1 + 1.9) = 22.2. A difference of 0.1T.

To determine the fuel burn per hour requires the number of hours for the trip. Not knowing the specific date of the trip, I referred to Flighradar24 for the average flight time of for ET602 (approximately 3:37 for the last seven or so trips). The burn per hour was therefore 22.1 / 3.616667 = 6.110.

majano wrote:

andrej wrote:

Hey guys,
today I came across this video on the YouTube.
Ethiopian 602 flight from Addis Ababa to Dubai. Allow me to share with you fuel page screen shot and a link to the video.
Maybe you will find it useful and it may act as another real world data on the fuel consumption.



Source: https://youtu.be/KItuLnhdPXo?t=243

Thank you for this screenshot and your input. I am not technical at all coming form an accounting background, so my attempt may have plenty of errors which I am happy to be corrected on.

The fuel burn on the trip was 22.1T, being the TOW (take-off weight) of 217.4T less the LW (landing weight) of 195.3T. 217.4 – 195.3 = 22.1. As a cross-check, at the point of the trip when the screenshot was made, the GW (gross weight) was 197.1T, and FOB (fuel on board) 11.3T. To complete the trip, a further 1.9T was required. (217.4 – 197.1 + 1.9) = 22.2. A difference of 0.1T.

To determine the fuel burn per hour requires the number of hours for the trip. Not knowing the specific date of the trip, I referred to Flighradar24 for the average flight time of for ET602 (approximately 3:37 for the last seven or so trips). The burn per hour was therefore 22.1 / 3.616667 = 6.110.

Good maths-fu there, but 6.1/hour on such a short trip with such a low TOW seems quite high tbh. I'd expect it to be well below 6 tons/hour.

Starlionblue wrote:

majano wrote:

andrej wrote:

Hey guys,
today I came across this video on the YouTube.
Ethiopian 602 flight from Addis Ababa to Dubai. Allow me to share with you fuel page screen shot and a link to the video.
Maybe you will find it useful and it may act as another real world data on the fuel consumption.



Source: https://youtu.be/KItuLnhdPXo?t=243

Thank you for this screenshot and your input. I am not technical at all coming form an accounting background, so my attempt may have plenty of errors which I am happy to be corrected on.

The fuel burn on the trip was 22.1T, being the TOW (take-off weight) of 217.4T less the LW (landing weight) of 195.3T. 217.4 – 195.3 = 22.1. As a cross-check, at the point of the trip when the screenshot was made, the GW (gross weight) was 197.1T, and FOB (fuel on board) 11.3T. To complete the trip, a further 1.9T was required. (217.4 – 197.1 + 1.9) = 22.2. A difference of 0.1T.

To determine the fuel burn per hour requires the number of hours for the trip. Not knowing the specific date of the trip, I referred to Flighradar24 for the average flight time of for ET602 (approximately 3:37 for the last seven or so trips). The burn per hour was therefore 22.1 / 3.616667 = 6.110.

Good maths-fu there, but 6.1/hour on such a short trip with such a low TOW seems quite high tbh. I'd expect it to be well below 6 tons/hour.

Correct me if I'm wrong but if we assume a DOW of +-135t (may be high but ET does have a high density config), this flight looks like it was carrying quite a load.

ZFW 185.8t - DOW (+-)135t = (+-)50t payload. On an ET A359 that can account for +-35t pax/bags + 15t cargo.

Could this not account for a higher-than-average fuel burn?

MoKa777 wrote:

Starlionblue wrote:

majano wrote:

Thank you for this screenshot and your input. I am not technical at all coming form an accounting background, so my attempt may have plenty of errors which I am happy to be corrected on.

The fuel burn on the trip was 22.1T, being the TOW (take-off weight) of 217.4T less the LW (landing weight) of 195.3T. 217.4 – 195.3 = 22.1. As a cross-check, at the point of the trip when the screenshot was made, the GW (gross weight) was 197.1T, and FOB (fuel on board) 11.3T. To complete the trip, a further 1.9T was required. (217.4 – 197.1 + 1.9) = 22.2. A difference of 0.1T.

To determine the fuel burn per hour requires the number of hours for the trip. Not knowing the specific date of the trip, I referred to Flighradar24 for the average flight time of for ET602 (approximately 3:37 for the last seven or so trips). The burn per hour was therefore 22.1 / 3.616667 = 6.110.

Good maths-fu there, but 6.1/hour on such a short trip with such a low TOW seems quite high tbh. I'd expect it to be well below 6 tons/hour.

Correct me if I'm wrong but if we assume a DOW of +-135t (may be high but ET does have a high density config), this flight looks like it was carrying quite a load.

ZFW 185.8t - DOW (+-)135t = (+-)50t payload. On an ET A359 that can account for +-35t pax/bags + 15t cargo.

Could this not account for a higher-than-average fuel burn?

Gross weight is gross weight. When it comes to fuel burn per hour, the aircraft doesn't much care if the weight is OEW, cargo, pax, or fuel.

TOW of 217 isn't a big number for an A359, so 6+ tons/hours seems a bit high to me. That being said, I don't have the flight plan so I don't know if there are any specific considerations.

Starlionblue wrote:

MoKa777 wrote:

Starlionblue wrote:

Good maths-fu there, but 6.1/hour on such a short trip with such a low TOW seems quite high tbh. I'd expect it to be well below 6 tons/hour.

Correct me if I'm wrong but if we assume a DOW of +-135t (may be high but ET does have a high density config), this flight looks like it was carrying quite a load.

ZFW 185.8t - DOW (+-)135t = (+-)50t payload. On an ET A359 that can account for +-35t pax/bags + 15t cargo.

Could this not account for a higher-than-average fuel burn?

Gross weight is gross weight. When it comes to fuel burn per hour, the aircraft doesn't much care if the weight is OEW, cargo, pax, or fuel.

TOW of 217 isn't a big number for an A359, so 6+ tons/hours seems a bit high to me. That being said, I don't have the flight plan so I don't know if there are any specific considerations.

Aah, you're right. I hadn't considered that!

majano wrote:

Thank you for this screenshot and your input. I am not technical at all coming form an accounting background, so my attempt may have plenty of errors which I am happy to be corrected on.

The fuel burn on the trip was 22.1T, being the TOW (take-off weight) of 217.4T less the LW (landing weight) of 195.3T. 217.4 – 195.3 = 22.1. As a cross-check, at the point of the trip when the screenshot was made, the GW (gross weight) was 197.1T, and FOB (fuel on board) 11.3T. To complete the trip, a further 1.9T was required. (217.4 – 197.1 + 1.9) = 22.2. A difference of 0.1T.

To determine the fuel burn per hour requires the number of hours for the trip. Not knowing the specific date of the trip, I referred to Flighradar24 for the average flight time of for ET602 (approximately 3:37 for the last seven or so trips). The burn per hour was therefore 22.1 / 3.616667 = 6.110.

At 160 nm they should be above FL400, being at FL300 puts them well below profile.
They are flying at LRC not ECON
The temperature is not ISA
The video was taken probably in Q4 2017, the BUBIN 9C STAR is not longer in effect in DXB, they chart they are using is the AUG 2017 cycle.
DXB STARS get you down low early and a lot of low level track miles, they probably would have “made” fuel on the arrival as you hear them get directs
They are carrying Muscat (MCT) as an alternate which is a long way from DXB
None of the last 7 ET602 flights have been in an A350
Captain does not have his hand on the side stick during the final approach

majano wrote:

andrej wrote:

Hey guys,
today I came across this video on the YouTube.
Ethiopian 602 flight from Addis Ababa to Dubai. Allow me to share with you fuel page screen shot and a link to the video.
Maybe you will find it useful and it may act as another real world data on the fuel consumption.

Source: https://youtu.be/KItuLnhdPXo?t=243

Thank you for this screenshot and your input. I am not technical at all coming form an accounting background, so my attempt may have plenty of errors which I am happy to be corrected on.

The fuel burn on the trip was 22.1T, being the TOW (take-off weight) of 217.4T less the LW (landing weight) of 195.3T. 217.4 – 195.3 = 22.1. As a cross-check, at the point of the trip when the screenshot was made, the GW (gross weight) was 197.1T, and FOB (fuel on board) 11.3T. To complete the trip, a further 1.9T was required. (217.4 – 197.1 + 1.9) = 22.2. A difference of 0.1T.

To determine the fuel burn per hour requires the number of hours for the trip. Not knowing the specific date of the trip, I referred to Flighradar24 for the average flight time of for ET602 (approximately 3:37 for the last seven or so trips). The burn per hour was therefore 22.1 / 3.616667 = 6.110.

According to the producer of the video the flight time of ET602 was 3 minutes more than the average at 3h40

3h40 would take the burn down to 6.027.

zeke wrote:

Captain does not have his hand on the side stick during the final approach

I noticed that too. And the first officer is grabbing the reverse before touchdown.

346 vs 77w discussed before? its interesting too. and 744

Armadillo1 wrote:

346 vs 77w discussed before? its interesting too. and 744

Very relevant between the A350-1000 vs the 777-8, where the 777-8 would carry more payload mass, less cabin area, less cargo area, slower, higher navigation charges, and higher fuel burn.

However between the A350-900 and 787-9 you can see from above data for the same payload the A350-900 burns slightly less fuel at longer ranges, and has more cabin area than the 787-9.

The empty weight difference between the 787-9 and A350-900 is not that much, less than 5%, where the empty weight difference between the A350–1000 and 777-8 is more like 15%. A loaded A350-1000 is about the weight of an empty 77X.

thanks, but i asked for something else?

Well if you could actually compose a sentence that contained verbs and present a question rather than a statement with an embedded question mark, we could then address it.

Armadillo1 wrote:

346 vs 77w discussed before? its interesting too. and 744

Ever cared to notice the thread name?

I guess you should go and open a new thread, with a title reflecting your question.

Cheers, Adam

346, 77W and 744 fuel burn comparison was discussed earlier?

my english very bad now, but i believe digits 346 and 778 still different a bit.

I am having enough trouble getting the time to look at the A350-1000 data than opening up the books to get the data on the 346, 77W, and 744. I am not that interested in those anymore as they are all yesterdays technology.

zeke wrote:

Armadillo1 wrote:

346 vs 77w discussed before? its interesting too. and 744

Very relevant between the A350-1000 vs the 777-8, where the 777-8 would carry more payload mass, less cabin area, less cargo area, slower, higher navigation charges, and higher fuel burn.

However between the A350-900 and 787-9 you can see from above data for the same payload the A350-900 burns slightly less fuel at longer ranges, and has more cabin area than the 787-9.

The empty weight difference between the 787-9 and A350-900 is not that much, less than 5%, where the empty weight difference between the A350–1000 and 777-8 is more like 15%. A loaded A350-1000 is about the weight of an empty 77X.

You keep stating in thread after thread that the fuel burn is basically the same between the 789 and the A359. What you do not say is you arbitrarily picked a heavy payload of 40t that favors the A359.

I would love to see the same comparison at a more realistic payload of 30 to 35t. When I asked your "peer review" pal pink machine this question he said he had no idea how the two planes would compare at these payload levels because the analysis was never done.

So before you flame me, run the analysis at different payload levels and see if the same numbers hold. My guess is they do not, but I do not accept the numbers at only one (high) payload level. If the numbers hold across different payloads and distances you have a solid argument.

ElroyJetson wrote:

You keep stating in thread after thread that the fuel burn is basically the same between the 789 and the A359. What you do not say is you arbitrarily picked a heavy payload of 40t that favors the A359.

I would love to see the same comparison at a more realistic payload of 30 to 35t. When I asked your "peer review" pal pink machine this question he said he had no idea how the two planes would compare at these payload levels because the analysis was never done.

I didn’t pick the payload, go back earlier in this thread you will find it was thepinkmachine. You have accused me several times of doing this to favour A350 when it wasn’t me in the first place. Not the first time I have corrected you, you are now just deliberately trying to antagonise me.

If you were to look at the Breguet Range Equation, keeping everything the same for the same range, except for the landing weight (Wf to take into account the payload difference), Wi the takeoff weight would need to be adjusted by the same proportion to keep the ratio of ln(Wi/Wf) the same.



That equation assumes constant altitude.

However in reality lowering the payload will favour the A350 as higher cruise altitudes would be achieved earlier, and it would subsequently step climb also earlier. That would be valid over commercially viable loads.

If the aircraft is so light it goes straight to FL430 on a long haul flight it isn’t commercially viable in my view.

zeke wrote:

ElroyJetson wrote:

You keep stating in thread after thread that the fuel burn is basically the same between the 789 and the A359. What you do not say is you arbitrarily picked a heavy payload of 40t that favors the A359.

I would love to see the same comparison at a more realistic payload of 30 to 35t. When I asked your "peer review" pal pink machine this question he said he had no idea how the two planes would compare at these payload levels because the analysis was never done.

I didn’t pick the payload, go back earlier in this thread you will find it was thepinkmachine. You have accused me several times of doing this to favour A350 when it wasn’t me in the first place. Not the first time I have corrected you, you are now just deliberately trying to antagonise me.

If you were to look at the Breguet Range Equation, keeping everything the same for the same range, except for the landing weight (Wf to take into account the payload difference), Wi the takeoff weight would need to be reduced by the same proportion to keep the ratio of ln(Wi/Wf) the same.



That equation assumes constant altitude.

However in reality lowering the payload will favour the A350 as higher cruise altitudes would be achieved earlier, and it would subsequently step climb also earlier. That would be valid over commercially viable loads.

If the aircraft is so light it goes straight to FL430 on a long haul flight it isn’t commercially viable in my view.

My apologies if you did not pick the payload level. The fact remains the analysis is limited to only one payload.

If we were to compare the 77L as an example versus the A359, and I arbitrarily picked a 50t payload over a 6000 nm distance, I would think the 77L would compare favorably. However, i have no doubt the A359 across most missions looks much better. The 77L carries more payload farther.

The A359 carries more payload farther than the 789. However, unless you look at different payloads across different distances to make a blanket statement that fuel burn is essentially the same is misleading imho. That is my only point.

ElroyJetson wrote:

If we were to compare the 77L as an example versus the A359, and I arbitrarily picked a 50t payload over a 6000 nm distance, I would think the 77L would compare favorably. However, i have no doubt the A359 across most missions looks much better. The 77L carries more payload farther.

The A350-900 will do 50 tonnes to 6000 nm, and would not be MTOW limited.

ElroyJetson wrote:

The A359 carries more payload farther than the 789. However, unless you look at different payloads across different distances to make a blanket statement that fuel burn is essentially the same is misleading imho. That is my only point.

I didnt say the fuel burn would be the same, I said keeping the everthing constant except the ratio of ln(W initil/W landing) would be the same.



W initial = Landing weight + fuel
W landing = landing weight

let S = ln(W initil/W landing)
let f = fuel
let b = W landing
Let a = W initial = b + f

Therefore S = ln((b+f)/b) = ln(b+f) - ln(b) (standard law of logarithms)

rearranging

ln(b+f) = S + ln(b)
b+f = e^(S + ln(b))
f=[e^(S + ln(b))]-b

Take numbers from earlier in the thread, 787-9, 6000 nm 40 tonne payload, fuel burn 70 tonnes, landing weight 175 tonnes, takeoff weight 245 tonnes

S=ln(245/175)=0.3364

Now reduce payload by 15 tonnes down to 25 tonnes, the landing weight would now be 160 tonnes.

f=[e^(0.3364 + ln(160))]-160 = 64 tonnes, look above thepinkmachine had 64.6 tonnes.

Now do the same for the A350-900, 6000 nm 40 tonne payload, fuel burn 70.3 tonnes, landing weight 183 tonnes, takeoff weight 253.3 tonnes

S=ln(253.3/183)=0.3250

f=[e^(0.3250 + ln(168))]-168 = 64.53 tonnes

So at 40 tonnes payload at 6000 nm it was 70 vs 70.3 which is 0.4285%, and at 25 tonnes the estimate by the equation would be 64 (787-9) to 64.53 (A350-900) which is 0.8281 %. That is very little fuel burn difference for the flexibility the the airframe would provide. Using the equation I see the 787-9 would hit the MTOW limit at a payload of 46.25 tonnes at 6000 nm, that gives a fuel burn of 72.5 tonnes. For the same payload and range the equation gives 72.7 tonnes of fuel for the A350-900. The A350-900 could carry 57 tonnes (about 10 tonnes more than the 787-9) before it hits a MTOW of 277 tonnes for a fuel burn of 76.86 tonnes.

I noted above the equation assumes constant altitude, where in real life the aircraft would step climb resulting in lower fuel burns.

zeke wrote:

That equation assumes constant altitude.

Whilst I agree with the basic premise of what you are trying to say and without knowing location specific conditions for every flight then an approximation to Breguet is close enough. It does however not assume constant altitude it assumes constant L/D and a constant velocity so must be assuming a cruise climb and not constant altitude. We will then of course get in to a scenario that L/D will not actually be constant in that case because of the compressability effects but still its a good enough approximation as everything becomes a total hassle to calculate because its completely non linear and needs wind tunnel data on specific sections and that's where we need the big bucks! I'm willing to do that testing if someone wants to stump up that cash to keep this thread going

Fred

flipdewaf wrote:

Whilst I agree with the basic premise of what you are trying to say and without knowing location specific conditions for every flight then an approximation to Breguet is close enough. It does however not assume constant altitude it assumes constant L/D and a constant velocity so must be assuming a cruise climb and not constant altitude. We will then of course get in to a scenario that L/D will not actually be constant in that case because of the compressability effects but still its a good enough approximation as everything becomes a total hassle to calculate because its completely non linear and needs wind tunnel data on specific sections and that's where we need the big bucks!

Strictly speaking yes, everything apart from the ln(Wi/Wf) would be called the Range Factor (Fr) for a climbing cruise at MRC or LRC. I agree the variations are non linear at constant altitude, they are however small enough for the application here when looking at constant altitude. Prior experience in this sort of work has given me confidence within 0.1% to use what is effectively an average TSFC and L/D.

The method I presented is a quick way to extrapolate from known data with new boundary conditions that is close enough to the data published Boeing and Airbus.

There is reportedly up to 300kg per hour fuel burn difference between older a350-900s and the newest ones with larger winglets (and other mods) for similar payloads and trip lengths.

xwb565 wrote:

There is reportedly up to 300kg per hour fuel burn difference between older a350-900s and the newest ones with larger winglets (and other mods) for similar payloads and trip lengths.

Dear xwb565,

This 300kg figure would mean a 5.5% difference between "old" and newer 350-900s - this sounds quite a lot to me.
The figures that were mentioned here were more like 2% for the wing and winglet modifications, which is already quite a big improvement on a still almost brand-new clean sheet aircraft design.

Would you have a source for us?

Best regards,
Hendric

hitower3 wrote:

xwb565 wrote:

There is reportedly up to 300kg per hour fuel burn difference between older a350-900s and the newest ones with larger winglets (and other mods) for similar payloads and trip lengths.

Dear xwb565,

This 300kg figure would mean a 5.5% difference between "old" and newer 350-900s - this sounds quite a lot to me.
The figures that were mentioned here were more like 2% for the wing and winglet modifications, which is already quite a big improvement on a still almost brand-new clean sheet aircraft design.

Would you have a source for us?

Best regards,
Hendric

As I said- it is "up to" 300kg per hour. I did not want to push the individual who told me this for any further details.

hitower3 wrote:

The figures that were mentioned here were more like 2% for the wing and winglet modifications, which is already quite a big improvement on a still almost brand-new clean sheet aircraft design.

New A359s have the option of the Trent XWB EP engine which incorporates Trent Advance3 and Trent XWB-97 technology into the Trent XWB 84.

With reduced block fuel, the altitude capability improves as well.

Thanks again for keeping this informative thread running.

xwb565 suggests to continue discussion of A359 performance here instead of the A35K thread, let me start then. xwb565 claims that 280t 359 lifts 36t payload for 17 hours. However, there are two data points of actual flights in the Civil Aviation board:

1. SQ31 SFO-SIN, TOW 271t, payload 25t, 16 hours viewtopic.php?t=1408737
2. DL188 PEK-DTW, TOW 275.4t, payload 48t, 13 hours: viewtopic.php?f=3&t=1396117&start=53

Those two data points are consistent with each other by a simple calculation of trading payload for fuel. Assuming 6 ton per hour fuel burn, from SQ31's TOW 271t, subtract 3 hour (18t fuel) you get 253t TOW. To lift 48t instead of 25t, add 23t, you are at 276t. Almost the same as the actual DL188 data point.

Both data points are quite far away from what xwb565 claimed. They also confirms some members said in another thread (viewtopic.php?f=3&t=1424673), that Airbus "brochure" range of 8100 nm @ 280t TOW is about 1 to 1.5 hour too optimistic.

Now which is true? Is 8100 nm really too optimistic for 359?

ITSTours wrote:

First, 25t payload is mentioned nowhere in your "source".
Second, PAL JFK-MNL (278t 359) reports available payload of 37.1-35.6t (Nov-Dec 2018).
Thus, "280t 359 lifts 36t payload for 17 hours" is a conservative statement.

First, 25t doesn't come from my source, xwb565 says 25t here, post #105. viewtopic.php?f=3&t=1424673&start=100#p21437649
Second, JFK-MNL is 15 to 16 hours, https://www.flightradar24.com/data/flights/pr127, please show me how "280t 359 lifts 36t payload for 17 hours" is a conservative statement.

mintxwb wrote:

xwb565 suggests to continue discussion of A359 performance here instead of the A35K thread, let me start then. xwb565 claims that 280t 359 lifts 36t payload for 17 hours. However, there are two data points of actual flights in the Civil Aviation board:

1. SQ31 SFO-SIN, TOW 271t, payload 25t, 16 hours viewtopic.php?t=1408737
2. DL188 PEK-DTW, TOW 275.4t, payload 48t, 13 hours: viewtopic.php?f=3&t=1396117&start=53

Those two data points are consistent with each other by a simple calculation of trading payload for fuel. Assuming 6 ton per hour fuel burn, from SQ31's TOW 271t, subtract 3 hour (18t fuel) you get 253t TOW. To lift 48t instead of 25t, add 23t, you are at 276t. Almost the same as the actual DL188 data point.

Both data points are quite far away from what xwb565 claimed. They also confirms some members said in another thread (viewtopic.php?f=3&t=1424673), that Airbus "brochure" range of 8100 nm @ 280t TOW is about 1 to 1.5 hour too optimistic.

Now which is true? Is 8100 nm really too optimistic for 359?

Firstly the SQ flight is 16.5 hrs not 16. You also need to account in to consideration that the newer a350's burns substantially less and my 36t example is from a brand spanking new bird. You need to look at different dows of different carriers.You also need to keep in mind that all payload is not equal. Fuel burns off and allows higher cruise levels sooner. If the same headroom is used for actual payload the aircraft will remain heavier at later stages of a flight. I repeat the figures- 135t oew, 6t fob at landing, 36t payload.

Just a reminder to debate the topic and not other users. The moderating team is well aware of at least one user opening multiple accounts however we can not take action without supporting evidence. If you feel another user is operating multiple accounts please either report the post or email the moderators at [email protected] to discuss further. Please do not discuss it in open forum

mintxwb wrote:

Now which is true? Is 8100 nm really too optimistic for 359?

Over 8100 nm is possible even at 268 tonne TOW. This is what a 8100 nm trip looks like in the aircraft in flight performance software with a 268 tonne takeoff keeping everything standard, ISA, nil wind, RVSM odd levels (eastbound). They are the "ideal" conditions that the ACAPS graphs would use.

Real world is not ACAPS world, we have wind, we have ISA variations, we have tropopause variations, we have loading variations, we vary directions, we do not get the ideal levels exactly as want them, calorific value of fuel varies, aircraft run into and collect insects, paint imperfections and scratches, dents, worn seals etc etc.

I have had to blank out the fuel burn as that is confidential information.

zeke wrote:

mintxwb wrote:

Now which is true? Is 8100 nm really too optimistic for 359?

Over 8100 nm is possible even at 268 tonne TOW. This is what a 8100 nm trip looks like in the aircraft in flight performance software with a 268 tonne takeoff keeping everything standard, ISA, nil wind, RVSM odd levels (eastbound). They are the "ideal" conditions that the ACAPS graphs would use.

Real world is not ACAPS world, we have wind, we have ISA variations, we have tropopause variations, we have loading variations, we vary directions, we do not get the ideal levels exactly as want them, calorific value of fuel varies, aircraft run into and collect insects, paint imperfections and scratches, dents, worn seals etc etc.

very good, highly informative

i'm wondering why then you blankly state a35k design range is 8400 as if that number has any real world meaning for the basis of a project sunrise discussion

it's an acaps range dependent upon very specific DOW and other conditions, as you know. this 268t 8100nm segment would be with how many people aboard? like an empty plane? there is an absolut 0% chance a 359/268 could 8100 or anywhere near it with a full cabin.

what good does it do to insert an edge case into a discussion like this? the issue is not what a ferry flight could travel or something otherwise past the 2nd range kink. it is how far with a full passenger count and bags

xwb565 wrote:

I repeat the figures- 135t oew, 6t fob at landing, 36t payload.

at 17:02. this was not a commercial flight. dow was therefore low. why even cite this? on a real flight, 6t of that payload would be eaten by cabin/crew/catering/toilet paper/etc.

in reading thru past threads, over and over again this happens. range discussions get sidetracked talking about non-representative a350 flights which are being passed off as the opposite.

I've watched people try to do that with the 789, saying bc qf9 the range is 7800. every quickly they are corrected with less payload, 236 psngr, light cabin dow. all true statements. but here real flight data is being countered by a "268t can do 8100" and a 17:02 flight on a new 359 that was not a std passenger flight.

mintxwb wrote:

1. SQ31 SFO-SIN, TOW 271t, payload 25t, 16 hours viewtopic.php?t=1408737

nothing in that thread indicates a payload of 25t on that flight. Do we know for sure that it had zero cargo?

SQ generates 9% of its revenue from belly cargo.

mintxwb wrote:

that Airbus "brochure" range of 8100 nm @ 280t TOW is about 1 to 1.5 hour too optimistic.

What if you factor in the 2% better fuel burn in more recent A359s?

h1fl1er wrote:

I'm wondering why then you blankly state a35k design range is 8400 as if that number has any real world meaning for the basis of a project sunrise discussion

It is a statement of fact. The design range of the 316 tonne W/V is 8400 nm, with a design payload of 366 passengers at 95 kg = 37440 kg.

h1fl1er wrote:

this 268t 8100nm segment would be with how many people aboard? like an empty plane?

315 passengers, was the design payload at the 268 tonne W/V and promised to 7750 nm, Airbus exceeded that objective. (Please note Airbus increased their design payload subsequently from 315 pax to 325 pax, and increased the range it would carry).

h1fl1er wrote:

there is an absolut 0% chance a 359/268 could 8100 or anywhere near it with a full cabin.

It will take a full cabin, that is what the performance software shows.

h1fl1er wrote:

what good does it do to insert an edge case into a discussion like this?

This is not an edge case, it is when the aircraft is MTOW limited at 268 tonnes, without using full fuel.

h1fl1er wrote:

at 17:02. this was not a commercial flight. dow was therefore low. why even cite this?

You will see above the performance software is saying 8100 nm in still wind conditions will take 17:05, that means the flight xwb565 was referring to 17:02 was basically 8100 nm air miles, i.e. the flight was into headwinds. It is a representative example of the A350 flying the design payload, the design range.

zeke wrote:

h1fl1er wrote:

this 268t 8100nm segment would be with how many people aboard? like an empty plane?

315 passengers, was the design payload at the 268 tonne W/V and promised to 7750 nm, Airbus exceeded that objective. (Please note Airbus increased their design payload subsequently from 315 pax to 325 pax, and increased the range it would carry).

The software shows: 17 hours, 30t payload @ 268 TOW
The DL flight: 13 hours, 48t payload @ 275.4 TOW. Reduce 18t payload and add 4 more hours, 275.4 + 4*6 - 18 you are at 281.4t TOW.
The SQ flight: 16.5 hours, 25t payload @ 271 TOW. Add 0.5 hour and 5t payload, 271 + 3 + 5 = 279t TOW

The difference between the software and real world commercial flight seems to be too high to be explained by

zeke wrote:

ISA variations, we have tropopause variations, we have loading variations, we vary directions, we do not get the ideal levels exactly as want them, calorific value of fuel varies, aircraft run into and collect insects, paint imperfections and scratches, dents, worn seals etc etc.

Eyad89 wrote:

nothing in that thread indicates a payload of 25t on that flight. Do we know for sure that it had zero cargo?

SQ generates 9% of its revenue from belly cargo.

xwb565 says the payload is 25t, s/he has better information than I do. Plus assuming zero cargo, the data is consistent with DL's data point.

Eyad89 wrote:

What if you factor in the 2% better fuel burn in more recent A359s?

Can you point me to a source saying a "recent" A359 is 2% better than what SQ/DL has?

h1fl1er wrote:

I've watched people try to do that with the 789, saying bc qf9 the range is 7800. every quickly they are corrected with less payload, 236 psngr, light cabin dow. all true statements. but here real flight data is being countered by a "268t can do 8100" and a 17:02 flight on a new 359 that was not a std passenger flight.

Agreed. And people constantly says "SQ non-ULR can do LAX-SIN" because once in November 2018 a non-ULR was used on LAX-SIN, without realizing that the one-time equipment change means there is only about 161 passengers on board...Why we don't say 781 can do IAD-PEK because UA used it multiple times this year?

When we discuss ranges, let's all use the same payload assumption, full cabin, no cargo, otherwise it is meaningless.

mintxwb wrote:

The software shows: 17 hours, 30t payload @ 268 TOW

Actually shows in excess of that, I just cannot say what it is as the fuel burn numbers are confidential.

mintxwb wrote:

The difference between the software and real world commercial flight seems to be too high to be explained by

And the other main one is the company fuel policy. QF for example are happy to depart without a destination alternate as long as they PLAN to have at least 70 minutes endurance on arrival, where if we depart without an destination alternate we will have PLAN to have at least 2 hours endurance. If we have a close by alternate, we will still arrive with at least 80 minutes of fuel at the destination. Without that fuel policy QF would not be able to operate LHR-PER, as it is they arrive sometimes with only 4.5 tonnes total fuel onboard which is nothing considering the lack of options around PER.

SQ always have good fuel allowance on arrival, think it was at least 10 tonnes for the 777 and 8 tonnes for the A330, so I assume the A350 would also be 8 tonnes. They like to have fuel for KUL as SIN is subject to thunderstorms all year. DL I think from what I have read needs to carry more contingency fuel under their Ops Spec than a lot of other carriers.

mintxwb wrote:

Agreed. And people constantly says "SQ non-ULR can do LAX-SIN" because once in November 2018 a non-ULR was used on LAX-SIN, without realizing that the one-time equipment change means there is only about 161 passengers on board..

I thought the person on the flight said it was full ? LAX-SIN in summer is very different to winter, in winter the westerly jet streams around Japan can hit in excess of 300 kts.

Have a read of this case study on what a normal SQ A350 can do from SFO-SIN

"Figure 3 shows the resultant payload range diagram for the Airbus A350-900XWB aircraft. Three curves are included, the first of which is the published payload range diagram of the Airbus A350-900XWB aircraft. In addition to this are the two resultant payload range diagrams that results from the east bound and west bound annual wind average. Marked on the payload range diagram is the corresponding range between Singapore (SIN) and San Francisco (SFO). This mission range intersects with the raw payload range curve at 39.1 tonnes, while including the annual average wind the values are 37.1 tonnes and 40.9 tonnes for the westbound and eastbound flights, respectively. Using the typical value of 95 kg per passenger with baggage and a full passenger payload (European Aviation Safety Agency, 2009), the passenger payload is 24.0 tonnes, leaving an excess cargo payload of 13.1 tonnes and 16.9 tonnes for the westbound and eastbound flights, respectively. If there are no prevailing winds in either direction of the flight, then the available air cargo payload with a full passenger load is 15.0 tonnes. If we include the Singapore Airlines annual load factor of 79% (Singapore Airlines, 2017), the expected passenger payload becomes 19.0 tonnes, leaving an excess cargo payload of 18.2 tonnes and 21.9 tonnes for the westbound and eastbound flights, respectively. When flights are operated with an average load-factor and there are no winds enroute then the available air cargo payload is 20.1 tonnes. These results are summarized in Table 7."

"Comparison of the air cargo-carrying potential Airbus A350-900XWB vis-à-vis Boeing 787-9 All of the relevant air cargo carrying parameters are summarised in Table 7. As can be seen, the payload potential of the Singapore Airlines Airbus 350-900XWB aircraft is always slightly greater than the United Airlines Boeing 787-9 aircraft, particularly when there are no prevailing wind penalties. Specifically, the Singapore Airlines Airbus 350-900XWB on average offers 5.5 tonnes more than United Airlines Boeing 787-9. Based on the current air cargo proxy yield ($0.375/tonne/km) (Boeing Commercial Airplanes, 2016), and the distance (13,596.09 km) then there could be an additional $27,900 in revenue potential when the aircraft operates daily services. This equates to an annual revenue potential of $USD 20.3 million"

https://www.researchgate.net/publicatio ... _Singapore

mintxwb wrote:

Can you point me to a source saying a "recent" A359 is 2% better than what SQ/DL has?

SQs non ULR A350s are original, their ULRs are the improved versions.

"The aircraft also incorporates structural improvements, lowering the empty weight of the aircraft.

In total, the changes improve the fuel consumption of the A350-900 by 1%. The improved aerodynamics also means a range improvement of 100nm. For the IBERIA 280t version of the A350-900, this means a range of 8,200nm when flying with a 3-class cabin of 325 passengers"

https://leehamnews.com/2018/01/31/iberi ... -a350-900/

"Rolls-Royce has launched an enhanced version of its Trent XWB engine, with Singapore Airlines (SIA) as the first customer.

The enhanced engine will offer a 1% improvement in fuel consumption."

https://www.flightglobal.com/news/artic ... wb-421971/

mintxwb wrote:

Eyad89 wrote:

nothing in that thread indicates a payload of 25t on that flight. Do we know for sure that it had zero cargo?

SQ generates 9% of its revenue from belly cargo.

xwb565 says the payload is 25t, s/he has better information than I do. Plus assuming zero cargo, the data is consistent with DL's data point.

The original information provider is not xwb565, and even xwb565 only said they saw in the board.

Your "source" only comes from someone else's not-a-clear memory.....
It is not a source.
Also the original SQ thread someone mentions 32t. Why do you conveniently ignore that?