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MrHMSH
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QF Project Sunrise A35K performance

Thu Jan 21, 2021 11:49 am

Since I can't find an existing thread in Tech Ops, I'd like to start a discussion about what payload/range QF could get from the A35K (ULR) given the information we have about the A35K's existing capabilities and anything else that has been reported about Sunrise.

For example, if we assume 319T MTOW (I've seen this figure given in past discussions), how far could it carry maximum payload, and what would the payload be at the ranges needed to make JFK and (especially) LHR? Say the aircraft has a similar density to the 789s (or maybe a little less). Would there be any way to estimate the trip fuel and fuel burn/hour?

Any of the excellent contributions from our resident experts would be very much appreciated.

 
flipdewaf
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Re: QF Project Sunrise A35K performance

Thu Jan 21, 2021 5:58 pm

The airbus website states that
MTOW = 319t
Fuel capacity = 159000l
Spec mission Capacity assumed = 350pax (@95kg each)
Spec Range= 8700nm

Assumptions:
OWE is 155t
Fuel on landing for spec mission is 5t
Pantry + crew = 5t
Fuel density = 0.8kg/l

Then spec mission Landing weight = (OWE+Reserve Fuel + Pantry+Crew + pax) = 198.25
TOW-LW = fuel use = 319-198.25 = 120.75t (151000l)
Applied to breguet over a 8700nm flight you get a range factor of 18290.

If we then apply breguet back with that figure on a 9500nm flight (the assumed required for sunrise) with the same 319t MTOW we get a landing weight of 189.8t.
Thus a fuel use of 129t (161500l*)
If we remove the assumed weights as before we get a pax load of 261pax.

* I see that this is above the max available volume but I would expect that this is a relatively simple mod as this tank capacity already exists on the A359ULR.

Hope this is what you were looking for,

Fred
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CRJockey
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Re: QF Project Sunrise A35K performance

Thu Jan 21, 2021 7:40 pm

flipdewaf wrote:
Fuel on landing for spec mission is 5t


Always interesting to read your contribution, Fred. Thanks for providing the numbers.

I just wonder how 5t of fuel on landing suffice? Not sure about the fuel burn, but I guess in the region of 8t/hour during low level final reserve? That alone would bring you to 4t for 30min + diversion fuel + possibly unused contigency. I would have seen more in line with 7-8t of landing fuel as realistic.

Quite possible I am missing something - what is it?
 
flipdewaf
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QF Project Sunrise A35K performance

Thu Jan 21, 2021 9:25 pm

CRJockey wrote:
flipdewaf wrote:
Fuel on landing for spec mission is 5t


Always interesting to read your contribution, Fred. Thanks for providing the numbers.

I just wonder how 5t of fuel on landing suffice? Not sure about the fuel burn, but I guess in the region of 8t/hour during low level final reserve? That alone would bring you to 4t for 30min + diversion fuel + possibly unused contigency. I would have seen more in line with 7-8t of landing fuel as realistic.

Quite possible I am missing something - what is it?

Fair question,

Firstly I would say that what I have put on here is a pretty crude (but generally pretty accurate over longer sectors) type of analysis. The logic I initially used to get to the 5t was to estimate based on what we know QF9 has planned to arrive in London with and that’s 4.5t. QF rules state they need enough fuel over destination to hold for 70mins. I guessed the A35k is a bit bigger then the 787 so I’d add a bit. I have then looked up a sunrise thread from ~2years back when I used a first principles model I have developed to estimate fuel burn.

viewtopic.php?f=3&t=1402165&start=487

In this you can see that it estimates that for 70mins at 1500ft you’d need just over 4.5t.

It’s the difference between “missed approach weight” and “landing weight”
Even though this may seem low on further reflection it may well be right. At the end of a Low cargo ULH flight the aircraft will be fairly light and whilst holding there is no requirement to maximise range but instead maximise endurance.

If the aircraft were travelling at max range speed (UL/D) for cruise (488kts) and using 5t/hr at low weights then we would expect 70mins of low airspeed flight (250kts) to burn fuel at a much lower rate. I’m sure one of the pilots on here who fly the airbus could give accurate/reasonable figures.

Fred


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zeke
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Re: QF Project Sunrise A35K performance

Thu Jan 21, 2021 11:39 pm

CRJockey wrote:
flipdewaf wrote:
I just wonder how 5t of fuel on landing suffice? Not sure about the fuel burn, but I guess in the region of 8t/hour during low level final reserve? That alone would bring you to 4t for 30min + diversion fuel + possibly unused contigency. I would have seen more in line with 7-8t of landing fuel as realistic.

Quite possible I am missing something - what is it?


Typically final reserve (30 minutes holding at 1500 ft) is less than 2.5 tonnes on the A35K, we could (and do) at times plan with that sort of minimum division fuel to our alternate with the A35K. It all depends on where you are going to LHR there is LGW and STN which are close by.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949
 
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MrHMSH
Topic Author
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Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 3:39 am

flipdewaf wrote:
The airbus website states that
MTOW = 319t
Fuel capacity = 159000l
Spec mission Capacity assumed = 350pax (@95kg each)
Spec Range= 8700nm

Assumptions:
OWE is 155t
Fuel on landing for spec mission is 5t
Pantry + crew = 5t
Fuel density = 0.8kg/l

Then spec mission Landing weight = (OWE+Reserve Fuel + Pantry+Crew + pax) = 198.25
TOW-LW = fuel use = 319-198.25 = 120.75t (151000l)
Applied to breguet over a 8700nm flight you get a range factor of 18290.

If we then apply breguet back with that figure on a 9500nm flight (the assumed required for sunrise) with the same 319t MTOW we get a landing weight of 189.8t.
Thus a fuel use of 129t (161500l*)
If we remove the assumed weights as before we get a pax load of 261pax.

* I see that this is above the max available volume but I would expect that this is a relatively simple mod as this tank capacity already exists on the A359ULR.

Hope this is what you were looking for,

Fred


Exactly what I was after, your contributions are very much appreciated! I guess the next logical question would be for the 778, but with a lot more assumptions and much less hard data.
 
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zeke
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Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 7:42 am

155 is a bit high, all of ours are under 150.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949
 
CRJockey
Posts: 193
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Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 9:01 am

flipdewaf wrote:
CRJockey wrote:
flipdewaf wrote:
Fuel on landing for spec mission is 5t


Always interesting to read your contribution, Fred. Thanks for providing the numbers.

I just wonder how 5t of fuel on landing suffice? Not sure about the fuel burn, but I guess in the region of 8t/hour during low level final reserve? That alone would bring you to 4t for 30min + diversion fuel + possibly unused contigency. I would have seen more in line with 7-8t of landing fuel as realistic.

Quite possible I am missing something - what is it?

Fair question,

Firstly I would say that what I have put on here is a pretty crude (but generally pretty accurate over longer sectors) type of analysis. The logic I initially used to get to the 5t was to estimate based on what we know QF9 has planned to arrive in London with and that’s 4.5t. QF rules state they need enough fuel over destination to hold for 70mins. I guessed the A35k is a bit bigger then the 787 so I’d add a bit. I have then looked up a sunrise thread from ~2years back when I used a first principles model I have developed to estimate fuel burn.

viewtopic.php?f=3&t=1402165&start=487

In this you can see that it estimates that for 70mins at 1500ft you’d need just over 4.5t.

It’s the difference between “missed approach weight” and “landing weight”
Even though this may seem low on further reflection it may well be right. At the end of a Low cargo ULH flight the aircraft will be fairly light and whilst holding there is no requirement to maximise range but instead maximise endurance.

If the aircraft were travelling at max range speed (UL/D) for cruise (488kts) and using 5t/hr at low weights then we would expect 70mins of low airspeed flight (250kts) to burn fuel at a much lower rate. I’m sure one of the pilots on here who fly the airbus could give accurate/reasonable figures.

Fred



Thanks again for opening up your method. Seems reasonable. And with the addition of Zeke's numbers, it seems 5t make good sense.
 
flipdewaf
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Joined: Thu Jul 20, 2006 6:28 am

Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 10:11 am

MrHMSH wrote:
Exactly what I was after, your contributions are very much appreciated! I guess the next logical question would be for the 778, but with a lot more assumptions and much less hard data.


No problem, The problem with the 778 is there is no spec mission data that really passes the smell test, the range factor for a shrink should be higher for a shrink but with the published spec mission for the 778X showing a lower range factor than the 779X I'm not sure how useful that is. There is some data flying around for actual A35Ks which would not have any potential airbus spin on them but not found any complete data to extract a range factor from a single flight that is public knowledge. There are pilots on this forum who would be able to get such data but I doubt they'd be flying for their airline much longer if they released that data on here.

zeke wrote:
155 is a bit high, all of ours are under 150

I think your are probably right (my estimates on weight put the A35k at 147.7t. I also hear that the QR ones which have a heavy cabin are at 151-152t typically.

The issue that we have is that we dont know what Airbus have used to get their Range/Payload marketing figures.

Fred
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tommy1808
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Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 11:31 am

flipdewaf wrote:
The issue that we have is that we dont know what Airbus have used to get their Range/Payload marketing figures.


wouldn´t the APAC imply 162t going 319t - (366 x 0.095t pax) - 122t fuel?

best regards
Thomas

Edit: i guess some of that 122t usable fuel should still be there when they land :banghead: :biggrin:
Well, there is prophecy in the bible after all: 2 Timothy 3:1-6
 
WIederling
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Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 12:46 pm

flipdewaf wrote:
* I see that this is above the max available volume but I would expect that this is a relatively simple mod as this tank capacity already exists on the A359ULR.


use of that extra fuel volume on the ULR leads to CoG issues and thus blocking of the forward hold.

IMU the "Sunriser" needs an ACT behind the wingbox just to "work" this issue.(?)
Murphy is an optimist
 
flipdewaf
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Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 12:51 pm

WIederling wrote:
flipdewaf wrote:
* I see that this is above the max available volume but I would expect that this is a relatively simple mod as this tank capacity already exists on the A359ULR.


use of that extra fuel volume on the ULR leads to CoG issues and thus blocking of the forward hold.

IMU the "Sunriser" needs an ACT behind the wingbox just to "work" this issue.(?)

Yes, I think you are right. I had my wires crossed about where the extra tank capacity is gained for the A359ULR, i had assumed that the wing tankage was increase but I think it was more along the lines of the A35K systems installed on to the A359 centre tank. The A35k is already at its "built in" tank limits and would likely have to go ACT to increase.

Fred
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flipdewaf
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Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 1:27 pm

Image

I have shown the expected pax volumes that come from the payload range chart (316t and the expectation from the 319t MTOW), I have also added a line for the case of 300pax (28.5t) which shows an MTOW of about 324t. Note that I have neglected available fuel volume being a limit in this.
Assumed 9500nm range required for sunrise.

Fred
Last edited by flipdewaf on Fri Jan 22, 2021 1:36 pm, edited 1 time in total.
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WIederling
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Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 1:32 pm

flipdewaf wrote:
WIederling wrote:
flipdewaf wrote:
* I see that this is above the max available volume but I would expect that this is a relatively simple mod as this tank capacity already exists on the A359ULR.


use of that extra fuel volume on the ULR leads to CoG issues and thus blocking of the forward hold.

IMU the "Sunriser" needs an ACT behind the wingbox just to "work" this issue.(?)

Yes, I think you are right. I had my wires crossed about where the extra tank capacity is gained for the A359ULR, i had assumed that the wing tankage was increase but I think it was more along the lines of the A35K systems installed on to the A359 centre tank. The A35k is already at its "built in" tank limits and would likely have to go ACT to increase.

Fred

You first fill up wing tankage. If enabled you continue with center wing box tankage ( early A330, A380 : fully unused )

Available for fuel volume on the A350 is sensor/software driven.
Existing volume obviously is equal or more than the 165kl on the ULR. More room available ? not known.
But it would not be useful anyway as the CoG shift becomes prohibitive.

My tentative guess is that CWB fuel gets expanded but also an ACT added. This would allow for inproved CoG management.
( the A350 per design does this via variable camber of the wing obviating the need for the trim tank of the previous gen models ( 330/340/380 )
Murphy is an optimist
 
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JerseyFlyer
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Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 1:32 pm

flipdewaf wrote:
WIederling wrote:
flipdewaf wrote:
* I see that this is above the max available volume but I would expect that this is a relatively simple mod as this tank capacity already exists on the A359ULR.


use of that extra fuel volume on the ULR leads to CoG issues and thus blocking of the forward hold.

IMU the "Sunriser" needs an ACT behind the wingbox just to "work" this issue.(?)

Yes, I think you are right. I had my wires crossed about where the extra tank capacity is gained for the A359ULR, i had assumed that the wing tankage was increase but I think it was more along the lines of the A35K systems installed on to the A359 centre tank. The A35k is already at its "built in" tank limits and would likely have to go ACT to increase.

Fred


I think I have seen in previous threads that the 359 max theoretical fuel capacity without extra tanks is always higher than the 35k because some of the 359 centre tank capacity is needed to house the larger 35K MLG.
 
WIederling
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Re: QF Project Sunrise A35K performance

Fri Jan 22, 2021 3:16 pm

JerseyFlyer wrote:
I think I have seen in previous threads that the 359 max theoretical fuel capacity without extra tanks is always higher than the 35k because some of the 359 centre tank capacity is needed to house the larger 35K MLG.


NO.
MLG retracts into the room behind the center wing box.
see: https://www.fzt.haw-hamburg.de/pers/Sch ... 350XWB.pdf page 10

capacity is "software defined". The available empty space is equal or bigger than the 165kl of the ULR.
Murphy is an optimist
 
RJMAZ
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Re: QF Project Sunrise A35K performance

Sat Jan 23, 2021 12:51 am

I think Airbus will simply take a standard A350-1000 and fill the existing tanks up to between 168,000 and 170,000 liters with a further improved fuel system and call it a day. Putting an extra tank in the rear cargo hold requires pipes to run through the landing gear area. That is a big job for a couple percent of extra fuel. Filling the existing tanks higher is a far lighter and more elegant solution.

The center of gravity will not be an issue either. Airlines deal with center of gravity when loading most flights. Qantas would simply load most of the passenger bags into the rear cargo hold. On such a long route there wouldn't be extra revenue cargo and all of the passenger bags will comfortably fit in the rear hold. On shorter routes where the fuel loaded is far less then Qantas can load both the front and rear cargo holds. Qantas could choose to disable the front cargo bay completely as that allow a dozen aircraft passengers from the weight saved.

My calculations show that a 319t MTOW taking off with 168,000 liters of fuel will allow 280 passengers to fly Sydney to London at least 90% of the time. The weather plays a big part in the economics. When the weather is in the worst 10% the flight will be forced to carry 250-260 passengers and around 170,000 liters of fuel required. This does not kill the economics of the route. The 787-9 flying Los Angeles to Singapore was blocking seats on half of the westbound routes and that route was cancelled.

The A350-1000 has 25% more cabin area than the 787-9. With Qantas having 236 seats in their 787-9 aircraft that works out to be 295 seats on the A350-1000 with similar density. It is highly likely the project sunrise route will have the lowest seating density of any Qantas aircraft. 280 seats would be the highest I would expect.

If the MTOW goes above 319t they will have enough lift to hit the 300 passenger mark. At that point it is highly likely we will see the first class and business class toilets placed in the front cargo hold like the Lufthansa A340 aircraft. We have already seen silly ideas from Qantas for using this space. We will probably see the toilets become very spacious as empty space does not add weight but that makes the flight look very premium. Also they might have an empty waiting room with a couple chairs as they may as well use up the full front cargo hold. This solves any center of gravity issues as the front hold will be mostly empty space.
 
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Starlionblue
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Re: QF Project Sunrise A35K performance

Sat Jan 23, 2021 3:16 am

Both wing and centre tanks on the A350 are pretty close to the CoG. I doubt more fuel will make a big difference.
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