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jagraham
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Wed May 08, 2019 6:02 pm

flipdewaf wrote:
zeke wrote:
flipdewaf wrote:
it is still only 20% more, you cannot choose to only include both upper and lower surfaces in one example and not the other.


Fred

Skin friction drag is the shear force between the fluid and the surface. It is based upon wetted area.

When we talk about total lift and drag we refer to a reference wing area which is just a reference platform area, the definition of which is different depending on who you work for.

This old thread goes though some of the differences

viewtopic.php?t=769539

I am aware of the different methodologies used as well as the fundamentals of incompressible flows, I have a master in aero engineering and I am currently employed as an engineer.

If wing reference are increases 10% then wing wetted area will go up 10%, the wetted area will increase by 20% of the reference area but I'm not sure why that is a useful number? One will only increase faster than the other if you are looking in absolute terms and if one is to do this it makes no sense to limit it to the wing and the percentage increase in wetted area should be done on an aircraft level not the wing level.

My updated model with the correct wing area for the 778X, representative alternative for QF and updated engine diameters is complete and the results are as follows.
Mission:
SYD-LHR (9198nm according to my slightly too sperical world model).
No alternate but 1500ft for 70mins reserve.
Payload -30000kg

A350-1000
Assumed TSFC 0.51lb/hr/lb
DOW 151000kg
Landing weight 187491kg
Takeoff weight required 332104kg
Fuel used 144613kg
Flight time 20hrs 44mins

B778X
Assumed TSFC 0.49lb/hr/lb
DOW 173000kg
Landing weight 209564kg
Required takeoff weight 352756kg
Fuel used 143 192kg
Flight time 21hrs 01mins

Please ask questions but also please note that at this point I am an excel warrior and the level of accuracy in the figures does not indicate that the surety is to that level only that excel calculates to that level without much effort.

Fred


This model shows the 778 can do SYD-LHR without major modifications (they have to lose 1 ton of DOW to get TOW down to 351T), but fuel used is just over 143t, and the standard 778 holds 159t.
That is the benefit of the GE9X. If it meets its promises, the main one of which is 5% better than XWB at EIS (not to make this an A vs B contest, but pointing out why Boeing and GE might accept an engine which is 3000 lb heavier than an already heavy GE90-115 rather than PIPing the GE90-115 one more time), then the heavier plane is more efficient. Otherwise, why bother with the GE9X? When they could have taken the weight savings from going to a composite wing and been done with it?
 
jupiter2
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Wed May 08, 2019 6:11 pm

seabosdca wrote:
lightsaber wrote:
Sharpen your pencils everyone, this is a high profile campaign that will be brutal. I would be shocked if QF isn't taking the opportunity to expand the bid to get the best A350 (various models) vs. 778/779/787 (various models possible). In other words, QF can cut the costs of fleet replacement due to the visibility of the relatively small project sunrise fleet decision.


:checkmark:

Joyce is certainly not an executive who is going to let a discount slip away.

I'd feel more confident in guessing if I knew how the airline felt about A380 economics. I think in a situation where the A380 is doing well and will stick around for a decade or more, the A350 has the upper hand. On the other hand, if the numbers are saying the A380 will have a hard time competing with newer equipment on the trunk routes, the 777X starts to look pretty compelling for revenue potential on those trunk routes.


I'm firmly of the opinion that whatever is chosen, the largest variant will also be used to replace the 380 in the future. If QF chose the 350-1000 then they will have two seating configurations, a premium heavy for the Sunrise flights and a denser configuration for the remainder. If QF chose the 777, then they will get 8's for the Sunrise and 9's for the 380 replacement.

The QF 380's start to get cabin refurbishment later this year, this is being done by Airbus and is said to be where the cancelled 380 deposits are going.

Any order will see the Sunrise aircraft delivered first and once completed, then the heavier aircraft will come in and start to replace the 380's, but that wouldn't be till 2025 at least and going through till the end of the 2029-2030. That still gives 10 years of 380 ops at QF.
 
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RyanairGuru
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Wed May 08, 2019 9:32 pm

Naincompetent wrote:
Also what Etops is needed for the route?


EDTO 180.

The only routes out of Australia that require 180< are to Africa and South America.
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flipdewaf
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Wed May 08, 2019 9:33 pm

zeke wrote:
flipdewaf wrote:
zeke wrote:

Fred

Skin friction drag is the shear force between the fluid and the surface. It is based upon wetted area.

When we talk about total lift and drag we refer to a reference wing area which is just a reference platform area, the definition of which is different depending on who you work for.

This old thread goes though some of the differences

viewtopic.php?t=769539

I am aware of the different methodologies used as well as the fundamentals of incompressible flows, I have a master in aero engineering and I am currently employed as an engineer.

If wing reference are increases 10% then wing wetted area will go up 10%, the wetted area will increase by 20% of the reference area but I'm not sure why that is a useful number? One will only increase faster than the other if you are looking in absolute terms and if one is to do this it makes no sense to limit it to the wing and the percentage increase in wetted area should be done on an aircraft level not the wing level.

My updated model with the correct wing area for the 778X, representative alternative for QF and updated engine diameters is complete and the results are as follows.
Mission:
SYD-LHR (9198nm according to my slightly too sperical world model).
No alternate but 1500ft for 70mins reserve.
Payload -30000kg

A350-1000
Assumed TSFC 0.51lb/hr/lb
DOW 151000kg
Landing weight 187491kg
Takeoff weight required 332104kg
Fuel used 144613kg
Flight time 20hrs 44mins

B778X
Assumed TSFC 0.49lb/hr/lb
DOW 173000kg
Landing weight 209564kg
Required takeoff weight 352756kg
Fuel used 143 192kg
Flight time 21hrs 01mins

Please ask questions but also please note that at this point I am an excel warrior and the level of accuracy in the figures does not indicate that the surety is to that level only that excel calculates to that level without much effort.

Fred


Fred

There is issues with your model, there isn’t a 5% difference in TSFC between the engines.
easily changed but I’m not sure where to get reasonable data from.

zeke wrote:
Your cruise speeds are also too close between them.
broadly speaking (I’ll explain below the a350 will cruise at M0.85 and the 778x at M0.84 and with this difference over 21hrs one would expect about 15mins difference.

zeke wrote:
Is the model at constant cruise level and speed ? What is the vertical profile you are assuming ?

The model climbs to the max attainable altitude based on meeting a number of functions.
1. The aircraft must be able to climb at least 600ft/minute at max continuous thrust ( there is a function to broadly determine thrust lapse based on velocity and local air density).
2. It must be within the aircrafts max allowable altitude.
3. It must allow the aircraft to have suitable buffet margin. I have a function involving Mcrit, lift coefficient, wing sweep, wing thickness and assumes a level of ‘peakiness’ from a modern supercritical aero foil.

One of the reasons that the 777 seems often to go fast in my models is that (particularly for the 77W) when it has to be low at the start of cruise and the aircraft hasn’t yet reached the tropopause it cruises at a constant Mach which is higher in the hotter air (standard atmosphere model is used).

He model works backwards from landing after divert/contingency and steps once per second through decent cruise (including steps) and then climb.

I was working on a function that would effectively ‘hunt’ for a max UL/D speed and height but:
A. It took so long to hunt that a 1second step ends up taking several seconds as it was accessing sheets that changed. As you can imagine this does not help the model when a 20 hr flight takes 6 days to compute.
B. A reliable method for computing drag rise due to compressibility is several PHDs with of work and made the spreadsheet almost unworkable.

The solution for the compressibility effects is ongoing.

Fred



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moa999
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Wed May 08, 2019 9:36 pm

Agree. I see no more than 6-8 Sunrise aircraft in an initial order with an option for additional variants in the late 2020s as the A380s likely retire.
And consider timing of a 350 neo or stretched 350-1100/2000

Remember QF still has a boatload of very cheap 787 options which can replace the international 330 fleet, and possibly will purchase 797 for domestic.
 
Gemuser
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 2:46 am

seabosdca wrote:
lightsaber wrote:
Sharpen your pencils everyone, this is a high profile campaign that will be brutal. I would be shocked if QF isn't taking the opportunity to expand the bid to get the best A350 (various models) vs. 778/779/787 (various models possible). In other words, QF can cut the costs of fleet replacement due to the visibility of the relatively small project sunrise fleet decision.


:checkmark:

Joyce is certainly not an executive who is going to let a discount slip away.

I'd feel more confident in guessing if I knew how the airline felt about A380 economics. I think in a situation where the A380 is doing well and will stick around for a decade or more, the A350 has the upper hand. On the other hand, if the numbers are saying the A380 will have a hard time competing with newer equipment on the trunk routes, the 777X starts to look pretty compelling for revenue potential on those trunk routes.

Australian tax law makes very difficult for QF to keep aircraft less than 20 - 25 years, it would havey to be a really, really strong fincial case for to retire the A380 in less time than that.

Gemuser
 
Gemuser
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 3:04 am

moa999 wrote:
Agree. I see no more than 6-8 Sunrise aircraft in an initial order with an option for additional variants in the late 2020s as the A380s likely retire.
And consider timing of a 350 neo or stretched 350-1100/2000

Remember QF still has a boatload of very cheap 787 options which can replace the international 330 fleet, and possibly will purchase 797 for domestic.

I see a minimum of 8 Sunrise aircraft in the first order; 5 for SYD/MEL - LHR, 2 for SYD - JFK & 1 spare/maintance. Remember it took 5 A380s to operate the SYD/MEL - LHR route before and due to curfews on BOTH ends plus time differances I don't think they will be able to do it with 4 aircraft.

Gemuser
 
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zeke
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 3:11 am

flipdewaf wrote:
Edit: forgot DOW. I would have used OWE (operators empty weight) in the past but after looking at discussions here I have realised that DOW (direct operating weight) is more suitable. DOW is the weight without fuel or payload so includes food, cutlery, water, toilet paper, 3 extra bottles of fizz if my employer lets me go n the pointy end. That sort of thing. From Zekes posts I take that to be ~5t for a long/ultralong flight.


OEW - Operating Empty Weight, not used by airlines, we use Basic Weight which includes:
• aircraft structure.
• systems.
• engines.
• unremovable equipment.
• unusable liquids (fuel, oil and others).
• standard loose equipment.
DOW = Dry Operating Weight. Basic weight plus operational items such as crew and pantry (equipment, food, beverages).

flipdewaf wrote:
I would have assumed that the maximum volume of 124t (artificially limited) would be the volume to cover the 8400nm spec range flight with 360pax. This would arguably be around 3.5hrs longer than that flight and at 6t/hr would give another 18t+.


There is a fundamental problem somewhere with your model somewhere, the fuel burn on the A350 is too high. The nominal payload/range for both the A350-1000 and 777-8 are MTOW limited, not fuel volume. Your assumption that 8400 is fuel volume limited is incorrect.

jagraham wrote:
That is the benefit of the GE9X. If it meets its promises, the main one of which is 5% better than XWB at EIS (not to make this an A vs B contest, but pointing out why Boeing and GE might accept an engine which is 3000 lb heavier than an already heavy GE90-115 rather than PIPing the GE90-115 one more time), then the heavier plane is more efficient. Otherwise, why bother with the GE9X?


Have a look at what GE has said about the GE9x, it is aimed to be 10% better than GE90. It has taken GE 15-20 years to aim for that efficiency, the GE9x will not reach that 10% at EIS. There is only 2 years development between the Trent XWX-97 and the GE9x (first run 2014 vs 2016), rule of thumb for engine efficiency technology improvement is circa 0.5% reduction in TSFC per year.

In reality I would expect the difference in TSFC between the GE9X at EIS and Trent XWB-97 to be in the order of 0.005 lb/lbf/h (the ICAO emissions database has no difference between the engines). I would only expect a total improvement in the order of 0.05 lb/lbf/h between the GE90 and GE9X.

jupiter2 wrote:
I'm firmly of the opinion that whatever is chosen, the largest variant will also be used to replace the 380 in the future. If QF chose the 350-1000 then they will have two seating configurations, a premium heavy for the Sunrise flights and a denser configuration for the remainder. If QF chose the 777, then they will get 8's for the Sunrise and 9's for the 380 replacement.

The QF 380's start to get cabin refurbishment later this year, this is being done by Airbus and is said to be where the cancelled 380 deposits are going.

Any order will see the Sunrise aircraft delivered first and once completed, then the heavier aircraft will come in and start to replace the 380's, but that wouldn't be till 2025 at least and going through till the end of the 2029-2030. That still gives 10 years of 380 ops at QF.


I agree the A380 will be for sometime, but I dont agree the Sunrise aircraft will dictate what they purchase in a decade. They will reassess the situation when it is time to make the order.

flipdewaf wrote:
broadly speaking (I’ll explain below the a350 will cruise at M0.85 and the 778x at M0.84 and with this difference over 21hrs one would expect about 15mins difference.


That just will not be the case, difference today on 15 hr sectors between the A350 and 77W is already 20+ minutes.

flipdewaf wrote:
The model climbs to the max attainable altitude based on meeting a number of functions.
1. The aircraft must be able to climb at least 600ft/minute at max continuous thrust ( there is a function to broadly determine thrust lapse based on velocity and local air density).
2. It must be within the aircrafts max allowable altitude.
3. It must allow the aircraft to have suitable buffet margin. I have a function involving Mcrit, lift coefficient, wing sweep, wing thickness and assumes a level of ‘peakiness’ from a modern supercritical aero foil.


I don’t think this is working over this scenario. The aircraft should be stepping throughout the flight, at each step the L/D and TSFC will change. As fuel is burnt off L/D will also change. The 787/A350 also have variable camber wings which enables near optimum L/D to be maintained by moving the CP as weight is reduced (reduces drag from horizontal stabilizer).
Could I suggest EDSU 73019 and “Aircraft conceptual design synthesis” by Denis Howe are useful references. The book by Howe has spreadsheet methods for range analysis included.

flipdewaf wrote:
One of the reasons that the 777 seems often to go fast in my models is that (particularly for the 77W) when it has to be low at the start of cruise and the aircraft hasn’t yet reached the tropopause it cruises at a constant Mach which is higher in the hotter air (standard atmosphere model is used).


Which in reality probably is not accurate, more likely to see a constant TAS of around 485 KTAS on the 77W below transition to Mach 0.84 which is LRC (FL300 M0.81, FL320, M0.82, FL340 M0.83 FL360 M0.84), in airline operation the aircraft would fly between Mrc and Lrc at ECON speed. The A350 would be ballpark 5 kts faster, initial climb after takeoff to FL340 and maintaining 0.84 (490 KTAS).
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
flipdewaf
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 6:12 am

zeke wrote:

OEW - Operating Empty Weight, not used by airlines, we use Basic Weight which includes:
• aircraft structure.
• systems.
• engines.
• unremovable equipment.
• unusable liquids (fuel, oil and others).
• standard loose equipment.
DOW = Dry Operating Weight. Basic weight plus operational items such as crew and pantry (equipment, food, beverages).


My take on DOW was that it is the weight without payload as fuel?
zeke wrote:
flipdewaf wrote:
I would have assumed that the maximum volume of 124t (artificially limited) would be the volume to cover the 8400nm spec range flight with 360pax. This would arguably be around 3.5hrs longer than that flight and at 6t/hr would give another 18t+.


There is a fundamental problem somewhere with your model somewhere, the fuel burn on the A350 is too high. The nominal payload/range for both the A350-1000 and 777-8 are MTOW limited, not fuel volume. Your assumption that 8400 is fuel volume limited is incorrect.
what I mean was it is fuel volume limited in the same sense as the A359 is fuel volume limited and had to be increased for the ULR, i.e. not physically but more software sensors and pipes. I agree that the numbers look high and I will investigate where the anomaly lies. I will check the model on known sectors and known aircraft ( likely SQ22/21 and qf9/10 as there are actual numbers floating around for them).


zeke wrote:
Have a look at what GE has said about the GE9x, it is aimed to be 10% better than GE90. It has taken GE 15-20 years to aim for that efficiency, the GE9x will not reach that 10% at EIS. There is only 2 years development between the Trent XWX-97 and the GE9x (first run 2014 vs 2016), rule of thumb for engine efficiency technology improvement is circa 0.5% reduction in TSFC per year.
The rule of thin I had heard was 1% per year for new engines and 0.5% per year from launch year for a derivative engine (may be semantics for this example) but I shall apply that to see the reasoning.

zeke wrote:
In reality I would expect the difference in TSFC between the GE9X at EIS and Trent XWB-97 to be in the order of 0.005 lb/lbf/h (the ICAO emissions database has no difference between the engines). I would only expect a total improvement in the order of 0.05 lb/lbf/h between the GE90 and GE9X.

The next part of my model I want to concentrate on is making the engines ‘behave’ correctly rather than being a fixed sfc at any given time.
zeke wrote:

flipdewaf wrote:
broadly speaking (I’ll explain below the a350 will cruise at M0.85 and the 778x at M0.84 and with this difference over 21hrs one would expect about 15mins difference.


That just will not be the case, difference today on 15 hr sectors between the A350 and 77W is already 20+ minutes.

flipdewaf wrote:
The model climbs to the max attainable altitude based on meeting a number of functions.
1. The aircraft must be able to climb at least 600ft/minute at max continuous thrust ( there is a function to broadly determine thrust lapse based on velocity and local air density).
2. It must be within the aircrafts max allowable altitude.
3. It must allow the aircraft to have suitable buffet margin. I have a function involving Mcrit, lift coefficient, wing sweep, wing thickness and assumes a level of ‘peakiness’ from a modern supercritical aero foil.


I don’t think this is working over this scenario. The aircraft should be stepping throughout the flight,

Yes, sorry, missed that bit, the next attainable altitude is constantly looked at and set in the code to be defined before starting. Normally I set this to be 1000ft steps so it cannot start a climb to the next step until the aircraft can maintain all 3 scenarios at that step.
zeke wrote:
at each step the L/D and TSFC will change. As fuel is burnt off L/D will also change.

L/D changes all the time but the TSFC is still pretty basic in my model. There was a function that had a simple altitude variation for sfc but I want to change to something a bit more geeky that automates based on engine geometries and temps rather than reference data.
zeke wrote:
The 787/A350 also have variable camber wings which enables near optimum L/D to be maintained by moving the CP as weight is reduced (reduces drag from horizontal stabilizer).
Could I suggest EDSU 73019 and “Aircraft conceptual design synthesis” by Denis Howe are useful references. The book by Howe has spreadsheet methods for range analysis included.

Thanks for the recommendation, I would traditionally keep away from text books as my experience from my university days was that text books for this would normally require a mortgage but this seems reasonable. Wit regard to th variable camber I will need to understand it in a bit more detail in its operation to understand a reasonable way to implement in to the model.
zeke wrote:
flipdewaf wrote:
One of the reasons that the 777 seems often to go fast in my models is that (particularly for the 77W) when it has to be low at the start of cruise and the aircraft hasn’t yet reached the tropopause it cruises at a constant Mach which is higher in the hotter air (standard atmosphere model is used).


Which in reality probably is not accurate, more likely to see a constant TAS of around 485 KTAS on the 77W below transition to Mach 0.84 which is LRC (FL300 M0.81, FL320, M0.82, FL340 M0.83 FL360 M0.84), in airline operation the aircraft would fly between Mrc and Lrc at ECON speed. The A350 would be ballpark 5 kts faster, initial climb after takeoff to FL340 and maintaining 0.84 (490 KTAS).

That sounds reasonable, I want my model to represent a normal type flight as much as possible. I can easily set a speed or Mach number based on any particular part of the flight. I’d have to remember off the top of my head but I have it set to 250kts tas below 10K then it raises to something else up to 30k ( I think then moves to constant Mach above that) What is a reasonable way to set the speed at different altitudes and how/when would one normally go from speed to mach derived speed control?

Sorry this is going off topic.

Fred



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seabosdca
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 6:20 am

I don't find this conversation off topic at all, as it provides a nice window into one of the (many) categories of analysis QF will need to do in order to make an informed decision between A350 and 777X.
 
Waterbomber2
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 6:25 am

speedbird52 wrote:
qf789 wrote:
MrHMSH wrote:
Not sure it's been answered or not, but what would happen to SYD-SIN-LHR? Would it be cancelled?


QF have indicated previously it will stay as is

If that remains true it will be good to see that Qantas is growing again!


Could you please state what part of replacing B744's/A380's one for one with B789's leads to growth?

A lot of fuss about a dozen aircraft. AJ seems to like the free publicity.
I don't see the A350 winning this one though.
AJ is a die hard Boeing fan, and Airbus' new sales department is moving like they are trying to sell ice to eskimo's. Also, AJ wants to stuff as many pax in a dense a configuration as possible without regards for comfort so this is a clear win for the 10 abreast B778.

I think that either aircraft are wrong for this mission.
This is a mission for a VLA. This is a hub to hub, flagship, low frequency, high added value service.
Putting a B778 or A350-1000 on this route is like flying JFK-LHR with a single daily A321.

I also doubt that a higher frequency would make a difference on a 20 hour route.

My prediction is that QF international will go from barely profitable to heavily loss making in the coming few years, with ramifications for the domestic network as well. Like BA, QF is hoping that passengers will keep paying their higher prices while constantly downgrading their product.
 
jagraham
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 7:38 am

At this time the GE9X has completed ground test, has completed flight test on the 747, and is mounted on the first 779 test plane. We will soon know if GE knows what they are talking about.
 
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zeke
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 8:24 am

flipdewaf,

Your understanding of DOW is correct just had the D term wrong.

Neither aircraft is fuel volume limited at the nominal design range. And the sectors SQ has been flying the ULR missions on I see they are still within the normal -900 tank capacity. They are neither MTOW or fuel volume limited on the ULR flights, if I recall correctly the first flight was around 100 tonnes of fuel and takeoff around 272 tonnes.

Sent you a PM with a link to the book. The book has some engine models for inspiration. Ideally the TSFC curve will be flat enough, if you are making altitude corrections it should be close enough.

The variable camber in part works by moving the lift distribution towards the tip, in doing so it moves the CP relative to the CG, thus the tail drag can be minimised.

Steps should be 2000 ft, sometimes 4000 ft, westbound at even levels. I haven’t looked to see if that assumption is correct, they may even go north east say SYD-PKC-LHR to get an average 20kts of wind assistance, flight time of around 19 hrs, in that case it would be odd levels.

Climb profile 250 below 10,000, then accelerate to initial cruise IAS and climb at that IAS to cruise altitude for the 777 or climb at 310 transition to 0.84 for the A350 is close enough. Descent, cruise Mach into 300 indicated, then 250 kts below 10,000.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
moa999
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 8:43 am

Waterbomber2 wrote:
I think that either aircraft are wrong for this mission.

I also doubt that a higher frequency would make a difference on a 20 hour route..


QF already has VLAs on the routes in A380 (with 787 LAX-JFK) and will continue to do so for many years.

You might want to look at the load factors on PER-LHR to see whether consumers care about saving time
 
FluidFlow
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 10:51 am

flipdewaf wrote:

zeke wrote:
flipdewaf wrote:
One of the reasons that the 777 seems often to go fast in my models is that (particularly for the 77W) when it has to be low at the start of cruise and the aircraft hasn’t yet reached the tropopause it cruises at a constant Mach which is higher in the hotter air (standard atmosphere model is used).


Which in reality probably is not accurate, more likely to see a constant TAS of around 485 KTAS on the 77W below transition to Mach 0.84 which is LRC (FL300 M0.81, FL320, M0.82, FL340 M0.83 FL360 M0.84), in airline operation the aircraft would fly between Mrc and Lrc at ECON speed. The A350 would be ballpark 5 kts faster, initial climb after takeoff to FL340 and maintaining 0.84 (490 KTAS).

That sounds reasonable, I want my model to represent a normal type flight as much as possible. I can easily set a speed or Mach number based on any particular part of the flight. I’d have to remember off the top of my head but I have it set to 250kts tas below 10K then it raises to something else up to 30k ( I think then moves to constant Mach above that) What is a reasonable way to set the speed at different altitudes and how/when would one normally go from speed to mach derived speed control?

Sorry this is going off topic.

Fred

Sent from my iPhone using Tapatalk


I know this is a bit off topic but it is interesting so I would like to ask a few questions:

What atmosphere model do you use for the calculation of the engine performance at assumed flight levels?

While crossing the tropical air the air density at a given flight level will be reduced and the increased temperature will lead to a relatively high water content at FL360 compared to the same FL at a TATL service.

Therefore the aircraft might fly in conditions where the engines are not as efficient as possible.

If you look here at Figure 5 in the paper linked (https://www.researchgate.net/publication/252404738_The_fine-scale_structure_of_the_global_tropopause_derived_from_COSMIC_GPS_radio_occultation_measurements) the flight path will be about 50 percent of the time (during northern winter) and 60 percent (during northern summer) in tropical conditions. Especially the segment Melbourne/Sidney to London will be in less favourable conditions as the "hot and wet" segment comes first. In addition to the density and temperature there will also be way more turbulence as the aircraft will fly nowhere near the tropopause (Figure 1: https://www.researchgate.net/publication/279520629_Characteristics_of_Tropopause-penetrating_Convection_determined_by_TRMM_and_COSMIC_GPS_radio_occultation_measurements) and therefore winds are way more likely to be present.

I suspect for normal segments this effects are negligible but for such a ULH?

The benefit of the Singapore - NY flight is that it is mostly in polar air.

I wonder what the reduction in fuel consummation of the Perth - London flight would be if it were all in polar air.
 
emiratesdriver
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 11:19 am

jupiter2 wrote:
emiratesdriver wrote:
I attended the 777X briefing day before yesterday for EK pilots, and the question regarding project sunrise was asked by one of the attending austronought 777 captains, the vague answer and the body language of the Boeing rep and test engineers in attendance suggested that it’s the A350s order to lose.


Why would Boeing staff give a competitor to QF inside knowledge on how their R.F.P. is progressing ? Probably being polite in giving an answer at all.


Spoken with the authority of someone who wasn’t there...
 
flipdewaf
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 11:22 am

FluidFlow wrote:

I know this is a bit off topic but it is interesting so I would like to ask a few questions:

What atmosphere model do you use for the calculation of the engine performance at assumed flight levels?
It is an ISA +0 model, I dont actually have the data for other models at the moment. I'm sure I would try to derive some but then there is a issue as to which one to use etc.

FluidFlow wrote:
While crossing the tropical air the air density at a given flight level will be reduced and the increased temperature will lead to a relatively high water content at FL360 compared to the same FL at a TATL service.

Therefore the aircraft might fly in conditions where the engines are not as efficient as possible.
So the engine model is very very basic. It basically has a set SFC at the moment (I did have it set to vary between about SFC*0.6 at sea level going to SFC 1 at 11+km, it was implemented in a fairly clunky way and for the long haul flights didn't make much difference due to the % time at low levels and added time to the computations. It would likely be worth reinstating that in a sensible way for this as the QF rules have 70mins hold at 1500ft which would make a big difference to the reserves at landing and so make the rest of the flight take a lot more.

FluidFlow wrote:
If you look here at Figure 5 in the paper linked (https://www.researchgate.net/publication/252404738_The_fine-scale_structure_of_the_global_tropopause_derived_from_COSMIC_GPS_radio_occultation_measurements) the flight path will be about 50 percent of the time (during northern winter) and 60 percent (during northern summer) in tropical conditions. Especially the segment Melbourne/Sidney to London will be in less favourable conditions as the "hot and wet" segment comes first. In addition to the density and temperature there will also be way more turbulence as the aircraft will fly nowhere near the tropopause (Figure 1: https://www.researchgate.net/publication/279520629_Characteristics_of_Tropopause-penetrating_Convection_determined_by_TRMM_and_COSMIC_GPS_radio_occultation_measurements) and therefore winds are way more likely to be present.

I suspect for normal segments this effects are negligible but for such a ULH?
certainly not my expertise but it may be worth me looking in to it when I do the engine modelling in more detail. I guess I would look at what factors will determine the engine outputs in my model and then determine if its worth it.

Fred
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FluidFlow
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 12:11 pm

flipdewaf wrote:
FluidFlow wrote:

I know this is a bit off topic but it is interesting so I would like to ask a few questions:

What atmosphere model do you use for the calculation of the engine performance at assumed flight levels?
It is an ISA +0 model, I dont actually have the data for other models at the moment. I'm sure I would try to derive some but then there is a issue as to which one to use etc.

FluidFlow wrote:
While crossing the tropical air the air density at a given flight level will be reduced and the increased temperature will lead to a relatively high water content at FL360 compared to the same FL at a TATL service.

Therefore the aircraft might fly in conditions where the engines are not as efficient as possible.
So the engine model is very very basic. It basically has a set SFC at the moment (I did have it set to vary between about SFC*0.6 at sea level going to SFC 1 at 11+km, it was implemented in a fairly clunky way and for the long haul flights didn't make much difference due to the % time at low levels and added time to the computations. It would likely be worth reinstating that in a sensible way for this as the QF rules have 70mins hold at 1500ft which would make a big difference to the reserves at landing and so make the rest of the flight take a lot more.

FluidFlow wrote:
If you look here at Figure 5 in the paper linked (https://www.researchgate.net/publication/252404738_The_fine-scale_structure_of_the_global_tropopause_derived_from_COSMIC_GPS_radio_occultation_measurements) the flight path will be about 50 percent of the time (during northern winter) and 60 percent (during northern summer) in tropical conditions. Especially the segment Melbourne/Sidney to London will be in less favourable conditions as the "hot and wet" segment comes first. In addition to the density and temperature there will also be way more turbulence as the aircraft will fly nowhere near the tropopause (Figure 1: https://www.researchgate.net/publication/279520629_Characteristics_of_Tropopause-penetrating_Convection_determined_by_TRMM_and_COSMIC_GPS_radio_occultation_measurements) and therefore winds are way more likely to be present.

I suspect for normal segments this effects are negligible but for such a ULH?
certainly not my expertise but it may be worth me looking in to it when I do the engine modelling in more detail. I guess I would look at what factors will determine the engine outputs in my model and then determine if its worth it.

Fred


The ISA model is fine.

What you can do is calculate for every Flight level the according temperature and air density profile.

For simplicity, you could assume a linear profile along the flight path (in a first step, later you could also split it up in smaller segments) and calculate the local temperature and air density at the point where the aircraft reaches the chosen flight level and at the point where the aircraft leaves said flight level.

With that you can calculate the temperature and air density along the flight path with given flight level.

To calculate the local temperature, you need either the altitude of the tropopause and the temperature at the tropopause as well as the corresponding ground values in the area where the aircraft reaches and leaves the flight level or the lapse rate and the ground temperature and altitude (the second should be easier to obtain if the local authorities provide the values).

Converting the atmosphere temperature at the flight level into air density is then straight forward.

These calculations are strongly seasonal (actually, they change daily).


For the engine part, I actually have no clue, only that the engines are optimised for a certain flight level and that temperature (air density) and humidity change the efficiency/performance but how much, I have no clue.
 
smartplane
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 12:12 pm

Gemuser wrote:
Australian tax law makes very difficult for QF to keep aircraft less than 20 - 25 years, it would havey to be a really, really strong fincial case for to retire the A380 in less time than that.

Qantas depreciating new aircraft over 20 years - a decade ago up to 25 years. Globally, commercial aircraft depreciation periods are falling, with many leasing companies at 15 years.

Interior refurbishment depreciation policy at Qantas would provide some insight. Seems to differ model to model, perhaps based on the nature of the refurbishment. Most major, non-US airlines depreciate up to 12 years, with ME3 over 5-7 years, and EU3 10-12 years.
 
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 12:20 pm

For this sort of analysis ISA is fine. Real flight planning systems will look at the actual wind and temperature from GRIB data.

The amount of water in air at cruise level is negligible for changing density height, where change temperature has a large impact on airframe/engine performance. We assume standard dry air, likewise we do not take into account the actual calorific value of fuel uplifted, just assume a generic a Jet fuel model.

SIN-JFK is via the North Pacific not polar.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
jupiter2
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 12:22 pm

emiratesdriver wrote:
jupiter2 wrote:
emiratesdriver wrote:
I attended the 777X briefing day before yesterday for EK pilots, and the question regarding project sunrise was asked by one of the attending austronought 777 captains, the vague answer and the body language of the Boeing rep and test engineers in attendance suggested that it’s the A350s order to lose.


Why would Boeing staff give a competitor to QF inside knowledge on how their R.F.P. is progressing ? Probably being polite in giving an answer at all.


Spoken with the authority of someone who wasn’t there...


Absolutely, but why would/should they ? It's none of your business.
 
FluidFlow
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 12:45 pm

zeke wrote:
For this sort of analysis ISA is fine. Real flight planning systems will look at the actual wind and temperature from GRIB data.

The amount of water in air at cruise level is negligible for changing density height, where change temperature has a large impact on airframe/engine performance. We assume standard dry air, likewise we do not take into account the actual calorific value of fuel uplifted, just assume a generic a Jet fuel model.

SIN-JFK is via the North Pacific not polar.


Thanks for the information.

JFK-SIN aswell? I assume they will circumvent the jet stream northwards like it is done on TATL.
 
flipdewaf
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 12:59 pm

FluidFlow wrote:

zeke wrote:


What I use in terms of the values is the ISA in increments from 0m up to 15000m in 500m increments with values of
Elevation (m)
Temp (K)
Pressure (bar)
Relative density
Density
Kinematic Viscosity
Kinematic Viscosity
Thermal Conductivity

and then use a linear interpolation between the relevant heights to get the value at the specific altitude. All my calculations are done in SI units then converted back to what people normally use people will switch off if you say a flight was 15025876m long...

Fred

Fred
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morrisond
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 1:06 pm

flipdewaf wrote:
FluidFlow wrote:

I know this is a bit off topic but it is interesting so I would like to ask a few questions:

What atmosphere model do you use for the calculation of the engine performance at assumed flight levels?
It is an ISA +0 model, I dont actually have the data for other models at the moment. I'm sure I would try to derive some but then there is a issue as to which one to use etc.

FluidFlow wrote:
While crossing the tropical air the air density at a given flight level will be reduced and the increased temperature will lead to a relatively high water content at FL360 compared to the same FL at a TATL service.

Therefore the aircraft might fly in conditions where the engines are not as efficient as possible.
So the engine model is very very basic. It basically has a set SFC at the moment (I did have it set to vary between about SFC*0.6 at sea level going to SFC 1 at 11+km, it was implemented in a fairly clunky way and for the long haul flights didn't make much difference due to the % time at low levels and added time to the computations. It would likely be worth reinstating that in a sensible way for this as the QF rules have 70mins hold at 1500ft which would make a big difference to the reserves at landing and so make the rest of the flight take a lot more.

FluidFlow wrote:
If you look here at Figure 5 in the paper linked (https://www.researchgate.net/publication/252404738_The_fine-scale_structure_of_the_global_tropopause_derived_from_COSMIC_GPS_radio_occultation_measurements) the flight path will be about 50 percent of the time (during northern winter) and 60 percent (during northern summer) in tropical conditions. Especially the segment Melbourne/Sidney to London will be in less favourable conditions as the "hot and wet" segment comes first. In addition to the density and temperature there will also be way more turbulence as the aircraft will fly nowhere near the tropopause (Figure 1: https://www.researchgate.net/publication/279520629_Characteristics_of_Tropopause-penetrating_Convection_determined_by_TRMM_and_COSMIC_GPS_radio_occultation_measurements) and therefore winds are way more likely to be present.

I suspect for normal segments this effects are negligible but for such a ULH?
certainly not my expertise but it may be worth me looking in to it when I do the engine modelling in more detail. I guess I would look at what factors will determine the engine outputs in my model and then determine if its worth it.

Fred


Hi - How much of an effect does Wing Flex have? Does the model take this into account? From cruise Images the A350 doesn't seem to have that much flex - I'm assuming the 777X will set new standards of flexiness.
 
FluidFlow
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 1:27 pm

flipdewaf wrote:
FluidFlow wrote:

zeke wrote:


What I use in terms of the values is the ISA in increments from 0m up to 15000m in 500m increments with values of
Elevation (m)
Temp (K)
Pressure (bar)
Relative density
Density
Kinematic Viscosity
Kinematic Viscosity
Thermal Conductivity

and then use a linear interpolation between the relevant heights to get the value at the specific altitude. All my calculations are done in SI units then converted back to what people normally use people will switch off if you say a flight was 15025876m long...

Fred

Fred


Do you use the ISA standard model without attributing for actual values?

Because the ISA only describes the standard atmosphere while in zones like the ICT or the Himalayan the actual atmosphere can be very different.

As zeke wrote, the conditions along the flight path will be obtained "live", but for your model, you could build it with average values and split the flight into segments of the same flight level.

You only need four parameters for a given point on the globe to calculate the other values:

Ground temperature at given point [K]
Elevation of given point [m]
Temperature gradient [K/m]
Altitude of the aircraft at this point [m]

The density of the air at the altitude and the pressure are calculated by solving the ideal gas law and the equation for hydrostatic equilibrium.
 
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 1:35 pm

smartplane wrote:
Gemuser wrote:
Australian tax law makes very difficult for QF to keep aircraft less than 20 - 25 years, it would havey to be a really, really strong fincial case for to retire the A380 in less time than that.


Qantas depreciating new aircraft over 20 years - a decade ago up to 25 years. Globally, commercial aircraft depreciation periods are falling, with many leasing companies at 15 years.

Interior refurbishment depreciation policy at Qantas would provide some insight. Seems to differ model to model, perhaps based on the nature of the refurbishment. Most major, non-US airlines depreciate up to 12 years, with ME3 over 5-7 years, and EU3 10-12 years.


Yes, but Qantas were on record decades ago stating that Australian tax law when it comes to depreciation puts them at a disadvantage compared to the likes of SQ who, as you point out, can depreciate over 12 years. They don't like having to do it over 20 years, but that's how it is and that is why the aircraft are generally kept that long in Australia.
I do enjoy a spot of flying, especially when it's not in economy!
 
flipdewaf
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 1:45 pm

morrisond wrote:
flipdewaf wrote:
FluidFlow wrote:

I know this is a bit off topic but it is interesting so I would like to ask a few questions:

What atmosphere model do you use for the calculation of the engine performance at assumed flight levels?
It is an ISA +0 model, I dont actually have the data for other models at the moment. I'm sure I would try to derive some but then there is a issue as to which one to use etc.

FluidFlow wrote:
While crossing the tropical air the air density at a given flight level will be reduced and the increased temperature will lead to a relatively high water content at FL360 compared to the same FL at a TATL service.

Therefore the aircraft might fly in conditions where the engines are not as efficient as possible.
So the engine model is very very basic. It basically has a set SFC at the moment (I did have it set to vary between about SFC*0.6 at sea level going to SFC 1 at 11+km, it was implemented in a fairly clunky way and for the long haul flights didn't make much difference due to the % time at low levels and added time to the computations. It would likely be worth reinstating that in a sensible way for this as the QF rules have 70mins hold at 1500ft which would make a big difference to the reserves at landing and so make the rest of the flight take a lot more.

FluidFlow wrote:
If you look here at Figure 5 in the paper linked (https://www.researchgate.net/publication/252404738_The_fine-scale_structure_of_the_global_tropopause_derived_from_COSMIC_GPS_radio_occultation_measurements) the flight path will be about 50 percent of the time (during northern winter) and 60 percent (during northern summer) in tropical conditions. Especially the segment Melbourne/Sidney to London will be in less favourable conditions as the "hot and wet" segment comes first. In addition to the density and temperature there will also be way more turbulence as the aircraft will fly nowhere near the tropopause (Figure 1: https://www.researchgate.net/publication/279520629_Characteristics_of_Tropopause-penetrating_Convection_determined_by_TRMM_and_COSMIC_GPS_radio_occultation_measurements) and therefore winds are way more likely to be present.

I suspect for normal segments this effects are negligible but for such a ULH?
certainly not my expertise but it may be worth me looking in to it when I do the engine modelling in more detail. I guess I would look at what factors will determine the engine outputs in my model and then determine if its worth it.

Fred


Hi - How much of an effect does Wing Flex have? Does the model take this into account? From cruise Images the A350 doesn't seem to have that much flex - I'm assuming the 777X will set new standards of flexiness.
None. trying to model aeroelastic effects while modeling the drag of an aircraft whilst going through varying climatic conditions makes CERN shudder.

My own understanding on the phenomenon of wing flex is that whilst it looks nice it isn't particularly useful and it is more an artifact of the differing historical choices and approaches to wing design. Airbus traditionally used a single slot flap with continuous uninterrupted flow as it didn't utilise a high speed aileron, this meant a lower complexity and lower weight system This however forced them to use a wing with more torsional stiffness so that at high speed the aileron on the outboard didn't cause a control reversal. This gave a stiffer but thicker wing less suited to high mach mumbers but with a sampler flap mechanism, horses for courses, neither approach has a particular overall advantage.

I havent studied the 777X wings but they seem to be single slotted, not sure if they still have the high speed aileron or not to be honest but they may have gone more with the Airbus approch. Not sure.

On the topic of is wing flex useful...
It can help to make the wing lighter by using a raked wingtip and helping load alleviation.
It can detract as the lift isn't going completely up as the force vector has a more sideways component. Again, there is no clear way that is better than the other.


Fred
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Waterbomber2
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 3:35 pm

As you say, wingflex only results in waste, due to unnecessarily increased dihedral. It may reduce wing tip induced drag to some extent, but it will be punished by a much larger additional profile drag and general induced drag components.

The A350 wing isn't that straight either. If you draw the intrados line, you will see a marked positive arch at the wing root.

IMO at the end of the day, the wing can only make that much of a difference in the greater scheme.
 
flipdewaf
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 3:37 pm

FluidFlow wrote:
flipdewaf wrote:
FluidFlow wrote:

zeke wrote:


What I use in terms of the values is the ISA in increments from 0m up to 15000m in 500m increments with values of
Elevation (m)
Temp (K)
Pressure (bar)
Relative density
Density
Kinematic Viscosity
Kinematic Viscosity
Thermal Conductivity

and then use a linear interpolation between the relevant heights to get the value at the specific altitude. All my calculations are done in SI units then converted back to what people normally use people will switch off if you say a flight was 15025876m long...

Fred

Fred


Do you use the ISA standard model without attributing for actual values?

Because the ISA only describes the standard atmosphere while in zones like the ICT or the Himalayan the actual atmosphere can be very different.

As zeke wrote, the conditions along the flight path will be obtained "live", but for your model, you could build it with average values and split the flight into segments of the same flight level.

You only need four parameters for a given point on the globe to calculate the other values:

Ground temperature at given point [K]
Elevation of given point [m]
Temperature gradient [K/m]
Altitude of the aircraft at this point [m]

The density of the air at the altitude and the pressure are calculated by solving the ideal gas law and the equation for hydrostatic equilibrium.

Yes, just standard 15°C at sea level ISA. I could implement that given time but at the moment the values are obtained from a table. I have though about taking it all in to code so it runs faster and that would be the time to do it but that's a big undertaking that I cannot justify (mainly due to small person at home demanding time).

I ran the model/simulation with a A350-900 SIN-EWR and fudged a landing weight of 171t. I took the TSFC down to 0.5 from 0.51 and the fuel usage was 100838kg for the trip with a time of 17hrs 17mins with no headwind.

I will try with the A350-1000 on a 8400nm run with no wind and 360pax load and see what I get. Anyone know what the airbus standard rules are?

Fred
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VirginFlyer
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Thu May 09, 2019 5:44 pm

flipdewaf wrote:
I havent studied the 777X wings but they seem to be single slotted, not sure if they still have the high speed aileron or not to be honest but they may have gone more with the Airbus approch. Not sure.

From this photo, it looks like they still have the high speed aileron:



V/F
It is not for him to pride himself who loveth his own country, but rather for him who loveth the whole world. The earth is but one country, and mankind its citizens. —Bahá'u'lláh
 
xwb565
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 3:29 am

From someone who knows better than me- A ulh 320t mtow a35k with a lightweight interior seating ~300pax should have a dow of ~147t. A payload of 30t will result in 139t of trip fuel with 4t as reserves. At 6.7t/hour 21 hours should be possible. This without any aerodynamic improvements that are in the works at TLS. That laminar flow contraption on the tail of msn1 may not be that far from seeing service.
 
FluidFlow
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 7:52 am

flipdewaf wrote:

Fred



Just if you are interested, I did not had enough time for the complicated segments and I can not tell you when I will but I made a simple excel to calculate temperature at pressure at given flight level for two segments: Central Europe and Northern Australia to Thailand.

It is interesting that the temperature at FL does no change much but the pressure is almost double in the tropical climate.

It is not really scientific, as I had to read the values out of the figures and the tropopause altitude was calculated with a simple tool but it gives an estimate.

Image: https://ibb.co/C5JmLmX

There is a little mistake in the results, in the central European segment the temperature at FL should be equal to the one at the troposphere but the difference is negligible. The reason is, that FL is bigger than the tropopause altitude and the temperature gradient is assumed to be 0 inside the tropopause.

I used the following sources:
https://en.wikipedia.org/wiki/Berlin#Climate
https://en.wikipedia.org/wiki/Singapore#Climate
https://www.researchgate.net/publication/252404738_The_fine-scale_structure_of_the_global_tropopause_derived_from_COSMIC_GPS_radio_occultation_measurements
https://rechneronline.de/physik/luftdruck-hoehe.php
https://www.dwd.de/EN/ourservices/rcccm/int/rcccm_int_ppp.html
https://www.researchgate.net/publication/252404738_The_fine-scale_structure_of_the_global_tropopause_derived_from_COSMIC_GPS_radio_occultation_measurements
 
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 8:10 am

We fly at constant pressure altitude (STD altimeter at flight levels), not constant height (distance between the aircraft and the ground).
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
FluidFlow
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 8:24 am

zeke wrote:
We fly at constant pressure altitude (STD altimeter at flight levels), not constant height (distance between the aircraft and the ground).


Oh good to know, is this a general statement or are there exceptions?

Must have made the wrong assumptions then, I always thought the flight level is given to the pilots from atc.
 
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 8:43 am

FluidFlow wrote:
zeke wrote:
We fly at constant pressure altitude (STD altimeter at flight levels), not constant height (distance between the aircraft and the ground).


Oh good to know, is this a general statement or are there exceptions?

Must have made the wrong assumptions then, I always thought the flight level is given to the pilots from atc.
The flight level refers to the 100 ft increments in altitude based on the aircraft altimeter wtih a ground level pressure setting of 1013hpa *shudders at the 'nearly' SI unit* from the standard atmosphere. In terms of if its given to the pilots or do the pilots choose then its probably down to airspace type and how the flight plan was filed. I fly bug smashers mostly so never really have cause to use flight levels. A mode-C transponder will give the info to eh ATC I'd guess that with mode A there would be some geometry where ATC would be able to have an estimate, the military can surely do it from primary radar to it should be fairly easy.

Fred
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 8:59 am

flipdewaf wrote:
FluidFlow wrote:
zeke wrote:
We fly at constant pressure altitude (STD altimeter at flight levels), not constant height (distance between the aircraft and the ground).


Oh good to know, is this a general statement or are there exceptions?

Must have made the wrong assumptions then, I always thought the flight level is given to the pilots from atc.
The flight level refers to the 100 ft increments in altitude based on the aircraft altimeter wtih a ground level pressure setting of 1013hpa *shudders at the 'nearly' SI unit* from the standard atmosphere. In terms of if its given to the pilots or do the pilots choose then its probably down to airspace type and how the flight plan was filed. I fly bug smashers mostly so never really have cause to use flight levels. A mode-C transponder will give the info to eh ATC I'd guess that with mode A there would be some geometry where ATC would be able to have an estimate, the military can surely do it from primary radar to it should be fairly easy.

Fred


Alright, now everything makes sense. Thanks for the clarification.

Fun fact about use of weird units instead of the SI-units. When I was typing the tables this morning, half asleep, I pressed one 0 too much, so the actual values in Bar are wrong by one order of magnitude. As the values are always given in hPa i wanted to multiply all of them by 100 but did by 1000.
 
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 11:05 am

ClassicLover wrote:
smartplane wrote:
Gemuser wrote:
Australian tax law makes very difficult for QF to keep aircraft less than 20 - 25 years, it would havey to be a really, really strong fincial case for to retire the A380 in less time than that.


Qantas depreciating new aircraft over 20 years - a decade ago up to 25 years. Globally, commercial aircraft depreciation periods are falling, with many leasing companies at 15 years.

Interior refurbishment depreciation policy at Qantas would provide some insight. Seems to differ model to model, perhaps based on the nature of the refurbishment. Most major, non-US airlines depreciate up to 12 years, with ME3 over 5-7 years, and EU3 10-12 years.


Yes, but Qantas were on record decades ago stating that Australian tax law when it comes to depreciation puts them at a disadvantage compared to the likes of SQ who, as you point out, can depreciate over 12 years. They don't like having to do it over 20 years, but that's how it is and that is why the aircraft are generally kept that long in Australia.

The QF A380 refurbishment depreciation period will be specific to the aircraft and work done, so should provide a good indication of the aircraft's planned remaining time with the airline.

New aircraft depreciation is about profit (or loss) smoothing, something which is more related to the self-interest of senior management and shareholders, than the actual operational life of the aircraft. Taking hypothetical examples, if two airlines each purchase a new aircraft for USD200m, both depreciate straight line, one over 10 years, and one over 20 years, but both sell after 10 years for USD50m, one airline will have over depreciated, and will need to write back USD50m in Y10, while the other will have under-depreciated, and will take a one off hit of USD50m.

With over depreciation, shareholders and senior management will have been under-rewarded in Y1-9, perhaps corrected in Y10, while with under depreciation, profit participants will have been over-rewarded Y1-9, and take a hit in Y10.

You can see the attraction of leasing and fixed price maintenance contracts (for life of lease), in respect to no surprises.
 
flipdewaf
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 11:27 am

I guess this is the best way to post this. There i to variants of the A35K for comparison. One with DOW at 147000kg and one with DOW at 150000kg. The TSFC is listed in the data.
Image

Fred
Image
 
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MoKa777
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 11:50 am

flipdewaf wrote:
I guess this is the best way to post this. There i to variants of the A35K for comparison. One with DOW at 147000kg and one with DOW at 150000kg. The TSFC is listed in the data.
Image

Fred


Wow! Thanks for this!

The A35K may use 2-3% less fuel than the 778 and may be 1-2% quicker as well. Add to this the fact that the A35K will be more versatile within the network than the 778, I see no operational (non-commercial) reason for QF to go for the 778.

The 779 may be useful in the QF network but with the A388 still around for some time to come, it is unnecessary.

A 789/A35K/A388 mix for long-haul at QF will be a wonderfully efficient and versatile one.
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zeke
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 1:00 pm

Fred,

I don’t think you are going to get much better that that. I will have a look at the route options based on winds and see if I can shave another hour off the flight time.

The TSFC I don’t see being different when they enter service. I expect the GE9X to improve once they have in service data, however the Trent XWB will also improve.
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StTim
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 1:16 pm

If the TSFC was the same for the Bus what sort of difference would it make?
 
jupiter2
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 1:31 pm

MoKa777 wrote:
flipdewaf wrote:
I guess this is the best way to post this. There i to variants of the A35K for comparison. One with DOW at 147000kg and one with DOW at 150000kg. The TSFC is listed in the data.
Image

Fred


Wow! Thanks for this!

The A35K may use 2-3% less fuel than the 778 and may be 1-2% quicker as well. Add to this the fact that the A35K will be more versatile within the network than the 778, I see no operational (non-commercial) reason for QF to go for the 778.

The 779 may be useful in the QF network but with the A388 still around for some time to come, it is unnecessary.

A 789/A35K/A388 mix for long-haul at QF will be a wonderfully efficient and versatile one.


I'm surprised at how efficient the 778 looks to be compared to the 35K considering the weight differences. However, I don't agree with you that this points to the 35K being more versatile for QF. Whichever aircraft is chosen is going to be in a unique, premium heavy configuration and when placed on shorter routes will equally be more fuel efficient than when doing the Sunrise flights, so while the 35K may burn less fuel, the percentage difference implied by the excellent table provided by Fred I wouldn't consider to be enough to rule out the 778. The flight time differences shown also aren't that great to make a significant difference, especially if QF are in a monopoly position on a route.

A fleet choice of 789/778/779 would also be a very efficient fleet, the 779 replacing the 380 from 2026 onward.

I believe that both manufacturers will be looking for an order that goes beyond the Sunrise fleet, the battle for 8-10 Sunrise aircraft while not to be discounted as insignificant, would be of far greater value if it included another 12-14 aircraft for the eventual replacement of the 380 fleet as well. Unless Airbus stretch the 35K further, this is where I see Boeing having the edge with the 779 and and perhaps a future 77K.

Also, thanks to flipdewaf (Fred), Zeke and FluidFlow, for providing some interesting and ultimately enlightening information, especially for the less technically inclined such as myself.
 
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zeke
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 1:52 pm

jupiter2 wrote:
I'm surprised at how efficient the 778 looks to be compared to the 35K considering the weight differences. However, I don't agree with you that this points to the 35K being more versatile for QF.


Where we have run the 779 with plans over our network the fuel burn delta and flight time delta is greater, but what Fred has done is still a lot better than guessing.

jupiter2 wrote:
Whichever aircraft is chosen is going to be in a unique, premium heavy configuration and when placed on shorter routes will equally be more fuel efficient than when doing the Sunrise flights, so while the 35K may burn less fuel, the percentage difference implied by the excellent table provided by


Fuel is only part of the consideration, other direct costs like landing and navigation fees are based upon weight. The QF crew wages are also linked to weight of the aircraft, an A380 captain earns more than an A330 one.

Maintenance costs will be higher for the 778, and the purchase price is likely to be around 25 million more per frame.

Realistically I think it’s too close to call, I see advantages and disadvantages either way.
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lightsaber
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 2:01 pm

zeke wrote:
Realistically I think it’s too close to call, I see advantages and disadvantages either way.

I agree.

I also think QF will use the prestige of the project sunrise aircraft for maximum negotiating advantage on a package of A350 vs. 787/777X. Price, delivery times, as well as project sunrise specific performance will be included in the decision.

QF has a huge negotiating advantage here. It would be a shame to waste it.

Lightsaber
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Mrakula
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 2:03 pm

jupiter2 wrote:
MoKa777 wrote:
flipdewaf wrote:
I guess this is the best way to post this. There i to variants of the A35K for comparison. One with DOW at 147000kg and one with DOW at 150000kg. The TSFC is listed in the data.
Image

Fred


Wow! Thanks for this!

The A35K may use 2-3% less fuel than the 778 and may be 1-2% quicker as well. Add to this the fact that the A35K will be more versatile within the network than the 778, I see no operational (non-commercial) reason for QF to go for the 778.

The 779 may be useful in the QF network but with the A388 still around for some time to come, it is unnecessary.

A 789/A35K/A388 mix for long-haul at QF will be a wonderfully efficient and versatile one.


I'm surprised at how efficient the 778 looks to be compared to the 35K considering the weight differences. However, I don't agree with you that this points to the 35K being more versatile for QF. Whichever aircraft is chosen is going to be in a unique, premium heavy configuration and when placed on shorter routes will equally be more fuel efficient than when doing the Sunrise flights, so while the 35K may burn less fuel, the percentage difference implied by the excellent table provided by Fred I wouldn't consider to be enough to rule out the 778. The flight time differences shown also aren't that great to make a significant difference, especially if QF are in a monopoly position on a route.

A fleet choice of 789/778/779 would also be a very efficient fleet, the 779 replacing the 380 from 2026 onward.

I believe that both manufacturers will be looking for an order that goes beyond the Sunrise fleet, the battle for 8-10 Sunrise aircraft while not to be discounted as insignificant, would be of far greater value if it included another 12-14 aircraft for the eventual replacement of the 380 fleet as well. Unless Airbus stretch the 35K further, this is where I see Boeing having the edge with the 779 and and perhaps a future 77K.

Also, thanks to flipdewaf (Fred), Zeke and FluidFlow, for providing some interesting and ultimately enlightening information, especially for the less technically inclined such as myself.


I do not guess A380 need replacement. Emirates is going to struggle in near future because of a lot of heavy metal on network. QF also would like have more smaller planes in fleet. If they need big aircraft for trunk routes, 778 get plus points in form of 779.
 
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ElroyJetson
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 2:04 pm

flipdewaf wrote:
I guess this is the best way to post this. There i to variants of the A35K for comparison. One with DOW at 147000kg and one with DOW at 150000kg. The TSFC is listed in the data.
Image

Fred



It is amazing how close fuel burn is for both frames. My question is in regards to the assumed 30t payload.

Where is this assumption coming from? Second, is it certain both frames have the legs to fly the mission at 30t?

And btw....thanks for the information. It is very interesting.
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Mrakula
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 2:04 pm

and what about wb fleet 789/359/35K? :-)
 
RJMAZ
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 2:21 pm

MoKa777 wrote:
The A35K may use 2-3% less fuel than the 778 and may be 1-2% quicker as well. Add to this the fact that the A35K will be more versatile within the network than the 778, I see no operational (non-commercial) reason for QF to go for the 778.
You have completely misinterpreted the table. The 777-8 absolutely smashes the A350-1000 by a massive 10% in terms of fuel per kg of payload carried.

The 777-8 is listed in the table as performing the flight 10T below MTOW. The A350-1000 with a 150T DOW is taking off at the limit of the 316T MTOW.

So the 777-8 could essily add 5T of extra payload and 5T of fuel and take off at MTOW. This changes things completely.

The 777-8 would be lifting 35,000kg of payload burning 138,422kg of fuel. The A350-1000's would lift 30,000kg of payload burning 130,566kg of fuel.

4.3522 litres per kg versus 3.95 litres is more than a 10% advantage to the 777-8.

The 777-8 could then carry 5T of extra payload in the hold on your average flight. Or on a day when the weather is poor the 777-8 can can use that hesdroom to still carry a full passenger load the A350-1000 would require blocked rows of seats.

The A350-1000 needs a MTOW bump above 320T to come close to the 777-8.
 
mig17
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 2:45 pm

xwb565 wrote:
From someone who knows better than me- A ulh 320t mtow a35k with a lightweight interior seating ~300pax should have a dow of ~147t. A payload of 30t will result in 139t of trip fuel with 4t as reserves. At 6.7t/hour 21 hours should be possible. This without any aerodynamic improvements that are in the works at TLS. That laminar flow contraption on the tail of msn1 may not be that far from seeing service.


Those seem to be the more accurate data about the A35K here for now. Now we lack the same for the 778 to be able to complete the comparaison. Almost everything in this thread seems to optimistic about the 778 performances.
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leo467
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Re: Updated: Qantas saying it is almost ready to select Project Sunrise aircraft

Fri May 10, 2019 2:53 pm

I wonder wether the ultrafan anouncement plays into this decision. After all, the 778 won't be available until 2022/23 which gives a fairly short window of opportunity to Boeing.
Airbus could probably offer 351 as early as 2021/22 which could do the mission albeit clearly with some compromises and "replace" these birds (which could then take over other tasks within the network) with 351 ultrafan birds in 2025.

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