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flipdewaf
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NMA/MOM/797 variant performance analysis

Sun Feb 09, 2020 4:22 pm

So....I have done some analysis...I have decided to keep this away from the Civ-Av forum as it will sit much better in here and although will get less traffic here I'd look for quality over quantity. :wink2:

I have taken 3 cross sections, estimated their weights using a mix of Stamford/Raymer weight estimation methods allied to my custom home-brewed performance estimation model (buildup method in excel allied to some VBA applying some basic mission rules with fuel flow calculated every second, I am not goig to post every second of results but the results of the mission/aircraft). You can see some of the results of the performance analysis tool being used to compare the 77W/779X and 77W+GE9x else ware in these forums.

The analysis is based on 3 models of the NMA.
1. The 7W ovoid. 17" seats with 2" armrests and 16" aisles. The overall width is 4724.4 and height of 4320
2. The large single aisle, width of 4.064 and a height of 4.216. Applying the same 3 abreast seats of the above scenario leaves the aircraft able to have a 28" aisle.
3. The narrow single aisle utilizing the same seat width and aisle as applied to the 7W Ovoid. This allows a width of 3.74m as a circular fuselage.

There is an assumed 100mm wall thickness in all 3 models and the floor thickness of 150mm

Image

The missions are based on each of the aircraft in their two Normal and stretched versions going over the missions seen in the data. The name of the aircraft refers to WB= Wide body (the 7Wovoid) NB = Narrow body and the NNB = Narrow narrow body. The lengths of the fuselages are based around those of the 757 (200 and 300) for the Narrow body variants and the 767 (200 and 300) for the WB. The number refers to the maximum passenger capacity (250/300 for the NBs, and 300/350 for the WB), each aircraft takes 50 pax less for the particular mission and uses 100kg/pax for the payload.

7W ovoid Mission Data.
Image

6W Narrow body
Image

6W Narrow Narrow body
Image


NB. The umber of significant figures should not be taken as sign of accuracy. From the previous models I have done it seems that it is generally within about 2-3% of real world data.

Hopefully this data can be used to have and to guide fruitful discussions.

Fred
Last edited by SQ22 on Sun Feb 09, 2020 6:28 pm, edited 1 time in total.
Reason: Typo fixed
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Stitch
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Re: NMA/MOM/797 variant performance analysis

Sun Feb 09, 2020 7:29 pm

So the "wide narrowbody" has a 6% higher trip fuel than the "narrowbody", but 20% lower than the "widebody".
 
flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Sun Feb 09, 2020 7:46 pm

Stitch wrote:
So the "wide narrowbody" has a 6% higher trip fuel than the "narrowbody", but 20% lower than the "widebody".

Yes (I’m now using phone so don’t have the computer in front of me) but the WB have got a higher capacity.

Fred


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Stitch
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Re: NMA/MOM/797 variant performance analysis

Sun Feb 09, 2020 7:58 pm

Stitch wrote:
So the "wide narrowbody" has a 6% higher trip fuel than the "narrowbody", but 20% lower than the "widebody".

flipdewaf wrote:
Yes (I’m now using phone so don’t have the computer in front of me) but the WB have got a higher capacity.


So 20% higher capacity for 20% higher trip cost.

Of course, the fare per passenger is probably more than the fuel bill to carry them, but when you add in the other costs, I wonder if NMA's per-passenger operating costs were any better than the A321XLR's.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Sun Feb 09, 2020 10:51 pm

Hi Fred,

Thanks for doing this.

I’m quite busy today so I won’t have much time to look at this until tomorrow.

Just a few simple questions.

What wingspans are you assuming?

What lengths are you assuming for 300 Seat WB and 300 Seat Narrowbody?

Does your model give you enough detail to say what weight per meter of fuselage you are assuming?

Does your model assume a value for wetted area of the fuselage? What are those numbers?

Thanks!
 
RJMAZ
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 5:55 am

Good work as always.

I assume the wing dimensions are scaled with the MTOW. They would all exceed code C gates. The heavier widebody would need huge folding tips to fit code C gates.

The big missing piece of the puzzle is the weight penalty of going ovoid. It could vary by quite a bit.

Does the surface drag reduction offset the weight increase? The weight increase itself will also increase drag.

The floor would be in compression but vertical beams on either side of the cargo containers would work well to brace the floor. I think the weight increase will be very minor.
 
flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 7:54 am

morrisond wrote:
Hi Fred,

Thanks for doing this.

I’m quite busy today so I won’t have much time to look at this until tomorrow.

Just a few simple questions.

What wingspans are you assuming?

41/48m
morrisond wrote:

What lengths are you assuming for 300 Seat WB and 300 Seat Narrowbody?

300seat NB = 54m, 300seat WB = 48.5.

think 753 and 762
morrisond wrote:

Does your model give you enough detail to say what weight per meter of fuselage you are assuming?

It gives me a total fuselage weight so we can back calculate.
morrisond wrote:

Does your model assume a value for wetted area of the fuselage? What are those numbers?

Thanks!

It calculates it from the height and width and assumes and eclipse. There are two options that I have toyed with in the past, one assumes that it is a constant cylinder and one assumes a domed front and coned back, length proportional to the width. I’ll see which one is is use on this one. The ovoid as shown the the pictures has a perimeter of 4.8% less than if it were circular.

RJMAZ wrote:
Good work as always.

I assume the wing dimensions are scaled with the MTOW. They would all exceed code C gates. The heavier widebody would need huge folding tips to fit code C gates.

The big missing piece of the puzzle is the weight penalty of going ovoid. It could vary by quite a bit.

As I don’t use FEA I had to make some assumptions on the weight, I assumed that it would have equal weight to that of a round fuselage with a diameter of the top section.
RJMAZ wrote:

Does the surface drag reduction offset the weight increase? The weight increase itself will also increase drag.

Harder than you’d imagine to assess and in this instance impossible because of the assumptions made on weight. In this case it would because there is no increase in weight and a decrease in surface area but it’s not right to compare an assumed value directly with a calculated one.
RJMAZ wrote:

The floor would be in compression but vertical beams on either side of the cargo containers would work well to brace the floor. I think the weight increase will be very minor.


If the skin were to only carry the hoop stresses it would be 4.8% lighter and at about 12t ( from the top of my head) thats about 0.5t that can be used without penalty to beef up the floor and extra areas of stress in the fuselage.

Fred



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keesje
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 9:08 am

Great work Fred, 3 relevant cross sections.

Lots of assumptions, but eduicated ones it seems.

300 seats seems a stretch for the narrow NB. Probably lots of material needed to make it strong & stiff enough.
That would up the empty weight dramatically. A narrow single narrow would create trouble for lav visits, dinner
service etc on long long flight. And probably not only on long flights.

I can't distract it from your tables, what do you think would be the OEW's for the three configurations for
252 seats economy (36 rows 2-3-2, 42 rows 3-3) for the flight you included.

As you know I've been promoting fat NB / wide aisle configs for a while, because I feel they could neutralize
some of the typical single aisle / higher capacity range challenges. Slight wider circular cross section than
your NB, enabling it to offer comfortable 300 economy seats and/or 1-2-1 or 1-1-1 premium seats on longer
flights. I tried to include the extra required galley, crew rests and lavatories for longer flights.

Image

Shorter, longer range, premium seats variant. https://lh3.googleusercontent.com/-r6OQ ... keesje.jpg

In my opinion Boeing should focus first on developping a extremely efficient 150-200 seater, with execellent
industralization options, engine choice etc. If they could use a same cross section for the NMA segment is
a good question. It would need a unique wing box/ wing/ engines / landing gear set anyway IMO.
"Never mistake motion for action." Ernest Hemingway
 
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Taxi645
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 9:56 am

Following with interest.
Innovation is seeing opportunity before obstacle.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 11:18 am

flipdewaf wrote:
morrisond wrote:
Hi Fred,

Thanks for doing this.

I’m quite busy today so I won’t have much time to look at this until tomorrow.

Just a few simple questions.

What wingspans are you assuming?

41/48m
morrisond wrote:

What lengths are you assuming for 300 Seat WB and 300 Seat Narrowbody?

300seat NB = 54m, 300seat WB = 48.5.

think 753 and 762
morrisond wrote:

Does your model give you enough detail to say what weight per meter of fuselage you are assuming?

It gives me a total fuselage weight so we can back calculate.
morrisond wrote:

Does your model assume a value for wetted area of the fuselage? What are those numbers?

Thanks!

It calculates it from the height and width and assumes and eclipse. There are two options that I have toyed with in the past, one assumes that it is a constant cylinder and one assumes a domed front and coned back, length proportional to the width. I’ll see which one is is use on this one. The ovoid as shown the the pictures has a perimeter of 4.8% less than if it were circular.

RJMAZ wrote:
Good work as always.

I assume the wing dimensions are scaled with the MTOW. They would all exceed code C gates. The heavier widebody would need huge folding tips to fit code C gates.

The big missing piece of the puzzle is the weight penalty of going ovoid. It could vary by quite a bit.

As I don’t use FEA I had to make some assumptions on the weight, I assumed that it would have equal weight to that of a round fuselage with a diameter of the top section.
RJMAZ wrote:

Does the surface drag reduction offset the weight increase? The weight increase itself will also increase drag.

Harder than you’d imagine to assess and in this instance impossible because of the assumptions made on weight. In this case it would because there is no increase in weight and a decrease in surface area but it’s not right to compare an assumed value directly with a calculated one.
RJMAZ wrote:

The floor would be in compression but vertical beams on either side of the cargo containers would work well to brace the floor. I think the weight increase will be very minor.


If the skin were to only carry the hoop stresses it would be 4.8% lighter and at about 12t ( from the top of my head) thats about 0.5t that can be used without penalty to beef up the floor and extra areas of stress in the fuselage.

Fred



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Hi - What are the weights of the two Fuselage's? 300 WB vs 300NB?

Are the containers in the belly the same size (or another way to say it is can the belly on the WB be squished more so it takes a Container of the same height as the NB but it of course more width)?
 
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seahawk
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 11:27 am

Very interesting analysis. I talked to some CFRP structure guys, over coffee this morning and they think that the penalty of an wide oval fuselage would be higher than the structural penalty of a longer circular fuselage. According to them a longer fuselage is a very easy load distribution and can easily be handled by CFRP, the ovid creates a very complex multi-linear load distribution, which they call not favourable for a CFRP application, as the material would need to have high strength in all 3 dimensions, which creates a difficult layout for the fibre panels and a generally thick and heavy CFRP product.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 11:48 am

seahawk wrote:
Very interesting analysis. I talked to some CFRP structure guys, over coffee this morning and they think that the penalty of an wide oval fuselage would be higher than the structural penalty of a longer circular fuselage. According to them a longer fuselage is a very easy load distribution and can easily be handled by CFRP, the ovid creates a very complex multi-linear load distribution, which they call not favourable for a CFRP application, as the material would need to have high strength in all 3 dimensions, which creates a difficult layout for the fibre panels and a generally thick and heavy CFRP product.


Interesting. Were they talking about a pure Ovoid - or the Ostrower's Child shape?

What about doing it in metal or Metal Skins on Composite Structure? Or are there too many isolation issues. Composites are used in Floor Beams. Monolithic Carbon structure for the floor beam and lower lobe rib as one piece, with Upper Lobe as another Monolithic piece and both attached at the sides of the floor beam.

Would the compression on the floor be up so struts attached from the beams at the sides of the cargo area running down to the lower rib are in tension and help the lower from wanting to bow out? (Or just the Monolithic concept above with passthroughs for cabling/ductwork).

Whether or not Boeing goes 6W or 7W I doubt they will throw out the work they did on 777X with the ribs that reduce in thickness as they go up - then widen out again in the crown to provide a few more inches of shoulder room.

That may get an aisle in the narrowbody concept a few inches wider - or make 16" aisles in the WB 17-18".
 
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seahawk
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 12:03 pm

Our coffee breaks are not that long.

But the basic problem you need to understand is that the pressurised vessel wants to become a circle. So in the wide ovid, it is not actually the side ends wanting to push inside, but the centre of the shape wanting to push outside. That is a big difference to a A350 like shape, where actually the centre of the section does not experience such loads and the load is limited to the side ends, the want to push outside. Imagine a rubber balloon with the floor as a fixed (round) structure inside it. When pressurised it would aim to become a circle with the diameter the same as the diameter of the round floor inside the balloon. A fuselage of a plane does not act differently.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 12:41 pm

seahawk wrote:
Our coffee breaks are not that long.

But the basic problem you need to understand is that the pressurised vessel wants to become a circle. So in the wide ovid, it is not actually the side ends wanting to push inside, but the centre of the shape wanting to push outside. That is a big difference to a A350 like shape, where actually the centre of the section does not experience such loads and the load is limited to the side ends, the want to push outside. Imagine a rubber balloon with the floor as a fixed (round) structure inside it. When pressurised it would aim to become a circle with the diameter the same as the diameter of the round floor inside the balloon. A fuselage of a plane does not act differently.



So Basically take the Diameter of the whole Ostrower shape (Fred can your CAD calculate this?) and use that to figure out the radius of the new circle that the fuselage wants to assume?
 
flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 1:53 pm

flipdewaf wrote:
It gives me a total fuselage weight so we can back calculate.

morrisond wrote:
Hi - What are the weights of the two Fuselage's? 300 WB vs 300NB?

WB350 = 13968kg
WB300 = 12545kg
NB300 = 11506kg
NB250 = 9630kg
NNB300 = 10888kg
NNB250 = 8768kg

You'll see that the increase is greater for the NB types as they are no longer in the pressure dominated regime due to the length/load/height ratios, the NNB is actually out of it at the shorter length already albeit only slightly so makes knack all difference.

morrisond wrote:
Are the containers in the belly the same size (or another way to say it is can the belly on the WB be squished more so it takes a Container of the same height as the NB but it of course more width)?


The drawings all show LD3-45s

morrisond wrote:
So Basically take the Diameter of the whole Ostrower shape (Fred can your CAD calculate this?) and use that to figure out the radius of the new circle that the fuselage wants to assume?

Perimeter of the shape is 14.13m equating to a radius of 2.249mm, 4.498m diameter (177 in Victorian numbers).

Fred
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flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 1:57 pm

Duplicate - please Delete.
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seahawk
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 2:31 pm

morrisond wrote:
seahawk wrote:
Our coffee breaks are not that long.

But the basic problem you need to understand is that the pressurised vessel wants to become a circle. So in the wide ovid, it is not actually the side ends wanting to push inside, but the centre of the shape wanting to push outside. That is a big difference to a A350 like shape, where actually the centre of the section does not experience such loads and the load is limited to the side ends, the want to push outside. Imagine a rubber balloon with the floor as a fixed (round) structure inside it. When pressurised it would aim to become a circle with the diameter the same as the diameter of the round floor inside the balloon. A fuselage of a plane does not act differently.


So Basically take the Diameter of the whole Ostrower shape (Fred can your CAD calculate this?) and use that to figure out the radius of the new circle that the fuselage wants to assume?


That is not the same, because a circle of a similar diameter, still has a much more benign load distribution. For a circle the pressurisation loads are the simplest possible load distribution, a area load in a 90° angle to the surface of the fuselage. The opposite load vectors kind of cancel each other out. In a non circle this becomes a lot more complex.
 
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keesje
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 2:42 pm

morrisond wrote:
Whether or not Boeing goes 6W or 7W I doubt they will throw out the work they did on 777X with the ribs that reduce in thickness as they go up - then widen out again in the crown to provide a few more inches of shoulder room.

That may get an aisle in the narrowbody concept a few inches wider - or make 16" aisles in the WB 17-18".


In general aerospace constructions are compromises. So if you reduce thickness you pay the price elsewhere. In weight, wider ribs, stronger more expensive materials, lower noise cabin, costlier production, less insulalted for temperature, heavier constructions elsewhere (e.g. skin thickness). Maybe the 777x fuselage (fatigue ?) rupture orginated there.. Seldom win-wins..

In general aisles on longer flights are 19-20 inch. Not 16. Your would unintentionally touch most aisle seat passenger walking through.
"Never mistake motion for action." Ernest Hemingway
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 4:28 pm

Hi Fred,

So the Fuselage weight goes up by 1,000kg (which makes sense and I agree with it) on a 300 Seat WB vs 300 Seat NB and the DOW weight goes from 63,000 to 74,000kg.

That seems a little excessive. I accept that weight of everything else goes up with a higher fuselage weight. But basically are you saying that if the 6W was made of Aluminum it's DOW would go up by 11,000 KG as well with an 48M wing. Which kind of makes sense - but why are you using different wings? 1,000 KG is peanuts.

Please understand I am not criticizing - just trying to understand how you get to your numbers.

All along I have been assuming the same wing size - a folding 41M makes a lot of sense to me. Basically stick the 7W fuselage on the same Wing/Wingbox/Gear as the 6W. Or if you are not going to limit yourself to 737/A320 gate sizes stick the 6W on the 48M wing. Although that seems to be somewhat overwinged given the fuel fraction will be less and less of the MTOW and that could take you well beyond 5,000NM.

The 7W gear could be a little shorter as rotation angle is not as big a problem either.

How does it look when you do that?
 
flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 10, 2020 5:01 pm

morrisond wrote:
Hi Fred,

So the Fuselage weight goes up by 1,000kg (which makes sense and I agree with it) on a 300 Seat WB vs 300 Seat NB and the DOW weight goes from 63,000 to 74,000kg.

That seems a little excessive. I accept that weight of everything else goes up with a higher fuselage weight. But basically are you saying that if the 6W was made of Aluminum it's DOW would go up by 11,000 KG as well with an 48M wing. Which kind of makes sense - but why are you using different wings? 1,000 KG is peanuts.

Well the wing has to lift the plane, the payload and the fuel off the ground, not just the fuselage and whilst the difference in the fuselage might only be ~9% which if carried through the rest of the system would equate to an overall weight of ~9% higher. If you look at the mission ~4000nm vs 5000nm (+~25%) then you will arguable need 25% higher fuel. This doesn't just equate to bumping the fuel up by the required amount but also the structure to carry that extra weight and the structure to carry that structure. This is why excess weight is so frowned upon.
morrisond wrote:

Please understand I am not criticizing - just trying to understand how you get to your numbers.

All along I have been assuming the same wing size - a folding 41M makes a lot of sense to me. Basically stick the 7W fuselage on the same Wing/Wingbox/Gear as the 6W. Or if you are not going to limit yourself to 737/A320 gate sizes stick the 6W on the 48M wing. Although that seems to be somewhat overwinged given the fuel fraction will be less and less of the MTOW and that could take you well beyond 5,000NM.

An herein lies the issue but the other way around. You can put a smaller wing on the heavier structure but you won't get the performance (payload/range).
morrisond wrote:

The 7W gear could be a little shorter as rotation angle is not as big a problem either.

And a larger set of tail structures to maintain swept volume. As Keesje says, it's all a compromise.
morrisond wrote:

How does it look when you do that?


Without running the actual analysis one would hazard that the shorter version may get some ~3500nm range and the larger version could go island hopping.

Fred
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morrisond
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 12:28 pm

It seems to me that if you are going to compare one to another you have to hold a few things constant.

If you ever get some time and could rerun the 300WB with the narrow wing and 9% higher DOW and same mission as the 300NB that would be greatly appreciated.

The two planes you have built have two different capabilities. If Boeing is going for a certain capacity and choosing between WB or NB they will be aiming for the same mission as well. They won't be comparing one size to another with two different ranges.

And if you do run it - just for fun put 1,000 more payload on the NB (vs similar capacity/winged WB)and see what happens.

I'm assuming your model takes into account for the bigger cross section - really curious to see what the shorter length with reduction in wetted area (and I assume slightly bigger tail to account shorter length) does for overall drag.

Thanks
 
flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 1:30 pm

morrisond wrote:
It seems to me that if you are going to compare one to another you have to hold a few things constant.

In this instance the technology level are the things being held constant (SFC, oswald factor).

Did you miss the fact that there is also the stretched version of the WB doing the shorter route?

morrisond wrote:
If you ever get some time and could rerun the 300WB with the narrow wing and 9% higher DOW and same mission as the 300NB that would be greatly appreciated.
A 9% increase in DOW wont give you an aircraft capable of the mission if you keep the same wing. It needs a different, bigger wing to maintain the mission. I can do some thinking and do it but not sure when.

morrisond wrote:
The two planes you have built have two different capabilities. If Boeing is going for a certain capacity and choosing between WB or NB they will be aiming for the same mission as well. They won't be comparing one size to another with two different ranges.

They absolutely will.
Would you not say that the 787/77W/779X/A350-1000 had an impact on the viability of the A380?
Look at the range of sizes of aircraft on any europe-NA route today and you'll see all sorts of size ranges operating, the fungibility of the market is real.
morrisond wrote:
And if you do run it - just for fun put 1,000 more payload on the NB (vs similar capacity/winged WB)and see what happens.

I'm assuming your model takes into account for the bigger cross section - really curious to see what the shorter length with reduction in wetted area (and I assume slightly bigger tail to account shorter length) does for overall drag.

Thanks

See what I can do.

Fred
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seahawk
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 1:54 pm

Size is secondary. If a 250 seat plane can do the same mission at lower costs than the 300 seat version, it will sell and the other will not. It makes no sense to adjust the parameters until the ovid widebody is competitive.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 2:06 pm

flipdewaf wrote:
morrisond wrote:
It seems to me that if you are going to compare one to another you have to hold a few things constant.

In this instance the technology level are the things being held constant (SFC, oswald factor).

Did you miss the fact that there is also the stretched version of the WB doing the shorter route?

morrisond wrote:
If you ever get some time and could rerun the 300WB with the narrow wing and 9% higher DOW and same mission as the 300NB that would be greatly appreciated.
A 9% increase in DOW wont give you an aircraft capable of the mission if you keep the same wing. It needs a different, bigger wing to maintain the mission. I can do some thinking and do it but not sure when.

morrisond wrote:
The two planes you have built have two different capabilities. If Boeing is going for a certain capacity and choosing between WB or NB they will be aiming for the same mission as well. They won't be comparing one size to another with two different ranges.

They absolutely will.
Would you not say that the 787/77W/779X/A350-1000 had an impact on the viability of the A380?
Look at the range of sizes of aircraft on any europe-NA route today and you'll see all sorts of size ranges operating, the fungibility of the market is real.
morrisond wrote:
And if you do run it - just for fun put 1,000 more payload on the NB (vs similar capacity/winged WB)and see what happens.

I'm assuming your model takes into account for the bigger cross section - really curious to see what the shorter length with reduction in wetted area (and I assume slightly bigger tail to account shorter length) does for overall drag.

Thanks

See what I can do.

Fred


Thanks - or instead of 1,000 KG more payload on the equivalent Capacity NB - just make the fuselage weigh 1,000 kg more on the NB (assume it's made out of Aluminum vs Carbon 7W) then it will really isolate the aero differences. Same thrust engines, same wing.

I'm just thinking about the 9% difference as well. Yes that is what a Carbon 7W fuselage 20% shorter could weigh more vs a Carbon 6W probably in a worst case - But with the same 250 seats in typical density which you are using which makes sense for both and Luggage and people - that's 25,000 kg of Payload (250 passengers x 100KG) - the total weight of the loaded fuselages only have a difference of about 2.8% (37,545/36,506KG). Loaded up at Maximum Capacity of 300 People the difference would fall to 2.5% (42,545/41,506kg) which is what I assume they would have to design for.

I would have to assume that the wing, wingbox and gear don't care whether or not that extra 25,000-30,000kg is in Passengers/Cargo - or a super heavy empty Fuselage.
 
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 2:16 pm

seahawk wrote:
Size is secondary. If a 250 seat plane can do the same mission at lower costs than the 300 seat version, it will sell and the other will not. It makes no sense to adjust the parameters until the ovid widebody is competitive.


I would agree - but we have to compare Apples to Apples vs Apples to Oranges. A 300 Seat Widebody able to fly 4,800 NM is not the same as a 300 Seat NB able to only fly 3,800 NM.

That is why I'm asking for planes with the same Capability and Capacity - only valid way to compare.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 4:29 pm

I just did some quick math - the wetted area of an 54M Cylinder (too hard to calculate an actual aircraft fuselage) that is 4.13M in diameter is approximately 700m2. This is the NB fuselage.

A 48.5 M WB with an average Diameter of 4.5M is 685m2. That is an 2.1% advantage for the shorter WB. I think you could take a little more off the WB in length as well (maybe a M to get equivalent capacity) - putting the advantage more like 4-5%.

Interesting.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 5:08 pm

Oops - I forgot the ends of the cylinders - I’ll have to redo the calcs after I get back from lunch - it may be closer to a wash.

Edit - quick calc - adding the ends in only reduces advantage of WB by about a third.

Plus shorter WB would probably need a larger tail.
 
DenverTed
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 5:33 pm

The logical case for a 55m long 7,000nm range single aisle and ending production of the 787 and A350.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 7:29 pm

So more precise numbers.

Looking at the Narrow Body. Radius of 2.065M. Passenger Cabin 39.4M at 31" Seat pitch.

I took the Radius of 2.065 and calculated the nose as a Hemisphere - that gave me 26.8m2 without the base. I assumed about another 3m (2.935m) behind the Nose plus the passenger cabin of 39.4M to get a surface area of that cylinder of 549m2 not including the ends.

Then I figured out the surface area of a cone for the remaining fuselage length of 54m-44.4M or 9.6m - that is 63.7m2 not including the base.

That is a total of 639.5m2 for the 6W.

For the 7W - the nose with a radius of 2.25m is 31.8m2. The cabin is 33.9M long - which fits with total length of 48.5 vs 54M for the Single Aisle. Assume total length in front of cabin of 5M (you get a little more width to pack more in) giving you a constant section of 36.68M and a surface area of 518.6m2.

The surface area of a cone for the remaining fuselage length of 48.5- 33.9M + 5M = 69.7m2.

That gives an approximate of the wetted surface of the 7W = 620.1m2

That gives an advantage to the 7W of 3.0%.

Not bad.
 
flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 7:33 pm

morrisond wrote:
Thanks - or instead of 1,000 KG more payload on the equivalent Capacity NB - just make the fuselage weigh 1,000 kg more on the NB (assume it's made out of Aluminum vs Carbon 7W) then it will really isolate the aero differences. Same thrust engines, same wing.


What makes you think CFRP is lighter?

morrisond wrote:
That is why I'm asking for planes with the same Capability and Capacity - only valid way to compare.

Voila
Image
Capacity and capability met, wing size not. 185m2 44m span. The structure of the fuselage is ~1000kg higher
the horizontal tail is 700kg heavier, the vertical tail is 300kg heavier, and thus requiring control surface weights (think how much of those rear surfaces are made of movable controls) of ~670kg more.
all this requires a wing that is heavier by 2000kg to lift itself off the ground due to being bigger by some 20m^2 X 2. So all of a sudden the 700m^2 vs 685m^2 being the difference in surface area turns in to a 1340m^2 for the ovoid
1233m^2 for the NB
8.7% increase.

Lets not also forget that the comparison is being made between the wider of the two narrowbodies used in this analysis, with an aisle width of 28", the narrowbody with the same seat width and same aisle width (apples to apples being key of course) comes in with a surface area of 1103m^2.

With regard to the variant of the WB that uses the exact same 165m^2 wing for the true apples to apples comparison, its sinking to the bottom of the atlantic about 400nm of fthe coast of florida :wink2:

So we have compared the 4000nm variant, what are you thinking the 5000nm looks like now you hobbled it for this mission?

Fred
Image
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 7:55 pm

flipdewaf wrote:
morrisond wrote:
Thanks - or instead of 1,000 KG more payload on the equivalent Capacity NB - just make the fuselage weigh 1,000 kg more on the NB (assume it's made out of Aluminum vs Carbon 7W) then it will really isolate the aero differences. Same thrust engines, same wing.


What makes you think CFRP is lighter?

morrisond wrote:
That is why I'm asking for planes with the same Capability and Capacity - only valid way to compare.

Voila
Image
Capacity and capability met, wing size not. 185m2 44m span. The structure of the fuselage is ~1000kg higher
the horizontal tail is 700kg heavier, the vertical tail is 300kg heavier, and thus requiring control surface weights (think how much of those rear surfaces are made of movable controls) of ~670kg more.
all this requires a wing that is heavier by 2000kg to lift itself off the ground due to being bigger by some 20m^2 X 2. So all of a sudden the 700m^2 vs 685m^2 being the difference in surface area turns in to a 1340m^2 for the ovoid
1233m^2 for the NB
8.7% increase.

Lets not also forget that the comparison is being made between the wider of the two narrowbodies used in this analysis, with an aisle width of 28", the narrowbody with the same seat width and same aisle width (apples to apples being key of course) comes in with a surface area of 1103m^2.

With regard to the variant of the WB that uses the exact same 165m^2 wing for the true apples to apples comparison, its sinking to the bottom of the atlantic about 400nm of fthe coast of florida :wink2:

So we have compared the 4000nm variant, what are you thinking the 5000nm looks like now you hobbled it for this mission?

Fred


Somehow I don't think the tail would get 3,700 lbs heavier. Are you doubling the size? Come on a whole A320 fuselage only weighs 4,500KG. It 's in the article where it also talks about if you used Carbon to build an A320 fuselage it would get lighter by about 1,200kg.

https://www.dlr.de/fa/Portaldata/17/Res ... srw_10.pdf
 
flipdewaf
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NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 8:48 pm

morrisond wrote:
flipdewaf wrote:
morrisond wrote:
Thanks - or instead of 1,000 KG more payload on the equivalent Capacity NB - just make the fuselage weigh 1,000 kg more on the NB (assume it's made out of Aluminum vs Carbon 7W) then it will really isolate the aero differences. Same thrust engines, same wing.


What makes you think CFRP is lighter?

morrisond wrote:
That is why I'm asking for planes with the same Capability and Capacity - only valid way to compare.

Voila
Image
Capacity and capability met, wing size not. 185m2 44m span. The structure of the fuselage is ~1000kg higher
the horizontal tail is 700kg heavier, the vertical tail is 300kg heavier, and thus requiring control surface weights (think how much of those rear surfaces are made of movable controls) of ~670kg more.
all this requires a wing that is heavier by 2000kg to lift itself off the ground due to being bigger by some 20m^2 X 2. So all of a sudden the 700m^2 vs 685m^2 being the difference in surface area turns in to a 1340m^2 for the ovoid
1233m^2 for the NB
8.7% increase.

Lets not also forget that the comparison is being made between the wider of the two narrowbodies used in this analysis, with an aisle width of 28", the narrowbody with the same seat width and same aisle width (apples to apples being key of course) comes in with a surface area of 1103m^2.

With regard to the variant of the WB that uses the exact same 165m^2 wing for the true apples to apples comparison, its sinking to the bottom of the atlantic about 400nm of fthe coast of florida :wink2:

So we have compared the 4000nm variant, what are you thinking the 5000nm looks like now you hobbled it for this mission?

Fred


Somehow I don't think the tail would get 3,700 lbs heavier. Are you doubling the size? Come on a whole A320 fuselage only weighs 4,500KG. It 's in the article where it also talks about if you used Carbon to build an A320 fuselage it would get lighter by about 1,200kg.

https://www.dlr.de/fa/Portaldata/17/Res ... srw_10.pdf


The surfaces need to be bigger. The higher weight, thrust and the lower moment arm combine to require them to increase in size. Like any cantilevered udl carrying structure they increase weight at the cube of their length (span) in this case the lever arm is ~12% lower and the thrust ~5% more. The increase in area is about 45%, the increase in weight is about 50%.

Out of interest What would you expect it to be?

Fred


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LH707330
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 11, 2020 11:29 pm

Fred, thanks for putting this together. Looks like a 6W 757 replacement is likely the way to go of these options. Now my question is whether the OEW/m^2 compares favorably to an A321, and whether this new design has enough of a per-seat advantage. You have numbers on that?
 
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keesje
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 12:07 am

At some point a larger cross section becomes a requirement to make the fuselage both strong, stiff and structurally efficient enough to hold 40+ seat rows. You specified an 28 inch aisle to make possible people passing each and trolleys during flight and during (de)boarding.


Starting with the all paying passengers, I would love do do/see some operational research / simulations on this process, to see where the optimal trade-off in aisle width lays.

Image
https://www.jetphotos.com/photo/187727

Standard trolleys seem to be 0.31m / 11.9 inch wide. Removing the sharpish corners / edges would help also. It's also related to seats/armrest. If you make those very narrow, people hang in the aisle more, avoiding shoulder rubbing with their neighbours.

Image
"Never mistake motion for action." Ernest Hemingway
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 1:33 am

flipdewaf wrote:
morrisond wrote:
flipdewaf wrote:

What makes you think CFRP is lighter?


Voila
Image
Capacity and capability met, wing size not. 185m2 44m span. The structure of the fuselage is ~1000kg higher
the horizontal tail is 700kg heavier, the vertical tail is 300kg heavier, and thus requiring control surface weights (think how much of those rear surfaces are made of movable controls) of ~670kg more.
all this requires a wing that is heavier by 2000kg to lift itself off the ground due to being bigger by some 20m^2 X 2. So all of a sudden the 700m^2 vs 685m^2 being the difference in surface area turns in to a 1340m^2 for the ovoid
1233m^2 for the NB
8.7% increase.

Lets not also forget that the comparison is being made between the wider of the two narrowbodies used in this analysis, with an aisle width of 28", the narrowbody with the same seat width and same aisle width (apples to apples being key of course) comes in with a surface area of 1103m^2.

With regard to the variant of the WB that uses the exact same 165m^2 wing for the true apples to apples comparison, its sinking to the bottom of the atlantic about 400nm of fthe coast of florida :wink2:

So we have compared the 4000nm variant, what are you thinking the 5000nm looks like now you hobbled it for this mission?

Fred


Somehow I don't think the tail would get 3,700 lbs heavier. Are you doubling the size? Come on a whole A320 fuselage only weighs 4,500KG. It 's in the article where it also talks about if you used Carbon to build an A320 fuselage it would get lighter by about 1,200kg.

https://www.dlr.de/fa/Portaldata/17/Res ... srw_10.pdf


The surfaces need to be bigger. The higher weight, thrust and the lower moment arm combine to require them to increase in size. Like any cantilevered udl carrying structure they increase weight at the cube of their length (span) in this case the lever arm is ~12% lower and the thrust ~5% more. The increase in area is about 45%, the increase in weight is about 50%.

Out of interest What would you expect it to be?

Fred


Sent from my iPhone using Tapatalk


I think the first problem is that we are differing on weight. I think it should only be 2.5% more like I showed above - at most - not 9% like you are assuming.

You are talking about an increase in fuselage weight of only 1,000KG which is less than 1% of the MTOW.

I could accept 2.5% more overall for DOW but that is about it. The difference in thrust about the same. However with the shorter wide body you could get a better rotation angle (reducing thrust requirement) or shorter gear (lowering weight)Somehow I don't think that justifies a tail 50% larger. That seems absurd.
 
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seahawk
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 6:11 am

I just leave this link, maybe you get a better understanding that your calculation are just too simple. Just an example, why wetter area does not equal drag:

https://www.fzt.haw-hamburg.de/pers/Sch ... 3_Drag.pdf
 
flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 10:47 am

morrisond wrote:
flipdewaf wrote:
morrisond wrote:

Somehow I don't think the tail would get 3,700 lbs heavier. Are you doubling the size? Come on a whole A320 fuselage only weighs 4,500KG. It 's in the article where it also talks about if you used Carbon to build an A320 fuselage it would get lighter by about 1,200kg.

https://www.dlr.de/fa/Portaldata/17/Res ... srw_10.pdf


The surfaces need to be bigger. The higher weight, thrust and the lower moment arm combine to require them to increase in size. Like any cantilevered udl carrying structure they increase weight at the cube of their length (span) in this case the lever arm is ~12% lower and the thrust ~5% more. The increase in area is about 45%, the increase in weight is about 50%.

Out of interest What would you expect it to be?

Fred


Sent from my iPhone using Tapatalk


I think the first problem is that we are differing on weight. I think it should only be 2.5% more like I showed above - at most - not 9% like you are assuming.

Well I'm not assuming 9% DOW increase, I am putting the relevant parameters into a weight estimation algorithm and that's what comes out.

The fuselage structure is 8.7% heavier, the tail surfaces are in the order of 45-50% heavier, the controls are ~45% heavier, the wing is ~20% heavier, the pneumatics are 20% heavier.
the gear scales with MTOW, although the engines should scale with thrust in this instance they are equal.

morrisond wrote:

You are talking about an increase in fuselage weight of only 1,000KG which is less than 1% of the MTOW.

Hold it right there, the apples to apples comparison shows 1657kg difference.
The more version of the NB with the wider aisle shows the ~1000kg difference.
And why are you changing between fractions of the fuselage and fractions of the MTOW?

The wing area should be broadly based on MTOW and the wing weight driven by SPAN^3 * MZFW.
The drivers on MZFW and wing weight are centered aroun the lump that is being carried Fuselage weight, payload, avionics, Tail surfaces cabin fittings APU, electrics, Gear.

The sum of the things that effectively drive MZFW in the 7W vs the 6W with the wide aisle gives a 5% increase in weight.
If the wing scaled linearly (it doesnt) you would expect a 5% increase in weigh too giving a 5% overall increase in DOW.
But to establish the MTOW required for the
We know from the Breguet range equation that to match the range at equal tech levels ((UL/D)/TSFC = constant) that the fuel fraction must stay the same too so the increase of 5% in the DOW would equate to an increase of 5% of MTOW required to do the mission becuase the 5% more fuel so you need.
a. Larger heavier landing gear
b. Increased thrust
c. Increased wing area
d. Increased span

The problem is that when you add those things in the DOW increases again so you have to then increase the MTOW a little more and the other things go up again. The reality is that for what you are discussing the Ovoid that you only focus on the benefits whereas there are numerous drawbacks around weight and other surface area additions that outweigh those from the 'ovidness', the most problematic of which is weight as not only does it increase induced drag it increases the surface area and skin friction drag as a second order. Weight is always your number 1 foe, it is often ignored because it isnt sexy,.


morrisond wrote:

I could accept 2.5% more overall for DOW but that is about it.

This isn't a market where you can either accept or deny something, the truth doesn't care whether you accept it, its still true.

morrisond wrote:
The difference in thrust about the same. However with the shorter wide body you could get a better rotation angle (reducing thrust requirement)

What?
morrisond wrote:
or shorter gear (lowering weight)

Its engines we're worried about with the gear... Unless you somehow think the ovid needs smaller engines?
morrisond wrote:


Somehow I don't think that justifies a tail 50% larger. That seems absurd.

Interestingly the Tail on the longer NB version is sized more around the shorter version so probably can shrink too but I think its better to have an aircraft family of more than 1. Unless you think that this ovid is going to shrink another 7m to ~41m for a 250 seat all econ version?

Fred
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seahawk
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 11:22 am

Just look at the tail difference between an A318 and A319. In fact A320 and especially A321 have a tail that is too big.

And just to add some background on the calculations:

https://www.fzt.haw-hamburg.de/pers/Sch ... -04-15.pdf
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 12:34 pm

seahawk wrote:
Just look at the tail difference between an A318 and A319. In fact A320 and especially A321 have a tail that is too big.

And just to add some background on the calculations:

https://www.fzt.haw-hamburg.de/pers/Sch ... -04-15.pdf


I understand that the tail should be a different size - I just don't believe it is that much of a difference. If it was there would be a massive benefit to doing custom tails for every length of an Airliner and the payoff would far outweigh the cost.

Something just doesn't seem right.

Fred - you continue to ignore the fact that the Wing and Landing gear feel the weight of the loaded Fuselage. That difference between the NB and WB loaded fuselage is only 2.5%.

The only way to really know what is going on is to set there weights equal (which they could be as the WB is 5.5 shorter and Boeing or Airbus may be capable of engineering an Ovalish cross section that does not have that much of a penalty), and then you are just down to the Aero differences.

And if is that much work to do custom tails - you would have to assume that the 300 seat NB would have a non-optimized tail as it's the longest variant - just like the A321. But let's ignore that for now.
 
flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 1:37 pm

morrisond wrote:
seahawk wrote:
Just look at the tail difference between an A318 and A319. In fact A320 and especially A321 have a tail that is too big.

And just to add some background on the calculations:

https://www.fzt.haw-hamburg.de/pers/Sch ... -04-15.pdf


I understand that the tail should be a different size - I just don't believe it is that much of a difference. If it was there would be a massive benefit to doing custom tails for every length of an Airliner and the payoff would far outweigh the cost.

Or nobody is actually stupid enough to try an do what you're suggesting...
morrisond wrote:
Something just doesn't seem right.

Fred - you continue to ignore the fact that the Wing and Landing gear feel the weight of the loaded Fuselage.

I haven't. It also feels the weight of the avionis and electrical systems and the cabin and the tail structures and the APU and the vertical tail, and the horizontal tail. What you are lacking is lookng at the bigger picture and assessing it from a pre-determined position.
morrisond wrote:
That difference between the NB and WB loaded fuselage is only 2.5%.
Well whilst you are busy marveling at your loaded fuselage I'll be estimating the performance with all the relevant pieces that make an aircraft work. Which without the wings engines and pneumatics and anti ice systems you'll find that the difference is ~8.8%, again not assumed as you seem to believe put an output of the weight estimation algorithm.

morrisond wrote:
The only way to really know what is going on is to set there weights equal

No it isn't, I think everyone can see what is going on, you are saying is "If this thing doesn't work because it weighs too much, maybe if we ignore the weight increase it will work"
If you are unable to see that the weight and aero are not independent of each other then I think you input to this thread may have reached its limitations. I shall not begin to put ridiculous inputs to my models lest this gets misinterpreted and taken as being somehow truthful in the future.

morrisond wrote:
(which they could be

No, there is no good reason to believe this.
morrisond wrote:
as the WB is 5.5 shorter and Boeing or Airbus may be capable of engineering an Ovalish cross section that does not have that much of a penalty),
to remove 15% + of the weight?
I see no evidence that that is possible. In neither this thread or the others you are posting this self same stuff in have you presented any evidence that this is possible. And even if it were why would this detract from the NB proposal which surely could benefit from the self same technology?


morrisond wrote:
and then you are just down to the Aero differences.

The aero differences will be huge, are you thinking about the aero differences of the NB in flight vs the WB thats gone off the end of the runway because the wings arent big enough to lift it off the ground or the aero of the WB that's sinking tot the bottom of the atlantic because it didn't make the flight? or maybe you are thinking about the one that had to leave the passengers behind when it ran out of available payload capability?


morrisond wrote:
And if is that much work to do custom tails - you would have to assume that the 300 seat NB would have a non-optimized tail as it's the longest variant - just like the A321
That's what I have assumed.


morrisond wrote:
But let's ignore that for now.
...

Fun times!

Fred
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morrisond
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 2:16 pm

flipdewaf wrote:
I haven't. It also feels the weight of the avionis and electrical systems and the cabin and the tail structures and the APU and the vertical tail, and the horizontal tail. What you are lacking is lookng at the bigger picture and assessing it from a pre-determined position.

Fred


You keep thinking about the two as being materially different in size (cross section) but they really aren't. You are not going from an A320 to a 767. You are increasing the cross section/frontal area of the fuselage by 19% and reducing the wetted area by 3% vs the 166" by 160: NB. The A320 over an 737 is 10.1% and that doesn't seem to hurt it that much.

I'm ignoring the NNB as you aren't going to be able to stretch an fuselage height that is almost 9" less than an 737 (and only 1" higher than an A220) to 300 seats.

So How would the Avionics, electrical systems and APU be heavier on a 20' shorter Slightly wider bodied fuselage (13" each side and only 4" higher) with the same capacity? A lot would be the same - all the service runs shorter. Yes - Tail heavier.

Avionics would be the same, Electrical systems/ pneumatic system runs would be shorter. 20' less of interior fittings (walls, ceilings - ceiling panels slighty longer but not enough to offset the 20'. Heavy APU is 10' Closer to the Main gear which saves structure.

Tail - length of fuselage is 10' shorter (to the main gear), nose gear is 10' closer to Main gear meaning less structure needed. Yes Vertical and Horizontal tail surfaces could have to be slightly bigger.

Rotation angle makes a difference as the wing at a higher angle of attack will generate more lift - hence less required take off speed and less thrust, it won't run off the end of the runway.

No - I'm looking at it from another perspective - you don't seem to want to take your thumb off the scale.
 
flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 3:09 pm

morrisond wrote:
flipdewaf wrote:
I haven't. It also feels the weight of the avionis and electrical systems and the cabin and the tail structures and the APU and the vertical tail, and the horizontal tail. What you are lacking is lookng at the bigger picture and assessing it from a pre-determined position.

Fred


You keep thinking about the two as being materially different in size (cross section) but they really aren't.

Im not, and they aren't. They are however materially different in weight.
morrisond wrote:
You are not going from an A320 to a 767.

Absolutely, you are going from a 753 to a 762...
morrisond wrote:
You are increasing the cross section/frontal area of the fuselage by 19% and reducing the wetted area by 3% vs the 166" by 160: NB.

yes, the one with the 28" aisle? not the apples to apples comparison that has the same seat and aisle width and ends up with a fuselage surface are significantly less? Why are apples less important in that regard than in the weight parameter? Plus what has cross sectional area go to do with it?
morrisond wrote:
The A320 over an 737 is 10.1% and that doesn't seem to hurt it that much.
10.1% in cross sectional area or (1.101)^(1/2) in terms of linear comparability. Please stop changing the terms of reference to suit you argument, it is a 4.9% difference. The A320 weighs around a ton more.

morrisond wrote:
I'm ignoring the NNB as you aren't going to be able to stretch an fuselage height that is almost 9" less than an 737 (and only 1" higher than an A220) to 300 seats.

See:DC8-73

morrisond wrote:

So How would the Avionics, electrical systems and APU be heavier on a 20' shorter Slightly wider bodied fuselage (13" each side and only 4" higher) with the same capacity? A lot would be the same - all the service runs shorter. Yes - Tail heavier.

Avionics would be the same, Electrical systems/ pneumatic system runs would be shorter. 20' less of interior fittings (walls, ceilings - ceiling panels slighty longer but not enough to offset the 20'. Heavy APU is 10' Closer to the Main gear which saves structure.

I never said all those things were heavier, just that that is what the wings have to lift. The cabin fittings etc would be the same.
Wing is 1998kg heavier
Horizontal tail is 701kg heavier
Vertical tail is 369kg heavier
Fuselage is 1010kg heavier
Gear is 400kg heavier
Control weight is 668kg heavier
Propulsion is 0kg heavier
APU is 0kg heavier
Nav equipment is 0kg heavier
Hydraulics and pnue is 63kg heavier
electrics is 0kg heavier
electronics is 0kg heavier
furnishings is 0kg heavier
Ant ice&A/C is 0kg heavier
op items is 0kg heavier


morrisond wrote:
Tail - length of fuselage is 10' shorter (to the main gear), nose gear is 10' closer to Main gear meaning less structure needed.


That structure is called the fuselage, that's already in there and the length taken account of.

morrisond wrote:
Yes Vertical and Horizontal tail surfaces could have to be slightly bigger.

Rotation angle makes a difference as the wing at a higher angle of attack will generate more lift
same lift, higher lift coefficient.... and drag, Cdi = Cl^2/(pi*e*AR).. :banghead:

morrisond wrote:
- hence less required take off speed and less thrust, it won't run off the end of the runway.
More thrust. :banghead:

morrisond wrote:
No - I'm looking at it from another perspective - you don't seem to want to take your thumb off the scale.
I don't know what you mean, im looking from the perspective how things work.

Fred
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DenverTed
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 3:54 pm

[quote="flipdewaf"

Image

Fred[/quote]

I assume the A321 is the apples to apples comparison of an aircraft with a 3-3 plus LD-3-45 container. Can't go much smaller, right?
Looking at the 2-3-2, what if they went with a circular fuselage and dropped the floor another six inches which gives more room at shoulder level and more room in the overhead bins. They should be able to use a 15.5' (4.7m) o.d. fuselage.
Or for overhead bin space, 2-2-3 or 3-1-3 seating.
 
oschkosch
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 4:18 pm

Fred, I admire your calculations and your patience! Well done!

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zeke
Posts: 14961
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 5:03 pm

seahawk wrote:
Our coffee breaks are not that long.

But the basic problem you need to understand is that the pressurised vessel wants to become a circle. So in the wide ovid, it is not actually the side ends wanting to push inside, but the centre of the shape wanting to push outside. That is a big difference to a A350 like shape, where actually the centre of the section does not experience such loads and the load is limited to the side ends, the want to push outside. Imagine a rubber balloon with the floor as a fixed (round) structure inside it. When pressurised it would aim to become a circle with the diameter the same as the diameter of the round floor inside the balloon. A fuselage of a plane does not act differently.


Years ago I worked on a team where we looked at blending space frames and composites together to build stiffened panels with various geometries, looked at replacing typical stringers and frames with internal geometric frames. The aim was to look at lighter pressure vessels like used on spacecraft tanks, and also to replace the traditional honeycomb core filled control surfaces with something that did not absorb water. We were actually able to build lighter and stronger panels that had triangular and honeycomb shaped stiffeners that were bonded to the inside.

If designed properly that sort of internal space frame can be very efficient in carrying pressurization loads. I see the current art has extended that idea a fair way.

Image

From http://web.aeromech.usyd.edu.au/WCSMO20 ... _paper.pdf

We were fairly limited with computing power back then even when using supercomputers, I could only assume these days that sort of work is easier to do. The hardest part would be to industrialize the manufacturing.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
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seahawk
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 5:16 pm

That is not the problem, the basic problem is minimising the disadvantage of the ovid shape, when using the same construction methods for a circle.
 
morrisond
Posts: 2664
Joined: Thu Jan 07, 2010 12:22 am

Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 5:58 pm

flipdewaf wrote:
morrisond wrote:
flipdewaf wrote:
I haven't. It also feels the weight of the avionis and electrical systems and the cabin and the tail structures and the APU and the vertical tail, and the horizontal tail. What you are lacking is lookng at the bigger picture and assessing it from a pre-determined position.

Fred


You keep thinking about the two as being materially different in size (cross section) but they really aren't.

Im not, and they aren't. They are however materially different in weight.
morrisond wrote:
You are not going from an A320 to a 767.

Absolutely, you are going from a 753 to a 762...
morrisond wrote:
You are increasing the cross section/frontal area of the fuselage by 19% and reducing the wetted area by 3% vs the 166" by 160: NB.

yes, the one with the 28" aisle? not the apples to apples comparison that has the same seat and aisle width and ends up with a fuselage surface are significantly less? Why are apples less important in that regard than in the weight parameter? Plus what has cross sectional area go to do with it?
morrisond wrote:
The A320 over an 737 is 10.1% and that doesn't seem to hurt it that much.
10.1% in cross sectional area or (1.101)^(1/2) in terms of linear comparability. Please stop changing the terms of reference to suit you argument, it is a 4.9% difference. The A320 weighs around a ton more.

morrisond wrote:
I'm ignoring the NNB as you aren't going to be able to stretch an fuselage height that is almost 9" less than an 737 (and only 1" higher than an A220) to 300 seats.

See:DC8-73

morrisond wrote:

So How would the Avionics, electrical systems and APU be heavier on a 20' shorter Slightly wider bodied fuselage (13" each side and only 4" higher) with the same capacity? A lot would be the same - all the service runs shorter. Yes - Tail heavier.

Avionics would be the same, Electrical systems/ pneumatic system runs would be shorter. 20' less of interior fittings (walls, ceilings - ceiling panels slighty longer but not enough to offset the 20'. Heavy APU is 10' Closer to the Main gear which saves structure.

I never said all those things were heavier, just that that is what the wings have to lift. The cabin fittings etc would be the same.
Wing is 1998kg heavier
Horizontal tail is 701kg heavier
Vertical tail is 369kg heavier
Fuselage is 1010kg heavier
Gear is 400kg heavier
Control weight is 668kg heavier
Propulsion is 0kg heavier
APU is 0kg heavier
Nav equipment is 0kg heavier
Hydraulics and pnue is 63kg heavier
electrics is 0kg heavier
electronics is 0kg heavier
furnishings is 0kg heavier
Ant ice&A/C is 0kg heavier
op items is 0kg heavier


morrisond wrote:
Tail - length of fuselage is 10' shorter (to the main gear), nose gear is 10' closer to Main gear meaning less structure needed.


That structure is called the fuselage, that's already in there and the length taken account of.

morrisond wrote:
Yes Vertical and Horizontal tail surfaces could have to be slightly bigger.

Rotation angle makes a difference as the wing at a higher angle of attack will generate more lift
same lift, higher lift coefficient.... and drag, Cdi = Cl^2/(pi*e*AR).. :banghead:

morrisond wrote:
- hence less required take off speed and less thrust, it won't run off the end of the runway.
More thrust. :banghead:

morrisond wrote:
No - I'm looking at it from another perspective - you don't seem to want to take your thumb off the scale.
I don't know what you mean, im looking from the perspective how things work.

Fred


Humor me - what happens if you keep the Fuselage weight the same? We are all making large assumptions about how much heavier Ovalish Cross Section would weigh.

I still can't believe the tail gets that much heavier
 
flipdewaf
Topic Author
Posts: 3509
Joined: Thu Jul 20, 2006 6:28 am

Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 6:44 pm

morrisond wrote:
flipdewaf wrote:
morrisond wrote:

You keep thinking about the two as being materially different in size (cross section) but they really aren't.

Im not, and they aren't. They are however materially different in weight.
morrisond wrote:
You are not going from an A320 to a 767.

Absolutely, you are going from a 753 to a 762...
morrisond wrote:
You are increasing the cross section/frontal area of the fuselage by 19% and reducing the wetted area by 3% vs the 166" by 160: NB.

yes, the one with the 28" aisle? not the apples to apples comparison that has the same seat and aisle width and ends up with a fuselage surface are significantly less? Why are apples less important in that regard than in the weight parameter? Plus what has cross sectional area go to do with it?
morrisond wrote:
The A320 over an 737 is 10.1% and that doesn't seem to hurt it that much.
10.1% in cross sectional area or (1.101)^(1/2) in terms of linear comparability. Please stop changing the terms of reference to suit you argument, it is a 4.9% difference. The A320 weighs around a ton more.

morrisond wrote:
I'm ignoring the NNB as you aren't going to be able to stretch an fuselage height that is almost 9" less than an 737 (and only 1" higher than an A220) to 300 seats.

See:DC8-73

morrisond wrote:

So How would the Avionics, electrical systems and APU be heavier on a 20' shorter Slightly wider bodied fuselage (13" each side and only 4" higher) with the same capacity? A lot would be the same - all the service runs shorter. Yes - Tail heavier.

Avionics would be the same, Electrical systems/ pneumatic system runs would be shorter. 20' less of interior fittings (walls, ceilings - ceiling panels slighty longer but not enough to offset the 20'. Heavy APU is 10' Closer to the Main gear which saves structure.

I never said all those things were heavier, just that that is what the wings have to lift. The cabin fittings etc would be the same.
Wing is 1998kg heavier
Horizontal tail is 701kg heavier
Vertical tail is 369kg heavier
Fuselage is 1010kg heavier
Gear is 400kg heavier
Control weight is 668kg heavier
Propulsion is 0kg heavier
APU is 0kg heavier
Nav equipment is 0kg heavier
Hydraulics and pnue is 63kg heavier
electrics is 0kg heavier
electronics is 0kg heavier
furnishings is 0kg heavier
Ant ice&A/C is 0kg heavier
op items is 0kg heavier


morrisond wrote:
Tail - length of fuselage is 10' shorter (to the main gear), nose gear is 10' closer to Main gear meaning less structure needed.


That structure is called the fuselage, that's already in there and the length taken account of.

morrisond wrote:
Yes Vertical and Horizontal tail surfaces could have to be slightly bigger.

Rotation angle makes a difference as the wing at a higher angle of attack will generate more lift
same lift, higher lift coefficient.... and drag, Cdi = Cl^2/(pi*e*AR).. :banghead:

morrisond wrote:
- hence less required take off speed and less thrust, it won't run off the end of the runway.
More thrust. :banghead:

morrisond wrote:
No - I'm looking at it from another perspective - you don't seem to want to take your thumb off the scale.
I don't know what you mean, im looking from the perspective how things work.

Fred


Humor me - what happens if you keep the Fuselage weight the same? We are all making large assumptions about how much heavier Ovalish Cross Section would weigh.

I still can't believe the tail gets that much heavier


It scales on many things, wing area, h-tplane area, v-tplane area, g loading. Taper, sweep, span. Whilst it’s possible to change all of these I have simply chosen to base the current ones off the the afformentuined Boeing planes that fit within the right category. Effectively it happens because as the area increases so does the span and Just like a wing (because that’s what it is) it’s weigh is hugely impacted by span. The A380 for example has nigh on 20t of weight attributed to the tail surfaces in one form or another, we’re talking ~4t here.

Effectively read the Stanford course notes and you’ll get it, it’s about a comprehensive read on aircraft design you can get. Then read torenbeek, then read Raymer.

And I don’t regard your statement of “all making assumptions” as an even remotely fair assessment, not all assumptions are equally valid.

Your previous triumphalism incorrectly pointing at my work as proof of your position in a different thread dissuades me from dancing to your tune anymore. I do not wish to be associated with that behaviour.

Fred


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morrisond
Posts: 2664
Joined: Thu Jan 07, 2010 12:22 am

Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 7:02 pm

flipdewaf wrote:
morrisond wrote:
flipdewaf wrote:
Im not, and they aren't. They are however materially different in weight.

Absolutely, you are going from a 753 to a 762...

yes, the one with the 28" aisle? not the apples to apples comparison that has the same seat and aisle width and ends up with a fuselage surface are significantly less? Why are apples less important in that regard than in the weight parameter? Plus what has cross sectional area go to do with it?
10.1% in cross sectional area or (1.101)^(1/2) in terms of linear comparability. Please stop changing the terms of reference to suit you argument, it is a 4.9% difference. The A320 weighs around a ton more.


See:DC8-73


I never said all those things were heavier, just that that is what the wings have to lift. The cabin fittings etc would be the same.
Wing is 1998kg heavier
Horizontal tail is 701kg heavier
Vertical tail is 369kg heavier
Fuselage is 1010kg heavier
Gear is 400kg heavier
Control weight is 668kg heavier
Propulsion is 0kg heavier
APU is 0kg heavier
Nav equipment is 0kg heavier
Hydraulics and pnue is 63kg heavier
electrics is 0kg heavier
electronics is 0kg heavier
furnishings is 0kg heavier
Ant ice&A/C is 0kg heavier
op items is 0kg heavier




That structure is called the fuselage, that's already in there and the length taken account of.

same lift, higher lift coefficient.... and drag, Cdi = Cl^2/(pi*e*AR).. :banghead:

More thrust. :banghead:

I don't know what you mean, im looking from the perspective how things work.

Fred


Humor me - what happens if you keep the Fuselage weight the same? We are all making large assumptions about how much heavier Ovalish Cross Section would weigh.

I still can't believe the tail gets that much heavier


It scales on many things, wing area, h-tplane area, v-tplane area, g loading. Taper, sweep, span. Whilst it’s possible to change all of these I have simply chosen to base the current ones off the the afformentuined Boeing planes that fit within the right category. Effectively it happens because as the area increases so does the span and Just like a wing (because that’s what it is) it’s weigh is hugely impacted by span. The A380 for example has nigh on 20t of weight attributed to the tail surfaces in one form or another, we’re talking ~4t here.

Effectively read the Stanford course notes and you’ll get it, it’s about a comprehensive read on aircraft design you can get. Then read torenbeek, then read Raymer.

And I don’t regard your statement of “all making assumptions” as an even remotely fair assessment, not all assumptions are equally valid.

Your previous triumphalism incorrectly pointing at my work as proof of your position in a different thread dissuades me from dancing to your tune anymore. I do not wish to be associated with that behaviour.

Fred


Sent from my iPhone using Tapatalk


Fred - you were the one pointing out that as the Fuselage was 9% heavier everything else increases as well. I pointed out that you have to look at the weight of the loaded fuselage which would only be 2.5% more in an all Y configuration and you have been backpedaling ever since and have not refuted that position.

I appreciate the effort you put in but let's just agree to disagree and not make this a thing.

Thank you for trying.
 
flipdewaf
Topic Author
Posts: 3509
Joined: Thu Jul 20, 2006 6:28 am

Re: NMA/MOM/797 variant performance analysis

Wed Feb 12, 2020 7:30 pm

morrisond wrote:
flipdewaf wrote:
morrisond wrote:

Humor me - what happens if you keep the Fuselage weight the same? We are all making large assumptions about how much heavier Ovalish Cross Section would weigh.

I still can't believe the tail gets that much heavier


It scales on many things, wing area, h-tplane area, v-tplane area, g loading. Taper, sweep, span. Whilst it’s possible to change all of these I have simply chosen to base the current ones off the the afformentuined Boeing planes that fit within the right category. Effectively it happens because as the area increases so does the span and Just like a wing (because that’s what it is) it’s weigh is hugely impacted by span. The A380 for example has nigh on 20t of weight attributed to the tail surfaces in one form or another, we’re talking ~4t here.

Effectively read the Stanford course notes and you’ll get it, it’s about a comprehensive read on aircraft design you can get. Then read torenbeek, then read Raymer.

And I don’t regard your statement of “all making assumptions” as an even remotely fair assessment, not all assumptions are equally valid.

Your previous triumphalism incorrectly pointing at my work as proof of your position in a different thread dissuades me from dancing to your tune anymore. I do not wish to be associated with that behaviour.

Fred


Sent from my iPhone using Tapatalk


Fred - you were the one pointing out that as the Fuselage was 9% heavier everything else increases as well.

I genuinely didn’t think I had to point out that the pilots didn’t 9% heavier, nor did the seats.

morrisond wrote:
I pointed out that you have to look at the weight of the loaded fuselage which would only be 2.5% more in an all Y configuration
you pointed out incorrectly that that’s what I have to look at. Why needs to be looked at is the weigh of what it weighs. Which is remarkably ~9% more.

morrisond wrote:
and you have been backpedaling ever since and have not refuted that position.
why would I refute something that isn’t incorrect? As has been stated numerous times the weight and increased surface area is coming from the tail surfaces.

morrisond wrote:
I appreciate the effort you put in but let's just agree to disagree and not make this a thing.
No, I’m not making it a thing. I’m stating the numbers that come from well regarded aircraft weight estimation algorithms. You just don’t like the answers.

morrisond wrote:
Thank you for trying.
Bye Bye!



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