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A350-100 Versus B777-9X(407 Seats) Analysis  
User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Posted (2 years 4 months 3 weeks 5 days 20 hours ago) and read 21243 times:

My motivation for this thread is based on the following article in Flightglobal.
http://www.flightglobal.com/news/art...rgets-year-end-777x-launch-369074/

Summary of changes to B77W to create B777-9X(407 Seats) :
CFRP wings with 234 ft wingspan
MTOW of 753,000 while preserving current payload/range capability of 77W
Engine thrust at 99,500 lbf. with higher bypass and ceramic matrix
Larger wing with its increased lift to drag ratio, coupled with the a 10% improvement in specific fuel consumption for the GE9X engine.

The 777-9X will be 2 meter longer than the 77W, and will have a slightly wider cabin for more comfortable 10Y. The OEW of 777-9X is an estimate that reflects the longer and lighter fuselage due to use of lighter material, higher wingarea, lighter composites for wings, lighter engines, and additional furnishings for the 42 seats.

General Specifications:
....................................A3510.......................B777-9X
Fuselage Length..............242..........................249 feet
Fuselage Width.................19.6........................20.33
Wingspan.......................213..........................234
Wingarea......................4767.........................5050 sq. feet(my estimate)
Seats(3 class).................350..........................407 (210 lbs. per passenger/baggage)


MTOW.....................679,000....................753,000 lbs.
MZFW......................485,000...................525,000
OEW........................335,000...................375,000 (my estimates)
MSP.........................150,000...................150,000
Design Range................8,400.....................8,200 nm (passenger only, and zero cargo)
List Price........................$309......................$320(?) million
Engine Thrust..............97,000...................99,500 lbf

Ratois
OEW/MTOW.....................0.49...........................0.50
OEW/MZFW......................0.69...........................0.71
MTOW/Wingarea............143............................149 (777 has higher wingloading)
MTOW/Thrust....................3.50...........................3.78 (A350-10 has more powerful engines normalised for MTOW)

Under the assumption of a 7,300 nm (LAX-DXB) mission at MTOW:
B777-9X burns about 3,500 gallons more at a current cost of $13,000.
Negligble difference in cargo payload for the above mission length.
B777-9X has the potential to earn about $24,000 in additional 57 seat revenues at 70% load factor.

Overall, B777-9X has a net operating advantage of $11,000 for a 7,300nm mission in 10-abreast 777-9X configuration, and more if one accounts for 7-abreast J class layout of EK, which would be difficult to arrange in A350-1000. This translates to annual operating advantage of nearly $4 million for B777-9X. One can see why EK is excited about 777-9X.

For an operator like CX which is more likely to configure 777-9X in 9-abreast, the numbers for a 6,300nm mission(LAX-HKG) are as follows:

B777-9X burns about 3,000 gallons more at a current cost of $10,500.
Negligble difference in cargo payload for the above mission length.
B777-9X has the potential to earn about $8,000 in additional 18 Y seat(2 meter stretch) revenues at 70% load factor.

A350-1000 has an operating advantage of $2,500 per trip, which is about $1 million annually.

For long dense routes, B777-9X with 9-abreast is at a slight disadvantage against A350-1000. A350-1000 has a trip cost advantage that bodes well for it with operators looking for flexibilty in deploying one aircraft across many types of route profiles, capacity wise .

74 replies: All unread, showing first 25:
 
User currently offlineDocLightning From United States of America, joined Nov 2005, 19411 posts, RR: 58
Reply 1, posted (2 years 4 months 3 weeks 5 days 16 hours ago) and read 21201 times:

Quoting LAXDESI (Thread starter):
B777-9X burns about 3,000 gallons more at a current cost of $10,500.
Negligble difference in cargo payload for the above mission length.
B777-9X has the potential to earn about $8,000 in additional 18 Y seat(2 meter stretch) revenues at 70% load factor.

How come that is 57 additional seats for EK and 18 additional seats for CX?


User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 2, posted (2 years 4 months 3 weeks 5 days 16 hours ago) and read 21190 times:

Quoting DocLightning (Reply 1):
How come that is 57 additional seats for EK and 18 additional seats for CX?

I am assuming that CX will configure B777-9X 9-abreast in Y, whereas EK will configure 10-abreast in Y. The 18 additional seats for CX are due to two additional Y rows on the 777-9X(9 X2) relative to A350-1000.


User currently offlineDocLightning From United States of America, joined Nov 2005, 19411 posts, RR: 58
Reply 3, posted (2 years 4 months 3 weeks 5 days 15 hours ago) and read 21184 times:

Quoting LAXDESI (Reply 2):
I am assuming that CX will configure B777-9X 9-abreast in Y, whereas EK will configure 10-abreast in Y. The 18 additional seats for CX are due to two additional Y rows on the 777-9X(9 X2) relative to A350-1000.

So if there are two additional rows, EK gets 20 extra fares and CX gets 18 extra fares. Assuming $500/ea, EK only gets $10k.

How did you arrive at 57 extra fares for EK?


User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 4, posted (2 years 4 months 3 weeks 5 days 15 hours ago) and read 21179 times:

Quoting DocLightning (Reply 3):
How did you arrive at 57 extra fares for EK?

EK is expected to configure its B777-9X 10-abreast, as its B77Ws are 10-abreast Y. So relative to A358-1000, it will have one extra seat for each Y row(37 seats) and two additional Y rows(20 seats) than A350-1000(marketing comparisons).


User currently offlineCX Flyboy From Hong Kong, joined Dec 1999, 6588 posts, RR: 55
Reply 5, posted (2 years 4 months 3 weeks 5 days 14 hours ago) and read 21123 times:

How about cargo in terms of not payload but container carrying capability?

User currently onlineStitch From United States of America, joined Jul 2005, 30584 posts, RR: 84
Reply 6, posted (2 years 4 months 3 weeks 5 days 6 hours ago) and read 20974 times:
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Quoting CX Flyboy (Reply 5):
How about cargo in terms of not payload but container carrying capability?

The 777-9 would add another 4-6 LD3 positions (so 48-50 compared to 44 on the A350-1000), but they A350-1000 should have more available for revenue cargo due to a lower passenger baggage count.


User currently offlineDocLightning From United States of America, joined Nov 2005, 19411 posts, RR: 58
Reply 7, posted (2 years 4 months 3 weeks 4 days 22 hours ago) and read 20842 times:

Quoting LAXDESI (Reply 4):
EK is expected to configure its B777-9X 10-abreast, as its B77Ws are 10-abreast Y. So relative to A358-1000, it will have one extra seat for each Y row(37 seats) and two additional Y rows(20 seats) than A350-1000(marketing comparisons).

Ahhh!!! I get it. Thanks.

Your comparison shows that the A3510 seems to be a superior aircraft to the 777 in all but extremely long-range, high-density situations. From your analysis, I wonder why any carrier would order it with the possible exception of EK.


User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 8, posted (2 years 4 months 3 weeks 4 days 21 hours ago) and read 20819 times:

Quoting DocLightning (Reply 7):
Your comparison shows that the A3510 seems to be a superior aircraft to the 777 in all but extremely long-range, high-density situations. From your analysis, I wonder why any carrier would order it with the possible exception of EK.

Air France and Air New Zealand are also 10-abreast in Y. Competitive pressure and a slightly wider Y cabin may entice more airlines to go 10-abreast on 777-9X.


User currently offlinezeke From Hong Kong, joined Dec 2006, 8870 posts, RR: 75
Reply 9, posted (2 years 4 months 3 weeks 4 days 20 hours ago) and read 20799 times:

Quoting LAXDESI (Thread starter):
Engine thrust at 99,500 lbf. with higher bypass and ceramic matrix.......10% improvement in specific fuel consumption for the GE9X engine.

Turbojet/turbofan engines use TSFC, not SFC, i.e. the mass of the fuel burned per unit time, per unit thrust. The takeoff thrust is being reduced from 115 klb to 99.5 klb, one would expect a similar reduction in the cruise thrust.

Quoting LAXDESI (Thread starter):
Wingarea......................4767

I have pointed this on a number of threads, that is the wing area of the -800/-900. The OEWs are also too high.

Quoting LAXDESI (Reply 2):

I am assuming that CX will configure B777-9X 9-abreast in Y, whereas EK will configure 10-abreast in Y. The 18 additional seats for CX are due to two additional Y rows on the 777-9X(9 X2) relative to A350-1000.

Why is the assumption that the plug will be only aft of the wing ? The 777 today is geometry limited for takeoff and landing, if anything I would see them increasing the length in the forward cabin.

Quoting Stitch (Reply 6):

The 777-9 would add another 4-6 LD3 positions

I suggest you have a look at the dimensions of an LD-3 again, they are around 60" deep, by implication you are suggesting an increase in the cargo hold of 120-180" (3-4.5m) which is out of proportion compared to the length increase in the aircraft (78 " or 2m).



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently onlineStitch From United States of America, joined Jul 2005, 30584 posts, RR: 84
Reply 10, posted (2 years 4 months 3 weeks 4 days 20 hours ago) and read 20795 times:
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Which is why I think if a 2m stretch is all Boeing can get, they shouldn't bother.

User currently offlineDocLightning From United States of America, joined Nov 2005, 19411 posts, RR: 58
Reply 11, posted (2 years 4 months 3 weeks 4 days 17 hours ago) and read 20757 times:

Quoting LAXDESI (Reply 8):

Air France and Air New Zealand are also 10-abreast in Y. Competitive pressure and a slightly wider Y cabin may entice more airlines to go 10-abreast on 777-9X.

Given a higher yield from the premium cabins, I wonder if the airlines would benefit from the 779X in those classes, as well.


User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 12, posted (2 years 4 months 3 weeks 4 days 13 hours ago) and read 20715 times:

I think it is useful to see how the proposed 777-8X(224 feet) stacks up against A350-1000(242 feet) in EK configuration. Assuming 4-abreast F, 7-abreast J, 10-abreast Y for 777-8X, and 4-abreast F, 6-abreast J, 9-abreast Y for A350-1000, here's what I come up with:

......................................F....................J.......................Y...........Total
B777-8X.....................12.....................35...................260..........307 seats
A350-1000..................12.....................36...................261..........309 seats

Based on my OEW estimate for 777-9X as laid out in OP, I expect the 777-8X to weigh about 35,000 lbs. less than 777-9X at 340,000 lbs., which is about 5,000 lbs. more than A350-1000 at 335,000 lbs.

It seems to me that 777-8X will come up short against A350-1000 on fuel burn per seat even in the most advantageous configuration of EK. Perhaps the shorter model is likely to be 777-8LX for ULH range.


User currently offlineDocLightning From United States of America, joined Nov 2005, 19411 posts, RR: 58
Reply 13, posted (2 years 4 months 3 weeks 4 days 2 hours ago) and read 20587 times:

Quoting LAXDESI (Reply 12):
I think it is useful to see how the proposed 777-8X(224 feet) stacks up against A350-1000(242 feet) in EK configuration.

That's a 6M difference. What about against the A359?


User currently offlinemffoda From United States of America, joined Apr 2010, 1056 posts, RR: 0
Reply 14, posted (2 years 2 months 3 weeks 6 days 3 hours ago) and read 19254 times:

For all you tech types that like running numbers... aeroturbopower has run some of his own if your interested.

http://aeroturbopower.blogspot.com/2...more-than-challenge-a350.html#more

There are some mistakes, but an interesting take.



harder than woodpecker lips...
User currently offlinenomadd22 From United States of America, joined Feb 2008, 1832 posts, RR: 0
Reply 15, posted (2 years 2 months 3 weeks 6 days 2 hours ago) and read 19218 times:

That sure seems like a small thrust difference for that large a MTOW difference.


Andy Goetsch
User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 16, posted (2 years 2 months 3 weeks 5 days 15 hours ago) and read 19012 times:

Quoting mffoda (Reply 14):
For all you tech types that like running numbers... aeroturbopower has run some of his own if your interested.

http://aeroturbopower.blogspot.com/2...#more

Thanks for the link. As pointed out in the comments section, MTOW numbers are incorrect.

Quoting nomadd22 (Reply 15):
That sure seems like a small thrust difference for that large a MTOW difference.

Some of it is being compensated by the bigger wings of B777-9X. The current 77W has more powerful(normalised for MTOW) engines than the proposed B777-9X. Ratos for all three with ranks in parenthesis:


Ratois.............................A3510.......................B777-9X...................B77W

MTOW/Wingarea............143(1)........................149(2) ........................168(3)
MTOW/Thrust.....................3.50(2).......................3.78(3)........................3.35(1)

The 77W has the most powerful engines(normalised for MTOW) of the three, but also has the highest wingloading. B777-9X at current spec. is expected to have the lowest MTOW/Thrust ratio. As for wingloading, B77W has the highest wingloading and the A350-1000 the lowest.

Both A350-1000 and 777-9X are designed with lower wingloading than B77W, and lower MTOW normalised thrust than B77W.

However, A350-1000 at current spec. has higher normalised thrust than B777-9X, and also a lower wingloading. At a superficial level it seems that B777-9X should need more thrust than is currently being proposed.


User currently offlinepanais From Cyprus, joined May 2008, 462 posts, RR: 0
Reply 17, posted (2 years 2 months 3 weeks 5 days 9 hours ago) and read 18953 times:

Quoting LAXDESI (Thread starter):
Seats(3 class).................350..........................407 (210 lbs. per passenger/baggage)

Your numbers do not add up. If you take EK, they have configured the B777-300ER at 358 seats 3-class config. The extra 7 feet in length for the B777-9X will give at best 3 additional rows of economy, or most likely an extra row of business and a row of economy class seating. So this is from 16 to 30 seats in total.


User currently offlinenomadd22 From United States of America, joined Feb 2008, 1832 posts, RR: 0
Reply 18, posted (2 years 2 months 3 weeks 5 days 8 hours ago) and read 18915 times:

Quoting panais (Reply 17):
Quoting LAXDESI (Thread starter):
Seats(3 class).................350..........................407 (210 lbs. per passenger/baggage)

Your numbers do not add up. If you take EK, they have configured the B777-300ER at 358 seats 3-class config. The extra 7 feet in length for the B777-9X will give at best 3 additional rows of economy, or most likely an extra row of business and a row of economy class seating. So this is from 16 to 30 seats in total.

Maybe the part about 10 accross being more practical.



Andy Goetsch
User currently onlineStitch From United States of America, joined Jul 2005, 30584 posts, RR: 84
Reply 19, posted (2 years 2 months 3 weeks 5 days 8 hours ago) and read 18922 times:
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Well an EK A350-1000 will have 317 seats (per EK), so the gap between it and a 777-9 will be not insubstantial.

User currently offlinepanais From Cyprus, joined May 2008, 462 posts, RR: 0
Reply 20, posted (2 years 2 months 3 weeks 5 days 1 hour ago) and read 18800 times:

Quoting nomadd22 (Reply 18):
Maybe the part about 10 accross being more practical.

EK is already 10 seats across in economy.

Quoting Stitch (Reply 19):
Well an EK A350-1000 will have 317 seats (per EK), so the gap between it and a 777-9 will be not insubstantial

When did they say that? The 777-300ER and the A350-1000 have the same length. At 9 abreast economy for the entire length of the A350-1000 compared to the 777-300ER which the last 5 rows are at 8 abreast, the A350-1000 in EK configuration should be 337, 20-21 seats less than the 777-300ER. Therefore, the gap with the 777-9 is going to be 36 to 50 seats. I am of the opinion that it will becloser to 36 seat difference.


User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 21, posted (2 years 2 months 3 weeks 5 days ago) and read 18773 times:

Quoting panais (Reply 20):
When did they say that? The 777-300ER and the A350-1000 have the same length. At 9 abreast economy for the entire length of the A350-1000 compared to the 777-300ER which the last 5 rows are at 8 abreast, the A350-1000 in EK configuration should be 337, 20-21 seats less than the 777-300ER. Therefore, the gap with the 777-9 is going to be 36 to 50 seats. I am of the opinion that it will becloser to 36 seat difference.

EK long haul 77W is configured with 304 Y seats, which is about 30 rows. At 9-abreast, A350-1000 will have about 30 less Y seats.

I think it will be difficult to fit the current 77W 7-abreast J seats(6 rows) on to A350-1000, leading to a loss of 6 J seats on A350-1000. That is a total loss of 36 seats on A350-1000 relative to EK 77W(358 seats), leaving it with nearly 322 seats, which is very close to Stitch's figure of 317 seats for EK A350-1000.


User currently onlineStitch From United States of America, joined Jul 2005, 30584 posts, RR: 84
Reply 22, posted (2 years 2 months 3 weeks 4 days 21 hours ago) and read 18719 times:
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Quoting panais (Reply 20):
When did they say that?

March 2008 - EK Vice President of Route and Fleet Planning Richard Jewsbury

Quoting panais (Reply 20):
The 777-300ER and the A350-1000 have the same length.

True, but EK fits 10-abreast in the 777-300ER and will fit 9-abreast in the A350-1000. So the 777-300ER gains one extra seat per row of Economy.


User currently offlinepanais From Cyprus, joined May 2008, 462 posts, RR: 0
Reply 23, posted (2 years 2 months 3 weeks 4 days 14 hours ago) and read 18630 times:

Quoting LAXDESI (Reply 21):
EK long haul 77W is configured with 304 Y seats, which is about 30 rows. At 9-abreast, A350-1000 will have about 30 less Y seats.

I really hope that you are not dividing 304 by 10 to make the statement of ...30 rows. EK 77Ws have more than 40 rows of seating. Also , according to the EK website, 77W is 338 seats in regular 3 class seating and 304 seats with private suites.

Quoting LAXDESI (Reply 21):
I think it will be difficult to fit the current 77W 7-abreast J seats(6 rows) on to A350-1000, leading to a loss of 6 J seats on A350-1000.

It is an opinion. They have 7 seats across on the A332 and it is a good product. With the A350 being wider, this will give them another 2.5 inches of width per seat. EK is great at squeezing space with a premium product offering.

Quoting Stitch (Reply 22):
True, but EK fits 10-abreast in the 777-300ER and will fit 9-abreast in the A350-1000. So the 777-300ER gains one extra seat per row of Economy.

Totally agree. therefore, you should be looking at the economy seating difference taking into consideration that EK's 77Ws have 4-8 abreast in the last 4-5 rows.

Quoting LAXDESI (Reply 21):
relative to EK 77W(358 seats),

EK does not seem to agree with this number. More information at http://www.emirates.com/cy/English/f...ng/our_fleet/boeing_777_300ER.aspx

Quoting LAXDESI (Reply 21):
leaving it with nearly 322 seats, which is very close to Stitch's figure of 317 seats for EK A350-1000.

Therefore I stand correct when I am saying that the difference is 20 -21 seats. 338 for today's EK 77W compared to Stitch's 317 is 21 seats.

Quoting Stitch (Reply 22):
March 2008 - EK Vice President of Route and Fleet Planning Richard Jewsbury

You are aware that this statement was more than 4 years ago, there has not been any update or confirmation and you are the only one who keeps quoting it in the last 4 years.

On August 2011 an article at ATW states that "Emirates is drawing up a new configuration plan for the A350-1000 taking advantage of new and more compact galley technology that lifts the seat count to 340" which is an extra 23 seats. EK can do the same with the 77W and add another 2 rows, which fits with what Airbus is saying that the EK 77W is about 15 seats larger than the EK A350-1000.


User currently offlineCXB77L From Australia, joined Feb 2009, 2597 posts, RR: 5
Reply 24, posted (2 years 2 months 3 weeks 4 days 9 hours ago) and read 18577 times:
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CHAT OPERATOR

Quoting panais (Reply 17):
Your numbers do not add up.

Those numbers are based on Boeing's and Airbus' claims. With the 777-9X being longer than the A350-1000, and wider, thus enabling 10-abreast Y and 7-abreast J, it's not inconceivable that the 777-9X will carry substantially more passenger than the A350-1000. Assuming that the 777-9X can fit 3 more rows of economy - that's 30 seats. Then add 1 extra seat per row over 27 rows of Y class seating and you have 57 seats additional seats all up.

Quoting panais (Reply 17):
If you take EK, they have configured the B777-300ER at 358 seats 3-class config. The extra 7 feet in length for the B777-9X will give at best 3 additional rows of economy, or most likely an extra row of business and a row of economy class seating. So this is from 16 to 30 seats in total.

An additional row of economy and an additional row of business class in EK's configuration is 17 seats, not 16. Therefore, the projected total seats for the 777-9X in EK's configuration would be around 374-388 seats, which is still substantially more than the A350-1000's 317.

Quoting panais (Reply 23):
They have 7 seats across on the A332 and it is a good product.

Their A332's J class product is not the same product as on their 77Ws. The product on their A332s is their old regional product.

Quoting panais (Reply 23):
EK does not seem to agree with this number. More information at


That link clearly shows that one of their 3-class 77W configurations add up to 358 seats.

Quoting panais (Reply 23):
Therefore I stand correct when I am saying that the difference is 20 -21 seats. 338 for today's EK 77W compared to Stitch's 317 is 21 seats.

Where did you get 338 seats from?



Boeing 777 fanboy
User currently offlinepanais From Cyprus, joined May 2008, 462 posts, RR: 0
Reply 25, posted (2 years 2 months 3 weeks 4 days 4 hours ago) and read 18664 times:

Quoting CXB77L (Reply 24):
it's not inconceivable that the 777-9X will carry substantially more passenger than the A350-1000.

Nobody is arguing that the 777-9X will not carry substantially more passengers.

Quoting CXB77L (Reply 24):
Assuming that the 777-9X can fit 3 more rows of economy - that's 30 seats. Then add 1 extra seat per row over 27 rows of Y class seating and you have 57 seats additional seats all up.

I do not think that you can get more than 3 economy rows and this might be a stretch. The length of the 777-9x over the 777-300ER is 79.2 inches. EK has 34 inch economy legroom. That means 2.3 rows. But then again EK is really the Ryanair of longhaul so I would not be surprised if they go to 30 inch legroom slimline seats like LH and squeeze more seats.

Quoting CXB77L (Reply 24):
Where did you get 338 seats from?

I have no idea. I counted the seats again and they are more. Maybe my eyes are playing games with me. Apologies for that.


User currently onlineStitch From United States of America, joined Jul 2005, 30584 posts, RR: 84
Reply 26, posted (2 years 2 months 3 weeks 4 days 3 hours ago) and read 18601 times:
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Quoting panais (Reply 23):
On August 2011 an article at ATW states that "Emirates is drawing up a new configuration plan for the A350-1000 taking advantage of new and more compact galley technology that lifts the seat count to 340" which is an extra 23 seats.


ATW Online picked a fine time to have a web server crash, but I did find a cached copy of that article (from August 1st), so thank you (but I will note that it was 317 seats up until that galley change so Mr. Jewbury's comments were still valid over three years after he made them). I will also note that when those same galleys are fitted on the 777-300ER (and 777X), they will add two more rows of Economy seating (so 20 seats).


User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 27, posted (2 years 2 months 3 weeks 4 days 2 hours ago) and read 18750 times:

Quoting Stitch (Reply 26):
ATW Online picked a fine time to have a web server crash, but I did find a cached copy of that article (from August 1st), so thank you (but I will note that it was 317 seats up until that galley change so Mr. Jewbury's comments were still valid over three years after he made them). I will also note that when those same galleys are fitted on the 777-300ER (and 777X), they will add two more rows of Economy seating (so 20 seats).

In summary, with the new galleys fitted on all three, here's what I get:


A350-1000.......340 seats
B77W...............378(358 +20)
B777-9X...........398(2 additional Y rows over B77W)

The difference between 777-9X and A350-1000 in EK configuration with compact galleys is 58 seats, which is almost the same as marketing difference of 57 seats in OP.


User currently onlinenicoeddf From Germany, joined Jan 2008, 1099 posts, RR: 1
Reply 28, posted (2 years 2 months 3 weeks 3 days ago) and read 18451 times:

So, where is the usual disclaimer, that this many seats are obviously only helpful, if you can fill them...  

User currently onlineStitch From United States of America, joined Jul 2005, 30584 posts, RR: 84
Reply 29, posted (2 years 2 months 3 weeks 3 days ago) and read 18492 times:
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Quoting nicoeddf (Reply 28):
So, where is the usual disclaimer, that this many seats are obviously only helpful, if you can fill them...   

Trip cost is what really matters. If the 777-9 could hypothetically match the A350-1000's trip cost, then those extra seats effectively can't hurt you if they are not filled (but do help you if they are).


User currently offlinezeke From Hong Kong, joined Dec 2006, 8870 posts, RR: 75
Reply 30, posted (2 years 2 months 3 weeks 2 days 18 hours ago) and read 18391 times:

Quoting Stitch (Reply 29):
Trip cost is what really matters. If the 777-9 could hypothetically match the A350-1000's trip cost, then those extra seats effectively can't hurt you if they are not filled (but do help you if they are).

And that is never going to happen, the 777 is carrying too much weight, and will always have more drag, it is a physically bigger tube.

The squabbling about seats above is pointless, we saw in the many 787 vs A330 "Analysis" which like this "Analysis" is next to useless when one looks at the actual seat configurations that airlines will operate the aircraft long distance. No 777 with 400ish seats is going to go anywhere with any sort of payload under the floor, let alone normal catering and passenger baggage. The seat count will be reduced to make way for range/payload.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlinerheinwaldner From Switzerland, joined Jan 2008, 2213 posts, RR: 5
Reply 31, posted (2 years 2 months 3 weeks 2 days 10 hours ago) and read 18281 times:

Quoting Stitch (Reply 29):
If the 777-9 could hypothetically match the A350-1000's trip cost

This will not happen. As simple as that.

The 777X will need every additional seat to be cramped in, to become competitive per seat. That's why it will be about as successful as a 300 or 350 seater, as the A358 will be as 250 seater...


User currently onlineStitch From United States of America, joined Jul 2005, 30584 posts, RR: 84
Reply 32, posted (2 years 2 months 3 weeks 2 days 6 hours ago) and read 18200 times:
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Quoting zeke (Reply 30):
And that is never going to happen...
Quoting rheinwaldner (Reply 31):
This will not happen. As simple as that.

I'm aware of that, gentlemen, hence my use of the word "hypothetical".  

I was just illustrating that you don't have to fill every seat in order to justify a larger plane.

[Edited 2012-05-07 08:35:16]

User currently offlinezeke From Hong Kong, joined Dec 2006, 8870 posts, RR: 75
Reply 33, posted (2 years 2 months 3 weeks 2 days 5 hours ago) and read 18172 times:

Quoting Stitch (Reply 32):
I'm aware of that, gentlemen, hence my use of the word "hypothetical"

"hypothetical" can be used to suggest it is based upon unproven fact, it maybe possible. I have clarified that such a hypotheses is impossible to obtain for the 777, but not impossible for a new generation twin.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 34, posted (2 years 2 months 3 weeks 1 day 6 hours ago) and read 18005 times:

Re seats etc, here a more useable measure on how the -1000 and -8X and -9X differ:

Aircraft.............................A350-1000.......777-300ER..........777-8X.......777-9X
Seating, 3 class typical.........350..................365..................353............407
Fuselage length....................73,9.................73,9.................68,6...........76,5
Fuselage wetted area m2......1250................1286.................1182..........1337
Maximum cabin width...........5,61.................5,87..................5,97...........5,97
Cabin lenght........................58,8.................58,5...................53,3...........61,1
Cabin floor m2....................329,8................343,4.................318,0.........364,7

As can be seen the 777X is an interesting frame for those airlines that is prepared to go to 10 abrest, if not the -1000 is better from a cabin perspective. Here frame level data I got from my A vs B wing thread:

Aircraft.............................787-10.......A350-900.....A350-950...A350-1000N....777-8X......777-9X
EIS....................................2018............2014...........2018...........2017............2019.........2019

MTOW.kg...........................250.837......268.000.......268.000......308.000........315.247....344.277
MZFW................................188.000......192.000.......202.000......220.000........225.000....245.000
MSP.....................................56.000........57.000........59.000........68.000.........67.000......73.000
OEW..................................132.000.......135.000......143.000......152.000........158.000....172.000
OEW/MTOW..........................0,526...........0,504.........0,535..........0,494...........0,500........0,500

Seating, 3 class typical.........320.............314.............350............350..............353...........407
Spec range model nm .........6.700..........8.100...........6.700.........8.400...........8.600........8.500
FF kg/hr.............................5.700..........5.700...........5.800.........6.500...........6.500.........7.000
FF kg/nm/per Pax..............0,0365........0,0370.........0,0350.........0,0370..........0,0370......0,0350


The only reason the 777X is competitive (-8X) but not better then the -1000 on a fuel burn level is because it can compensate higher weights with one later engine generation (-2% TSFC). The -8X cabin is more cramped however, if you don't accept to stuff the Y people it will not work, the -9X has the same base for working, if you put people 9 abrest you end up burning 0.0380 level kg/nm/pax ie beyond the -1000 (the -950 is a proposal by CM in the -1000 Ethiad cancellation thread, interesting economy   ).

A note about the weights, the -8X and 9X have the 71m wing, other wings does not work for the -8X. That is an extra 6m span and 10m2 area, add new engines with higher PR and the CFRP wing+engines will weight more then the 77W. The extra lenght fuselage eats up the Al Li gain for the -9X as well, the seating then brings 2 etra tons.

[Edited 2012-05-08 08:12:06]


Non French in France
User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 35, posted (2 years 2 months 3 weeks 2 hours ago) and read 17780 times:

Quoting ferpe (Reply 34):

Aircraft.............................787-10.......A350-900.....A350-950...A350-1000N....777-8X......777-9X
EIS....................................2018............2014...........2018...........2017............2019.........2019

MTOW.kg...........................250.837......268.000.......268.000......308.000........315.247....344.277
MZFW................................188.000......192.000.......202.000......220.000........225.000....245.000
MSP.....................................56.000........57.000........59.000........68.000.........67.000......73.000
OEW..................................132.000.......135.000......143.000......152.000........158.000....172.000
OEW/MTOW..........................0,526...........0,504.........0,535..........0,494...........0,500........0,500

Seating, 3 class typical.........320.............314.............350............350..............353...........407
Spec range model nm .........6.700..........8.100...........6.700.........8.400...........8.600........8.500
FF kg/hr.............................5.700..........5.700...........5.800.........6.500...........6.500.........7.000
FF kg/nm/per Pax..............0,0365........0,0370.........0,0350.........0,0370..........0,0370......0,0350
Quoting ferpe (Reply 34):
if you don't accept to stuff the Y people it will not work, the -9X has the same base for working, if you put people 9 abrest you end up burning 0.0380 level kg/nm/pax ie beyond the -1000

Thanks for the numbers. Your assessment of 9-abreast A350-1000 being better than 9-abreast B777-9X matches what my model indicates as laid out in the OP.

My estimates on OEW and MTOW for B777-9X are about 4,000-5,000 lbs. less than your estimates. Furthermore, my estimate of FF difference between B777-9X and A350-1000 is about 11%, whereas your numbers indicate a difference of 8%.

If your numbers on FF turn out to be correct, B777-8X in EK configuration(10-abreast Y, 7-J, 6-F) is nearly on par with A350-1000--except for LD3 positions.


User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 36, posted (2 years 2 months 2 weeks 6 days 18 hours ago) and read 17638 times:

Quoting ferpe (Reply 34):

Aircraft.............................787-10.......A350-900.....A350-950...A350-1000N....777-8X......777-9X
EIS....................................2018............2014...........2018...........2017............2019.........2019

MTOW.kg...........................250.837......268.000.......268.000......308.000........315.247....344.277
MZFW................................188.000......192.000.......202.000......220.000........225.000....245.000
MSP.....................................56.000........57.000........59.000........68.000.........67.000......73.000
OEW..................................132.000.......135.000......143.000......152.000........158.000....172.000
OEW/MTOW..........................0,526...........0,504.........0,535..........0,494...........0,500........0,500

Seating, 3 class typical.........320.............314.............350............350..............353...........407
Spec range model nm .........6.700..........8.100...........6.700.........8.400...........8.600........8.500
FF kg/hr.............................5.700..........5.700...........5.800.........6.500...........6.500.........7.000
FF kg/nm/per Pax..............0,0365........0,0370.........0,0350.........0,0370..........0,0370......0,0350

Back of the envelope calculations based on your estimates:

B777-9X(at MTOW) carries 11.7% more weight while burning only 7.6% more fuel per hour than A350-1000N--a gain of about 4%. As you have indicated, 2% is accounted for by relative advantage of newer engines on 777-9X over TXWB engines on A350-1000N.

I am still trying to get my head around the remaining 2% advantage of B777-9X. Perhaps Boeing 777-9X has a better wing(design, aspect ratio) that is able to generate the remaining 2%. Time will tell.


User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 37, posted (2 years 2 months 2 weeks 6 days 17 hours ago) and read 17632 times:

Quoting LAXDESI (Reply 35):
My estimates on OEW and MTOW for B777-9X are about 4,000-5,000 lbs. less than your estimates. Furthermore, my estimate of FF difference between B777-9X and A350-1000 is about 11%, whereas your numbers indicate a difference of 8%.

Here my reasoning around the weight:

WING
The wing weighs typically 12.5% of the MTOW,. CFRP ideally buys you if you can change 100% of the wing weight 20%, but your can't, tank equipment etc is not CFRPs, some ribs might be AlLi etc. Damage tolerance for outer skins etc also reduces your practical gains. Wing size increases 10% and engines get heavier as pressure ratios increase 50% (40 to 60). MLG can be a tad lighter (from 352t to 344) but the RR engine is larger dia so it might be a wash. In the end your are lucky if the wing + engines + MLG weighs the same as the 77W, most likely slightly heavier.

FUSELAGE
Fuselage structure is about 10%, AlLi buys you 5% for the parts you can change, say 2/3 so you gain about 1t. The frame is 2.6m longer however and each m cost you something like 1.5t. Finally those 47 extra Pax nead to sit and eat so that cost you (if all are Y) another ton.

All things counted B have done a great job if the -9X is only 4t heavier then the 77W.



Non French in France
User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 38, posted (2 years 2 months 2 weeks 6 days 16 hours ago) and read 17612 times:

Quoting ferpe (Reply 37):
Fuselage structure is about 10%
Quoting ferpe (Reply 34):

Aircraft.............................A350-1000.......777-300ER..........777-8X.......777-9X
Seating, 3 class typical.........350..................365..................353............407
Fuselage length....................73,9.................73,9.................68,6...........76,5
Fuselage wetted area m2......1250................1286.................1182..........1337
Maximum cabin width...........5,61.................5,87..................5,97...........5,97
Cabin lenght........................58,8.................58,5...................53,3...........61,1
Cabin floor m2....................329,8................343,4.................318,0.........364,7

The 777-8X fuselage is shorter by nearly 11%. Applying your 10% rule on fuselage structure, and assuming no change in wings and MLG, B777-8X should be about 4 ton lighter, whereas your estimates show it to be 14 ton lighter than B777-9X?

What way is the B777-8X different than B777-9X?


User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 39, posted (2 years 2 months 2 weeks 6 days 15 hours ago) and read 17609 times:

Quoting LAXDESI (Reply 38):
The 777-8X fuselage is shorter by nearly 11%. Applying your 10% rule on fuselage structure, and assuming no change in wings and MLG, B777-8X should be about 4 ton lighter, whereas your estimates show it to be 14 ton lighter than B777-9X?

What way is the B777-8X different than B777-9X?

The -8X has another parent structure, the 287t -200ER. There is not point in downsizing a 352t structure to a 315t -8X, also upsizing the -200ER 28t is also questionable with such methods. For the -9X it is a 2.6 m stretch and a modes 8t decrease of MTOW, there one can apply such rules if one also checks the OEW/MTOW ratio for reason. For the -8X I have gone on the OEW/MTOW ratio for the 777 (about 0.48) but the engines are heavier (50% in PR) and the wing is larger, therefore I have kept the -9X ratio also for the -8X, it will be close to 0.50 for both of these, give or take 0.5% IMO.

The new engines and wings lowered fuel burn reduces the fuel fraction so much that the ratios goes towards 0.50 rather then the old state of the art 0.48.



Non French in France
User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 40, posted (2 years 2 months 2 weeks 6 days 4 hours ago) and read 17474 times:

Quoting ferpe (Reply 39):
The -8X has another parent structure, the 287t -200ER.

IMO, Boeing is likely to use the same wing and MLG on B777-8X and B777-9X.

B77W is 14% longer than B772LR and weighs 14% more(OEW). B772LR's MTOW is just 4 ton(1%) less than that of B77W. B772LR has an OEW/MTOW ratio of 0.42.

If the B777-8X has the same engines, wings, and MLG as B777-9X, then effectively it is a B777-8XLR. Assuming it to be XLR, it should weigh about 11% less than B777-9X(going by B772LR to B77W comparison)--about 19 tons less than B777-9X. This brings the OEW of B777-8X very close to that of A350-1000.

B777 -8XLR should have a range of about 10,000 nm, which should make SYD-LHR non-stop(9,200 nm) more likely.


User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 41, posted (2 years 2 months 2 weeks 6 days 2 hours ago) and read 17454 times:

Quoting LAXDESI (Reply 40):
B77W is 14% longer than B772LR and weighs 14% more(OEW). B772LR's MTOW is just 4 ton(1%) less than that of B77W. B772LR has an OEW/MTOW ratio of 0.42.

If the B777-8X has the same engines, wings, and MLG as B777-9X, then effectively it is a B777-8XLR. Assuming it to be XLR, it should weigh about 11% less than B777-9X(going by B772LR to B77W comparison)--about 19 tons less than B777-9X. This brings the OEW of B777-8X very close to that of A350-1000.

B777 -8XLR should have a range of about 10,000 nm, which should make SYD-LHR non-stop(9,200 nm) more likely.

This was in the original article by John Ostrower, it has since been refuted by Jim Albaugh in an interview with Flightglobal, B has no interest in doing a follow up to 200LR, the -8X and the -9X are aimed at the mainline "8000nm" market and the -8X has a 315t MTOW. You can't make a -8XLR on a MTOW of 315t, it will fall out of the sky after 8600nm   .

Thus to base it on the 200LR fuselage you would have to reduce dimensions on every single part being made for the flightloads of the 200LR (352t). In essence it will be a 777 fuselage but stressed from the beginning for the 315t case. The wing, engines will be the same (but the wing restressed) as the -9X, the MLG need to be a lighter variant.

My point is in such a case any extrapolations up or down is more error prone then the natural law that all frames are certified and stressed to the same standards. The ULH ones then end up at between 49-51% if they employ the new engine generations and the "mid range" or really long to midrange ones (333, 7810...) end up between 51-53%,

this all being just my    .



Non French in France
User currently offlinezeke From Hong Kong, joined Dec 2006, 8870 posts, RR: 75
Reply 42, posted (2 years 2 months 2 weeks 6 days 2 hours ago) and read 17482 times:

Quoting LAXDESI (Reply 40):
Assuming it to be XLR, it should weigh about 11% less than B777-9X(going by B772LR to B77W comparison)--about 19 tons less than B777-9X. This brings the OEW of B777-8X very close to that of A350-1000.


The 77L/77W fuselage mass is around 2230 kg/m, the A350 fuselage is around 90% less per meter.

Based upon the additonal fuselage length alone the additional 2.64 m of the 777-9X would make that fuselage 5.9t heavier than the 77W, and the 777-8X being 5.26 m shorter, would make it around 11.7 t lighter than the 77W. This does not include the proposed high denisty seating which will drive up OEW as well.

I also think the 777-8X/9X wing will be heavier than the current 777 wing, not lighter.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 43, posted (2 years 2 months 2 weeks 6 days 1 hour ago) and read 17420 times:

Quoting zeke (Reply 42):
The 77L/77W fuselage mass is around 2230 kg/m, the A350 fuselage is around 90% less per meter.

Are you sure the A350 fuselage only weighs 223 kg/m? Seems a bit light, since that would be about 12.5 lb/in.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlinezeke From Hong Kong, joined Dec 2006, 8870 posts, RR: 75
Reply 44, posted (2 years 2 months 2 weeks 5 days 23 hours ago) and read 17399 times:

Quoting OldAeroGuy (Reply 43):

Are you sure the A350 fuselage only weighs 223 kg/m?

No, typo on part, 90% of what the 777 does.

It is line with the gross error check of 90% of the volume per meter, which would be the about the same mass if one assumes a similar density.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 45, posted (2 years 2 months 2 weeks 5 days 19 hours ago) and read 17320 times:

Quoting ferpe (Reply 41):
You can't make a -8XLR on a MTOW of 315t, it will fall out of the sky after 8600nm .

I wasn't suggesting an MTOW of 315t.  

My comments on B777-8XLR implied an MTOW closer to that of B777-9X. It may be that it will build B777-8X and not XLR.

Edited to delete incorrect MTOW weight on B772ER.

[Edited 2012-05-10 20:03:54]

User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 46, posted (2 years 2 months 2 weeks 5 days 2 hours ago) and read 17161 times:

Quoting zeke (Reply 44):
No, typo on part, 90% of what the 777 does.

It also matches the 9 A/B (A350) vs 10 A/B (777X) Y class seating.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineRoseflyer From United States of America, joined Feb 2004, 9503 posts, RR: 52
Reply 47, posted (2 years 2 months 2 weeks 4 days 22 hours ago) and read 17094 times:

Quoting zeke (Reply 44):
Quoting OldAeroGuy (Reply 43):

Are you sure the A350 fuselage only weighs 223 kg/m?

No, typo on part, 90% of what the 777 does.

It is line with the gross error check of 90% of the volume per meter, which would be the about the same mass if one assumes a similar density.

Are you analyzing weight divided by length? That is a very strange metric to compare airplanes since less than half the weight of the airplane is fuselage structure. An empty fuselage tube is about 25-35% of the weight of the airplane (from what I have been told). The rest is the wing, systems, empennage, landing gear, etc which does not depend on length of the airplane.

LAXDESI was comparing OEW/MTOW which is a very useful comparison. Length to weight would indicate that the 757-300 would be a best selling airplane. I've never seen length to weight ever compared in my engineering experience in aviation.

[Edited 2012-05-11 16:27:11]


If you have never designed an airplane part before, let the real designers do the work!
User currently offlinezeke From Hong Kong, joined Dec 2006, 8870 posts, RR: 75
Reply 48, posted (2 years 2 months 2 weeks 3 days 19 hours ago) and read 16890 times:

Quoting Roseflyer (Reply 47):

Not when one is looking at aircraft that have fuselage plugs added/removed to change capacity. It is easy to estimate the OEW change due to the plugs as the remainder of the aircraft often changes little.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineMax Q From United States of America, joined May 2001, 4378 posts, RR: 19
Reply 49, posted (2 years 2 months 2 weeks 3 days 16 hours ago) and read 16860 times:

I guess I just don't get it.


This new 777 weighs just a little less than the current 77w but has substantially less power.



What am I missing ?!



The best contribution to safety is a competent Pilot.
User currently offlinenomadd22 From United States of America, joined Feb 2008, 1832 posts, RR: 0
Reply 50, posted (2 years 2 months 2 weeks 3 days 9 hours ago) and read 16796 times:

Quoting Max Q (Reply 49):
guess I just don't get it.

This new 777 weighs just a little less than the current 77w but has substantially less power.

What am I missing ?!

I gather better aerodynamics means better lift and better acceleration, so you don't need the same power to weight ratio to cruise or get off the ground.



Andy Goetsch
User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 51, posted (2 years 2 months 2 weeks 3 days 4 hours ago) and read 16751 times:

Quoting Max Q (Reply 49):
This new 777 weighs just a little less than the current 77w but has substantially less power.

The key is the new wing and especially it's 71m span, at the start some 75% of the drag is induced drag which is dependent on the span. Look in the thread A vs B wing design philosophies, you will see in the post 42 that the -8X overall drag is some 7000 lbf lower then the 35J despite the latter being 7 ton lighter and some 20.000 lbf lower then the 77W.

Boeing Vs. Airbus Wing Design Philosophies (by ferpe Apr 16 2012 in Tech Ops)

The major difference is in the induced drag where only the span, weight and speed counts ( ( Weight / Span )^2 * speed^2 * konstant = drag ).



Non French in France
User currently offlinezeke From Hong Kong, joined Dec 2006, 8870 posts, RR: 75
Reply 52, posted (2 years 2 months 2 weeks 2 days 11 hours ago) and read 16624 times:

Quoting ferpe (Reply 51):
where only the span, weight and speed counts

Wrong.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 53, posted (2 years 2 months 2 weeks 2 days 5 hours ago) and read 16517 times:

Quoting zeke (Reply 52):
Quoting ferpe (Reply 51):
where only the span, weight and speed counts

Wrong.

When you include a konstant to account for span efficiency, which Ferpe does, he is correct.

Do you have a better explantion for the factors that influence Induced Drag?



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineRoseflyer From United States of America, joined Feb 2004, 9503 posts, RR: 52
Reply 54, posted (2 years 2 months 2 weeks 2 days 4 hours ago) and read 16498 times:

Quoting OldAeroGuy (Reply 53):
Quoting zeke (Reply 52):
Quoting ferpe (Reply 51):
where only the span, weight and speed counts

Wrong.

When you include a konstant to account for span efficiency, which Ferpe does, he is correct.

Do you have a better explantion for the factors that influence Induced Drag?

That is where the factor for various wing designs comes in. In reality induced drag depends on airspeed, aspect ratio and wing area. Ferpe’s overall comment was that a longer wing reduces induced drag, which is exactly true. The small variations in wing span efficiency do not negate the fact that more efficiency will come with a longer wing.

Going to a composite wing changes the way that weight, stiffness and strength factor into the wing calculation and allow a longer optimized wing which can result in more efficiency. If only induced drag mattered, then wings would be far longer, but in reality there are other factors at play.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 55, posted (2 years 2 months 2 weeks 2 days 3 hours ago) and read 16488 times:

Quoting Roseflyer (Reply 54):
airspeed, aspect ratio and wing area.

aspect ratio = span^2 / wingarea , this is why induced drag reduces to span, weight, dynamic pressure (more correct then airspeed) and your span efficiency.



Non French in France
User currently offlinezeke From Hong Kong, joined Dec 2006, 8870 posts, RR: 75
Reply 56, posted (2 years 2 months 2 weeks 1 day 22 hours ago) and read 16427 times:

Quoting OldAeroGuy (Reply 53):

When you include a konstant to account for span efficiency, which Ferpe does, he is correct.

I take it you are referring to Oswald's efficiency factor ?

Quoting OldAeroGuy (Reply 53):

Do you have a better explantion for the factors that influence Induced Drag?

If they were the ONLY factors that dictate induced drag, the aerodynamic design of wing would be simple to optimise, and devices such as raked wingtips, winglets etc would have no effect on reducing the drag produced. However we know wing design is very complex trade-off of multiple factors, especially with transonic effects. Other factors include wing twist, and viscous flow effects which are not constant. You may recall on the A380 they changed the wing twist after the production of a number of frames to reduce the drag as a result of flight test data. The 787 and A350 also have variable geometry wings, the idea of thinking of a wing as being a "fixed" shape is not true, they change automatically during cruise.

Quoting Roseflyer (Reply 54):
In reality induced drag depends on airspeed, aspect ratio and wing area.

It is not ONLY those factors.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 57, posted (2 years 2 months 2 weeks 1 day 22 hours ago) and read 16415 times:

Quoting zeke (Reply 56):
You may recall on the A380 they changed the wing twist after the production of a number of frames to reduce the drag as a result of flight test data.

This is likely the result of finding the 1 g flight shape was different than the predicted deflections.

Quoting zeke (Reply 56):
I take it you are referring to Oswald's efficiency factor ?

Oswald is a little simple for the high lift region with flaps deployed. None the less, span efficiency is nearly contant in the linear region of the flaps down lift curve. In this region, pre-dominant induced drag variables are Weight, Span and Equivalent Airspeed. Ferpe had a mistake when he wrote his equation as induced drag varies as a function of (1/(Equivalent Airspeed)^2).

Quoting zeke (Reply 56):
However we know wing design is very complex trade-off of multiple factors, especially with transonic effects.

Induced drag is much lower in transonic flight than at takeoff. In cruise, induced drag is about 30% of total drag. At takeoff, it's about 75%.

Quoting zeke (Reply 56):
Do you have a better explantion for the factors that influence Induced Drag?

If they were the ONLY factors that dictate induced drag,

At low speed, Weight, Span and Equivalent Airspeed (dynamic pressure) are the primary influencers. Ferpe has it right for the flight region he was discussing.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlinezeke From Hong Kong, joined Dec 2006, 8870 posts, RR: 75
Reply 58, posted (2 years 2 months 2 weeks 1 day 21 hours ago) and read 16410 times:

Quoting OldAeroGuy (Reply 57):

Simple question, are the factors he listed the ONLY factors, yes or no ?

And no, the press comments at the time of the twist chage said to improve efficiency.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 59, posted (2 years 2 months 2 weeks 1 day 10 hours ago) and read 16311 times:

Quoting OldAeroGuy (Reply 57):
This is likely the result of finding the 1 g flight shape was different than the predicted deflections.
Quoting zeke (Reply 58):
And no, the press comments at the time of the twist chage said to improve efficiency.

Same thing, if the inflight twist had matched the design value (ie most efficient), there would be no need for a change.

Quoting zeke (Reply 58):
Simple question, are the factors he listed the ONLY factors, yes or no ?

He was explaning why use of a 71m span allowed use of reduced engine thrust as compared to a 65m span. A 16% reduction in induced drag due to the span change is more important in explaining the thrust reduction as compared to a few percentage points change (if any) in span efficiency.

One word responses like "Wrong" or "Yes" don't help explain a complex situation and we should avoid using them.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlinerheinwaldner From Switzerland, joined Jan 2008, 2213 posts, RR: 5
Reply 60, posted (2 years 2 months 2 weeks 1 day 10 hours ago) and read 16315 times:

Quoting ferpe (Reply 51):
you will see in the post 42 that the -8X overall drag is some 7000 lbf lower then the 35J despite the latter being 7 ton lighter

This result seems not to be plausible, IMO. At least not if induced drag shall be responsible for the difference.

Induced drag is Di = 2 * L^2 / (Rho0 * IAS * wingarea * PI * e * ar) as acknowledged by wikipedia.

ar = wingspan^2 / wingarea

so

Di = 2 * L^2 / (Rho0 * IAS * PI * e * wingspan^2)

In words:

The 77X requires more lift (L) so drag grows as square of L (=weight). This is compensated by the larger wingspan (induced drag is reduced as square of the wingspan).

So, when I check how much the weight grows between A351 and 778X (X%) and how much the wingspan grows between the two (less than X%), I can see, that the 778X will still have more induced drag than the A351 in absolute terms.

So this consideration seems to challenge your above conclusion.


User currently offlineastuteman From United Kingdom, joined Jan 2005, 9978 posts, RR: 96
Reply 61, posted (2 years 2 months 2 weeks 1 day 3 hours ago) and read 16221 times:
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Quoting OldAeroGuy (Reply 59):
He was explaning why use of a 71m span allowed use of reduced engine thrust as compared to a 65m span. A 16% reduction in induced drag due to the span change is more important in explaining the thrust reduction as compared to a few percentage points change (if any) in span efficiency

Understanding the reduction in induced drag, I thought that the physical characteristics of wing loading and the sheer size of the area producing lift were the primary drivers of the ability to reduce the required thrust....

Rgds


User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 62, posted (2 years 2 months 2 weeks 1 day 3 hours ago) and read 16219 times:

Quoting rheinwaldner (Reply 60):
So, when I check how much the weight grows between A351 and 778X (X%) and how much the wingspan grows between the two (less than X%), I can see, that the 778X will still have more induced drag than the A351 in absolute terms.

1. You shall use the effective wingspan of both wings, ie including the induced drag mitigating effect of the wingtip devices, otherwise you will discredit 35J who has winglets.

2. If you set speed, height and efficiency factor equal between the two and if you search the weight for equal induced drag of the -8X the equations becomes:

308000^2 / 65.8^2 = X^2 / 70.2^2

X = ( 308000^2 * 70.2^2 / 65.8^2 )^0.5 = 328 596 kg

This is the result I get, how did you count?



Non French in France
User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 63, posted (2 years 2 months 2 weeks 1 day 2 hours ago) and read 16204 times:

Quoting astuteman (Reply 61):
Understanding the reduction in induced drag, I thought that the physical characteristics of wing loading and the sheer size of the area producing lift were the primary drivers of the ability to reduce the required thrust....

The start is the case were the induced drag is your real problem, look in the thread Boeing Vs. Airbus Wing Design Philosophies, there are some simulations there (with some degree of inexactness cause it is a simplified model) that shows where the problem is. I started this work for the very reason we discuss, I was convinced the -8X was severely underpowered for the start case, I have not been able to prove that.

I am about to make a new post where I have improved the model (less shortcuts in the parasitic drag calculation, the diff is in the few % range). Here the start drag simulated for flaps 15 ISA both climbing out on one engine with gear in at 170kts:

............................350-1000N...........-8X
Total drag lbf.............. 55.637.........50.537
Parasitic drag lbf.........14.790.........12.326
Induced drag lbf...........40.847.........38.211

By virtue of it's stronger engines the 35J achieves a 2.4% climb rate at 164kts vs the -8X 170kts in the model. The low powerload of the -8X does also show in climbrate at 1500ft and 250kts, there the 35J climb at some 3500ft/min vs 3000 for the -8X.



Non French in France
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 64, posted (2 years 2 months 2 weeks 1 day 2 hours ago) and read 16200 times:

Quoting astuteman (Reply 61):
Understanding the reduction in induced drag, I thought that the physical characteristics of wing loading and the sheer size of the area producing lift were the primary drivers of the ability to reduce the required thrust....

These parameters are of more interest for takeoff field length characteristics.

You can have two wings with the same wing loading (W/S) and span efficiency, but if one has 10% more span, it will have 17% less induced drag when operating at the same speed (dynamic pressure).



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlinesweair From Sweden, joined Nov 2011, 1811 posts, RR: 0
Reply 65, posted (2 years 2 months 2 weeks 1 day ago) and read 16155 times:

Can you guys do a run on the 779-X vs 748i? It would be interesting to compare these two frames. In 2014 LH expects to get a lighter frame and GE has promised PIPs that bring the SFC to spec or better. The freighter can carry about 30 tons more the same distance as the 77F if I remember correctly.

User currently offlineMax Q From United States of America, joined May 2001, 4378 posts, RR: 19
Reply 66, posted (2 years 2 months 2 weeks 17 hours ago) and read 16087 times:

I am only a Pilot, not an engineer but it still doesn't add up to me.


Regardless of what this new structure is made of or how much longer the wing is this Aircraft has significantly less power for its weight than the current version.



The best contribution to safety is a competent Pilot.
User currently offlineLAXDESI From United States of America, joined May 2005, 5086 posts, RR: 48
Reply 67, posted (2 years 2 months 2 weeks 15 hours ago) and read 16072 times:

Quoting sweair (Reply 65):
Can you guys do a run on the 779-X vs 748i? It would be interesting to compare these two frames. In 2014 LH expects to get a lighter frame and GE has promised PIPs that bring the SFC to spec or better.

Roughly speaking, for a 6,000nm trip:

B748 burns about 14,000 more gallons of fuel($45,000) than B777-9X.
B748 can carry up to 20,000 lbs. more cargo(if not volume constrained).
B748 has a 60 seat advantage(3 class marketing) over B777-9X.

Ignoring cargo and assuming 70% load factor on the additional 60 seats, the extra seats need to be sold at an average one way fare of nearly $1,100 to offset the higher fuel costs.

It seems to me that for most routes, B777-9X should have an advantage over B748. However, there may be dense routes with high yields( and slot issues) for which B748 may be a more attractive option.

The 748 has a list price of nearly $333 million, and I expect B777-9X list to be around $320+ million. It may be possible to get the B748 for a price equal to B777-9X on a net basis.


User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 68, posted (2 years 2 months 2 weeks 14 hours ago) and read 16041 times:

Quoting sweair (Reply 65):
Can you guys do a run on the 779-X vs 748i?

The model I have built is a simplified model of preliminary analysis tool described here: http://adg.stanford.edu/aa241/AircraftDesign.html. This in turn is simpler then the OEMs preliminary models let alone their project calculations when they use CFD and windtunnels. For the 747-8i there is even flight test data so there is no point in modeling the 748 and thinking one can find something that is not already done much better by the OEM and publicized in the ACAP.

For the 777X we only have sketchy leaked figures like 71m wingspan, 10% more wingarea then 77W and the MTOW and engine gereration, there are even quotes from GEs Aerospace mgr that the new GE90X is 6-8% better then the G90-115 in fuel burn and from the Trent mgr that the Trent offered to the 777X is some 2% better then the TXWB generation.

Here one can speculate what this all means with the tools one have, it is at least better then guessing, without all those calculations I would not have believed that the 777X engines make sense. I will post a better estimate for the 777X soon where I have worked on the important (for the cruise phase) parasitic drag modeling, the predicted ranges are in the order of -8X 8400nm and -9X 8200nm.

For the 748i the range is with 467 pax, this is debated. If one reduces this to the same pax and seat count as the -9X one lands per ACAP at about the same range bracket, 8200nm (when the 748i is mature in OEW and engines). The fuel burn is considerable higher but one is EIS and the other on PPT, so a comparison is not very fair.



Non French in France
User currently offlinerheinwaldner From Switzerland, joined Jan 2008, 2213 posts, RR: 5
Reply 69, posted (2 years 2 months 2 weeks 12 hours ago) and read 16018 times:

Quoting ferpe (Reply 62):
1. You shall use the effective wingspan of both wings, ie including the induced drag mitigating effect of the wingtip devices, otherwise you will discredit 35J who has winglets.

Ok, thanks. So the Di will favour the A351 even more.

Quoting ferpe (Reply 62):
2. If you set speed, height and efficiency factor equal between the two and if you search the weight for equal induced drag of the -8X the equations becomes:

308000^2 / 65.8^2 = X^2 / 70.2^2

X = ( 308000^2 * 70.2^2 / 65.8^2 )^0.5 = 328 596 kg

This is the result I get, how did you count?

I did not put in values. Just by looking at the formula, one can see that the 778X has more induced drag than the A351.

Just calculate the drag for both.

Even your figure proves the point. As the A351 weights less than than your calculated "aequivalent weight for 778X drag", the A351 will obviously generate less Di.

Di goes up with the square of the weight, so the 778X will suffer heavily against the less heavy A351 in this departement. The span increase gives some relieve but does not counter that penalty fully (because the span increase is less in % than the weigth increase between the two).

Quoting ferpe (Reply 63):
............................350-1000N...........-8X
Total drag lbf.............. 55.637.........50.537
Parasitic drag lbf.........14.790.........12.326
Induced drag lbf...........40.847.........38.211

Highly doubtful numbers IMO. Also please cap the number of significant digits. Realistic is about two.

(This is not a frontal confrontation vs your analysis. I respect and enjoy your analysises in 95% of all cases).

Quoting ferpe (Reply 63):
By virtue of it's stronger engines the 35J achieves a 2.4% climb rate at 164kts vs the -8X 170kts in the model.

Increased Vrotate by 6 kts alone lengthens the take off run of the -8X by severall seconds and makes the take of run hundreds of meters longer.


User currently offlineastuteman From United Kingdom, joined Jan 2005, 9978 posts, RR: 96
Reply 70, posted (2 years 2 months 2 weeks 3 hours ago) and read 15903 times:
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Quoting ferpe (Reply 63):
Here the start drag simulated for flaps 15 ISA both climbing out on one engine with gear in at 170kts:

............................350-1000N...........-8X
Total drag lbf.............. 55.637.........50.537
Parasitic drag lbf.........14.790.........12.326
Induced drag lbf...........40.847.........38.211

you will have to explain to me how the 777-8X ends up with 20% less parasitic drag with wings that have 10% more surface area than the A350-1000, and a wider, if shorter, fuselage..

Rgds


User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 71, posted (2 years 2 months 2 weeks 3 hours ago) and read 15893 times:

Quoting rheinwaldner (Reply 69):
Just calculate the drag for both.

This is what I did in the table below, sorry about the dots, it is an Excel delimiter for 1000 in European writing, my fault. The table should have been

............................350-1000N...........-8X
Total drag lbf.............. 55 637.........50 537
Parasitic drag lbf.........14 790.........12 326
Induced drag lbf...........40 847.........38 211

or if you like

...............................350-1000N........-8X
Total drag klbf................ 56..............51
Parasitic drag klbf...........15.............12
Induced drag klbf.............41.............38

Now do the sums yourselves if your don't believe me. Here the 170kt V2 case with e = 0.85 (0.85 could be reasonable for a wing with climb flaps, the formula is in Wikipedia, SI units kg and m):

Induced drag N = (MTOW * 9.81)^2 /( 0.5 * 1.225 * 89^2 * 3.14 * 0.85 * span^2)

You will find that my induced drag is slightly higher for both frames as I include the induced drag of the horizontal tail trimming the aircraft.

[Edited 2012-05-16 12:13:04]


Non French in France
User currently offlineferpe From France, joined Nov 2010, 2800 posts, RR: 59
Reply 72, posted (2 years 2 months 2 weeks 2 hours ago) and read 15894 times:

Quoting astuteman (Reply 70):
you will have to explain to me how the 777-8X ends up with 20% less parasitic drag with wings that have 10% more surface area than the A350-1000, and a wider, if shorter, fuselage..




It should not, if the wingarea is 10% larger then the wetted area is 20% larger and the 70m2 diff in fuselage area does not compensate that. The pressure drag diff is not dependent on the average 6.02 vs 6.20 fuselage dia diff it is the thickness ratio (dia / lenght) which gives the pressure drag factor (higher for -8X), check the site. The reason for the higher parasitic drag in this case is the difference in flap type (Dropped hinge vs Fowler, check the thread) and their assumed drag at Flaps 15 (or an equivalent flap config which gives a Cl increase of about 0.8 for the 35J, Rheinwaldner asked about the start case).

Here an example where both are in the same drag config (clean), climb at 250kt CAS at 1500ft:

....................................35J........-8X
Climb ft/min..................3 498.......2 980
Climb drag 1500ft lbf....30 601.....30 545
Climb drag Dp lbf.........12 732.....13 822
Climb drag Di lbf ..........17 869.....16 723


They are both at same drag with the -8X lower induced but higher parasitic as it should be.

The picture is the same at cruise :

...................................35J............-8X
Cruise drag lbf FL370....26 511......27 036
Cruise drag N FL370....117 925....120 263
Cruise Dp N FL370.......68 983......74 768
Cruise Di N FL370........48 942......45 495

The -8X lives on it's higher BPR and PR engines to gain parity with 35J.

[Edited 2012-05-16 12:25:46]


Non French in France
User currently offlinesweair From Sweden, joined Nov 2011, 1811 posts, RR: 0
Reply 73, posted (2 years 2 months 1 week 6 days 10 hours ago) and read 15708 times:

Maybe a combi model of the 748i is the best compromise, as a pure passenger hauler the 779-X will be better. The 748i is not the same NG as the 777 will get, sure a revised wing but no entirely new wing, no Al-Li, no internal stretching etc.

I think if they had gone all out on the 748i it would have made the 77X future a lot harder..


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5405 posts, RR: 30
Reply 74, posted (2 years 2 months 3 days 18 hours ago) and read 15085 times:

Good work folks. The back and forth is providing interesting insight into the theoretical future of the 777...especially considering those crunching the numbers are winging it based on Boeing's vague press offerings.

Interesting and nice and polite like...gotta love it.



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