Boeing Revises 787-9 Plan

Boeing has made some changes to the 787-9

The wingspan is being increased to 203 feet. That gives it a longer wing than the 777. Some changes to the chord are also being made. The change was done to improve its handaling charecteristics at lower speed that had been effected by its increased MTOW. Boeing officals further indicated that the stretched -10 version would have the same basic weight as the -9 (due to landing gear limits) and perhaps the revised wing would be its starting point on the -10.

The plane is also 2% above weight targets at this stage of the game and production freeze for the -9 variant is about a year away with deliveries scheduled for 2012.

In what has to be good news for Airbus, Boeing has said that production slots are pretty much sold out through 2011 unless they can ramp it up. So if airlines want to move an efficent a/c into thier stables, the A350 may be the only option they have which should boost sales once the final configuration is set

Boeing will lengthen its stretched 787-9's wing slightly to improve its aerodynamic efficiency, a move that takes it a few feet beyond the basic 777.

The design changes to the -9 will add about 6 ft. total to the wingspan, bringing it to about 203 ft. The wings of the 777-200/-200ER, which with standard seating of 301 passengers are at the top end of the 250-290 seating that 787-9 will offer, is 199 ft. 11 in. At an 8,600-8,800-naut.-mi. range, however, the 787-9 will have more than a 1,000-naut.-mi. advantage over the 777-200 Extended Range.
.Boeing Revises 787-9 Plan

Edit: I forgot to add: How many people remember the folding wingtip option for the 777-200's? No one actually selected the option for it. However with wingspans increasing, I wonder when they will be required???

[edit on 6/6/06 by FredT]

I remember the folding outer wings option on the 777, though I didn't realise no-one had taken it up. That makes sense to me as a folding wing on a 300 seat plane is quite a scary thought, not that it wouldn't be manufactured properly but I don't think it is something passengers would like to see.

Airbus specifically designed the A380 so that it wouldn't need folding tips and I think Boeing is likely to avoid them on the 787 too, especially given that no 777 customer has wanted them either.

Wait...wait, The posted wingspan of the 772-LR & 773-ER is 212'. The A358/9 is 200'. The 744-ER is 211'+. The A380 is a wopping 261'. How is this bad news for Boeing. So the wing got bigger. Sure that is not the planned lenght but it i still way within nominal length. If anything this is good news (longer wing= better cruise PPM). This may increase buys due to increased range.


[edit on 6-6-2006 by Imperium Americana]

Nobody said it was bad or wrong etc. Sheesh it was more of an update. Hardly cause for concern at all.

The only time it would be a concern is if they go into the smaller Cat I or Cat II airports that the bigger planes can't get into. Those airports can be pretty tight. (I THINK a 787 will be able to get into a Cat II, but I'll have to double check on that.) I KNOW that a 777 can get into a Cat I, so that really SHOULDN'T be an issue. I'll check on the Cat II and update when I find anything out.

From what I can find out, a 787 should have no trouble getting into most Cat II airports. Airports are broken down into categories based on passenger traffic. A Cat X airport is like O'Hare in Chicago, or Hartfield in Atlanta. A Cat I would be West Palm Beach, Florida or T.F. Green Municipal in Providence. A Cat II would be Harrisburg International in Pennsylvania. Cat III would be like Molokai in Hawaii. They have two incredibly short runways, and one tiny passenger terminal with two gates.

Boeing is discussing with its 787 partners the possibility of a second assembly line. They haven't decided yet. The wingspan increase seems to be in accordance with the introduction of the 787-10. I bet they are saving it for Farnborough and compete with Airbus A370 or whatever is that they are calling it...

Actually it is for the 787-9. It will be the baseline config for the -10. The -9 has a higher MTOW that degraded its low speed charecteristics hence the increase in wingspan to negate that.

Boeing is looking at a second line, but since the debacle that occured when they tried to ramp up 737 production a few years back, will be very carefull this time. One thing to remeber that both Airbus and Boeing are really more integrators of parts and do not produce all the part in house. So its also a matter of getting the suppliers on the bandwagon as well.

Originally posted by Imperium Americana
If anything this is good news (longer wing= better cruise PPM). This may increase buys due to increased range.

Doesn't always work like that (unfortunately), increasing the span will also increase the stresses through the wing spar, and to deal with this usually a thicker t/c aerofoil section through the wing is needed = extra weight.

Was the main advantage of composites not the ability to run lower t/c while maintaining span?

If so, Boeing are increasing span and taking the little hit on t/c. There are performance curves for determining the optimum. Obviously, I've no idea where exactly Boeing's initial design points are so I've no idea of all the side-effects of the increase in wingspan.

Could be a reduction in take-off T/W but a sacrifice of Cdo in cruise (against that, lift dependant drag should be reduced slightly). Depending how the numbers play out there may be no cruise benefit.

Originally posted by kilcoo316

Doesn't always work like that (unfortunately), increasing the span will also increase the stresses through the wing spar, and to deal with this usually a thicker t/c aerofoil section through the wing is needed = extra weight.

Was the main advantage of composites not the ability to run lower t/c while maintaining span?

If so, Boeing are increasing span and taking the little hit on t/c. There are performance curves for determining the optimum. Obviously, I've no idea where exactly Boeing's initial design points are so I've no idea of all the side-effects of the increase in wingspan.

Could be a reduction in take-off T/W but a sacrifice of Cdo in cruise (against that, lift dependant drag should be reduced slightly). Depending how the numbers play out there may be no cruise benefit.

You are right, it does not always work that way, but moving the wing tip vortices out farther from the main lifting area, most of the time, equates with better PPM @ Vc. I wonder effect this has on Vref? But you right an increase in span may = structural upgrades. it all depends on their margin.

Originally posted by FredT
Nobody said it was bad or wrong etc. Sheesh it was more of an update. Hardly cause for concern at all.

Sorry Fred! I did not mean to come across as jumping on ya.


[edit on 7-6-2006 by Imperium Americana]

Originally posted by Imperium Americana

You are right, it does not always work that way, but moving the wing tip vortices out farther from the main lifting area, most of the time, equates with better PPM @ Vc. I wonder effect this has on Vref? But you right an increase in span may = structural upgrades. it all depends on their margin.

What do you mean by Vref?

reference? [maybe screen height at takeoff? ]
rotation?


From Prandtl's lifting line -

Cd(induced) = [CL^2]/[pi*AspectRatio]

*for an elliptical lift distribution, which the aircraft manufacturer would be aiming for.

Increasing the span will increase aspect ratio, and increase wing area (lowering CL in cruise) - both lowering induced drag. But the zero lift drag coefficient will rise a little from larger wetted area.


Usually though, the initial wing is optimised for the job, and represents the best compromise between aerodynamics and weight. Having a bigger fuselage that requires a bigger wing can induce a small snowball effect. But I'm quite sure the people at Boeing know what they are doing.