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