justloveplanes From United States of America, joined Jul 2004, 1095 posts, RR: 1 Posted (3 years 7 months 6 days 22 hours ago) and read 3057 times:
The 789 notionally uses the 788 wing, though I heard it was reinforced. I am guessing this goes for the Wingbox as well. What will be the differences? The 789 is supposed to be on a better weight track and wondering what that is.
ferpe From France, joined Nov 2010, 2805 posts, RR: 59
Reply 1, posted (3 years 7 months 6 days 18 hours ago) and read 2998 times:
Quoting justloveplanes (Thread starter): The 789 notionally uses the 788 wing, though I heard it was reinforced. I am guessing this goes for the Wingbox as well. What will be the differences?
The 789 has a 10,5% higher MTOW then the 788, i.e. the worst loading case of the wing and the aircraft as a whole would load the wing structure accordingly higher (unless they change the span-wise pressure distribution of the wing which I don't think they have done). I would believe the ultimate load case would be something like the frame passing a thunderstorm at cruise speed, i.e. the ultimate load case is an upward directed gust.
The load-taking structure is the wingbox (central + wings) it needs to be beefed up the 10,5%, the body joint needs to handle a heavier fuselage (compression) and fuselage (longer heavier tube: upper skins tension and lower compression, side shear loads increase) as well. The tail is not experiencing any higher loads most probably (moment arm is longer, i.e. lower forces needed on the tail surfaces) except the dimensioning for a higher risk for tail strikes perhaps. Further the FLG and MLG fitting points need to be beefed up as well (higher MLW).
dynamicsguy From Australia, joined Jul 2008, 903 posts, RR: 9
Reply 2, posted (3 years 7 months 6 days 16 hours ago) and read 2965 times:
Pretty much all of the gauges (thicknesses) will have changed to meet the higher loads.
On the trailing edge we have a higher deployed angle for the flaps and higher approach speed, which then drives changes in the sizing of the flaps as well as greater loads going through the fixed trailing edge structure into the wing box.
I understand some more structure has changed from metallic to composite to meet the weight requirements, in spite of the extra cost involved for these parts.