The folding wingtip is actually a relatively small part of the wing. People worrying about problems with it likely didn’t realize how only a tiny part of the wing folds.
It's actually THE tip device (i.e. raked wingtip) that folds, it's not a part of the wing itself. It's not like in naval aviation where a significant part of the wing itself folds.
There are many good reasons why Boeing went for such a modest folding mechanism:
1- Wings tips won't house controls, so that would simplify the design, reliability, and complexity of the folding mechanism.
2- You can't carry fuel in the folding part of the wing. Increasing the size of the folding side just means less fuel for your trip. In commercial aviation, this is a no-no.
3- Since it only folds 3.5m on each side, it would be smaller and lighter. If it was too heavy and complex , like the original folding mechanism on the 777 that folds more than 7m on each side, it would just negate the whole purpose of extending the span.
4- Of course, maintenance costs would also be less since it's smaller and simpler.
5- And there is the safety aspect to it, a 777 won't lose lift if one wingtip device is gone, unlike in the case if half the wing would fold for example. Sure, it will be designed in a way that this would almost never happen, but then it would be heavy, complex, and expensive.
Or the A321 gets rewinged with folding tips in 10 years time.
Would it make sense for the A320/737 families to have folding wingtips as much as it does for the 777X? I don't know.
I mean, the blended wingtip for the A320 is only 2.5m long. In this case, each wingtip addes 1.125m to the effective span (2.5*0.45). If they switch to folding raked wingtip design, each wingtip would add 2.125m to the effective span (2.5*0.85). That's 1m gain in effective span on each side, does that justify the increased weight, cost, and complexity the folding mechanism adds? I don't know. But I guess the gains won't be as much as we will see in the 777X, which is a long-haul beast that has larger wingtip devices.
I could be wrong.
Last edited by Eyad89
on Fri Sep 14, 2018 11:52 am, edited 1 time in total.