KLM777 From Netherlands, joined Dec 2003, 372 posts, RR: 0
Reply 4, posted (11 years 11 months 1 week 6 days 1 hour ago) and read 5044 times:
The wing of the 777 is very long and at the end very thin. This means there is less induced drag than on a standard wing, because there is less air moving from below the wing to the top of the wing.
Maybe winglets could even increase the efficiency, but winglets means weight and especially at the end of the wing this is not a very positive thing (the weight itself has to be carrier up which costs fuel but it also creates more momentum and thus bigger joints and structure at the root of the wing). So if you weigh up the pros and cons winglets do not always increase efficiency.
Zak From Greenland, joined Sep 2003, 1993 posts, RR: 8
Reply 5, posted (11 years 11 months 1 week 6 days 1 hour ago) and read 5008 times:
i dont know how a wing is designed powerful, but besides that, the 777 wing was designed in a way that the wingtip vortex is minimal, therefore the weight of any special structure on the wingtip (rake or winglet or whatever) would outweight the gain from it.
that calculation seems to have changed in favour of the raked tip with the 300ER and 200LR, therefore they have raked tips.
it is all a matter of efficiency, similar with the 737NG. to some operators the savings make sense, to others the efficiency gain does not outweight the penalty from the weight, therefore they are not economical.
the wingtip game is just like any other game in aviation, you only add weight if you get enough improvement out of it to make up for it.
in some cases this is just not the case.