View Full Version : Winglets and super critical wings...
Turbofan
22nd Jan 2001, 13:15
As far as I know, the reason the 777 doesn't have winglets is becuase it has a super critical wing.
Now correct me if I'm wrong, but aren't winglets there to reduce induced drag at slow speeds and high angles of attack...
And aren't super critical wing sections employed to delay Mcdr during high speed cruise...
Well, one design feature is for slow speed flight, the other for fast. As far as I know...
You can't really trade one for the other.
So, have I missed something, or am I simply wrong???
Bleater
22nd Jan 2001, 14:11
I would say you are right. Also it is American so in about 5 years time they will bring out the new improved version with winglets so the Airlines can paint a Logo on the side and the SLF can tell who has invested in new Aircraft. :) :). Still the only way to tell an early 747 from a new one from the outside.
Turbofan
23rd Jan 2001, 05:29
Well I've heard a number of people say that one's traded for the other. Or to be more specific, that the reason a 777 doesn't have winglets is due to it having a super critical wing section.
Like they're interchangable... doesn't make an aweful lot of sense to me.
Why not have both, unless structural integrity won't permit it...?
So then, why doesn't the 777 have winglets? What design feature does its wing have that negates their effect to a large extent???
Here's a theory. Perhaps having a super critical wing won't allow winglets for structural reasons as stated above, and the advantages of the SC wing out-weighed those of winglets...
Anyone care to throw a theory my way.
Cheers.
The issue is somewhat religious to many people but I think this side of it makes sense, although I haven't done the calculus myself.
Supposedly, when structure and available room (airport size that is) gives you the option, you always benefit more from adding additional wing span than the same weight of winglets. When designing a new plane as opposed to retrofitting an old one, you do have this option.
Sounds like a plausible explanation to me.
Cheers,
/ft
Juliet November
24th Jan 2001, 06:29
Does this mean than Airbus A330/340 series does not fly a super critical wing ?
What about advanced GA jets such as the Bombardier Global Express, Challenger or Gulfstream IV & V ?
DoctorA300
25th Jan 2001, 16:30
Winglets are used to reduce wingtip vortexes,but they also cause an increase in drag, therefor it is a simple question of what is gained versus what is lost. As a general rule you could say that the higher the aspect ratio of an airfoil the less you need winglets/fences.
captmu2
27th Jan 2001, 02:50
Not sure if this helps but the 777 was built to compete for the dc-10 routes and therefore the gates as well (as we all know), but the 777 was also designed with an optional folding wing tip to fit it into small gates...no airlines have to date ordered this option but it may lead to the winglet problem. Also it is my understanding that winglets are utilized to benifit the a/c's range capability. 747 = 3% more range with added winglets, since the 777 is designed for medium range and has more than the capability in its fuel tanks to meet the design requirements the winglets again are possibly ommited here????? All theoretical......