AirWillie6475 From United States of America, joined Jan 2005, 2448 posts, RR: 1 Reply 1, posted (7 years 9 months 3 weeks 6 days 11 hours ago) and read 3573 times:
The winglets help reduce the turbulent airflow that is found at the end of the wings. They found that if you make the airflow smoother at that section the plane has better performance. The airbus probably knew this from the beginning and installed winglets on all their planes. The heavy aircraft need something there because they produce a lot more turbulent air at the end of the wings. Boeing was a little late to recognize the benefits of winglets.
It would be hard to see the performance of airbus winglets since they already came with the plane and they contributed to the AC performance specs, so we wouldn't know how the plane would have done without the winglets. But judging from the A380 winglets which are the a319/320 style winglets, those might be better than the a330/340 winglets since they chose that type for the new plane. We can however, see the benefits of the new 737 winglets.
Jetlagged From United Kingdom, joined Jan 2005, 2452 posts, RR: 17 Reply 2, posted (7 years 9 months 3 weeks 6 days 9 hours ago) and read 3562 times:
Not quite. Turbulence is random vorticity, the flow at the wingtip is a predictable strong vortex. Winglets reduce induced drag caused by the wingtip vortices by adjusting the airflow and locally rotating the lift vector. They also increase aspect ratio and so improve efficiency.
The original winglet designs were all variations of the kind seen on the 747-400. Airbus discovered they could get nearly the same benefits on the A310 and A320 with the smaller wingtip fences, a kind of low drag endplate. On the A330 and A340 it's more a case of increasing aspect ratio, and hence range, without having excessive wingspan. The A380 has a reverted to a larger version of the wingtip fence design.
The 777 wing was designed to be optimal without winglets. Adding winglets might even reduce overall efficiency. Boeing seem to have abandoned traditional winglets in favour of the raked wingtip design.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
Starlionblue From Hong Kong, joined Feb 2004, 15870 posts, RR: 66 Reply 3, posted (7 years 9 months 3 weeks 6 days 8 hours ago) and read 3549 times:
Quoting AirWillie6475 (Reply 1):
It would be hard to see the performance of airbus winglets since they already came with the plane and they contributed to the AC performance specs, so we wouldn't know how the plane would have done without the winglets.
Actually the A320-100 did not have fences, so it is possible to know how much more efficient the wing became.
Quoting Jetlagged (Reply 2): Boeing seem to have abandoned traditional winglets in favour of the raked wingtip design.
Only if wingspan is not a problem. On the A380 and 737, wingspan cannot be increased due to gate clearance, thus forcing a vertical variant.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
Jetlagged From United Kingdom, joined Jan 2005, 2452 posts, RR: 17 Reply 4, posted (7 years 9 months 3 weeks 6 days 7 hours ago) and read 3546 times:
Quoting Starlionblue (Reply 3): Only if wingspan is not a problem. On the A380 and 737, wingspan cannot be increased due to gate clearance, thus forcing a vertical variant.
The A380 is not a Boeing, which my comment you quoted referred to. Airbus have not adopted raked wingtips in any form so far as I'm aware. Boeing addressed the wingspan issue by offering folding wingtips on the 777, but nobody bought them. They would have made great billboards at the gate
The glass isn't half empty, or half full, it's twice as big as it needs to be.
Jetlagged From United Kingdom, joined Jan 2005, 2452 posts, RR: 17 Reply 6, posted (7 years 9 months 3 weeks 5 days 6 hours ago) and read 3448 times:
When the 777 was first launched, there were concerns that the wingspan would be too great for some operators so Boeing came up with the idea of folding wingtips to reduce wingspan on the ground. No one specified that option and I guess it's been quietly dropped.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
Troubleshooter From Germany, joined Feb 2005, 423 posts, RR: 5 Reply 7, posted (7 years 9 months 3 weeks 5 days 3 hours ago) and read 3437 times:
Quoting Jetlagged (Reply 6): When the 777 was first launched, there were concerns that the wingspan would be too great for some operators so Boeing came up with the idea of folding wingtips to reduce wingspan on the ground. No one specified that option and I guess it's been quietly dropped.
I´ve read in a german aviation magazine that these foldable wings are designed especially for operators flying to New York - La Guardia as there are very narrow parking positions. As no operator ordered this system Boeing used the space for increasing the wing fuel tanks on later versions.
AeroWeanie From United States of America, joined Dec 2004, 1600 posts, RR: 52 Reply 8, posted (7 years 9 months 3 weeks 5 days 2 hours ago) and read 3430 times:
For a first-order analysis of the benefit from a winglet, lay it down flat as if it was a span extension. Hence, taller is better. Then, look at whether the winglet joins the wing in a sharp break or a smooth flow. Smooth is better.
Using this criteria, I'll rank the winglets (and raked tip):
1) The A3100/310/318/319/320/321/380 "winglets" are the least effective, but also increase wing bending moments the least. I have never seen a published number for how much they reduce drag (even Jupp's patent US4,714,215 says little), but I'd guess they are worth 1-1.5% drag improvement.
2) The MD-11 winglets come next. They are a direct outgrowth of Whitcomb's original designs. I have some NASA reports on the flight testing of a similar winglet on a DC-10. According to CR-3704, these winglets are produce a 2-2.5% drag reduction in cruise.
3) The Valsan/Quietwing 727 winglets are a latter Whitcomb influenced design. Coupled with a flap droop on the 727, they are reputed to be worth about 5%. The flap droop reduces wing bending moments and helps reduce wave drag, so the 5% is a mixture of effects. The winglet by itself is probably worth about 3%.
4) The 747-400 and A330/340 winglets are rather similar. They fall on the wing span extension line. I've read that the 747-400 winglets produce about a 3.5% drag reduction.
5) The 776-400ER/777-300ER/777-200LR raked tips also fall on the span extension line. They produce varying amounts of drag reduction, depending on their span. They also increase wing bending moments quite a bit.
6) The API/APB blended winglets produce better results than the span extension line indicates. The 737NG winglets are first generation and I've read that they produce about a 4.5% drag reduction. Later API/APB winglets improve on this.
Starlionblue From Hong Kong, joined Feb 2004, 15870 posts, RR: 66 Reply 10, posted (7 years 9 months 3 weeks 4 days 13 hours ago) and read 3393 times:
Quoting Jetlagged (Reply 4): Quoting Starlionblue (Reply 3):
Only if wingspan is not a problem. On the A380 and 737, wingspan cannot be increased due to gate clearance, thus forcing a vertical variant.
The A380 is not a Boeing, which my comment you quoted referred to. Airbus have not adopted raked wingtips in any form so far as I'm aware. Boeing addressed the wingspan issue by offering folding wingtips on the 777, but nobody bought them. They would have made great billboards at the gate
Oops, didn't mean to do that. I knew you were only referring to Boeing.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
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