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Would Winglets Improve The 777s Performance?  
User currently offlineNoelG From , joined Dec 1969, posts, RR:
Posted (11 years 5 days 23 hours ago) and read 2906 times:

Is there a reason why the 777 does not have winglets fitted?

I would have thought that for such a modern aircraft winglets would improve the performance, and make it more efficient?

Or did Boeing not want to completely rip off the A330 design for fear of being accused of plagiarism?  Smile/happy/getting dizzy

(Ducks underneath the table at that comment.....)

NoelG

 Big thumbs up

13 replies: All unread, jump to last
 
User currently offlineN79969 From , joined Dec 1969, posts, RR:
Reply 1, posted (11 years 5 days 23 hours ago) and read 2858 times:

This is an interesting question. I am not an engineer so I do not understand the design considerations that go into determining whether winglets, tip-fences, or other devices are used.

I don't think Airbus innovated the use of winglets.


User currently offlineVs744 From United Kingdom, joined Aug 2001, 677 posts, RR: 1
Reply 2, posted (11 years 5 days 23 hours ago) and read 2830 times:

Apaprently not. There was a thread about this a while ago, i'll try and fish it out. It might be in the tech section...

User currently offlineDIA From United States of America, joined Jan 2001, 3273 posts, RR: 28
Reply 3, posted (11 years 5 days 23 hours ago) and read 2771 times:

Good question. I was wondering why they are putting raked wingtips on the 777-200LR and 777-300ER, but not offering them on the other 777 models. You would think that if Continental flies a 777-200ER from EWR to HKG, some type of winglets wouldn't be a bad idea. . .as far as fuel consumption is concerned.

Maybe the raked wingtips are mainly for extra fuel areas more so than fuel efficiency.




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User currently offlineMITaero From United States of America, joined Jul 2003, 497 posts, RR: 8
Reply 4, posted (11 years 5 days 23 hours ago) and read 2768 times:

There is probably a thread about this, but while Vs744 looks for it...

Winglets are considered "efficient" because they lower induced drag: at the wingtip, air from the high-pressure underside of the wing tries to wrap around to the top, creating a vortex. Winglets have been shown to dissipate this vortex to a point, lowering induced drag. There are probably tech threads about this which give more detail.

There are other considerations besides efficiency at work. Winglets add weight at the wingtip (structural considerations) and also take up extra room at airports, which could be troublesome for a large aircraft (space considerations). I'm probably forgetting some stuff, but it's not an easy or clear-cut decision to just pop on some winglets.


User currently offlineDIA From United States of America, joined Jan 2001, 3273 posts, RR: 28
Reply 5, posted (11 years 5 days 22 hours ago) and read 2719 times:

To answer part of my own thoughts above. . .

Maybe they are put on the higher MGTOW 772LR and 773ER for obvious reasons.



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User currently offlineSingapore_Air From United Kingdom, joined Nov 2000, 13738 posts, RR: 19
Reply 6, posted (11 years 5 days 22 hours ago) and read 2692 times:

http://www.airliners.net/discussions/tech_ops/read.main/63282/4/ might help and to a lesser extent http://www.airliners.net/discussions/tech_ops/read.main/61048/4/


Anyone can fly, only the best Soar.
User currently offlineSailorOrion From Germany, joined Feb 2001, 2058 posts, RR: 6
Reply 7, posted (11 years 5 days 22 hours ago) and read 2661 times:

Winglets do nothing else but to increase the aspect ratio of the wing, but not the actual wingspan (because they point upwards). Higher aspect ratio means generally higher performance, but you trade that off with strength and stiffness problems of the wing.

Celestar


User currently offlineBR715-A1-30 From , joined Dec 1969, posts, RR:
Reply 8, posted (11 years 5 days 20 hours ago) and read 2528 times:

The 777 wing is New, It doesn't need winglets as the "Winglet purpose" was built into the wing. Just as the DC9/717 does not need them, because that wing was and still is the most advanced wing of its time.

User currently offlineOsteogenesis From Germany, joined May 2003, 647 posts, RR: 2
Reply 9, posted (11 years 2 days 19 hours ago) and read 2315 times:

N79969,

I don't think Airbus innovated the use of winglets.

I don’t know but their where the first to offer them on an commercial airliner.

Does somebody really know who invented them?


User currently offlineAngelAirways From United Kingdom, joined Nov 1999, 502 posts, RR: 0
Reply 10, posted (11 years 2 days 19 hours ago) and read 2285 times:

Hmmm

makes me wonder too. remember boeing did put them on the 747-400. perhaps they thought the decrease in drag was so small that it was not worth adding them to the 777.

I've also wondered why the 777 has a lower aspect ratio. (smaller span per unit chord). Either the boeing stress engineers could not manage a wing like that on the A330, or perhaps they just decided to keep them 'short n sturdy' in line with boeing's 'sturdy and reliable' principles



User currently offlineBobrayner From United Kingdom, joined Apr 2003, 2227 posts, RR: 6
Reply 11, posted (11 years 2 days 19 hours ago) and read 2279 times:

Does somebody really know who invented them?

NASA.
http://www.google.com/search?num=100&q=%22first+use+of+winglets%22




Cunning linguist
User currently offlineOsteogenesis From Germany, joined May 2003, 647 posts, RR: 2
Reply 12, posted (11 years 2 days 18 hours ago) and read 2237 times:

Thanks Bobrayner very interesting to read.

User currently onlineHamlet69 From United States of America, joined Mar 2000, 2735 posts, RR: 58
Reply 13, posted (11 years 2 days 17 hours ago) and read 2182 times:

To make a very complex answer as simple as possible:

The 777 wing was a clean-sheet, new design. Thus, winglets were unnecessary, as the engineering advancements of the day (early 1990's) meant that the wing could be engineered as efficeintly (see MITaero's very concise write-up) without winglets as with them, without the corresponding penalty of wing-tip weight. This is still true today, as you'll notice that the raked wingtips of the 767-400ER/777LRs are not true winglets, but angled wingtip extensions which not only further reduce induced drag, but move it further off the wing.

The 747-400, A330/340, MD-11 all have winglets because they were the simplest, most cost-efficeint design solution at the time.


AngelAirways,

"I've also wondered why the 777 has a lower aspect ratio. (smaller span per unit chord). Either the boeing stress engineers could not manage a wing like that on the A330, or perhaps they just decided to keep them 'short n sturdy' in line with boeing's 'sturdy and reliable' principles"


Boeing's overriding engineering principle has always been to design their base designs with the possibility of future growth, while Airbus' used to be to design their wings to precisely match the current aircraft (this has sinced changed to match Boeing's philosophy on the A380). Thus the 777-200 had an oversized wing, while the A330-300 had a 'right-sized' wing. The 777's lower aspect ratio compared to the A330/340 allows Boeing to use the same wing on much larger versions of the aircraft (i.e. 777-200 = 777-200ER = 777-300ER). There was no way in hell Airbus could build an aircraft the size of the 777-300ER using the original wing of the A330/340. Thus the extensive modifications and triple the investment to bring out the A340NGs compared to Boeing's efforts on the 777LRs.

Regards,

Hamlet69



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