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Winglets For The 777?  
User currently offlineolddominion727 From United States of America, joined Jan 2012, 382 posts, RR: 0
Posted (2 years 2 months 2 weeks 1 day 5 hours ago) and read 24041 times:

I am not going to profess to know much about science etc. But how come there are no winglets for the 777? Wouldn't it have the legs to fly further on less fuel? I thought that's why all of the newer commercial equipment have them?

43 replies: All unread, showing first 25:
 
User currently offlineEGLL From United Kingdom, joined Oct 2010, 19 posts, RR: 0
Reply 1, posted (2 years 2 months 2 weeks 1 day 4 hours ago) and read 23999 times:

The 777 has Raked wingtips which are supposed to reduce drag even further than other types

(From wikipedia - http://en.wikipedia.org/wiki/Wingtip_device#raked_winglets )

"In testing by Boeing and NASA, raked wingtips have been shown to reduce drag by as much as 5.5%, as opposed to improvements of 3.5% to 4.5% from conventional winglets"

The 767-400, 787 and the 747-8 have the same type as well

[Edited 2012-06-16 16:50:38]


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User currently offlineViscount724 From Switzerland, joined Oct 2006, 25170 posts, RR: 22
Reply 2, posted (2 years 2 months 2 weeks 1 day 4 hours ago) and read 23968 times:

Quoting EGLL (Reply 1):
The 777 has Raked winglets

I think you mean raked wingtips. The 772LR, 773ER and 777F have the raked wingtips. The earlier models (772, 773 and 772ER) do not.


User currently offlineghifty From United States of America, joined Jul 2010, 891 posts, RR: 0
Reply 3, posted (2 years 2 months 2 weeks 1 day 4 hours ago) and read 23906 times:

I wonder how well the raked wingtip design will hold up against the 737 MAX's AT winglet. Or.. I assume the 737 MAX doesn't have raked wingtips (or the kind the B787 has) because of gate-space restrictions.


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User currently offlineEGLL From United Kingdom, joined Oct 2010, 19 posts, RR: 0
Reply 4, posted (2 years 2 months 2 weeks 1 day 4 hours ago) and read 23849 times:

Quoting Viscount724 (Reply 2):
I think you mean raked wingtips

woops, my bad.. thanks for the correction



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User currently offlineStitch From United States of America, joined Jul 2005, 30908 posts, RR: 87
Reply 5, posted (2 years 2 months 2 weeks 1 day 4 hours ago) and read 23803 times:
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Back in 2004, Boeing and Aviation Partners looked into winglets for the 777, but nothing seems to have come of it.

There just might not be enough frames to justify moving forward: while the 777-200ER was a strong seller, the 777-200 and 777-300 both delivered under 100 units, each. Compare this to the over 1000 757s and 767s delivered.

As for the 737, the P-8 does have raked wingtips, which were chosen in part, I believe, because they don't block the onboard sensors and because the P-8 spends much longer in cruise and that is where raked wingtips are most-advantageous.


User currently offlinejetjack74 From United States of America, joined Jul 2003, 7408 posts, RR: 50
Reply 6, posted (2 years 2 months 2 weeks 1 day 4 hours ago) and read 23785 times:
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Quoting ghifty (Reply 3):
I wonder how well the raked wingtip design will hold up against the 737 MAX's AT winglet. Or.. I assume the 737 MAX doesn't have raked wingtips (or the kind the B787 has) because of gate-space restrictions.

The P-8 has them, which is a 737



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User currently online1337Delta764 From United States of America, joined Oct 2005, 6490 posts, RR: 2
Reply 7, posted (2 years 2 months 2 weeks 1 day 3 hours ago) and read 23557 times:

Quoting ghifty (Reply 3):

I wonder how well the raked wingtip design will hold up against the 737 MAX's AT winglet. Or.. I assume the 737 MAX doesn't have raked wingtips (or the kind the B787 has) because of gate-space restrictions.

Actually, the 737 MAX wingtip devices resemble a three-way hybrid of a blended winglet, raked wingtip, and wingtip fence.



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User currently offlineDocLightning From United States of America, joined Nov 2005, 19575 posts, RR: 58
Reply 8, posted (2 years 2 months 2 weeks 1 day 3 hours ago) and read 23527 times:

Quoting Stitch (Reply 5):
As for the 737, the P-8 does have raked wingtips, which were chosen in part, I believe, because they don't block the onboard sensors and because the P-8 spends much longer in cruise and that is where raked wingtips are most-advantageous.

Why are raked wingtips better in cruise and winglets not as optimal for longer trips?


User currently offlinesolarflyer22 From US Minor Outlying Islands, joined Nov 2009, 1060 posts, RR: 3
Reply 9, posted (2 years 2 months 2 weeks 1 day 3 hours ago) and read 23353 times:

Quoting DocLightning (Reply 8):

Raked wingtips incur slightly less drag than winglets and have the added bonus of not needing to be checked as often (according to some other forum threads). Winglets are apparently better at high cycle (lots of take off and landings) vs raked wingtips which are better for long distance cruise (ie 777). 787 and 748 also fall into that category.

Winglets have the advantage of advertising (great sign post) and can be retrofitted. They also reduce gate space. I would not be surprised at all if the P-8 raked wingtip is on the 737 max but that wing is much stronger and heavier than a regular commercial plane so the entire design cannot be used. More likely, they'll do something similar to what Airbus does. A vertical element and smaller down element.

Personally, I would rather see a flexible but strong wingtip that can provide more lift at low speed (i.e. take off and landing) and then sweep backward above 300 knots (i.e. at high cruise). I think if you use a strong woven material like Kevlar like it would work.


User currently offlineatcsundevil From Germany, joined Mar 2010, 1199 posts, RR: 2
Reply 10, posted (2 years 2 months 2 weeks 1 day 3 hours ago) and read 23351 times:

Winglets on a 777-200 and -200ER would not improve performance enough to justify the costs. They came without winglets or raked wingtips because the -200 and -200ER were developed prior to their widespread use. As it is, it's a pretty well-designed aircraft aerodynamically. API looked into it a few years ago, but my understanding is the ROI wouldn't have been worth it to bother with flight testing.

Now that some of the 777-200s and -200ERs are getting old, my guess is there will be more research into this to improve their efficiency, thus allowing them to stay in service longer. I wonder if they'll come up with a way to install raked wingtips featured on the rest of the 777 line.



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User currently online1337Delta764 From United States of America, joined Oct 2005, 6490 posts, RR: 2
Reply 11, posted (2 years 2 months 2 weeks 1 day 3 hours ago) and read 23293 times:

Here is the 737 MAX wingtip device:


A hybrid of a blended winglet, wingtip fence, and raked wingtip.



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User currently offlinecheeken From Singapore, joined Feb 2010, 82 posts, RR: 0
Reply 12, posted (2 years 2 months 2 weeks 1 day 2 hours ago) and read 23123 times:

Quoting 1337Delta764 (Reply 11):

Here is the 737 MAX wingtip device:


A hybrid of a blended winglet, wingtip fence, and raked wingtip.

Is it just me, or does that look like an enlarged version of the Airbus winglets on the A320s and A380s?


User currently offlineStitch From United States of America, joined Jul 2005, 30908 posts, RR: 87
Reply 13, posted (2 years 2 months 2 weeks 1 day 2 hours ago) and read 23090 times:
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Quoting cheeken (Reply 12):
Is it just me, or does that look like an enlarged version of the Airbus winglets on the A320s and A380s?

Those wingtip devices are fences and are quite different in geometry from the 737 MAX.

The 737 MAX wingtip shares a closer relationship to the MD-11's.


User currently offlineLAXintl From United States of America, joined May 2000, 25166 posts, RR: 48
Reply 14, posted (2 years 2 months 2 weeks 1 day 1 hour ago) and read 22961 times:

Something might be around the corner...  


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User currently offlinePHX787 From Japan, joined Mar 2012, 7474 posts, RR: 18
Reply 15, posted (2 years 2 months 2 weeks 1 day 1 hour ago) and read 22929 times:

Quoting Viscount724 (Reply 2):
772, 773 and 772ER) do not.

I think the anti-drag was built into the wing, however. Different from the raked winglets but still designed as such. I highly doubt we'll see actual winglets on the early models of the T7.

Quoting 1337Delta764 (Reply 11):
A hybrid of a blended winglet, wingtip fence, and raked wingtip.

Kinda resembles a larger version of the Airbus winglet



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User currently offlinetravelhound From Australia, joined May 2008, 934 posts, RR: 12
Reply 16, posted (2 years 2 months 2 weeks 1 day 1 hour ago) and read 22850 times:

Quoting Stitch (Reply 5):
As for the 737, the P-8 does have raked wingtips, which were chosen in part, I believe, because they don't block the onboard sensors and because the P-8 spends much longer in cruise and that is where raked wingtips are most-advantageous.

You would think 737BBJ's would be better suited to the raked winged tips as the custiomers tend to fly longer trips?


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 17, posted (2 years 2 months 2 weeks 1 day ago) and read 22672 times:

Quoting ghifty (Reply 3):
I wonder how well the raked wingtip design will hold up against the 737 MAX's AT winglet.

Better. Aerodynamically, it's always better to go out (tip extension) than up (winglet). You only go up (and down) if there's some other constraint: wingspan, retrofit capability, etc.

If you don't have another constraint, you go out...that's why the most recent designs (787, 747-8, A350) all went with raked tips.

Quoting ghifty (Reply 3):
I assume the 737 MAX doesn't have raked wingtips (or the kind the B787 has) because of gate-space restrictions.

Bingo.

Tom.


User currently offlineDocLightning From United States of America, joined Nov 2005, 19575 posts, RR: 58
Reply 18, posted (2 years 2 months 2 weeks 23 hours ago) and read 21964 times:

Quoting solarflyer22 (Reply 9):
Winglets are apparently better at high cycle (lots of take off and landings) vs raked wingtips which are better for long distance cruise (ie 777). 787 and 748 also fall into that category.

Yes, but... why? What about raked wingtips make them better for cruise? What about winglets make them better for takeoff and climb? Why doesn't Airbus really use raked wingtips?

I know that Boeing has offered a PIP for existing 777's that replaces the vortex generators on the upper surface of the wing with smaller, more streamlined ones from the 737NG wing. It reprograms the outboard aileron to droop down by two degrees, which improves wing loading and twist. It also replaces the Ram Air intake with a more aerodynamic profile. Offers 1-1.5% improvement in performance.


User currently offlineRubberJungle From , joined Dec 1969, posts, RR:
Reply 19, posted (2 years 2 months 2 weeks 19 hours ago) and read 19518 times:

Quoting olddominion727 (Thread starter):
But how come there are no winglets for the 777?

Boeing's 777 test crew told me that winglets were considered, but that they would have needed to be extremely tall to be worth the effort, and the idea was dropped.


User currently offlineLoran From Germany, joined Jul 2005, 538 posts, RR: 4
Reply 20, posted (2 years 2 months 2 weeks 19 hours ago) and read 19516 times:

Quoting tdscanuck (Reply 17):
Aerodynamically, it's always better to go out (tip extension) than up (winglet). You only go up (and down) if there's some other constraint: wingspan, retrofit capability, etc.

Thats the key point. Drag is a function of the wing's aspect ratio. So the higher the aspect ratio, the lower the drag. That's why modern gliders have extremely large wingspans with a short chord. Hence raked wingtips contribute to a higher aspect ratio while generating lift whereas winglets do not provide as much additional lift. Of course other factors contribute such as weight, cost, gate clearance, etc.



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User currently offlineha763 From United States of America, joined Jan 2003, 3657 posts, RR: 5
Reply 21, posted (2 years 2 months 2 weeks 19 hours ago) and read 19192 times:
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This is a better view of what the 737 MAX's look like compared to the MD-11 winglet and Airbus wingtip fence


MD-11

View Large View Medium
Click here for bigger photo!

Photo © Andrew Hunt - AirTeamImages



Airbus wingtip fence

View Large View Medium
Click here for bigger photo!

Photo © Q. Tseng



Much closer to the MD-11, which has both upper and lower parts canted outward, while a wingtip fence is straight vertical.


User currently offlineEGLL From United Kingdom, joined Oct 2010, 19 posts, RR: 0
Reply 22, posted (2 years 2 months 2 weeks 18 hours ago) and read 18471 times:

Quoting DocLightning (Reply 18):
Why doesn't Airbus really use raked wingtips?

On the A380 airbus went for wingtip fences so that it would not increase the length of the wing which would have caused a problem with space when the aircraft was at a gate.



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User currently offlineSLCPilot From United States of America, joined Aug 2003, 583 posts, RR: 2
Reply 23, posted (2 years 2 months 2 weeks 17 hours ago) and read 17456 times:

Quoting EGLL (Reply 22):

Quoting DocLightning (Reply 18):
Why doesn't Airbus really use raked wingtips?

On the A380 airbus went for wingtip fences so that it would not increase the length of the wing which would have caused a problem with space when the aircraft was at the gate.

It's also safer for people in buildings near the airport!

http://www.airlinereporter.com/2011/...ng-hits-building-at-paris-airshow/

Cheers!

SLCPilot.  



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User currently offlineconnies4ever From Canada, joined Feb 2006, 4066 posts, RR: 13
Reply 24, posted (2 years 2 months 2 weeks 16 hours ago) and read 17162 times:

Quoting tdscanuck (Reply 17):
Better. Aerodynamically, it's always better to go out (tip extension) than up (winglet). You only go up (and down) if there's some other constraint: wingspan, retrofit capability, etc.

If you don't have another constraint, you go out...that's why the most recent designs (787, 747-8, A350) all went with raked tips.

What about structurally ? The longer a high aspect ratio wing gets, I would assume the bigger aeroelasticity issues you bring into the picture. You would counter this I suppose by beefing up the wing structure itself, and that puts a weight penalty into the picture. Winglets themselves impose a bit of a weight penalty, of course. I believe something around 150kg for the 73G might be fairly accurate.

Quoting Loran (Reply 20):
Thats the key point. Drag is a function of the wing's aspect ratio. So the higher the aspect ratio, the lower the drag.

I always thought the winglet effectively increased the aspect ratio for a given wing. ?? Also, it tends to reduce "lost" air due to tip vortex generation, to my understanding.



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25 richiemo : Not only would winglets for the 777-200 and 200ERs be too tall but I think they determined that the wings were pretty well designed even without wingl
26 tdscanuck : Turning corners is a pain; if you're designing from scratch and you don't have some constraint (typically span) you go outwards (tip extension). They
27 JerseyFlyer : The 777s were developed after the MD 11, B744, A330 and A340 which all had winglets. My recollection is that the 777 wings were designed to bend upwa
28 amccann : Something interesting to think about in regards to raked wingtips is that because they produce additional lift they induce a moment on the wing. This
29 pikachu : No discussion about the 777 and winglets is complete without knowing the aircraft has a supercritical wing. 757/767 has the same but early generation.
30 connies4ever : Exactly what I was trying to get at. So to counter the bending moment, the wing structure itself has to be stiffer, and not just around the wingtip,
31 Post contains links ferpe : There is a thread in Tech/Ops that goes into the subject a bit deeper (there were several before who also discussed the subject); Winglets Efficiency
32 Post contains images PlymSpotter : A major consideration is the wingspan. The -200/200ER and -300 have a 60.9m span and the -200LR/300ER have a 64.8m span. In ICAO terms the maximum spa
33 brilondon : I am not an engineer so this may be way off but the raked winglets on the longer range aircraft allow for the increased performance at altitude for l
34 DocLightning : But you just answered my question by repeating it. What specifically are raked winglets doing to airflow that makes them superior to winglets in crui
35 connies4ever : I find this to be interesting, I would have thought out of ignorance that by generating more lift there would be more torsion. I think Ferpe's point
36 brilondon : Sorry. The raked winglets are more aerodynamic and produce less drag on the aircraft. It allows for the air flow to be less turbulent thus allowing f
37 DocLightning : So what I am getting is that the raked wingtip is superior in all cases (given an original build), except that because it enlarges the span, for short
38 solarflyer22 : I'm splaining it to you Lucy! Its the drag issue. Winglets induce more drag and are longer and add more weight to the frame than raked wingtips. Thin
39 tdscanuck : I'm not really sure how those two things are related...you can do winglets or raked tips on supercritical or non-supercritical airfoils. The bend is
40 Post contains images connies4ever : Thinking about this aspect, your explanation makes more sense to me.
41 ferpe : US Patent 5039032 is the first basic B patent on the raked wingtip, it gives the reason for the high sweep of the forward surface: - to avoid wingtip
42 Post contains links and images 777222LR : Here's what it would look like, given a blended style winglet: [Edited 2012-06-19 09:10:57]
43 PHX787 : THAT is trippy! Those winglets would have to be as tall as an ERJ135 fuselage!
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