B767 No Winglets

[ARGREECE]

Hello fellow aviators,

i would appreciate any insight on the reason Why B767 aircraft have no winglets(and other widebodies like the A330 have). Any info would be highly welcome!Thank you, safe landings.

A.K. Greece

[Admiral346]

Probably because it was designed some 30+ years ago, and back then no aircraft had winglets...

[tubby linton]

Admiral 346 the Lear 55 appeared about the same time as the 767 and it had winglets.It gave the Lear the name Longhorn.

[Admiral346]

I knew when typing that someone would come up with some aircraft that of course did have winglets...

What I meant is that the design of the 767 is so old, that most airliners were built without them - I think the idea started getting hold on large aircraft with the A320s little triangle things and, very noticable, the huge winglets on 744s.

Nic

[tubby linton]

The 320 winglets were based on those fitted to some A310s and A300-600,.These are not much more than fences unlike the massive winglets seen on later model 737s.

[1.3vso]

B757s have after-market winglets avaiable. American (AAL) and Continental (COA) have been fitting those on some of their B757s. Have never seen these on a B767. Often wondered why.

[stilton]

Winglets will be coming soon to all 767 models except the -400 which already has 'rakelets'

I believe the design from APB is complete and flight test is imminent if not already in progress.

[Sid Departure]

I'd say Admiral346's answer is on the money.
Here's (http://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-15-DFRC.html) an interesting article on the design of winglets.

[jb2_86_uk]

Good find SD and an interesting read indeed. (If maybe a bit outdated "A3XX")

It sounds silly, but I am a fan of winglets (especally now after reading that article and seeing the figures!!!) but I think from an aesthetic point of view theyre great and a nice design touch... A330 - mmmm

Can anybody explain to me which the incident and cant angles are? I could guess - Incident is the angle where the face of the winglet meets the top surface of the wing, and the cant angle being the difference between the 'leading edge' of the winglet and the vertical axis - but I am more than likely wrong! :}

JB

[HotDog]

The B777 also has no winglets. They have a super efficient wing design that does not need winglets.

[enicalyth]

The question of winglets or no seems to be perplexing and is made doubly so if one assumes that every decision made is rigorous and thoroughly justifiable. My father was one of the “brain drain” and left his British employer in sunny Bedfordshire for the far sunnier climes of California. He was horrified to find that many designs of the sixties were as much influenced if not more influenced by their looks than pure science. In fact “streamlining” for the want of a better word could be anything but, which matters not when fuel is 5 cents a gallon. At that price it doesn’t even figure whose gallon we are talking about. In one of his writings Richard Shevell of Douglas pokes rather more than gentle fun at my father’s naivete and strict West Indian upbringing. “Last but by no means least there is always the fashion” and dad would splutter and reach for his pen. It is interesting to note that two of the great firms Dad worked for are no more and both were proud to be designers of “fashionable” aircraft. The last aircraft my father collaborated on is in production… just and enjoys a good but slow wing design that you might think would benefit from a bit of wingletting. Just supposing the weight and fixing pose no problems and there are no adverse resonances the looked for improvements must basically appear in significant reduction of induced drag because ideally zero-lift drag remains the same or increases only slightly whilst compressibility drag remains the same or might possibly reduce a little bit. At that decision moment pure science and economics should step in and do the speaking for you. But the wit of Richard Shevell can still be heard chuckling down the years. “A tarted up design is not so much mutton dressed as lamb as glutton dressed as glam”. The final decision might be exasperating but if the customer wants winglets for marketing reasons he’ll go for it and he well may be right if he fills the plane and his staider scientific rival does not. If winglets are to have a purpose they are best designed in from the start. If they are options then don’t bother if the distance is very short. I remember a particular 128 seater with an OWE of 37650kg and a wing area of 125sq m that cruises nicely at about 440ktas. It was being considered for a variety of routes, one of which was a real bread-winner although only 315nm. Realistically however it would take 90nm to get up and 90nm to get back down again leaving only 135nm for the cruise which meant an average of 30,500ft taking both there and back directions. As you might expect the lift coefficient at 55 tonnes was very low, about 0.378, the induced drag coefficient was also low, about 0.0061 and the compressibility drag coefficient similarly low at about 0.0010 for a total drag coefficient of about 0.0245. This gives a disappointing L/D less than 15.5 whereas a glib salesman would tell you that the wing capabilities were of the order of L/D = 17.1, without of course telling you the conditions. Try as I might with all the science I could muster to persuade my listeners that winglets could do nothing for such an application as this short route, “they” knew better. They went for the “looks” but it was to me that they came when they found the performance disappointing. The smaller aircraft such as I have described have a very difficult role to fill, being offered in many sizes for many routes. The economics of winglets or not is there to be considered but on the likes of certain large long-haul twins the wing design is much less of a compromise. Yet even here and now there will be someone whispering that it would look much nicer with winglets or that they look stupid, get rid of them. I hope this helps to keep us aware that one hat does not fit all. At the extremes of any industry there are those who know more and more about less and less so they are the experts. I think that at my age I know less and less about more and more so please spare me the ridicule and honour these grey hairs. Enjoy your ppruning.

Best Rgds

The “E”

[criticalmass]

The 757/767 are comparatively old designs now and perhaps Boeing felt the necessary R&D effort would be better deployed in the 787/747/737 series which had better prospects of longevity, sales etc.

Aftermarket winglets may appear, but the reality is the 757 has ceased production so that model is now entering the twilight of its life, and the 767 is likewise now coming into the latter stages of its lifetime. Operators must weigh up the cost of retro-fitting them over the anticpated remaining life of the airframes, versus disposal of the old hulls and re-equipping with the next generation of fuel-efficient and up-to-date aerodynamics.

Looking good with winglets isn't quite enough to justify fitting them onto older hulls, unfortunately. There have to be some pretty good economic benefits as well, especially in the short to medium term. You want to get a return on the investment, rather than the operator to whom you sell your older aircraft getting it for you.

[bvcu]

Hotdog 777 has no winglets as was originally designed with a folding tip option to enable use of smaller gates. The LR and 300ER have the raked tip which does the same job !

[hawk37]

"Realistically however it would take 90nm to get up and 90nm to get back down again leaving only 135nm for the cruise"

While we see figures of 4 or 5 percent fuel savings for the cruise portion (as a generic number), there seems little literature on the savings that winglets may provide for climb and descent.

Mr "E", can you perhaps elaborate on what approximate climb and descent fuel savings figures could be, and why they should be lower than cruise?

[Donkey497]

The 757/767 are comparatively old designs now and perhaps Boeing felt the necessary R&D effort would be better deployed in the 787/747/737 series which had better prospects of longevity, sales etc:confused:

78 fair enough, but even allowing for updates, I'd still say that the basic 73 & 74 designs were a fair bit longer in the tooth than the 75 /76 series.:hmm:

[Hardass56]

Having flown the 767 for a few years, I was delighted with the handling from the Pilot's perspective.
IMHO
Any winglets etc would be a benefit to the operators in terms of fuel savings.
My question:: Will you as the pilot see any bonus to your pay packet as a result of the winglets?
I think NOT!!
HA56

[Spooky 2]

I believe Aero Partners is very close to offering winglets for the B767. They have approached an operator down in the SFO area about putting winglets on the -200.

[Hussar 54]

A bit off thread but.....

In these days of super sophisticated computers and software producing most of the structural design and theoretical testing of performance at this design stage, I've always wondered why all aircraft don't end up being identical....

For instance,

Why would the wing for the 787 and A350 not be exactly the same other than for size/scale differences ?

Why would the location and length of the pylons ( relative to the size of the wing ) not be exactly the same ?

Why wouldn't the airframe's ribs and spars and the profile/shape of the v/s be exactly the same, again allowing for size/scale ?

And why were some aircraft conceived, designed and built with underwing mounted engines and others with fuselage mounted engines and T-Tails ?
And others designed with high wing construction rather than conventional low wing construction ? Presumably one method or combination of the these alternatives produces the better aerodynamics compared to the other(s) ?

I seem to recall reading an article a few months ago, but can't remember where, that Boeing actually hired-in an industrial designer to give the 787 a "more pleasing-on-the-eye" design, although I would have thought that this part of the design was not exactly high priority - unless there really is an element of 'individuality' required for marketing the arcraft....Perhaps this was the reason for the small winglets on the A320 when it first appeared, or the huge winglets now seen on the 737NG even though when Boeing were designing the new wing they had already acquired the knowledge and technology to produce a 'winglet-less' design based on their 'winglet-less' and strakes design for the 777....

Just me wondering....

[aa73]

AAL will be installing APB winglets on all B767s. They are already halfway through the 757 fleet and they have one 767 doing testing for Boeing with the new winglets.

Additionally, all AAL 757/767s will be getting the MAUI (Mid Life Avionics Upgrade) installed... which is basically the 4-tube 737NG/777 flat panel display. Should make an already great pilot's airplane even greater.

73

[wileydog3]

I always thought the "Long Horns" were the earlier Lear 28 29 and that was 1977.

[Mad (Flt) Scientist]

A bit off thread but.....

In these days of super sophisticated computers and software producing most of the structural design and theoretical testing of performance at this design stage, I've always wondered why all aircraft don't end up being identical....

For much the same reason as, if you were to ask ten different people for directions on how to get from A to B, you may get up to ten different answers. Because the answer isn't just a function of the question, but of how the person answering understands the question.

Let's say a design team is given the objective: design the best short-haul airliner you can. What is "best"? Most fuel efficient? fastest? Most pax? Fastest to turn around? Most reliable? Safest? Cheapest? How a given team balances all those competing criteria biases design choices. And there is no right answer to the question of balance - because there will be a customer who puts each individual item first.

Do you want an airliner that can do LCY? If I'm Southwest Airlines, no, of course not. If I'm BA, maybe it's my #1 priority?

The reason there are many different designs, is that there are many different design objectives. (Indeed even with identical design objectives, the exact same end result is unlikely. X-32 and X-35 were designed for the same contract, after all... )

To answer the specifics.

Why would the wing for the 787 and A350 not be exactly the same other than for size/scale differences ?

Ah, but WHICH scale difference? You can't just scale everything, even if it was the optimum. Materials come in finite sizes, as do fasteners and the like. Do you scale to keep constant wing loading? Or scale lengths (to keep cg loadability the same)? A thinner wing, in absolute terms, may be more susceptible to ice catch. Boundary layer issues arise.

Why would the location and length of the pylons ( relative to the size of the wing ) not be exactly the same ?

Do you have a "rubber engine"? You likely don't have that degree of flexibility.

Why wouldn't the airframe's ribs and spars and the profile/shape of the v/s be exactly the same, again allowing for size/scale ?

Again, not everything CAn scale, and how shall we scale? Cabin deltaP is the same - some structure may need to be identical, not scaled. The doors have to be the same (or similar) size.

And why were some aircraft conceived, designed and built with underwing mounted engines and others with fuselage mounted engines and T-Tails ?
And others designed with high wing construction rather than conventional low wing construction ? Presumably one method or combination of the these alternatives produces the better aerodynamics compared to the other(s) ?

No. Each configuration has good and bad points. The role of the aircraft may determine which is the best COMPROMISE. There is no absolute right answer.

[Hussar 54]

Yes....See your point about horses for courses, etc.....and why a 777 looks a bit different from my old t/p's.....

Just that it's always struck me that given aerodynamic law is more or less inflexible, then aircraft have to be designed within these parameters - so if Boeing and Airbus are both designing / marketing / building generic aircraft for a certain market but not for specific customers or to customers' specific specification, then why wouldn't the 777 and A330 or the 787 and A350 ( more or less same range. size, possibly engines ) look and be more or less identical ?

In particular, I was thinking about wing profile / sweep / area / location ( which provides all the lift ) when depending on the various models, the airframes are more or less the same size, all are twins, all have more or less the same flight envelope/mach requirements, etc....

Still have a hunch that there's a little bit of ' design branding ' goes into the final product - think cars, motor yachts, etc, all fairly easily identifiable to specific manufacturers....

No big thing, as I said, it's just that I have always been curious....

And, back to the original post, maybe it's just that winglets were not en vogue when the 757/767 were originally designed, even if the technology was already known and available....

[Mad (Flt) Scientist]

...why wouldn't the 777 and A330 or the 787 and A350 ( more or less same range. size, possibly engines ) look and be more or less identical ?

To a first approximation, they ARE. Same basic layout, similar sweep, t/c, wing loading, and so on. Tubes with reasonably swept high aspect ratio wings, and so on. But there's a significant difference in "are they similar?" (yes) and "are they the same?" (no!) The devil is, indeed, in the details.

Now, there are corporate biases too - you don't vary from what you already know without good reason. So if company A has a track record with, say, sidesticks and FBW, and company B is more comfortable with control wheels and more traditional control design, then that's what you'll likely see in their next products. Because one of the design constraints isn't "what is the best design option?" but also "which design option can WE do best?"