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Why No Winglets On The 777?

Sun Sep 12, 2004 7:19 pm

The 747-400 has them, as well as the 330 and 340. Why not in the tripple seven?
 
Leskova
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RE: Why No Winglets On The 777?

Sun Sep 12, 2004 7:39 pm

Because the wing of the B777 is quite efficient as it is, winglets would not have added anything of great value to it: especially the raked wingtips found on the B777NGs are, if I recall correctly, at least as - if not more - efficient as winglets.

Regards,
Frank
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frugalqxnwa
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RE: Why No Winglets On The 777?

Sun Sep 12, 2004 10:30 pm

As Leskova said, the wing is already very efficient. Boeing did not need to put winglets on the 777 when it was originally designed to meet performance estimates. Since then, Boeing has used the raked wingtips on the -200LR and -300ER for added performance with the extra weight, and wetn with the tips instead of the winglets because the tips are more efficient on long haul ops. Winglets are best at short haul.
 
whitehatter
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RE: Why No Winglets On The 777?

Sun Sep 12, 2004 10:50 pm

Winglets are best at short haul.

Nope

Medium to longhaul is where they pay back. That's why shorthaul operators like FR don't order their 737s with winglets, and CO are fitting them to the 757 fleet for transatlantic ops.

Expect Aviation Partners to have a long hard look at a winglet retrofit for the 777 when they get the 767 winglets established and proven. Just because a product is mature in the marketplace doesn't mean that fine tuning isn't possible (hence the 757WL)
Lead me not into temptation, I can find my own way there...
 
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Starlionblue
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RE: Why No Winglets On The 777?

Sun Sep 12, 2004 11:36 pm

A raked wingtip works like a winglet, with the disadvantage of increasing the span.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
DfwRevolution
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RE: Why No Winglets On The 777?

Sun Sep 12, 2004 11:39 pm

Nope. Medium to longhaul is where they pay back. That's why shorthaul operators like FR don't order their 737s with winglets, and CO are fitting them to the 757 fleet for transatlantic ops.

It obviously varies from airline to airline. WN estimates their winglet package becomes beneficial on all stages over 48 minutes long, while some airlines require an hour or more.

Winglets are best at short haul.

If any wing device is better than the other, it is probably the swept wingtips that will be on the 7E7 and would have been on the FD729. On paper these should be the most efficent in terms of structural penalty vs. aerodyamic benefit. The 777LR wingtips and winglets are probably close seconds.

Winglets are common because they take up less gate space, important for shorthaul aircraft
 
LHR27C
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RE: Why No Winglets On The 777?

Mon Sep 13, 2004 1:28 am

The 777 wing was designed almost entirely by computer and is, or certainly was when it was released, the most efficient wing ever for an airliner in terms of lift produced to wing area. So, as said, winglets would not have added much, and the raked wingtips for the 777NGs are at least as good as winglets.
Once you have tasted flight, you will walk the earth with your eyes turned forever skyward
 
Horus
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RE: Why No Winglets On The 777?

Mon Sep 13, 2004 1:38 am

Article from this month's Airliner World magazine:

Aviation Partners Boeing is studying a design to fit winglets on the B777 range of aircraft. The design will involve 13ft (3.95m) winglets that will increase wingspan to over 210ft (64m). The company is also looking at a winglet programme for the 767-300ER (Extended Range) and is currently looking for a launch customer.

Horus

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burnsie28
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RE: Why No Winglets On The 777?

Mon Sep 13, 2004 1:43 am

13 FREAKING FOOT WINGLETS!!!!!! HOLY CRAP
 
Thrust
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RE: Why No Winglets On The 777?

Mon Sep 13, 2004 3:49 am

First of all, the 777-300ER has raked wingtips...and in addition, the Boeing 777 is one of the most fuel-efficient airframes in the world right now...to the extent that I really don't believe winglets are necessary for the moment. I assume we will be asking why the 767 doesn't have winglets next?
Fly one thing; Fly it well
 
keesje
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RE: Why No Winglets On The 777?

Mon Sep 13, 2004 4:04 am

http://www.airliners.net/discussions/general_aviation/read.main/1693621

A dscussion rose if the wing could be improved ....
"Never mistake motion for action." Ernest Hemingway
 
DfwRevolution
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RE: Why No Winglets On The 777?

Mon Sep 13, 2004 4:49 am

First of all, the 777-300ER has raked wingtips...and in addition, the Boeing 777 is one of the most fuel-efficient airframes in the world right now...to the extent that I really don't believe winglets are necessary for the moment.

The 777 is almost 9 years old, there has been enough advancement in airfoil design to warrent a tweak of some sort. Also, as the oldest birds begin to show their wear in the next 5+ years, a winglet package will help them opperate at their prime.

I would suspect AA and CO to be the first North American customers. They are both coming close to having the necessary funds and are eager to cut cost. Improved performance might also help CO on the ERW-HKG run.
 
QantasA332
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RE: Why No Winglets On The 777?

Mon Sep 13, 2004 7:30 am

To me, it was almost an attitude of "we're too good for winglets" on Boeing's part. Winglets are unfortunately often thought of as cheap 'patch-ups,' and people in the know seem to alsmost look up to winglet-less aircraft nowadays. Once the design was dragged back to earth, yes, even the mighty 777 could benefit from these 'patch-ups.'

Cheers,
QantasA332
 
ConcordeBoy
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RE: Why No Winglets On The 777?

Tue Sep 14, 2004 2:11 am

it was almost an attitude of "we're too good for winglets" on Boeing's part.

What sort of moronic assessment is that:
if you can accomplish and/or exceed proposed EIS specifications; then why on Earth would you bother with the time, money, weight, and certification of extraneous materials?!
Faire du ciel le plus bel endroit de la terre c'est impossible sans Concorde!
 
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Starlionblue
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RE: Why No Winglets On The 777?

Tue Sep 14, 2004 4:14 am

it was almost an attitude of "we're too good for winglets" on Boeing's part.

What sort of moronic assessment is that:
if you can accomplish and/or exceed proposed EIS specifications; then why on Earth would you bother with the time, money, weight, and certification of extraneous materials?!


Not moronic at all. Even the most technocratic organizations will often do things for no better reason than tradition, policy, whim or other reasons.

Qantas332 can speak for himself, but he didn't say that the 777 needed winglets, simply that Boeing seemed to have an attitude about winglets.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
prebennorholm
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RE: Why No Winglets On The 777?

Tue Sep 14, 2004 7:08 am

Both winglets and raked wingtips are quite complicated stuff which have both advantages and disadvantages.

To say that some plane is "good enough without" or "don't need them" is oversimplified. Every planemaker tries as hard as he can to make his planes as efficient as possible in everyday use.

First let us have a look at the winglets:

Few planes have "true winglets", but one of them is the 737NG. A winglet is vertical. It has a cambered profile with the camber pointing against the fuselage. And it is installed with a negative angle of attack.

The purpose is to intercept the wingtip vortex and transform energy from the vortex into forward "thrust" - much like a sail on a ship.

Since the shape of the vortex changes mostly depending on the wing angle of attack (AOA), then the winglets are optimized for an average AOA.

Since angle of attack is a product of weight, speed and altitude, then it can vary a lot from take-off to landing. When the plane is flown in a way, for which the winglet was not designed (too light/heavy, too fast/slow, too high/low), then the vortex will hit in front of or behind the winglet. And all you get is extra drag and weight of the winglets to haul along.

Since winglets do not generate lift, then they have little influence on the wing structure.

Then Raked wingtips:

Raked wingtips are wingtip extensions which are designed in order to minimize energy loss due to tip vortex. They generate lift as the rest of the wing, so the wing structure must be beefed up to accept the lift from the extra long moment arm, meaning heavier wing structure.

And now the mixture:

The 744/330/340s have neither true winglets nor raked wingtips. They are rather a compromise between the two.

Real winglets would not work very well on these planes simply because they are too fast. The air in the tip vortex is accelerated and would at a/c speed at M=0.82 - 0.85 hit the winglet at almost sonic speed and generate severe transonic drag, and all the advantage - and more than that - would be gone.

On a 737NG mostly traveling at M=0.75 - 0.78 that is not a problem, since the air will hit the winglets at no more than M=0.90 or so.

Therefore the 744/330/340 "winglets" first of all are swept heavily backwards in order to accept extreme transonic speed. At the same time they are angled approximately 45 degrees outwards, which means that they also work as small raked wingtips when they can't generate forward thrust. They do generate a little extra lift in addition to little forward thrust when AOA is favorable. And they do reduce the vortex energy loss a little.

Now the 777:

I think that it is natural that an extreme long range plane as the 722LR/773ER has raked wingtips rather than winglets.

First of all, really efficient winglets would limit the speed to 737 level.

Secondly, A 777 taking off for a long flight is almost twice as heavy as when it lands due to the fuel burn en route. That would mean that for utilizing the winglets it would either have to gradually slow down during the flight in order to maintain the optimal AOA, or it would have to constantly climb to ultimate altitudes where the engines would be less efficient.

And who decides your altitude these days? The PIC or ATC?

The 777 has a new wing design utilizing the newest materials to its maximum. That limits the extra structure weight penalty.

Raked wingtips at least work positively all way from take-off to landing.

A 737 on the other hand will mostly fly for considerably less hours at more constant weight and at rather constant altitude, and then true winglets may pay off. As long as you don't overspeed them.

And then 744/330/340: Well, the designers went for something in between. That was probably a very clever choice or compromise. They accept high speed. Extra wing structure weight is small. And they have both advantages of true winglets and raked wingtips, but to a much reduced degree. You can't get it all.

We can be sure that all designers have done all the homework they possibly could in their wind tunnels - and all the structure weight penalties - before they chose a specific configuration on their planes.
Always keep your number of landings equal to your number of take-offs
 
jfkaua
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RE: Why No Winglets On The 777?

Mon Sep 27, 2004 4:14 am


------------------------------------------------
13 FREAKING FOOT WINGLETS!!!!!! HOLY CRAP
------------------------------------------------


I think 13 ft winglets would look pretty small on a 777
 
bongo
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RE: Why No Winglets On The 777?

Tue Sep 28, 2004 5:04 am

That was my first ever question here in a.net  Big grin
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Thrust
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RE: Why No Winglets On The 777?

Tue Sep 28, 2004 1:20 pm

Well, it definitely would be cool to see winglets on the Boeing 777, as well as every other Boeing aircraft for that matter...why not....it would contribute to the aerofoil design....also, is the 7E7 to have winglets?
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