Purpose of winglets on airplanes?
 

Does anyone know the purpose of putting the winglets on airplanes? I know the obvious answer is that aeronautical engineers found that wings fly better with them there. But could someone tell me how that works? I'm curious in the concepts of aeronautical engineering without the detailed equations. What exactly do they do for the airflow over the wings? Does any one have any recommendations about a book or webpage to view on this?

Thanks for your help!

They help reduce wingtip vortices and induced drag.
They reduce air being "spilt" off the end of the wing.

Plus they look cool!

Kind of like a spoiler on a Honda Accord!

The most efficient wing, aerodynamically speaking, is infinitely long. The reason is the nasty stuff that happens at the wingtip, basically as the result of lazy air. Air wants to go around the end of the wing, instead of over the wing where it has to do the heavy lifting.

An infinitely long wing raises problems of fitting into airports, structural strength, and so on, so real wings are somewhat shorter than that. This is a design compromise: designers make them as long as possible, until the added weight you need to hold things together exceeds the added lift you get from making the wing longer.

Winglets recreate some of the effect of an infinitely long wing by creating a "wall" that makes it harder for air to go around the end. Some of the air now finds it easier to stay on the wing, despite having to do some lifting there. A bit still spills over because the winglets aren't infinitely tall. Another design compromise.

a bit off topic here but

nice name/handle

AFAIK winglets improve fuel efficiency during flight but increase fuel consumption for take off and climb.

why aren't there winglets attached to some of the bigger planes like 747, 777, A330, A340, A380? thnx in advance

I think he confused user name and password ;)

The 747-400 has winglets. The 777 has a special wing geometry which doesn't need winglets. Same with the A380. The A330 and A340 have winglets.

Not sure about the A380 however I believe they are similarly beneficial to bigger planes, have definitely seen the on the newer QANTAS 747's that I have flown on over the past few years...

A-380 does have winglets (the kind that go above and below the wing - similar to A-320).

Although the 747-400 does have winglets, the upcoming 747-8 will not (similar wing design philosophy as 787).

Any chemists want to translate?

"Are you lonely? Don't be. You have a friend in tape hiss, in the background creak of wooden chairs, in the crackle and click of four-track recordings. And besides, I'm coming over later tonight, and I'm bringing S1C3R1A1B3B3L1E1 and mojitos. [Info]

Posted by Jordan at August 4, 2006 2:37 PM "

There is a plan to have 777 winglets as a retrofit package.

That's the best explanation. ^ It keeps the air from high pressure region to leak into low pressure region., which leads to loss of lift, vortices, which produce lift induced drag.

I think the user name is meant to evoke a reading of booking-class availability - not a chemical compound.

But how, and why? Efrem's post provides the real answer.

Using winglets increases lift and therefor shortens the take off distance. It also shortens the distance between two successive aircraft. I don't think the highlighted part of your claim is correct. I can't think of any reason why it would increase fuel consumption during take off and climb.

I think it's the name of a word game, with point values after each letter.

Boeing 777 will have wingtip devices.

Since OMNI is, generally, a forum for everything other than miles, points and travel topics, we're going to switch this over to TravelBuzz!

But we'll leave a re-direct here in OMNI too so it'll reach eyeballs in both forums.

Please follow at its new home.

Thanks.

_______________

Cholula
OMNI Co-Moderator

exactamundo. It spells scrabble for 14points ,unless it 's on a double or triple space.

it is my understanding that if the wing is "perfectly" designed, winglets are not necessary. the winglets correct errors after the "perfectly" designed wing is found to need a bit of assistance.

S1C3R1A1B3B3L1E1 is plenty fun by itself, but drunken S1C3R1A1B3B3L1E1 with Mojitos is even more fun!

Thank you for the information on the wing tips. I was curious about the 777. Plus, weren't the wingtips on the 747 added in the 1990s and 2000s? Why did it take the engineers so long to discover this and correct this? As I recall, wingtips were on the A300 and A320 for quite some time before being added to the 747.

Does anyone know the difference in design between the 777 wing and all the others that the engineers originally thought that it did not need a wingtip? I have also noticed that the 777 wing appears much stiffer than the A330 wing, in that it does not sag at the ends. Does this give it any advantages/disadvantages or is it just a difference in design?

Finally, thanks for moving this thread. I did not know where to start it.

Despite it's simple looks, a winglet is not just a piece of Home Depot 3/4 inch plywood bolted to the end of the wing. Winglets can cost hundreds of thousands of $ to retrofit.

Even if the advantages were known when the 747 was designed, it was designed in the 1960s when kerosene was 25 cents/gallon. Not cost effective to install.

Fast forward to 1990 or so, when the the next generation planes are being built, offering better fuel economy on two big engines than a 1969 design with 4 engines. Oh, and kerosene is now $2 a gallon. New generation were designed from the start with every fuel saving device known like winglets as standard equipment Adding winglets on later model 747-400s to cut fuel flow made economic sense and keeps the plane in the market so we can enjoy Upstairs.

The 747-300 first flew in 1982 and apart from the extended upper deck didn't get much of a redesign at that time, so it's wing design dates back to the 1960's. The A-320 was a completely new design that first flew in 1987, so was able to incorporate more modern design. the A-300 had very small winglets.

Not all of them. The newer models (773, 77L) have a raked wing design that provides similar benefit. The 77A and 772ER (the earlier 777 models) do not have the raked wingtips and can potentially benefit from winglets.

As for why they are less efficient at climb-out/landing it is an aerodynamics and speed thing. At the slower speeds the vortexes aren't as big a deal. At higher speed they are and that is why the winglets help at cruise. At least that is my understanding of it.

That's my understanding too: at low speeds, the winglet does not add anything (or much). And since it has a nontrivial weight to it, the take-out / climb-out requires more fuel consumption.

I've noticed that WN uses a mix of wingletted and nonwingletted 737's. I've wondered if they purposely assign the wingletted planes to their longer routes. Knowing that there always seems to be logic and purpose behind everything that WN does, it would not surprise me at all.

Actually there is a benefit at takeoff/landing as reduced vortexes allow for closer spacing and therefore higher capacity of the runway.

Yes technically these are winglets, too. Still the A380 has a wing geometry which doesn't make it necessary to put very large winglets on the ends. If you take a look at the the A380 wing it is bended already. So you only need this little tips at the end unlike the large ones you see on the 737-800 or the retrofitted 767.

The 747-400 passenger version has had winglets right from the beginning (1988, i believe). The 100, 200, and 300 series did not have them. I forget when the 320 had it's first flight, but it was clsoe to the same time the 747-400 came out. The A300 has had them for a long time.

Judging from the pictures I have seen, the 787 wing looks very different than the other wings with the tips more steeply raked. (I hope that is the correct terminology.) I guess that extra bit of raking at the end does the same thing as winglets. But, it is interesting to see the evolution of the shape of the wing over time.

I still remember watching the slats on the 727 fold forward from underneath the wing. I think the early generations of the 747 did the same thing, but I don't remember. They look so much more aerodynamic now with the slats sliding forward from their location. I always find it interesting as the slats and flaps are deploying and redeploying that the plane doesn't violently pitch up and down as the amount of lift changes dramatically.

Winglets add weight to the airplane and are only helpful in fuel consumption on longer routes once the added weight of the airplane is factored in. You would typically see them on airplanes designed for longer routes. On some airplanes, such as the 757, which are used in a wide mix or long and short routes some airlines will install them only on the airplanes intended for the longer routes. United did this with the 757ps fleet which is used for transcon flights. On their other 757s it is not cost effective at this point.

There is no difference in the required runway separation or enroute wake turbulence separation based on winglets. Air traffic control doesn't even know which airplanes have them.

Also, when planning the production of a new plane, it's probably really hard to figure out how long it will take, and how much this infinitely long wing will cost to build.

Actually I agree - that benefit is theoretical as there are only the 4 vortex classes (not considering the 380) and that´s not accurate enough to capture the benefits.

Still, there should be some safety benefit due to the reduced vortex. Hit the wake of a 763 that took off before the E75 I was in recently and that was not at all pleasant.

Another issue with Winglets is they affect crosswind performance, in addition to decreasing induced drag. It also affects wing stress and loading. This means the aircraft need to be re certified for the new configuration.

I once saw a design for a circular wing for this exact reason, to do away with the extra drag induced by wing tip vortices. Basically, the idea was for a wing wrapped around the fuselage, like slightly flattened cylinder. The idea was to avoid having wingtips, but it obviously never got past the drawing board! I can't begin to imagine trying to work out how it would fly.

A paper airplane with winglets generally flies a longer distance than a paper airplane without winglets. Therefore, a real plane with winglets would use less fuel to fly the same distance.

I believe that Boeing got the major carriers to commit millions of dollars into the winglets program using a similiar Paper Airplane A vs. Paper Airplane B, in-office demonstration.

And then the major US airlines got a presentation with a paper airplane that had food strapped to it and a paper airplane without. This rest is sad history :D

I just laughed out loud (very loud) in a VERY quiet office. Thanks....