New winglet design

I've known about this for some time and recently saw the illustrations the graphics guys in our group were preparing, but now that Boeing has announced it officially yesterday I can too.

Our aerodynamicists have created a new winglet design for the new 737 MAX. It uses a vertical component winglet very similar to what's on the current generation of 737s but adds another component, a downward curved wing extension that provides additional lift as well as helps reduce drag even more.

The released illustration, attached, does not do a very good job of showing the lower component. It's too bad they picked this view for the press release instead of one of the other illustrations our guys did. In this illustration it almost looks like the flat lower winglet extension that was used on the old MD-11. But if you see the wing more from the front or rear, the lower extension actually extends out horizontally a fair amount as well as curves downward. Very graceful.

It's one more step toward doing what the soaring birds like condors, eagles, etc. have been doing for thousands of years.

Marin,

Thanks, I'm always interested in seeing stuff about aviation, since my early school boy days of reading Carroll Colby books. I also saw this week that the lastest generation 747 has a graceful upward turned wingtip, am I right or was I seeing things.

Marin said:

It's one more step toward doing what the soaring birds like condors, eagles, etc. have been doing for thousands of years.

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... like a vulture.

scarletbison said:

Marin,

Thanks, I'm always interested in seeing stuff about aviation, since my early school boy days of reading Carroll Colby books. I also saw this week that the lastest generation 747 has a graceful upward turned wingtip, am I right or was I seeing things.

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Both the 747-8 and the 787 use a similar wing design. This design evolved from the raked wingtip that was first used on the 777-300ER and was then applied to the two latest versions of the 777, the 777-200LR and the 777F (freighter).

The basic principle of the raked wingtip and the later curved wingtip are exactliy what the bird in Mark's photo is doing. It is a more elegant way of reducing drag than the typical winglet. The blended winglet on the 737 is a big improvement over the "bolt on" winglet used on Airbus planes and the 747-400. But the curved wing on the 747-8 and the 787 goes even a step farther.

Why not put this wing on the 737 MAX is a logical question. If money was no object we probably would. But the competition is fierce in the single-aisle market and the challenge both Boeing and Airbus face is wringing more performance and reduced fuel burn out of the planes without adding any more than absolutely necessary to the cost. Improving the deisgn of the winglet treatment is a lot less expensive than creating an all-new wing from scratch (whch was what we did to turn the 737 "Classic" into the current 737 Next Generation).

Boeing is currently weighing the different ways of upgrading the 777 and the 747-787 wing design will undoubtedly play a role in this.

Ever thrifty Air New Zealand recently reported adding winglets to their 767 fleet (presumably under Boeing supervision and design), I think to increase fuel efficiency, thereby no doubt extending the economic life of the aircraft. BruceK

The winglets for the 757 AND 767 are from Aviation Partners, a company in which Boeing is involved. But the winglets themselves are installed either by the airline itself or by a maintenance shop contracted by the airline. Boeing is not involved in the installation of aftermarket winglets. Our only production involvement is installing new ones on 737s in the assembly process, and even then some airlines opt to install their own after taking delivery of the planes.

APB does some amazing things. The performance gains on the 767 are very impressive.

A good frind of mine who is now one of our lead pilots was a flight test engineer for the flight tests of the 737 winglet when it was first being tested on the BBJ. He told me they were regularly seeing performance increases, which translate into fuel burn reductions, of six percent. We do not claim this as the performance improvement for the 737 because there are so many variables. We officially claim a lower figure. But the existing winglets can result in a saving of that amount under optimum conditions. The new winglet for the 737 MAX will improve significantly on that, again more in many cases than we will officially claim.

Speaking of winglets... was just watching on the news where Delta just bumped two 767's with winglets at Kennedy. That's gonna be an expensive fix.

I was part of the team that designed and later integrated the provisions for the first 767 winglets. We worked with APB to offer them as a retrofit kit for our freighter conversions and that opened the door for passenger certification.

They really make their best efficiency over the long hauls.

And don't forget, the 767-400 has the swept "flat" winglet....at least ours do.

Those are raked wingtips though... not true winglets. Similar function but the -300's are fully blended winglets. Much different than the older technology the -400's have.

A senior aerodynamicist told me way back when we put the wing extension and winglets on the 747-400 that the drag reduction that resulted barely cancelled out the extra weight and drag of putting them on. In other words, in his opinion, no net gain at all.

And the reason we originally put the blended winglets on the 737 had nothing whatsoever to do wtih drag reduction or fuel consumption. It was initially all about image and marketing for the BBJ.

Winglets Are nothing new. Ultralights and home built AC have been using them for 20 years or so.

The small fixed plane sticking mostly down at the wingtip is not part of the winglet and has a different function. It's a droop tip and it increases drag. The winglet tremendously reduces the air under the wing at the wingtip from rushing around the wing tip and raising hell w lift near the tip. Winglets try to control airflow to increase lift on the upper surface and droop tips help control airflow underneath the wing to increase lift there.

Both surfaces increase drag and increase lift but the result is that the entire wing can operate at a lower angle of attack and the end result is less overall drag.

I had an ultralight that had short full chord turned up tips much like upturned droop tips. One UL pilot/owner turned the up-turned tips up side down creating very nice and rather large droop tips. The resulting UL was called "the ultralight that would'nt land". So much lift in ground effect it just kept on flying. Of course the 10-1 glide ratio of this UL added to the "would'nt land" part. BUT........The droop tips had a very wicked and abrupt stall. The guy scared himself half to death several times and then turned the tips back up. With the tips up that UL is a very stable and well mannered ultralight.

The benefits of both winglets and droop tips can be had by extending the wing but w large AC logistics on the ground beg for shorter wings.

I also had an UL that had droop tips and rudders at the wingtip that also functioned much like winglets.

manyboats said:

Both surfaces increase drag and increase lift but the result is that the entire wing can operate at a lower angle of attack and the end result is less overall drag.

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Well, not really. One of the major benefits of winglets is their reduction of the wingtip vortex. The vortex, caused by the spanwise flow of air over a wing, generates a huge amount of drag. Like the primaries on a soaring bird's wing when they angle them up, the winglet reduces the vortex and thus the drag and the bird (and plane) can stay aloft while expending a lot less energy.

Lift is the product of moving air down. So anything that helps move the air down more efficiently increases the efficiency of the wing. The downturned component of the new 737 "split winglet" adds lift while the upturned component reduces the vortex drag.

On the Navy Neptune s ,SP2h, P2V7 the claim was that the tip tanks ,200 or 400Gal including a carbon arc search light paid for themselves in reduced tip losses.

That's a 50's era design.

Induced drag is the word y'all are looking for....

Baker said:

Induced drag is the word y'all are looking for....

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Induced drag... caused by wingtip vortices. They do work very well... and they do pay for themselves very quickly. Nothing buys its way onto an airplane without a valid business case. Money rules supreme.

Haha Baker......I've forgotten some terminology.

Marin says in response to my post "well not really" I say really yes. The spanwise flow from UNDER the wing (not over) causes loss of lift on top of the wing ....not drag. But the loss of lift requires the wing to need to be at a higher angle of attack and THAT causes increased drag. Please do'nt discount my stuff so easily.

But Marin I think you are right in that the high tech tips are'nt all positive. With a light load and at high speeds (and airliners fly at high speeds) the parasitic drag from the wing tip devices will most likely be too too high to be of any overall advantage. Heavy...?? And they are usually heavy I think. But at low speeds (especially landing and taking off) they probably make a lot of difference. Imagine a hot day when a thermal just created a tailwind and the plane was w full passengers, full fuel, full freight and in Denver (at 5000'). The wing tip devices would probably have a profound effect on performance. But during cruise they probably do'nt.
aliron
SomeSailor
Indeed they must make money but I suspect that it must be to carry more weight or to have better aileron response at slow speeds or a wider CG envelope or to reduce the likelihood of tip stalling in high banked turns or to be able to operate at airports with wingspan limitations or any number or other performance advantages but I doubt they reduce fuel burn at cruise. John Baker have you encountered good data that shows airliners saving fuel at cruise?

Ummm.... no. You've got it exactly backwards. Winglets are most effective at reducing drag and saving fuel at cruise and over long distances. They are least effective in terms of overall efficiency at slower speeds and short distances. The 737's current blended winglet can reduce fuel burn by as much as 6% in cruise. This was recorded during the initial tests of the blended winglet on the BBJ, the first 737 to have them.

When we made the winglet an option on commercial 737s, they were at first pooh-poohed by airlines like Southwest and Alaska. Their reasoning at the time was that because most of their flights were short, and some were so short the plane spent hardly any time at higher altitude cruise, the high cost of the winglets would never be offset by the fuel savings that are at their maximum in cruise.

What happened is two things. One, the cost of fuel started to go up and still is. Two, airlines like Aloha found that the winglets significantly extended the range of the 737 because they reduced the drag at cruise and thus the fuel burn. So in the late 1990s Aloha broke new ground and started flying a couple of winglet-equipped 737s between Oakland and Honolulu. We did a video about Aloha's operation and distributed it to 737 operators around the world. And while I have no idea what role our video played, Aloha's experience broke it all loose.

More and more airlines, realizing the potential of the 737 on longer routes, began ordering their 737s with winglets or retrofitting them to their existing NextGen 737s. This allowed them to open routes with the 737 nobody had thought possible before. Alaska, one of the first naysayers, started equipping their 737s with winglets or buying them that way new and opened non-stop routes from Seattle to Washington, DC and other east coast destinations. COPA in Panama started flying what at the time was the longest 737 route in the world, LA to South America. Qantas began trans-Australia service with winglet 737s. Regional airlilne Westjet started the same kind of service in Canada. Norwegian today flies non-stop from Oslo to destinations in the Mediterranean and the Middle East like Dubai with winglet equipped 737s.

In talking to 737 operators all over the world the only comments on low-speed benefits from the winglets I have heard from pilots is that they make the plane more stable in landings in rough air.

So the big benefit of the blended winglet is at speed over long distances.

One of the reasons Southwest finally caved and started putting winglets on their planes is they want the flexibility to put any of their planes on any route. So while their shorter up-and-down routes benefit relatively little from having winglets, the ability to put the same plane on a very short route or a very long route (they are starting West Coast-Hawaii service, too) offsets in the long run the initial cost of the winglets.

One other example: I recently directed a project in China. Coming home we were booked on a Delta Airlines non-stop flight from Beijing to Seattle. We had gone over (via Tokyo) on an Airbus A330 so I assumed the plane back would also be an A330, a plane I know has the range to fly Seattle-Beijing non-stop because Hainan Airlines does it. But when we got to the gate I was amazed to see the plane was a 767. We travel business for international trips so we boarded first. When I walked on the pilot was standing in the forward galley, and I said, "Can this thing fly all the way to Seattle non-stop? I work for Boeing and I didn't think these things had that kind of range." He smiled at me and said, "Winglets." Which the plane had, a retrofit kit from Aviation Partners Boeing (APB).

So----- winglets are a cruise advantage, not a slow-speed advantage for the airlines.

OK Marin,
That's good enough for me. Obviously heavy AC are much different. The airliners must still (even at high speed) operate at high angles of attack. But I'm still sure the greatest actual effect will be at slow speeds where induced drag is highest. I know large AC landing can make very troublesome vortexes close to the runway and on approach.

Do you ever hear of any canard talk at Boeing? I think canards died out because they were sensitive to CG variations. One could make a really big canard with less wingspan.

Eric?, you keep talking about speed and angle of attack. They are related but not always. Also wingtip vortices are most prevalent at high angles of attack on a CLEAN wing. Guess what you are doing in cruise??? One reason an airliner is more efficient at high altitude is we can operate at high speeds very near stall margins. The greatest efficiency of a wing(L/D Max) occurs basically right at stall(angle of attack). So when we are high and heavy, we are very near the stall speed and therefore very near L/D max and therefore benefitting greatly from winglets. I hope my logic came together there...kinda tired...

manyboats said:

John Baker have you encountered good data that shows airliners saving fuel at cruise?

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Every single one of our(Continental) narrow body aircraft have winglets...that is proof enough. But, yes,they are the real deal. We even put them on our "classic" 737-500s which we knew would be retired by 2013...it was still worth it for just 3 years. Fuel is our number one cost and if you average 5% fuel saving over a year it is extremely significant. We spend BILLIONS a year on fuel....you do the math!!!!

Thank you very much John and Marin.

It's very hard for me to visualize flying 500 mph in the vicinity of stall. FAR OUT!
It all makes sense and that's a plus plus for the winglets. Slower landing speeds in the "thick air" near the ground and high speed and angles of attack way up in the thin stuff. Ida never thunk.

How high could you go if you had no regs?

The service ceiling is of a 737 NextGen which is the 737 model we make today is listed as 41,000 feet. This is the number given for all three versions we make currently, the -700, -800, and -900ER. I expect each model will have different individual figures. The -700 being the smallest and lightest would most likely have a service ceiling somewhat higher than the -900ER.

The service ceiling of the 787 is listed as 43,000 feet.

The service ceilings of our other models are in that same envelope.

manyboats said:

I know large AC landing can make very troublesome vortexes close to the runway and on approach.

Do you ever hear of any canard talk at Boeing? I think canards died out because they were sensitive to CG variations. One could make a really big canard with less wingspan.

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Larger aircraft can make troublesome vortices in regular flight, not just on landing. We have footage of a 757 flying just off the top of a solid cloud layers. The camera plane was in front of the 757 with the camera looking back. It is the best illustration of lift in action I have ever seen, and anyone seeing this footage will realize instantly that lift is the product of Neuton's Third Law or whatever it is of action-reaction, not the Bernoulli Theory. You don't need Bernoulli at all to produce lift. What the wing does to the cloud layer is amazing and beautiful to see. It also shows the wingtip vortices very plainly as they are formed and remain in the wake of the plane.

Canards---- Well, I know Boeing has messed around with them as a design element from time to time but we've never put one on a production jetliner. The prototype 757, a plane I spent a lot of time in in the early 80s, was leased or sold to the government after we were done with it and it became a test bed for various military airplane development projects. One of them was for (I think) the F22.

In any event, whatever it was for, the 757 had a large canard installed on the top of the fuslelage just aft of the flight deck. But this was to test a proposed control system and had nothing to do with any jetliner design. The plane is still based on our military ramp at Boeing Field and it still sports its rooftop canard.

The proposed Sonic Cruiser would have had a canard but that plane, as much as everyone including the airlines liked it, was destined to never be as soon as oil prices started going up, so we focused our attention on the "backup" project which we code-named Yellowstone. Yellowstone became the 7E7 and then the 787.

The canard, by the way, I believe is a French invention. I may be wrong on that but "canard" is the French word for "duck." As in the bird, not avoiding being hit in the head.

Today its in the computer , but all aircraft have tables that give the weight allowed at a particular density altitude.

FF

manyboats said:

Indeed they must make money but I suspect that it must be to carry more weight or to have better aileron response at slow speeds or a wider CG envelope or to reduce the likelihood of tip stalling in high banked turns or to be able to operate at airports with wingspan limitations or any number or other performance advantages but I doubt they reduce fuel burn at cruise. John Baker have you encountered good data that shows airliners saving fuel at cruise?

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Actually, you pay a weight penalty for them. I work at Boeing and can tell you they are VERY cost effective for longer haulers. Their performance gains are at cruise. No one who actually works for Boeing (or APB) would be able to share those numbers on a public forum, but APB's site gives some insight.

They are heavy though, so short-haulers don't care for them as much. With the cost of fuel as high as it is now, they're more attractive than ever.

Ironically, you mention low-speed handling and that's an issue they've had to watch carefully. Many smaller carriers fly in areas that have the FAA watching the challenges they will be presenting. They do save fuel though. I can assure you that.

Marin said:

In any event, whatever it was for, the 757 had a large canard installed on the top of the fuslelage just aft of the flight deck. But this was to test a proposed control system and had nothing to do with any jetliner design. The plane is still based on our military ramp at Boeing Field and it still sports its rooftop canard.

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Yep. The FTB was brought back online a few years back to test the latest block of F-22 improvements. Now if they could get pilots that would agree to fly the F-22.

It also has the F-22 nose on it.

manyboats said:

Thank you very much John and Marin.

It's very hard for me to visualize flying 500 mph in the vicinity of stall. FAR OUT!
It all makes sense and that's a plus plus for the winglets. Slower landing speeds in the "thick air" near the ground and high speed and angles of attack way up in the thin stuff. Ida never thunk.

How high could you go if you had no regs?

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Just depends how light you are. A light 767-200 has tons of power to spare since it has the same engines as the other 767s and much lighter. And like Marin said, the737-700 is the hot rod of that fleet for the same reason as the 767-200...same engines as it's bigger brothers but lighter.

Another consideration in high altitude flight is that you are also going transonic. So not only are you very close to the low speed stall buffet margin but you are also very close to the high speed buffet margin. This has been referred to as "coffin corner" because you can't go any slower or you will stall....or go any faster and you get into high speed mach buffet. I don't push it that far. Even though the computer says you can go that high, it is not really a good idea to go to the max altitude displayed on the cruise page of the flight management computer. We have had more than one airplane go into a high altitude stall. If you hit turbulence and/or your airspeed begins to decay, the engines are barely breathing and there just isn't enough power to power out of it. A high altitude stall usually results in 4000-10000 feet of lost altitude. I have only done it in the simulator and it is quite sobering.

Probably more than you wanted to know....

Well it is a bit of an ugly duckling is'nt it.

Most of my ultralights were flying wings. One was very stable and one was very unstable. Once one learned to fly it the unstable one was more capable and in many ways safer. I had two ULs that were flying wings w a fwd mounted elevator. Most called them canards but they could only be considered such below trim speed as then the elevator then became a wing....producing considerable lift. They were very efficient. I could fly over 100 miles w less than 5 gallons of gas and climb 1400 fpm at 40mph. At a 60 degree banked turn I could still climb about 500fpm. That was a very fun maneuver. Crank it over ....point the wing at a point on the ground about 200' below and just revolve around it. I'm gett'in excited just think'in about it.

OMAC is for Old Man Airplane Company and they were working on a canard about the size of a Cessna Citation. Had a fairly large canard wing. But in commercial aviation I think the stability of the tail is required for flexibility in payload position ...CG. With a canard flying slowly it's pitch control surface is providing lift. That's why they are so efficient. With a tailed AC flying slowly the tail is creating tremendous drag. But flying fast the tail could be providing lift. Does anybody know or think that could/would happen? If so the tailed AC (it would seem) could be as efficient as a canard but then no AC flying fast can be efficient. But that seems to be so w airliners flying fast at high altitude.

Marin what I asked about was how high CAN they fly .....not how high they should fly w passengers ect. What if you just opened the throttles and observed at what altitude you could'nt go any higher at any angle of attack?


We were posting at the same time. Thanks very much John .....no not too much info at all. Very interesting stuff we UL pilots are totally unaware of for obvious reasons. So you use power to recover from a stall Hmmmmm. With ULs we just dive our way out ....w enough altitude or die if not. I've never died. Thanks John.