Winglets

[pegleg]

Would anyone like to offer an opinion as to why Winglets, which are obviously beneficial to the Airbus family,MD11 and 747-400 were not fitted to the B777. Also, why are Boeing thinking of fitting integrated winglets designed by a contractor to all new a/c and even retrofitting on 747 Classics. Surely they can design and build their own integrated winglets!

[jtr]

Because the 777 is not even close to being cool enough for winglets. C 130 on roids IMHO

[pegleg]

Nice one IMHO!! Sadly I never got to fly either of them but would definitely have preferred the Herc!! I was a DC3 driver which I like to think of as C130's younger brother.

Cheers

[jtr]

Don`t get me wrong I`m not saying there`s anything wrong with the 777, it`s just Fugginungly. On the inside great cockpit <way better than the -400> Heaps of go. Never runs out of tank space etc..
And remember what your mother said
`It`s not what you look like on the outside that matters, it`s what`s inside that counts. So you go back out there, and ignore those children throwing rocks at you Johnny`

On a more serious note, I am loath to try and explain it, as I will spell sumfing rong and some techy will crucify me. <however if I say it quietly they may not hear... it has to do with the amount of time spent in cruize and induced drag. On a long haul where most time is spent in cruize, it is beneficial in fuel saving. Short haul, not so helpful. I fly something else that has winglets, and last time I taxied into something and knocked one off, we had a fuel penalty of 3%. Another answer may be that the 777`s wing was totally computer designed, and just has amazing aerodynaimcs.Now some may say `But the 777 can go long haul as well, so why no winglets?` To this one must reply...
`It`s just too fugginugly`

[Prof2MDA]

Not going to get too deep here, someone else might have the time for that...

Short answer is that it doesn't need them. They have a newer wing that took advantage of the latest from NASA, etc., it also has more span that makes a lot of difference. They are talking about adding them for some future versions, I have heard. The MD-11 should have had a new wing but MD couldn't afford to build the new plant it would have taken, so they just added winglets to the DC-10-30 wing. Unfortunate. They had also at one time considered a twin engine version, but old man McDonnell would have none of it, they say.

For some insight into the issue (besides the book rec I gave of Flightwise in another thread), check out http://aero.stanford.edu/aa241/AircraftDesign.html

[Prof2MDA]

Here's another for the aero-junkies here:
http://aerodyn.org/

[pegleg]

Thanks guys for the reponses and apologies for the delay in replying. Have been at work where I can view the posts but cannot respond. I had a look at AeroStanford Web site and decided you have to be a rocket scientist to get past the first page!You have at least sated my curiosity.
Cheers

[Narada]

You can also search this forum for "winglet" - here's one such thread that deals with the topic.
http://www.pprune.org/ubb/NonCGI/Forum3/HTML/000694.html

[Dagger Dirk]

Small company sells Boeing on idea of adding winglets
Monday, September 11, 2000
By JAMES WALLACE
SEATTLE POST-INTELLIGENCER REPORTER

Only a few years ago, Boeing's top airplane designers scoffed at the notion of putting winglets on the company's jetliners.
Those sexy tips at the airplane wing's end, they believed, did little to improve performance and were mostly for show, a fashion statement of the rich and famous who could afford a private business jet.
Then Boeing discovered that a "blended" winglet designed by a small Seattle company could do wonders for the next-generation 737.
Now, Boeing is looking at blended winglets for what could be one of its most important airplanes this decade -- a stretch version of the 747 that will go head to head against the Airbus A3XX superjumbo.
Aviation Partners, the small Seattle company that had a better idea, is flight testing a leased 747 freighter fitted with the 15-foot-high blended winglets.

Initial indications are that the winglets will reduce drag by 6 to 7 percent, said Joe Clark, chief executive officer of Aviation Partners. More complete data will not be available until the end of the month or later.
Making the 747 more efficient is critical to Boeing's success in the upcoming jumbo showdown with Airbus.
The European airplane maker has promised potential customers that the 555-passenger A3XX will be at least 15 percent more efficient than the 416-passenger 747-400. And Boeing is claiming that a 100-passenger stretch of its jumbo will be at least as efficient as the Airbus behemoth, even though the 747 is a 1960's design.
Boeing has not yet decided to put blended winglets on the 747-400X Stretch, as the longer jumbo jet is known. In fact, Boeing engineers are leaning toward raked wingtips, which could also improve performance. Raked tips were used for the first time on the new Boeing 767-400 that will soon enter service with Delta and Continental airlines.
But even if blended winglets are not used on the 747-400X Stretch, their day is coming for most Boeing models now in production, including older 747s.
"The market is huge, absolutely huge," said Clark, who co-founded the company in 1991. "We have just begun to scratch the surface."
The idea took root when Montana businessman Dennis Washington called Clark and asked his friend if anything could be done to extend the range of Washington's Gulfstream II business jet.
Clark gathered a team of mostly retired Boeing and Lockheed Martin engineers.
The blended winglet the team designed reduced the drag on Washington's Gulfstream II by more than 7 percent. Next came FAA certification.
Today, about 50 percent of the world fleet of more than 200 Gulfstream II jets have been retrofitted with blended winglets, at a cost of about $495,000 per plane.
At the recent Farnborough international air show near London, Clark announced that blended winglets will be available next year for Hawker business jets -- a potential market of some 500 planes. Dassault Falcons could follow.
Winglets were common on business jets before Aviation Partners arrived on the scene.But those traditional winglets, which are also found on all Airbus models and the Boeing 747-400, rise at a sharp angle from the wing.
Blended winglets gently curve up, as if they are part of the wing.
Winglets were first developed by NASA in the 1960s to help reduce drag. Increasing the wing span can produce the same results. But wings of jetliners can't get any longer and still fit at airport gates. That's why Boeing decided to put a traditional winglet on its 747-400, the fourth generation of its aging jumbo jet.
At the Paris Air Show in 1997, Boeing's Borge Boeskov approached Clark about blended winglets on the planned Boeing Business Jet, a next generation 737-700 with the strengthened wing of the 737-800.
Clark's subsequent business proposal for Boeskov said the Boeing Business Jet would get from 4 to 5 percent better performance with blended winglets.
"Borge sat down with me and said, 'The corporate guys like the looks of these things because they differentiate the product, but frankly my engineers have told me they don't work,'" Clark recalled.
So Clark told Boeskov his small company would foot the bill to design winglets for the Boeing Business Jet if Boeskov would test fly them on the plane.
Unable to get Boeing engineers to go along, Boeskov turned to an old friend, the German carrier Hapag-Lloyd, a longtime Boeing 737 customer. Hapag-Lloyd supplied one of its new 737s, and the results were better than Clark had predicted -- a nearly 7 percent reduction in drag.
The winglets for the Boeing Business Jet are 8 feet 3 inches high.
By the time of the 1999 Paris Air Show, Boeing and Aviation Partners had formed a joint venture.
Since then, Aviation Partners-Boeing has been very busy. Boeing announced earlier this year that blended winglets would be offered not only on its business jet, but as a factory option on 737-800s. And they will eventually be available for the 737-700 and for the new 737-900.
In March, South African Airways became the first airline to order winglet-equipped 737-800s. It was an important victory. Boeing beat out Airbus, which was offering its A320.
"I really believe that was the first time that Boeing realized there is a real benefit to the airlines," Clark said.
More recently, American Trans Air, the nation's 11th-largest airline, ordered 20 next-generation 737-800s with winglets.
As part of its joint venture with Boeing, Aviation Partners can retrofit existing planes with blended winglets. It has already signed contracts to retrofit about 70 737-800s with blended winglets, including 26 for Hapag-Lloyd and 19 for Air Berlin.
Deals with several other customers are in the works, Clark said.
Aviation Partners is also looking to retrofit Boeing's fleet of older "classic" 737s. It has completed a blended-winglet design for the 737-300. Flight tests could begin late this year.
The Federal Aviation Administration last week certified the blended winglets for the Boeing Business Jet. Certification for the 737-800 winglets is expected early next year.
About 800 of the 737-800s will have been delivered before the winglets are certified and Boeing can begin adding them in the factory. Clark expects about half those 800 planes will eventually be retrofitted with winglets.
Blended winglets are also planned as a retrofit option for operators of Boeing 757s, 767s and 747s, Clark said, noting that the payoff on long-haul planes will be significant for an airline.
"If we can save an airline 5 percent a year on fuel, that's huge," he said.
That's why Aviation Partners is paying for the current 747 flight testing. It hopes to one day retrofit hundreds of older 747s with blended winglets, assuming the flight test results come out as expected.
"We are not a big company," Clark said. "These big planes are real expensive to fly. When you load that baby with 56,000 gallons of fuel and pull out your credit card . . ." His sentence trailed off in laughter.
Those tests, using a leased 747-200 freighter, are being flown out of the former George Air Force Base near Los Angeles. Later, the same plane will be fitted with raked tips by Boeing for a comparison before it firms up the design for the 747-400X Stretch.
Boeing wind tunnel tests found that a raked tip on the 767-400 would provide better operating efficiency than traditional winglets such as those on the 747-400.
The recently completed 767-400 flight test program showed the raked tips boosted the plane's fuel mileage up to 1.5 percent better than the wind tunnel tests had predicted.
The blended winglets being tested on the 747 in California are more than twice as big as the winglets on the 747-400. So it remains to be seen if Boeing will opt for blended winglets or raked tips on the 747-400X Stretch.
Either way, it won't be that many years before passengers flying on many Boeing jetliners look out at the window and see the graceful curve of a blended winglet, according to Clark.
"We are looking at a business plan of (retrofitting) from 1,500 to 2,500 planes in the next five or six years," Clark said.
"We have customers screaming for them."
http://seattlep-i.nwsource.com/dayart/20000911/winglets.jpg http://seattlep-i.nwsource.com/dayart/20000911/winglets2.jpg

[Luscombe Driver]

The tip of a wing generates drag due to the high-pressure air beneath the wing rolling up and around the tip into the area of low pressure on top of the wing. This persistence toward equilibrium between two unequal pressures produces wing-tip vortices and is considered one type of parasitic drag. One way to overcome this inefficiency is to build a barricade between the two pressure gradients. This can be accomplished in three ways. The old fashioned way is to simply increase the wing span a bit. All the old birds did this by simply putting a rounded tip on the wing. Bush pilots flying high wing aircraft accomplish the same thing by putting “droopy” tips on the wings that hang down. The more modern airplanes opt for the "cool” looking winglets that point up. All three approaches accomplish the same effect. They each reduce parasitic drag thus increasing power available for speed and performance. The main reason for winglets being that an increase of 15 foot per wing on say the new “stretch” 747 would cause considerable parking and hangering problems and a 15 foot droopy tip would wreck havoc on runway lighting as well as ground equipment. Logic would dictate going up with any additional wing tip. Just makes sense and of course it does look “way cool.” You can bet your bootstraps that the aeronautical engineers didn’t forget anything. Most people just don’t realize that tips are tips and bigger just isn’t always better. An additional 15-foot of wingtip per wing induces additional parasitic drag by just being there and one form of drag must be weighed against another.