Wing tips on passenger aircraft which lift through 90 degrees

[gregcropper]

Why do some large jets have wing-tips which rotate through 90 degrees when they come into land

[VillageVicar]

Are you talking about like the newer 747s? They dont. The wing tip is fixed in place. heres a picture.

http://www.boeing.com/commercial/747family/

I will ask my dad if he knows. But I dont think there is one.

willem

[gregcropper]

Villagevicar. Many thanks. I may have jumped the wrong conclusion, thinking that the tips changed in flight. Can you ask your Dad why the tips are turned up on the newer 747's? Is it for flight stability or fuel economy or some other reason. Cheers Greg

[THECORBYLOON]

They are called winglets and there's some info about them here, http://www.b737.org.uk/winglets.htm

[VillageVicar]

Greg: I had encouraged my son to get involved with AB. You were the very first post he ever did. He and my daughter have been reading some of the questions posted and have found the site interesting.

The Corbyloon provided an excellent link for the winglets. Pilot friends of mine have commented on the stability factor and especially the beneficial lift and fuel conservation benefits.

I was on the flight deck of an A330 last year when we took off from Narobi to Bahrain. I was shocked by the faster than usual rate of climb. My captain friend explained it was the combination of an empty hold, very few passengers, and the winglets which gave better climbs.

Interestingly, you�ll find with the new Boeing 787 �Dreamliner,� they have dispensed with the winglets, instead making an alteration to the pitch and position of the wings.

http://www.newairplane.com/


I wish you well

Fr Bill

[Clanad]

All the answers so far are certainly descriptive of the winglets, however, having been an airline pilot for many years, I don't see the basic science well explained.
Firstly, like a lot of other inventions, the winglet phenomena actually came from the light aircraft sector. Burt Rutan, in his homebuilt Vari-eze was probably the first inventor and Peter Masak thought the process through for gliders and it was later adapted by several homebuilt. adaptations.
Secondly, in flight, because of the design of the wing, a higher air pressure is developed on the underside of the wing as compared to the pressure on top of the wing. At the end of the wing (wing-tip) the high presure air tends to spill off into the lower pressure area creating a great deal of turbulence. the phenomena is called (as related in some of the previous answers) as wing tip vortex. Engineers have tried to deal with this energy robbing, efficiency wasting fact for many years. In fact, one of the contributors to higher efficiency was the development of the high aspect ratio wing which dealt with some of the spillage. The winglet, as the charts, graphs and depictions illustrate lessens the effects greatly...
Some winglets don't look as dramatic as the ones discussed here. Airbus has a device which is actually fastened to the wing tip that provides, to a lesser degree, the same type of benefit... seen here: http://www.airliners.net/open.file?id=0969902. .. Many other variants exist or are in further development...

[VillageVicar]

Clanad: I haven�t come across your name before, but clearly you�ve been here a while. Thank you SO much. As an individual who traipses along the ionosphere by �other means� I was hoping there would be someone who could provide a more technical explanation to this. Thank you very much indeed!! May I ask please, if you�re not opposed to it, which EQUIP you fly and with whom? CIAO codes will do if you don�t wish to say outright.

Again, thank you very much indeed! It�s nice to have an expert here!

Fr Bill

[sddsddean]

Just as an aside, nature of course beat us to it! I'm sure I read somewhere that the person who came with the idea of winglets saw a hawk and wondered why the wingtip feathers were spread out. Apparently they negate wingtip eddies exactly the same way as a winglet. Heres a photo of a Harris hawk with the 'gaps' at the wingtips.
http://www.leightonhallfalconry.com/image/Open %20Wing%20Harris%20for%20web.jpg

[Clanad]

Thanks for the interest, Fr. Bill... I'm now an Aviation Safety Inspector for the FAA here in the U.S. I still accomplish check rides for Captain upgrades as well as approving check airman for various carriers. Most of the check rides are in Level D Simulators but I still stay current in DC-9's and MD-80's (Same type rating) Kinda like testing one's kids these days. I'm surprised they actually have to shave... I've shoe strings and neckties older than most of them!
I'm Type Rated on DC-3, CV-340, CV-440, CV-580, B-727, DC-9, DC-10, as well as some smaller transport category aircraft such as BE-1900, and BE-300. As you can see from the list, most of them are in the bone yards in the "desert" as they say. I did just return from training on the CRJ CL-600-2B19... all glass c0ckpit and all electric airplane...
I think you're referring to the ICAO (International Civil Aviation Organization) codes... previously with FALA, Golden Pacific, Key Airlines and a couple of others that were primarily supplemental carriers throughout international markets...
I've been on here for about 3 years now... usually in Science, Gardening and other How to threads and of course, Religion.. Avoid the socializing threads like the plague though... This is about as close as it comes to visiting...
Again, thanks for the interest... Are Vicars in England all Anglican? Our Episcopal denomination in the U.S. is probably as close as we come to C. of E... My education re: English villages is mostly from Midsomer Murders, all terribly valid, no?
Ad multos annos! (If that's appropriate...)

[gregcropper]

Fr.Bill and Clanad. Oh the power of the internet !! I am grateful to you both for the information and I am proud to have been the conduit for friendly exchange of information. Clanad - I live in the market town of Holmfirth, 'famed' as the location for the filming of Last of the Summer Wine. I don't know how widely broadcast it is in the States. Not typical of English villages either, but with much fewer murders than Midsommer! I am Catholic, but in these Eccumenical days, I'm sure that OK with you both! Best wishes and thanks again

[dundurn]

What a great conversation! I know Holmfirth well; my daughter lives in Huddersfield. I can confirm the low murder rate! Midsomer and it's satellite villages must be among the riskiest place to life on the planet and i'm surprised they don't have a resident SWAT team.

To return to the original question, Clanad, I knew the original purpose of the winglets was to improve energy efficiency and therefore to save weight and/or fuel or improve range. Presumably it also reduces the incidence and strength of wingtip vortices, per se. Does that mean it also improves safety or reduces the take-off intervals between aircraft?
In the UK we don't have the volumes of General Aviation that you have in the US but where heavy and light traffic does share runways I know that there have been some bad accidents where light aircraft taking off too soon after a departing commercial flight have got caught up in their wake and flipped over.

[Clanad]

Apologies for the late reply, dundurn... Aeronautical engineers that I've talked with about this very subject state that any aircraft retrofitted with such devices will experience a lessening of the intensity of the wing tip vortices. Problem is the cost. Around $2 million U.S. per aircraft and many have not been approved for such retrofit. One of the most common transport category aircraft used throughout the world is the Boeing 757... (believe it or not, it's a derivation of the great old standby the Boeing 727) but the "75", as it's affectionately known among pilots produces some of the most intense vortices measured. It has a lot to do with wing loading... the amount of the weight of the aircraft supported by the square feet of the wing area. The higher this ratio, the more intense the vortex. Several small, general aviation aircraft have been damaged or destroyed while on final approach behind one, although the danger has been known and made available to all pilots for years. Indeed, the vortices are so intense that an aircraft can be structurally damaged flying across both vortices in cruise flight. Since they (the vortices) revolve in opposite directions, drift down and apart slowly (in low wind conditions) the crossing aircraft experiences a sudden updraft followed almost immediately by an equally vicious downdraft. Sometime the phenomena can continue to exist near the earth's surface for several minutes after landing of the heavier aircraft. In fact air traffic control has a classification for "heavy" aircraft that has more to do with the vortex production than it does with the actual weight of the aircraft...Thanks for asking!

[dundurn]

Thanks for the reply, Clanad. One of my boyhood heroes was Joe Walker who flew the X15 above 100km (twice) which rated as spaceflights. He was killed in a "photo opportunity" flying a Starfighter in close formation with an XB-70. I think the conclusion of the FAA was that he got caught in the vortex from the XB-70. It was so powerful that it flipped the Starfighter up and sideways resulting in a collision that took out at least one of the XB-70's tailplanes. Both the Starfighter and the XB-70 were lost as was one of the XB-70 pilots. It was the first time I'd ever heard of the problem. Later there were some reports of Clear Air Turbulence that seemed to be associated with a preceding heavy flight.
As to retrofitting aircraft or waiting till they are all out of service, I guess there are too many groups of enthusiasts who will try and keep an example of just about any aircraft flying, so the day may never happen. Over here one such group has just got an Avro Vulcan back in the air!
Thanks again.