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okees
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What Are Winglets For?

Wed Apr 05, 2006 2:59 pm

I hope that it hasnt been discussed before, did a search but got nothing. What exactly do winglets do? (forgive my ignorance).

Thanks
 
Zed
Posts: 16
Joined: Thu Dec 22, 2005 1:06 pm

RE: What Are Winglets For?

Wed Apr 05, 2006 5:39 pm

The air pressure underneath a wing is higher than the air pressure above it.The difference between the low pressure on the top and the high pressure on the bottom accounts for the wing's lift. At the wingtip of a straight wing, some of the high pressure air underneath "spills over" to the upper surface, negating some of the lift. The winglet is a barrier preventing that spillover, preserving the pressure differential all the way to the tip. A wing without a winglet has to be longer to generate the same lift because the lift toward the wing tip is somewhat spoiled.
 
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Starlionblue
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RE: What Are Winglets For?

Wed Apr 05, 2006 8:43 pm

Zed explains it pretty well.

Raked wingtips are another way of doing the same thing. They have certain structural advantages but require more gate space. Gate space is why you see pretty vertical winglets on 737 and 380.

Not that we mind talking about winglets, but if you search for "winglet" you get several pages of results. Here's a good thread: https://www.airliners.net/discussions...h_ops/read.main/144783/6/#ID144783
 
Airmech56
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Joined: Wed Feb 25, 2004 11:03 pm

RE: What Are Winglets For?

Thu Apr 06, 2006 7:39 pm

winglets are also used by some airliners to save fuel. With no turbulent airflow flowing on the wingtip, means smoother airflow, and less drag. Our new gens could get as much as 5% fuel savings as opposed to not having them. May not sound like a lot, but if you multiply those 5%, by all the flights that an airplane will fly in a yaer, that's a whole lotta of percentage ($$$$)
 
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HAWK21M
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RE: What Are Winglets For?

Thu Apr 06, 2006 7:42 pm

LINK
regds
MEL
 
Skyslave
Posts: 44
Joined: Sat Oct 22, 2005 12:52 pm

RE: What Are Winglets For?

Fri Apr 07, 2006 4:53 am

Quoting Airmech56 (Reply 3):
winglets are also used by some airliners to save fuel. With no turbulent airflow flowing on the wingtip, means smoother airflow, and less drag. Our new gens could get as much as 5% fuel savings as opposed to not having them. May not sound like a lot, but if you multiply those 5%, by all the flights that an airplane will fly in a yaer, that's a whole lotta of percentage

When I figured out the cost saving abilities of winlets, I often wondered why all airliners dont have winglets. Even planes that were built before the winglet days (like a DC-9), you would think someone would make a conversion kit where it could be installed in a reasonable amount of time. I'm sure installing winglets would pay for them selves in time.
 
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Starlionblue
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Joined: Fri Feb 27, 2004 9:54 pm

RE: What Are Winglets For?

Fri Apr 07, 2006 5:42 am

Quoting Skyslave (Reply 5):
When I figured out the cost saving abilities of winlets, I often wondered why all airliners dont have winglets. Even planes that were built before the winglet days (like a DC-9), you would think someone would make a conversion kit where it could be installed in a reasonable amount of time. I'm sure installing winglets would pay for them selves in time.

You would think. But by installing winglets you change the load distribution on the wing. In other words, you subject the wing to a load it was not built for. And this requires at best recertification ($$) and at worst wing strengthening ($$$$$$$$$$). In the end it may be easier to just keep going as is ($$) or buy new planes ($$$$$).
 
ChicagoFlyer
Posts: 210
Joined: Fri Jan 20, 2006 9:00 am

RE: What Are Winglets For?

Fri Apr 07, 2006 8:34 am

Quoting Skyslave (Reply 5):
Even planes that were built before the winglet days (like a DC-9), you would think someone would make a conversion kit where it could be installed in a reasonable amount of time. I'm sure installing winglets would pay for them selves in time.

I am not an engineer, but a financial man, and I have the following understanding of the cost/benefits of the aftermarket winglets:

There's a difference between desinging airplanes from scatch and putting winglets on the ones designed without them. Just like a dealer-installed option on your car will cost much more than the factory-installed one, you need to think twice about whether or not you need it.

Case in point is 757-200 which was not designed for winglets. Aviation Partners Boeing (APB) has been promoting the aftermarket winglets with 5% fuel savings claim, plus additional engine derates leading to maintenance savings. As time passed, the current claim is now 3-4%, and in reality an airline will probably save 2-3% with no engine maintenance benefits. And these savings come at a cost, as follows:

The winglets cannot just be tacked on the wingtip. 757's wing needs to be strengthened. The process involves structural modifications to the wing and takes about 3 weeks (12 days are claimed by APB, but it's just marketing). That's the first hit on your cash register. The aircraft is taken out of service, not generating any revenue for this period of time--a huge opportunity cost--that's the second hit. Then the aircraft starts to fly and supposedly rack in the $ savings but as it turns out it's heavier and for longer missions flies at about 2% slower speed--you end up getting hardly any savings at all at 35000 feet!

I am a little too negative on this, of course. The takeoff performance is definitely improved, and the one great benefit of 757 winglets is the lengthened range of the aircraft. That is why Continental started serving all these secondary transatlantic markets with the wingleted 757s--it's a perfect fit for them given their hub location in EWR.

Of course another benefit claimed by APB is "dramatically improved appearance." Here I am making no attempt to cost it.

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