737 Blended Winglets

Tue May 30, 2000 6:57 am

Does anyone know If the blended winglets that are on the BBJ are available for commercial 737 NG's. Also are they able to retrofit them to older 737's. And if so, what kind of fuel savings are they expected to generate. thanx to everyone in advance. Love this forum  
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RE: 737 Blended Winglets

Tue May 30, 2000 8:13 am

Any major change on an aircraft calls for a new certification by the FAA. The winglets may change the behavior of the plane slightly and/or put different loads on wing structures. For instance landing in strong side wind may differ. Every single model of the 737NG - 600, 700, 800, 900 and BBJ must be certified individually.
The BBJ (and most likely the 900) will be certified from the beginning with the winglets.
Re-certification of the 600, 700 and 800 is a time consuming and costly process, but there is hardly any doubt that they will be certified with the winglets in a not too distant future. Then they may be retrofitted to excisting 737NG's when the operators want to do so.
It could be so that retrofitting demands so substantial changes to the wing structure that (some) operators choose not to do it.
In any case retrofitting will only be done while the plane is receiving major maintenance work.
Fuel saving will probably be in the order of 2 - 3 percent.
Always keep your number of landings equal to your number of take-offs
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RE: 737 Blended Winglets

Tue May 30, 2000 8:14 am

Boeing is offering winglets on the -800 series, and is considering appllying them to the -700 and -600 seires. These are the only planes you can put them on, as it requires a special wing design. And whether the NG planes already sold can be retrofitted has been argued for some time- Boeing does not say anything about it to my knowledge.
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RE: 737 Blended Winglets

Tue May 30, 2000 9:15 am

Talking about fuel saving is a very difficult issue.
The BBJ type winglets are of a different type from what we see on fast longhoulers. But they are more efficient - when they work best.
But they are not well suited for high Mach numbers. And they are very much "one alpha" winglets, meaning that they only work well within a narrow window of wing angle of attack (= alpha).
They are most likely optimised for a 737 avarage cruising speed (around M=.76) at 30,000 ft. with an avarage weight.
If ATC forces a heavily loaded plane high up in thin air, then alpha may increase to a level where the winglets do more damage than good. In the opposite scenario, on a light plane kept low they might work best at a low speed like M=.65, but if schedules demand that you keep M=.75, then the winglets may just give you extra drag costing extra fuel.
So the gain in fuel efficiency will depend very much upon how freely you will be allowed (by ATC) to fly the plane at its optimal performance.
Only one thing is sure: If Boeing claims for instance a 3% gain, then your gain will be less than 3% in everyday work. How much less, it depends...
Always keep your number of landings equal to your number of take-offs
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RE: 737 Blended Winglets

Tue May 30, 2000 9:35 am

I have read that the 737NG wing is being modified past a certain line number so that the winglets will be a bolt-on mod for the later airplanes. The earlier NG's will require extensive mods to the wing for which Boeing will offer a mod kit.
This plane is built to withstand anything... except a bad pilot.
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RE: 737 Blended Winglets

Tue May 30, 2000 2:52 pm

Blended winglets have been ordered by SAA and ATA for their new 737-800 aircraft. The upgrade is available only on the -800 and -900 for now, and is being studied for the -600 and -700. Hapag-Lloyd is close to an agreement to retrofit their existing 737-800s with winglets and have future deliveries with the winglets already fitted. Their current fleet will need some modification and strengthening to the wing, but is said to pay for itself over a number of years.

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RE: 737 Blended Winglets

Thu Jun 01, 2000 12:37 am

A friend at South African tells me that their initial 737-800s with NOT be delivered with winglets. They will be delivered in sets later on to be fitted when they are fully tested and certified. No doubt the wing will have the fittings ready for the winglets.
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RE: 737 Blended Winglets

Thu Jun 01, 2000 1:51 am

So when will one of the big boys start taking the 738 with winglets? Late last year a FI article said Boeing was close to signing AA.
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RE: 737 Blended Winglets

Thu Jun 01, 2000 2:42 am

Hapag-Lloyd will indeed be the first operator of a 738 with winglets. That will be a retrofited aircraft which should be ready early next year. The fuel savings will be around 3.5-4%. The winglets are 2.4m (7.9ft) tall. 26 738 will have had the modification by next May. One kit costs around 725,000$ and includes minor reinforcements at the tip of the wing. This reinforcement will be standard on all future 738. The flight testing will be done with a 738 form Hapag and will take around 125h. FAA aprovall for the wing modification is expected in November and certification of the winglet in January 2001. It takes around 900 man hours to retrofit an aircraft.
The blended winglet is also offered on the 739 and the 737-700C (uses 738 wing). The 736 and 737-700 have a different wing. Boeing is still studying on these aircraft.
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RE: 737 Blended Winglets

Thu Jun 01, 2000 4:19 am

They will also be fitted on the B737 900 as it has the same wing as the 800!

Jeremiah Teahan

Goodbye SR-LX MD-11 / 6th of March 1991 to the 31st of October 2004
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RE: 737 Blended Winglets

Thu Jun 01, 2000 1:16 pm

Interesting topic.

I have just finished looking at a Boeing publication promoting the winglets as optional on the 800 and 900 by February 2001, with 600 and 700 to be determined. As a retrofit, they appear to require a fair bit of work - maybe too much time to lay a new aircraft up at this stage (not sure on maintenance hours required to fit and test)?

Working from the fuselage out, the following modifications need to be made to the existing B737-800 wing:

- Wing center section strengthening
- New SOB rib, chords, and spar terminal fittings
- Lower panel wing skin and stringer gage change
- Upper and lower panel wing skin and stringer gage change
- Spar web and chord gage change
- Rib 20-24 and back up fittings gage change
- New Rib 25
- Flutter ballast provision (if needed)

The winglet itself:

- New upper and lower tip panels (including material change)
- New rib 27

All this information is straight out of the Boeing Proprietory book I have.

Boeing are claiming a 2.6 to 3.6% reduction in fuel burn as a result of the winglets.


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