winglets- whats the point in not having them!!
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I think that when you look at the bottom line, you have to consider exactly when the advertised benefits occur. The 5%-9% isnt for all phases of flight.
From Boeings chart, you can see that on take-off, there is little benefit.
From what it looks like to me, the benefit of winglets comes from a reduction in the angle of attack.
So for en-route, at the beginning when heavy, a decreased angle here would appear to be the most benefit. As the fuel load lightens, the angle would normally decrease, but there is a limit, or minimum angle for both with/without winglets, so, the benefits equal out at some point.
I suppose someone could actually calculate this out, and provide a real cost benefit analysis. So if the airline is really serious about the expenditure, perhaps this is the way to approach the issue.
In regards to the winglets providing a dampening effect in turbulence, I have not heard anyone say very much about this.
Swept wingtips and x wing configurations cloud the issue as well....
From Boeings chart, you can see that on take-off, there is little benefit.
From what it looks like to me, the benefit of winglets comes from a reduction in the angle of attack.
So for en-route, at the beginning when heavy, a decreased angle here would appear to be the most benefit. As the fuel load lightens, the angle would normally decrease, but there is a limit, or minimum angle for both with/without winglets, so, the benefits equal out at some point.
I suppose someone could actually calculate this out, and provide a real cost benefit analysis. So if the airline is really serious about the expenditure, perhaps this is the way to approach the issue.
In regards to the winglets providing a dampening effect in turbulence, I have not heard anyone say very much about this.
Swept wingtips and x wing configurations cloud the issue as well....
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Winglets: Bolt on fibreglass. Big deal.
The fact that they cost serious money has more to do with capitalism, the business of aviation, then certification and such.
The fact that they cost serious money has more to do with capitalism, the business of aviation, then certification and such.
Last edited by Sillypeoples; 20th Jun 2012 at 15:41.
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then certification and such.
There's a fair bit of resubstantiation necessary for wing structure, in particular. Certainly not just a case of bolting on some widgets with style and dash and away we go.
There's a fair bit of resubstantiation necessary for wing structure, in particular. Certainly not just a case of bolting on some widgets with style and dash and away we go.
Perhaps an aerodynamicist can correct me, but isn't the purpose of winglets to reduce the tip vortices caused by the high pressure air underneath the wing rushing round at the wingtip to the low pressure region above the wing? In doing so, a spinning vortex is generated which causes drag?
Also, why are the Boeing winglets huge, but the Airbus A300/320/321 ones tiny? - presumably they have different performance?
U
Also, why are the Boeing winglets huge, but the Airbus A300/320/321 ones tiny? - presumably they have different performance?
U
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uplinker,
No: there are no tip vortices.
Certification: the bending moment of the wing is increased substantially with a winglet, Boeing had to 'prove' the forces under circumstances, especially with speed brakes, so that the forces were in bounds of the wing design, and additional reinforcement was not required (ie re-cert of the ac)
Winglets are a balance that must be considered, when deciding to purchased them, or in fact offer them.
In offering them, its a doubled edge sword, as an add on, you are basically stating shortcomings in the wing design of the aircraft. Much like the advertised increased benefits of the air system of the 787, vs your current platforms.
To compound the issue, offer a completely different winglet design on the 737MAX....
As stated before, the airflow over the top of the wing, as the section decreases, becomes turbulent, creating drag.
The winglet design moves that turbulence outward, creating less drag, and allows for a decreased angle of attack on the wing.
This has the most benefit on the beginning of the enroute phase of flight.
As the fuel load decreases, and the required angle decreases, the benefit of the winglet decreases vs the minimum required for level flight.
No: there are no tip vortices.
Certification: the bending moment of the wing is increased substantially with a winglet, Boeing had to 'prove' the forces under circumstances, especially with speed brakes, so that the forces were in bounds of the wing design, and additional reinforcement was not required (ie re-cert of the ac)
Winglets are a balance that must be considered, when deciding to purchased them, or in fact offer them.
In offering them, its a doubled edge sword, as an add on, you are basically stating shortcomings in the wing design of the aircraft. Much like the advertised increased benefits of the air system of the 787, vs your current platforms.
To compound the issue, offer a completely different winglet design on the 737MAX....
As stated before, the airflow over the top of the wing, as the section decreases, becomes turbulent, creating drag.
The winglet design moves that turbulence outward, creating less drag, and allows for a decreased angle of attack on the wing.
This has the most benefit on the beginning of the enroute phase of flight.
As the fuel load decreases, and the required angle decreases, the benefit of the winglet decreases vs the minimum required for level flight.
Last edited by FlightPathOBN; 21st Jun 2012 at 01:10.
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Uplinker - There is a simple way to understand the main advantages of winglets...
High aspect ratio wings (eg long span narrow chord) are more efficient than low aspect ratio wings (short span, wide chord). Thats because the disturbed air at the wing tip represents less of a fraction of the span if the span is bigger. So anything you can do to increase the aspect ratio is generally a good thing.
Unfortunately you can't just increase the wing span indefinitely for practical real world reasons. Winglets work by increase the effective aspect ratio without increasing the span.
They aren't a totally free lunch. Increasing the efficiency at the tip effectively moves the center of lift (of each wing) outboard increasing the bending moment.
The AOA of the wing is easy to control. It's not so easy to adjust the AOA of the winglet. So the winglet might have to be optimised for one particular speed (eg cruise).
High aspect ratio wings (eg long span narrow chord) are more efficient than low aspect ratio wings (short span, wide chord). Thats because the disturbed air at the wing tip represents less of a fraction of the span if the span is bigger. So anything you can do to increase the aspect ratio is generally a good thing.
Unfortunately you can't just increase the wing span indefinitely for practical real world reasons. Winglets work by increase the effective aspect ratio without increasing the span.
They aren't a totally free lunch. Increasing the efficiency at the tip effectively moves the center of lift (of each wing) outboard increasing the bending moment.
The AOA of the wing is easy to control. It's not so easy to adjust the AOA of the winglet. So the winglet might have to be optimised for one particular speed (eg cruise).
They ended with a 2 degree toe- out.
Comparison of parasitic drag showed no appreciable difference to the 0 degree starting point.
However the AoA reducing effect off the winglets decreased slightly, thereby reducing the efficiency improvement by a small amount with flaps extended.
However, this is more then compensated by the reduction in wave drag, profile drag and trim drag (see figure 9 in linked document).
As a conclusion it appears the Winglet AoA is rather tolerant.
http://www.boeing.com/commercial/aer...7/winglets.pdf
OK.
And what's the difference between the Boeing and the small Airbus winglets? Do they work in the same way?
U
And what's the difference between the Boeing and the small Airbus winglets? Do they work in the same way?
U
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Uplinker #31
You may find some of the discussion with Takata on 17 July 2011 on pprune.org af447 Thread no5 pages 392-397
may be of help...
I would guess at 40,000 hours/ aircraft's life when the wing-tips should provide a benefit. For the rest... just be grateful !
I think that they are both aeroplanes.
( Sorry, cannot redirect you, my computer/I ... too old !)
LT
You may find some of the discussion with Takata on 17 July 2011 on pprune.org af447 Thread no5 pages 392-397
may be of help...
I would guess at 40,000 hours/ aircraft's life when the wing-tips should provide a benefit. For the rest... just be grateful !
I think that they are both aeroplanes.
( Sorry, cannot redirect you, my computer/I ... too old !)
LT
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I ponder the drag penalty of adding anything in the slip stream, and ponder if they are hyped to a certain extent.
Reminds of vortex generators....told that they wouldn't add drag in cruise...that was a lie, cost about 5 kts...but the slow flight advantages are worth it.
Reminds of vortex generators....told that they wouldn't add drag in cruise...that was a lie, cost about 5 kts...but the slow flight advantages are worth it.
Thanks.
U
U
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Folded for ground operations & high speed cruise & climb.
Extended for increased aspect ration benefits in takeoff, cruise and landing.
Any thoughts?
I believe that Boeing is doing this exact thing on the proposed 777X.
Extended for increased aspect ration benefits in takeoff, cruise and landing.
Any thoughts?
I believe that Boeing is doing this exact thing on the proposed 777X.
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Its a bit of hype for sure...how to introduce advances in wing design, without telling everyone the previous design wasnt all that good!
Notice the 787, no winglets there....they use a raked wingtip design, which I believe is what the 777x and A350 will all have..
With the wing, the airflow at the leading edge is at the same velocity across the wing. The trailing edge, as the wing section gets smaller, the laminar flow begins to separate from the wing skin surface, causing turbulence, or cavitation, drag...much the same as in all of the oversimplified stall sections we have seen.
The addition of the winglet reduces this turbulence in several ways. The one most likely to have the greatest benefit is the decreased angle of attack of the wing tip section.
This is fairly easy to correlate with data out there. From the charts, it shows that winglets have little difference in takeoff, and only slight increase when you get to heavy loading at higher altitude airports.
In cruise, when heavy, the winglets provide the most benefit. As the required angle of attack decreases with reduction in fuel load, the benefit of the winglet decreases.
If you are always running light, or short flights, you will likely see little benefit of the winglets...
Notice the 787, no winglets there....they use a raked wingtip design, which I believe is what the 777x and A350 will all have..
With the wing, the airflow at the leading edge is at the same velocity across the wing. The trailing edge, as the wing section gets smaller, the laminar flow begins to separate from the wing skin surface, causing turbulence, or cavitation, drag...much the same as in all of the oversimplified stall sections we have seen.
The addition of the winglet reduces this turbulence in several ways. The one most likely to have the greatest benefit is the decreased angle of attack of the wing tip section.
This is fairly easy to correlate with data out there. From the charts, it shows that winglets have little difference in takeoff, and only slight increase when you get to heavy loading at higher altitude airports.
In cruise, when heavy, the winglets provide the most benefit. As the required angle of attack decreases with reduction in fuel load, the benefit of the winglet decreases.
If you are always running light, or short flights, you will likely see little benefit of the winglets...
Last edited by FlightPathOBN; 23rd Jun 2012 at 17:35.
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Wings for the future ?
Who can predict what " my" new fleet of aircraft will be doing in thirty years from now, all short haul and lightly loaded, or what ?
I flew some of the Silver Wing scheduled services between Manston and Le Touquet (20 minutes each way) AND on passenger charter flights to Idlewild and back in a Hermes 4a. Perhaps we ought to have changed our wings for each kind of flight ! (But only at our base !)
The Martin Mars flying boat military transports are still around as fire fighters, probably not considered when they were first thought about .
TL
I flew some of the Silver Wing scheduled services between Manston and Le Touquet (20 minutes each way) AND on passenger charter flights to Idlewild and back in a Hermes 4a. Perhaps we ought to have changed our wings for each kind of flight ! (But only at our base !)
The Martin Mars flying boat military transports are still around as fire fighters, probably not considered when they were first thought about .
TL
It seems the older designs have usually rather (too) short span. This is where the winglets shine.
When designed from the get go with the optimum span winglets probably won't bring enough benefit to compensate for the additional wave drag/form drag + the added structural weight + costs.
Maybe due to rising fuel prices the additional costs / restrictions resulting from airport fees / limitations with increased span seem to take a bit of a back seat compared to raw efficiency nowadays. Last but not least improvements in structural design/computation allow for longer, higher aspect ratio wings without excessive structural weight penalty.
Looking at further rising fuel prices in future I would not be surprised to see even longer span airliners potentially with slightly reduced cruise speeds.
Last edited by henra; 24th Jun 2012 at 11:52.
Folded for ground operations & high speed cruise & climb.
Extended for increased aspect ration benefits in takeoff, cruise and landing.
Any thoughts?
Extended for increased aspect ration benefits in takeoff, cruise and landing.
Any thoughts?
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Concur, adding that to the end of a wing would likely negate any benefit...
The 787 and 350 wing flex should be designed to prevent the wingtip angle of attack creating separation of the laminar flow over the top, thus reducing the drag....I can see the sweep helping with the twist, but this is a tall order...
Anyone remember this?
I am looking forward to looking at the wake vortex from the 787, and the 747-8.
The 787 and 350 wing flex should be designed to prevent the wingtip angle of attack creating separation of the laminar flow over the top, thus reducing the drag....I can see the sweep helping with the twist, but this is a tall order...
Anyone remember this?
I am looking forward to looking at the wake vortex from the 787, and the 747-8.
Last edited by FlightPathOBN; 25th Jun 2012 at 18:48.
