bigphilnyc
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767-400 Raked Wingtips

Wed Aug 06, 2003 6:54 am

I am wondering what these do that is so special.


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Here is my theory, but remember I know nothing and am making a lot of assumptions.

I understnad that winglets help by forcing potential airflow that might be lost by going off the sides of the wings to go over the wing, giving it more lift.

The raked wingtips don't go up, so I don't think that they have that purpose, which is weird that it's compared to winglets on the 737-800.

But here's what I figure. You have a longer plane (209 feet), which is obviously heavier and you need all the help you can get to compensate. Extending the wings makes sense, but I guess you want to keep any extensions as light as you can, so instead of jsut extending the wing, you reshape the extension, which would probably be lighter, and you still get that extra lift.

I'm sure I'm wrong and stupid, but oh well.

Any input from you smart guys? Tell me about the raked wingtips!  Smile

-Phil

[Edited 2003-08-05 23:55:38]
Phil Derner Jr.
 
gigneil
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RE: 767-400 Raked Wingtips

Wed Aug 06, 2003 7:04 am

The high angle of the wingtips give you the at least some of the same effect as an increased wingspan without making the plane incompatible with existing 767, DC-10, or L-1011 sized gates.

Delta made it very clear that its 764s needed to fit in tight spaces, which is a large part of why the 764 isn't the world's most effective aircraft... its a bit big for its wing. The raked wingtips mitigate that problem.

They're also lighter than the 747 or 330/340 wingtips.

The 330 doesn't fit in 767 sized gates, which severely limits its possible markets or causes logistical nightmares at some crowded airports with insufficient facilities.

N
 
bigphilnyc
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RE: 767-400 Raked Wingtips

Wed Aug 06, 2003 9:38 am

What high angle? They are as flat as the rest of the wing.
Phil Derner Jr.
 
goboeing
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RE: 767-400 Raked Wingtips

Wed Aug 06, 2003 10:11 am

Winglets are designed to reduce the negative effects of vortices that are found behind the tips of an airfoil when air passes over it. If a never-ending wing was made (an infinite wingspan), there would be no vortices. But at the end of a wing, it creates drag. In ground effect, which occurs when the plane is about one wingspan high or less, these vortices don't complete their entire "circle" and are reduced, thus reducing total drag and making the plane more effecient, and perhaps making it "float" and cause a prolonged flare. In flight at higher altitudes, these vortices are not reduced by anything, and that's what the winglet tries to do.

I'm not exactly sure if the raked wingtip has a different goal, but I'm sure part of it is to reduce vortices like winglets do. They sure look good though!

Nick
 
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RE: 767-400 Raked Wingtips

Wed Aug 06, 2003 10:32 am

Goboeing, I havent a clue what you jsut said.

What's ground effect?

One wingspan high or less? That's like 300 feet high or less? higher or lesser than what?

What circle?

Making what float?

What's flare?

And I dont understand then what the winglet is doing that causes less drag liek you said.

I also dont understand what that has to do with the raked wingtips.

Thanks though.

-Phil
Phil Derner Jr.
 
goboeing
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RE: 767-400 Raked Wingtips

Wed Aug 06, 2003 10:50 am

Phil,

Ground effect is a phenomena that occurs when a plane of any size descends to within approximately a wingspan above the ground. So a 747 will enter ground effect before a J-3 Cub will. When the plane's in ground effect, it's more effecient. This is due to the lessening of "Wingtip Vortices."

Wingtip vortices are what cause "Wake Turbulence." Like wake from a boat in the water, the air behind the wingtips of a plane gets disrupted and turbulent. Air flows over a wing the same until you look towards the tip, when it's different. I can't really explain why it's different, but it is. And if you were to look at a wind tunnel that can show the flow of air over a wing, you'd see that, behind the tips, it's like a cyclone moving backwards and parallel to the body of the plane. It's like tipping a tornado on it's side. This cyclone effect happens as long as air is moving over the wing. As the wing (plane) comes in to land, for example, the cyclone itself is disrupted by the ground. Where the vortex would normally spin back and down from the wingtip, it's now hitting pavement. So it's reducing the entire thing. That means less drag, since vortices create drag.

Flaring is what planes do when they are in the last stages of flying down the approach. It's what you see after the expressway turn to 31 is complete, they're past your dock, and over the threshold. The nose comes up even farther and the main gear is about to touch. That maneuver is called the flare.

A "floated" landing is the opposite of a quick, abrupt touchdown. In a floated landing, the plane probably came in too fast. If you have flight sim on your PC, try flying down to the runway in a 172 at 130kts. Cut the power, and the plane won't want to land, because it's going way too fast. So a floated landing is basically a prolonged touchdown. This is bad on a short runway for obvious reasons. In fact, planes decelerate about 3 times faster on the ground than they do floating down the runway (I forget what plane was used in that example I read somewhere, but it's the same idea for any plane).

When the reduced wingtip vortices take away drag, the plane is flying more effeciently. Remember, thrust has to overcome drag for the plane to accelerate. When thrust is low on landing, any reduction in drag will make a difference. Less drag will keep the plane in the air longer, causing it to "float" down the runway.

Back to wingtip vortices, the winglet reduces them. So you can see how all this comes together. The less drag, the faster a plane can go, or if it flies the same speed, it can fly at it with less thrust because the winglet has taken away that little bit of drag that trailed from the wingtip.

I assume raked wingtips are designed to do the same thing, although I am not certain. But reducing drag and thus reducing fuel burn as well has got to be one of their primary reasons for being put on the end of a wing.

Hopefully this answered your questions.

Nick
 
goboeing
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RE: 767-400 Raked Wingtips

Wed Aug 06, 2003 11:00 am

A picture is worth 1000 words sometimes:


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Here you can see them coming from the end of the flaps:


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Nick
 
bigphilnyc
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RE: 767-400 Raked Wingtips

Wed Aug 06, 2003 11:28 am

Goboeing,

I had some clue about what some thigns were, but wasn't sure. I knwo abot the vortices a bit and have some nice video of them.

Your in-depth reply was extremely educational, adn you relating it to my dock was a nice touch.

I have videos of floated landings, and they are really cool, almost as much as crosswind landings.

You've earned a spot on my respected users list. As sincerely as I can say, thank you very much for putting such time towards teaching me that. It means a lot.

Email me at bigphilnyc@yahoo.com or IM me on AIM ay BigPhilNYC and I'll send you some plane videos.

Thanks again,

-Phil
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sims747
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RE: 767-400 Raked Wingtips

Wed Aug 06, 2003 8:56 pm

Air flows over a wing the same until you look towards the tip, when it's different. I can't really explain why it's different, but it is

As some of you may (or may not) know, a wing produces lift by creating an area lower pressure over the wing's curved surface than the area under the wing. Think of the atmosphere as being composed of an infinitesimal amount of minuscule air particles. An air particle from a region of high pressure always wants to go to an area of lower pressure. This same rule applies to the aircraft wing, an air particle in the higher pressure region under the wing, wants to go the lower pressure region over the wing. Over the whole wingspan, it is impossible because there is a wing in the way!! However, a the tip of the wing, the air particle has a path to join the lower pressure region at the top of the wing (it can "curve" around the wing tip and join the area of lower pressure). This will induce a rotating motion at the wingtips (clockwise on the left wing and counter-clockwise on the right wing when looking from the back of the aircraft) which combined with the forward speed of the aircraft will create a "vortice" which was described accurately by Goboeing. Winglets help in the sense that they provide an obstacle to the particle of air trying to reach the lower pressure region, therefore reducing "vortices" which are a direct contributor to induced drag (drag caused by lift, due to the fact that the vortices have drag component).

Regds,
Sims
 
MITaero
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RE: 767-400 Raked Wingtips

Wed Aug 06, 2003 11:56 pm

BigPhilNYC-

This is from http://cf.alpa.org/internet/alp/2001/feb01p22.htm:

Walk-around inspection revealed some interesting aerodynamic changes. First are the raked wingtips (see photo). Boeing considered installing winglets on this model, but found several competing considerations. The objective was to recover the performance lost by increasing the maximum gross weight of the airplane. Increasing the wing area (gaining lift) would enhance takeoff and climb performance, while decreasing drag (using winglets) would recover performance over a long period of time at cruise.

The existing wing could not support the loads that winglets would impose, so Boeing chose the raked wingtip design. Set at 57 degrees of sweep, the raked wingtips add 7 feet 8 inches to each wing and account for 74 square feet, or 2.4 percent, of the total wing area. The raked wingtips reduce balanced field length, make possible a higher initial cruise altitude, and still reduce fuel burn by 1 percent versus the basic wing design. Now, if the world’s tallest catering truck manages to wrinkle one of your wingtip extensions, you can still operate by removing both wingtips. They are designed to be removed easily, and the flight can continue to a repair destination with the wingtips MEL’d.
 
gigneil
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RE: 767-400 Raked Wingtips

Thu Aug 07, 2003 4:07 am

The purpose of the raked wingtip is to increase surface area, not just help air recombine.

Its not exactly like a winglet.

The swept angle allows an increase in wing surface area with a smaller ratio of increase in wingspan.

I'm sure it also does provide some of the basic aerodynamic effects of a winglet due to its shape.

N
 
vikkyvik
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RE: 767-400 Raked Wingtips

Thu Aug 07, 2003 4:00 pm

not to get too scientific here, but i remember some of this stuff from a basic flight mechanics class....
increasing the wingspan of any aircraft has a couple of purposes. first of all, obviously, the lift is increased due to the increased surface area of the wing. granted, the weight is also increased, but that depends on materials, shape of the airfoil, etc.
secondly, increasing the wingspan decreases the induced (or vortex) drag, which is caused by the vortices which have been explained in previous posts. to get a bit more scientific, the coefficient of induced drag (a non-dimensional measure of the induced drag), is as follows:
coeff. of induced drag = ((lift coefficient)^2)/(pi*e*AR)
where e is the span efficiency factor, which is a constant, and AR is the aspect ratio, which is defined as the wingspan (b) squared over the wing area (S)....that is....AR=b^2/S
basically, if you work it out, as the wingspan gets larger, the induced drag decreases, which reduces the overall drag. i don't remember the actual derivations, but you can see that increasing the wingspan would have a double purpose in increasing lift and decreasing drag. as a side note, planes with a large aspect ratio can generally attain higher altitudes with equal power(ex. the U-2).
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lehpron
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RE: 767-400 Raked Wingtips

Fri Aug 08, 2003 1:35 am

This is what I figure, they aren't just raked (a word I see as offensive -- i think of a garden rake for God's sake), they are little delta-wings that use their steep leading edge to produce extra lift with the induced drag from the wing, i.e. vortex lift. You know what they say about Concorde, apply that to this wingtip and we have a similar effect.

I think the use of deltas at the tip manipulates the strength and size of the induced flow by getting something out of it while loosing it.

If winglets were CDR's then delta-tips are the CDRW's -- that's how they relate.

I could be somewhat off but this has been what I thought, in fact i took it several steps further than this, no prob.

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MD-90
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RE: 767-400 Raked Wingtips

Fri Aug 08, 2003 6:13 am

Here's the thing about wingtips:

Rounded tips (think of a British Spitfire) are draggy. For optimal airflow around the tip, you need a sharp, straight edge. It doesn't really matter if there's a slight curve up or down (think lightplanes, like the Cirrus SR20 or Lancair 300).

However, the edge should trail backwards, not forwards. Imagine if the leading edge was farther outboard of the trailing edge. That would be bad, bad, bad. There's probably some kind of factor that I wouldn't know without seeing the numbers, but that's why the 764's wingtip extensions look like they do (I'm not sure why they're that swept, I'd think Boeing couldn't gotten off with less sweep [think 777] but hey...).
 
MITaero
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RE: 767-400 Raked Wingtips

Fri Aug 08, 2003 6:25 am

Do you have any theoretical explanation/data to back up the edge argument (just wondering)? Also, the Spitfire wing was actually ideal in terms of planform (elliptical lift distribution) but too hard/expensive to mass manufacture.
 
vikkyvik
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RE: 767-400 Raked Wingtips

Fri Aug 08, 2003 9:04 am

i'm not sure how one would use raked wingtips to increase lift using the vortices. the vortices in general create a downwash on the upper surface of the outer wing, decreasing the apparent angle of attack, and hence lift. also, i'm not sure if this is what MD-90 was saying or not, but swept wings are useful due to the apparent velocity that the airfoil sees. if one were to fly straight wings at airliner speeds, mach shock waves would develop at much lower speeds, increasing drag significantly, and thus preventing the airplane from flying as fast. swept wings (whether they're swept forwards or backwards) reduce the apparent velocity seen by the airfoil, and thus increase the airplane velocity at which the local air velocity above the wing will be supersonic. thus, airplanes can fly up to around mach 0.85 without seeing a significant mach drag increase. however, there are probably stability aspects to the swept-forward wing that prevent it from being widely used.
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PPVRA
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RE: 767-400 Raked Wingtips

Thu Aug 31, 2006 3:41 am

Sorry to bring this thread back from years ago, but it answered most of a question I was about to post. . . but not all of it.

So I see how it made sense for Boeing to use raked wingtips for the B764. It was the best solution given the restrictions on the wing size and extra re-enforcement (=extra weight) that would have been needed.

However, tell me about the B777- why not go with winglets? Was MTOW a problem--performance not quite what was promised to the airlines, therefore the choice for raked wingtips instead? Had the B773 anything to do with the choice (MTOW)?

Or maybe just an experiment? Did raked wingtips possibly offer better economics than non-blended winglets, which maybe were not technologically available or efficient at the time of design?

The reason I thought of this is because the B787/A350 don't make use of it and I was wondering why.

Thanks for any insight.

Cheers
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LTU932
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RE: 767-400 Raked Wingtips

Thu Aug 31, 2006 11:52 am

Quoting PPVRA (Reply 16):
However, tell me about the B777- why not go with winglets? Was MTOW a problem--performance not quite what was promised to the airlines, therefore the choice for raked wingtips instead? Had the B773 anything to do with the choice (MTOW)?

I don't think performance had anything to do. The 777 family is known to be overperforming, meeting and even exceeding performance promises made by Boeing during development.

I believe the 764 also served the purpose of being a bit of a testbed for the 773ER, by it using raked wingtips and not regular or blended winglets.

Quoting PPVRA (Reply 16):
the B787/A350 don't make use of it

Slight correction: the 787-3 does use blended winglets, while the 787-8 and the stretched 787s, along with the upcoming 747-8 will use raked wingtips.
 
aeroweanie
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RE: 767-400 Raked Wingtips

Thu Aug 31, 2006 2:05 pm

Quoting MITaero (Reply 9):
The existing wing could not support the loads that winglets would impose, so Boeing chose the raked wingtip design.

Absolute BS. Raked tips create more of wing bending increase than comparable winglets.

Raked tips are a planar span increase, where taper is used to reduce wetted area and drive up the lift coefficient on the tip.

Winglets are a non-planar span increase. To quote myself in RE: How Do Winglets Differ From Each Other? (by AeroWeanie Aug 1 2005 in Tech Ops)#ID123835

For a first-order analysis of the benefit from a winglet, lay it down flat as if it was a span extension. Hence, taller is better. Then, look at whether the winglet joins the wing in a sharp break or a smooth flow. Smooth is better.

Using this criteria, I'll rank the winglets (and raked tip):

1) The A3100/310/318/319/320/321/380 "winglets" are the least effective, but also increase wing bending moments the least. I have never seen a published number for how much they reduce drag (even Jupp's patent US4,714,215 says little), but I'd guess they are worth 1-1.5% drag improvement.

2) The MD-11 winglets come next. They are a direct outgrowth of Whitcomb's original designs. I have some NASA reports on the flight testing of a similar winglet on a DC-10. According to CR-3704, these winglets are produce a 2-2.5% drag reduction in cruise.

3) The Valsan/Quietwing 727 winglets are a latter Whitcomb influenced design. Coupled with a flap droop on the 727, they are reputed to be worth about 5%. The flap droop reduces wing bending moments and helps reduce wave drag, so the 5% is a mixture of effects. The winglet by itself is probably worth about 3%.

4) The 747-400 and A330/340 winglets are rather similar. They fall on the wing span extension line. I've read that the 747-400 winglets produce about a 3.5% drag reduction.

5) The 776-400ER/777-300ER/777-200LR raked tips also fall on the span extension line. They produce varying amounts of drag reduction, depending on their span. They also increase wing bending moments quite a bit.

6) The API/APB blended winglets produce better results than the span extension line indicates. The 737NG winglets are first generation and I've read that they produce about a 4.5% drag reduction. Later API/APB winglets improve on this.
 
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LTU932
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RE: 767-400 Raked Wingtips

Thu Aug 31, 2006 11:30 pm

Quoting AeroWeanie (Reply 18):
I have some NASA reports on the flight testing of a similar winglet on a DC-10.

I found the picture of that CO DC-10 with wingets.
 
AA777
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RE: 767-400 Raked Wingtips

Fri Sep 01, 2006 1:36 am

Its pretty simple, they create lift (winglets dont), while reducing drag- like winglets. Kills two birds with one stone....sorta- really it reduces drag with the added benefit of some extra lift.

-AA777
 
dakota123
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RE: 767-400 Raked Wingtips

Fri Sep 01, 2006 4:12 am

Quoting BigPhilNYC (Thread starter):
5) The 776-400ER/777-300ER/777-200LR raked tips also fall on the span extension line. They produce varying amounts of drag reduction, depending on their span. They also increase wing bending moments quite a bit.

Is the increase in wing bending moment due to added structure or aerodynamic loading?

Dakota123
 
lehpron
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RE: 767-400 Raked Wingtips

Fri Sep 01, 2006 4:40 am

God, my last response from three years ago made no sense to me at all, lol.

Quoting AA777 (Reply 20):
Its pretty simple, they create lift (winglets dont), while reducing drag- like winglets.

Careful, for most airplanes with a swept back wing, as it bends up to lift, it also twists downwards because of the backward sweep angle. As a result, the wingtip device lifts inwards, upwards and forwards due to the twist and bend of the wing. The drag reduction comes from the forward lift component.
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aeroweanie
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RE: 767-400 Raked Wingtips

Fri Sep 01, 2006 4:54 am

Quoting Dakota123 (Reply 21):
Is the increase in wing bending moment due to added structure or aerodynamic loading?

Structural weight is relieving (downwards). Aerodynamic load is the source, as it is upwards.
 
dakota123
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RE: 767-400 Raked Wingtips

Fri Sep 01, 2006 5:12 am

Quoting BigPhilNYC (Thread starter):
Structural weight is relieving (downwards). Aerodynamic load is the source, as it is upwards.

Doh! Of course.

Dakota123
 
EssentialPowr
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RE: 767-400 Raked Wingtips

Wed Sep 06, 2006 11:48 am

Quoting MITaero (Reply 9):
Walk-around inspection revealed some interesting aerodynamic changes. First are the raked wingtips (see photo). Boeing considered installing winglets on this model, but found several competing considerations. The objective was to recover the performance lost by increasing the maximum gross weight of the airplane. Increasing the wing area (gaining lift) would enhance takeoff and climb performance, while decreasing drag (using winglets) would recover performance over a long period of time at cruise.

The existing wing could not support the loads that winglets would impose, so Boeing chose the raked wingtip design. Set at 57 degrees of sweep, the raked wingtips add 7 feet 8 inches to each wing and account for 74 square feet, or 2.4 percent, of the total wing area. The raked wingtips reduce balanced field length, make possible a higher initial cruise altitude, and still reduce fuel burn by 1 percent versus the basic wing design. Now, if the world’s tallest catering truck manages to wrinkle one of your wingtip extensions, you can still operate by removing both wingtips. They are designed to be removed easily, and the flight can continue to a repair destination with the wingtips MEL’d.

MITAero's reference/substantiation for the raked tips is correct; ALPA's mag also notes that the main wheels on the -400 are the same as the 777.
There are cockpit diffs as well, which are also noted in the article.
 
aeroweanie
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RE: 767-400 Raked Wingtips

Wed Sep 06, 2006 1:04 pm

Quoting EssentialPowr (Reply 25):
MITAero's reference/substantiation for the raked tips is correct;

Don't believe everything you read! What you call substantiation is pure nonsense.

Raked tips and winglets are both span extensions that reduce induced drag. Raked tips are planar, winglets are non-planar. Both improve climb performance and reduce cruise drag. As I said before, the winglets produce less of a wing bending moment increase than comparable raked tips.
 
EssentialPowr
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RE: 767-400 Raked Wingtips

Wed Sep 06, 2006 1:37 pm

Well, friend, then I guess we need to get into specifics. Clearly you did not design the winglets for the -400...Maybe Boeing needs your help?

Non planar devices (winglets or end plate designs) typically add more mass, and add drag at low alpha, which would have been highly unsuitable in the case of the -400. The raked tips are also more functional in terms of the MEL as opposed to winglets.

One other element that hasn't been hit on yet...and I'll gladly provide it for you... is that the -400 is certified to a higher MGTOW with the tips (very easily) removed as dictated by the needs of the operator. Not so with non planar devices, due to aforementioned mass and other issues.

[Edited 2006-09-06 06:41:12]
 
aeroweanie
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RE: 767-400 Raked Wingtips

Thu Sep 07, 2006 2:32 am

Quoting EssentialPowr (Reply 27):
Clearly you did not design the winglets for the -400

The 767-400ER has raked tips, not winglets.

Quoting EssentialPowr (Reply 27):
Non planar devices (winglets or end plate designs) typically add more mass, and add drag at low alpha

Mass relieves bending moments, which is favorable (within reason). Both raked tips and winglets add drag at low alpha.

Quoting EssentialPowr (Reply 27):
The raked tips are also more functional in terms of the MEL as opposed to winglets.

How are raked tips better for the MEL? The MEL for winglet equipped aircraft says that you can depart with just one winglet. Can you depart with just one raked tip - your quoted text says you have to remove both.
 
EssentialPowr
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RE: 767-400 Raked Wingtips

Thu Sep 07, 2006 11:14 am

Quoting AeroWeanie (Reply 28):
The 767-400ER has raked tips, not winglets.

One can call them "tapered endlets" or whatever; we both know what we are talking about, right?

Quoting AeroWeanie (Reply 28):
How are raked tips better for the MEL? The MEL for winglet equipped aircraft says that you can depart with just one winglet.

Correct.

Quoting AeroWeanie (Reply 28):
Can you depart with just one raked tip - your quoted text says you have to remove both.

Removal of both, per the MEL, is an option which increases the MGTOW.

It detracts from a tech forum when someone rattles of design generalities, but is ignorant of specific parameters for a given a/c.

[Edited 2006-09-07 04:17:30]
 
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Starlionblue
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RE: 767-400 Raked Wingtips

Thu Sep 07, 2006 8:38 pm

Quoting Essentialpowr (Reply 29):
It detracts from a tech forum when someone rattles of design generalities, but is ignorant of specific parameters for a given a/c.


AeroWeanie has shown his extensive knowledge of wingtip technology on numerous occasions.

[Edited 2006-09-07 13:43:14]

[Edited 2006-09-07 13:44:01]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
2H4
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RE: 767-400 Raked Wingtips

Thu Sep 07, 2006 10:21 pm




Quoting Starlionblue (Reply 30):
AeroWeanie has shown his extensive knowledge of wingtip technology on numerous occasions.

Indeed. You'd be hard-pressed to find an individual with more first-hand experience and knowledge of aerodynamic design/engineering....




2H4


Intentionally Left Blank
 
EssentialPowr
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RE: 767-400 Raked Wingtips

Fri Sep 08, 2006 5:23 am

Quoting 2H4 (Reply 31):
Indeed. You'd be hard-pressed to find an individual with more first-hand experience and knowledge of aerodynamic design/engineering....



Quoting Starlionblue (Reply 30):
AeroWeanie has shown his extensive knowledge of wingtip technology on numerous occasions.

Noted. And MITaero's reference to the report in ALPA's mag came directly from a Boeing sponsored test flight of the 767-400. That article and data is from a solid source (Boeing) and explains Boeing's choice of the raked tips vs winglets. AeroWeanie's comment:

Quoting AeroWeanie (Reply 26):
Don't believe everything you read! What you call substantiation is pure nonsense.

was completely baseless (and a bit of a flame!), which is why I responded. When I challenged him, he claims that raked tips and (any type of) winglet increase drag at high alpha, which is inaccuracte as the raked tips are planar and have a higher sweep than the wings, therefore less local drag occurs on raked tips, as opposed to the wing, in a realms of flight.

cheers.
 
aeroweanie
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RE: 767-400 Raked Wingtips

Fri Sep 08, 2006 5:51 am

Quoting Essentialpowr (Reply 32):
was completely baseless (and a bit of a flame!), which is why I responded. When I challenged him, he claims that raked tips and (any type of) winglet increase drag at high alpha,

I think you need new reading glasses. I wrote:

Quoting AeroWeanie (Reply 28):
Both raked tips and winglets add drag at low alpha.

Regarding the ALPA mag article - its pure Boeing propaganda. As I am not ignorant on these matters, I know its nonsense.
 
EssentialPowr
Posts: 1646
Joined: Wed Sep 06, 2000 10:30 pm

RE: 767-400 Raked Wingtips

Fri Sep 08, 2006 11:29 pm

Quoting AeroWeanie (Reply 33):

I think you need new reading glasses. I wrote:

Maybe you need them, b/c I was opposoing what you had written...


Quoting Essentialpowr (Reply 32):
When I challenged him, he claims that raked tips and (any type of) winglet increase drag at high alpha, which is inaccuracte as the raked tips are planar and have a higher sweep than the wings, therefore less local drag occurs on raked tips, as opposed to the wing, in a realms of flight.



Quoting AeroWeanie (Reply 33):
Regarding the ALPA mag article - its pure Boeing propaganda. As I am not ignorant on these matters, I know its nonsense.

Obviously, b/c your company didn't design them (whatever type of device) then they are inferior? "Conspiracy theory" makes a weak argument. If you have facts, state them. If you are hiding behind the "I know the inside story, but can't state it here b/c I'll get fired" is annoying crap.
 
calpilot
Posts: 881
Joined: Sun Oct 17, 1999 5:16 am

RE: 767-400 Raked Wingtips

Sat Sep 09, 2006 3:10 am

You guys have some great answers, and I've learned some things.

All I tell you is that the airplane is a nice handling jet. lol!

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