Winglets

[Uncle Sparky]

HHhhokay...back on track....

I guess I was a lttle harsh in my response to Enigma, but you have to understand, it's a lot like someone calling your kid ugly. We invested a lot of our lives in the certification of the GV, each of us sometimes flying over 30 days in a row in one of the four test articles before getting a day off and we made the best no compromises jet we could.

We had a lot of talent in Flight Test during GV development - the Chief Test pilot for the B-1 Program, the Chief Test Pilot for the B-2 Program, test pilots from the F-14 and F-16 programs and we all came away feeling that on balance the GV was the best jet we had ever flown.

You'll have to forgive Uncle Spanky for his comments; he was just turned down for Gender Reassignment Surgery and he's been taking it out on everybody.

GV

Ya SEE!! That wasn't so hard now, was it?

And you were even able to take a cheap shot or two at my expense, enabling you to boost those glaring insecurities. Everyone comes out a winner.....


NOW, why is it that the latest large Boeings use a tapered wingtip instead of winglet?

And why do some smaller(where gate size isn't an issue)slower aircraft use winglets? (ie:the Navajo Panther)

 

[mzaharis]

He didn't.

If I may . . .


Original question, from Post #1:

GVFLYER offered tremendous insight into the desgin considerations and superiority of the GV wing, with winglets, but he failed to answer the question as to why a wing would be designed without winglets.

enigma's question received a direct answer, but uwochris's question (the original question of the thread) did not.

Maybe I missed it, but I haven't read anything about "spanwise flow" on this thread.

Sorry I missed the negative.

Regarding the Winglets vs. span extension debate, I guess it depends on very aircraft-specific design issues. If you're span-limited, or may have a wing-root bending moment problem due to an existing spar, winglets make more sense. Other times, mechanical integration for a wing extension may be simpler. Here's Boeing's (PR) explanation as to why they did extensions with the 767-400ER, which implies that adding winglets would have required more redesign of the tip:

"Another advantage of the raked wing-tip design is its simplicity. It is lightweight and bolts into place, with no additional design changes needed to the tip or leading edges of the 767-300 wing."

Here's some interesting stuff on spanwise flow related to winglets.

from my favorite explanation of lift:

http://www.av8n.com/how/htm/airfoils.html
<H4>* Winglets, etc.

It is a common misconception that the wingtip vortices are somehow associated with unnecessary spanwise flow, and that they can be eliminated using fences, winglets, et cetera. The reality is that the vortices are completely necessary; you cannot produce lift without producing vortices. By fiddling with the shape of the wing the designer can control where along the span the vortices are shed, but there is no way to get rid of the vorticity without getting rid of the lift.

Winglets encourage the vortices to be shed at the wingtips, not somewhere else along the span. This produces more lift, since it is only the amount of span that carries circulation that produces lift according to the Kutta-Zhukovsky theorem. Still, as a general rule, adding a pair of six-foot-tall winglets has no aerodynamic advantage compared to adding six feet of regular, horizontal wing on each side.18

The bound vortex that produces the circulation that supports the weight of the airplane should not be confused with the little vortices produced by vortex generators (to re-energize the boundary layer) as discussed in section 18.3.</H4>

 

[Uncle Sparky]

All sarcasm aside(I am capable on occasion)that is a good link and some interesting info. The author makes the point to the affect.."there is no difference between a six-foot winglet and an additional six-feet of span" so what is the advantage of one over the other ? The only answer that, I think, I'm getting so far, is that the winglet allows you, in affect, to increase lift without increasing span or inner wing load. BUT, the way that I read the responses thus far......GV is stating this is not entirely accurate.

Maybe I'm the slow one now but that's how I'm reading it.

 

[GVFlyer]

As for the original question - rather than a conventional wing as used on the G-V, Boeing used a aft-loaded supercritical wing design which is not given to the application of winglets.

The basic approach to supercritical wing design is to flatten the upper surface of the airfoil to reduce flow acceleration and to use a highly cambered aft section to generate most of the lift. The disadvantage of supercritical wings (as used on the Citation X) is that aft-loaded wings shift the center of lift back which necessitates moving the wings forward. This design tradeoff results in the need for larger and heavier control surfaces (increasing drag), larger pitching moments and the need for stronger and heavier wing structures (increasing weight).

The advantages of this design is that these aft-loaded wings are more efficient than a conventional wing because they reduce or delay the adverse effects of shock waves in transonic flight. Supercritical wings reduce wave drag above the drag divergence Mach number.

Gulfstream achieves much of the advantages of a supercritical wing design without the concomitant disadvantages by using a slender wing body.

GV

 

[Uncle Sparky]

Seems logical to me. Anyone who has closely examined a CX wing will noticethat the camber, especially near the trailing edge inboard wing area, is very pronounced.


Now lets say you RON somewhere in your GV. While your safe in bed at your hotel for the night, some no good, low-life, punk, gang member steals your winglets.

After the FBO manager apologizes and explains that this is a common occurrence because "the kids like to put Gulfstream winglets on the back of their lowriders these days!?" you decide to duct tape the holes and ferry it home.

What differences will that same wing, now wingletless, demonstrate?(from: a pilot's perspective, an efficiency standpoint, drag etc.)

 

[NJA Capt]

The disadvantage of supercritical wings (as used on the Citation X) is....

For crying out loud dude, Let it go!!!!!!
We get it, you don't like the X.

In my opinion, the wing on the CX is much more graceful than a gulfstream. Although beautiful in its' own right, it (G-anything) is as flat as a pancake with a H-U-G-E cord, with single section flaps. Like giant C172.

 

[Uncle Sparky]

.......maybe next time you should just PM the guy if you feel offended..........Geez, just when it finally seemed like we were getting somewhere?!.......

 

[NJA Capt]

...if you feel offended..........

Offended????
I'm far from offended. But it is annoying that he can't conclude a post without one, or both, of the following:

1) How pathetic the Citation X is.
2) How the G-V is the most perfect airplane ever conceived

It's gotten old....
(stepping off soapbox)

 

[mzaharis]

Now lets say you RON somewhere in your GV. While your safe in bed at your hotel for the night, some no good, low-life, punk, gang member steals your winglets.

After the FBO manager apologizes and explains that this is a common occurrence because "the kids like to put Gulfstream winglets on the back of their lowriders these days!?" you decide to duct tape the holes and ferry it home.

What differences will that same wing, now wingletless, demonstrate?(from: a pilot's perspective, an efficiency standpoint, drag etc.)

You think them G550 winglets will look good on my minivan? Maybe only if I get those bling-bling spinning spoke wheels.

OK, this is gleaned from posts on airliners.net (!), although supposedly ones by airline pilots, so take it for what it's worth.

Supposedly, wingletted airliners and those with "end plates" (Airbus) are qualified to fly w/o their winglets/endplates, in case they need to be removed. The range used for flight planning is decreased by a few percent. I THINK that the aircraft may be kept in service until it's repaired. So, the basic assumption is that, if an aircraft is designed with winglets, or winglets have been shown to increase performance, removal will result in a couple of points of drag increase, with an associated decrease in range/increase in fuel consumption.

OK, end of A.net navel-gazing, and beginning of my own navel-gazing.

I wasn't aware that supercritical sections were less amenable to winglets, but I suppose you could run into some compressibility effects.

One thought is that, if a wing has a particularly high aspect ratio, it will benefit less from winglets than a lower aspect ratio wing. That would explain why the GV uses winglets. They went for a cloud of wing area on that wing, if for no other reason than to reduce the difference in airspeed between buffet onset and stalling at FL510. To do this, they have a wing that has a greater chord than most other business jets, and that leads to a lower aspect ratio, making winglets (which have the same effect on induced drag as increasing span/aspect ratio) effective. Again, this is speculation on how the Gulfstream design team may have thought. My guess is that, despite not having a formal target, they did have informal targets as to a maximum span, along with a target wing area to make the aircraft, as GVflyer has said in other posts, a "non-buffet-limited" aircraft at FL510. To do so, they may have had to increase chord, and decrease aspect ratio, leading to the decision to add winglets.

As mentioned earlier, I don't think that there's any one factor that makes one design conducive to winglets, and another not. Design is an iterative process, and a tradeoff someplace else (wing area, chord, span, wing planform, airfoil section, structural considerations) affects whether a wing will benefit from winglets or not.

EDIT - There's a bit of a hole in my theory - I calculated the wing aspect ratios of a non-wingletted Citation X (7.74) and a wingletted GV (7.69), and they're practically identical.

 

[Uncle Sparky]

Chris, I'm going to try and answer this specific question. Manufacturers don't always incorporate winglets because winglets are not always the best way to accomplish the design goals. That's the answer. I suspect that you really are asking about winglets in a more general sense. More at the end.

I'll answer the first question (if they are so beneficial?) and that should answer the others. Winglets are not beneficial in all situations. You must first realize that all aircraft design is a series of compromises. If the designer is able to ignore all outside factors, he will be able to design a wing that doesn't need winglets. The Falcon series of business jets, and the Citation X are good examples.

Here's the secret to understanding winglets. A winglet gives the effect of increased span but it doesn't increase the wing root bending moment. In other words, a winglet can allow a short wing to act like a long wing, without modifying/strengthening the original wing structure.

With that understanding, let's look at one of the compromises that might allow/rule-out winglets from an airliner designers standpoint. One of the most obvious examples would be ramp space. If you're designing a new airliner, you may well have to work around the customers requirement that your new bird must be able to park at the existing gates. That limits your wingspan, and in that case, winglets might be your answer. If the designer was able to design the wing without regard to ramp space, he would most likely just make it longer to begin with.

I would guess that the question is asked in an attempt to determine the applicant understanding of aero structures and aerodynamics. I'd answer it like this: "Winglets do a good job of making an existing wing more efficient without increasing it's span and taking up more ramp space.
Some airplanes come from the factory with winglets because they are outgrowth designs (like the 747-400) where the original wing is being asked to be more efficient without a complete redesign; and some like the 777 come without winglets. Those that come without winglets do so because a properly designed, no-compromise, wing is more efficient without a big add-on winglet. "

regards,
enigma

...seems to me that this early response, after all that, is the most accurate The one potential "rub" would be the GV's reaction to the "no-compromise" wing comment. It would seem though, in the end, GV concurs with the statement after all.

Boeing used a aft-loaded supercritical wing design which is not given to the application of winglets........The advantages of this design is that these aft-loaded wings are more efficient than a conventional wing because they reduce or delay the adverse effects of shock waves in transonic flight. Supercritical wings reduce wave drag above the drag divergence Mach number.
Gulfstream achieves much of the advantages of a supercritical wing design without the concomitant disadvantages by using a slender wing body.
..

... so, as I understand it, the fact that the CX has engines that look like something Wile E. Coyote would put on HIS airplane are only half of the equation when considering the X's class record breaking Mmo.
The wing is the other critical element. And in the end the G550 does trade a modicum of outright speed in favor of better economy and as stated, better range(regardless of apples and oranges class comparisons).

 

[GVFlyer]

Seems logical to me. Anyone who has closely examined a CX wing will noticethat the camber, especially near the trailing edge inboard wing area, is very pronounced.


Now lets say you RON somewhere in your GV. While your safe in bed at your hotel for the night, some no good, low-life, punk, gang member steals your winglets.

After the FBO manager apologizes and explains that this is a common occurrence because "the kids like to put Gulfstream winglets on the back of their lowriders these days!?" you decide to duct tape the holes and ferry it home.

What differences will that same wing, now wingletless, demonstrate?(from: a pilot's perspective, an efficiency standpoint, drag etc.)

The AFM requirement is found in the Deviations List (they are a structure - not installed equipment so they are not in the MMEL) Appendix B, page B-10, which states that range must be reduced by 7%.

GV

 

[AA717driver]

Dudes! If having winglets will help me nail the chick behind the desk in the FBO, I say 'Bring 'em on!'. TC

P.S.--Yes, I know I'm a mental midget. I fully recognize that fact. But at least I didn't have to look up the word 'concomitant'.

 

[GVFlyer]

...seems to me that this early response, after all that, is the most accurate The one potential "rub" would be the GV's reaction to the "no-compromise" wing comment. It would seem though, in the end, GV concurs with the statement after all.

... so, as I understand it, the fact that the CX has engines that look like something Wile E. Coyote would put on HIS airplane are only half of the equation when considering the X's class record breaking Mmo.
The wing is the other critical element. And in the end the G550 does trade a modicum of outright speed in favor of better economy and as stated, better range(regardless of apples and oranges class comparisons).

Gulfstream had three design criteria in mind while developing the GV wing: speed, efficiency and safety. We achieved speed; it's a M 0.88 jet at 50,000 feet.

Gulfstream has also achieved efficiency. For instance, carrying a greater payload, it will fly 250 nm farther than a Global Express XRS while burning 3,700 lbs less fuel.

That leaves safety which is related to speed. We wanted to create a big wide-chord high altitude wing (the GV/G550 is never cruised lower than FL410) that at FL510 would give the jet a 100 knot margin between compressibility and stall and would provide flight qualities that would allow any pilot to safely do 45 degree banked turns at that altitude. We did that.

In order to go faster we would have to sweep the wings more than the nominal 30 degrees which Gulfstream scientists Ed Flynn and Dr. Bob Mills had determined to be ideal.

Further sweeping the wing would introduce undesireable flight characteristics incompatible with the Gulfstream Design Philosophy. Radical sweep on a wing causes aerodynamic penalties which are paid for minimal gain. As sweep increases longitudinal stability decreases, low speed handling becomes more difficult, Dutch Roll characteristics become worse, tip stall speeds decrease, and the wing aspect ratio decreases causing more induced drag.

Dutch roll characteristics in the GV/G550 are so benign that the jet can be safely flown at FL510 yaw damper off. The GV/G550 can also be flown with a complete hydraulics failure. It is unlikely that had we built a wing with a more dramatic sweep we could have made the jet flyable without hydraulic boost.


GV

 

[Uncle Sparky]

Kuum-by-yaaa............Kum-by-yaaaaa...aaaa kum-BY-yaaaaaa............Kuumm-byaa

Note to self: "when using example of aircraft with winglets for aerodynamic gouge discussion....refrain from, at ALL costs, using G-aircraft in future said discussions..."

........gotta go, my eye is starting to twitch again!

 

[GEXDriver]

Kuum-by-yaaa............Kum-by-yaaaaa...aaaa kum-BY-yaaaaaa............Kuumm-byaa

Note to self: "when using example of aircraft with winglets for aerodynamic gouge discussion....refrain from, at ALL costs, using G-aircraft in future said discussions..."

........gotta go, my eye is starting to twitch again!

What do you want, Sparky? The guy answered the question as honestly as he could. What do you want him to do, make up an answer just to suit you: "Yeah we really screwed the Pooch on the GV wing, we shoulda swept it. We made a lotta compromises, I don't know what we were thinking."

 

[Uncle Sparky]

I can't believe some of you guys fly airplanes?!(re: basic communication skills)
If someone wanted to know how lift was created and a second someone explained perfectly clearly while using a Cessna 172 as his guinea pig, wouldn't you be just a bit peeved if some guy who flys a Cherokee went on a tirade proclaiming "you're grossly misinformed CHEROKEES make lift too, they make more lift than any airplane ever built, heres all the stats from development to present to prove it!" ?

Once again ....(I'm gonna need some therapy after this) .....A question was asked and then it was answered.......somebody else (GV) piped in and threw a wrench in the gears. THAT is perfectly acceptable, especially in misinformation central(better known as the Internet).
My hangup is that the guy spouts off like a Gulfstream brochure and doesn't make any attempt to answer the question and anytime the mighty G-ship is used as an example off he goes again.
O-kaaaay we ALL get it he helped develop the airplane, were all very impressed, he can spout off stats and figures til' the cows come home but somehow during all of his training and experience he has, mysteriously, been rendered incapable of answering basic Aerodynamic questions.
Let me state it publicly, maybe that'll work(somehow I doubt it). I think the G550 is a wonderful airplane. I'm NOT trying to compare it against any other airplane in a, It's better than yours, argument. I am merely trying to continue the discussion using the aircraft that were already mentioned before I got here. NJA Capt........you ARE right........I apologize........I tried to give the guy the benefit of the doubt but he IS incapable of holding a normal, unbiased conversation.

 

[Muddauber]

I don't know, GexDriver. I thought NJA Capt was the d!ckhead on this thread, but it looks like Uncle Sparky is competing for that position.

Muddy

 

[enigma]

What do you want, Spanky? The guy answered the question as honestly as he could. What do you want him to do, make up an answer just to suit you: "Yeah we really screwed the Pooch on the GV wing, we shoulda sweep it. I don't know what we were thinking."

I should stay out of this, but no, I'm a little stupid. GEXDriver, I think that Uncle Sparky just got tired of GV taking a generic discussion and turning it into a passioned defense of a non-existant attack on the GV.

enigma

 

[Uncle Sparky]

You're "grossly misinformed" mudpacker!
I AM the one and only d!ckhead here.

I invented the word.

As a matter of fact I ghost wrote Websters dictionary.

It has 457 pages and weighs 3.67 pounds.

During the development of the book I was aided by over 350 scientists and scholars and the largest computers at MENSA.

It did all of the typing myself.

It took nearly 3.987 years and I visited over 50 countries.

The red paint that we use on the binder is cutting edge and has never been used on any other book to date.

We developed a font specifically for our dictionary which is designed to be easy on the eye yet bolster the researcher's confidence subliminally.

We developed a new space age paper which releases a combination of Jergens and Focus Factor each time you turn one of the elegant pages.

The latest edition excells in all areas light years beyond ALL of the slow, heavy, archaic dictionaries of the past.

 

[SkyGirl]

I should stay out of this, but no, I'm a little stupid. GEXDriver, I think that Uncle Sparky just got tired of GV taking a generic discussion and turning it into a passioned defense of a non-existant attack on the GV.

enigma

I should stay out of this, too, but wasn't it your inaccurate post that got him started?

Looks like he apologized to you, too.

And after being challenged by Uncle Sparky, didn't he do a pretty good job of answering the original question.

Anyways, I find GVFlyer's posts to be very informative and I enjoy reading them. I bet there are others that do, too, they just don't post because they are afraid of being attacked.

-SkyGirl-

 

[Uncle Sparky]

"... so, as I understand it, the fact that the CX has engines that look like something Wile E. Coyote would put on HIS airplane are only half of the equation when considering the X's class record breaking Mmo.
The wing is the other critical element. And in the end the G550 does trade a modicum of outright speed in favor of better economy and as stated, better range(regardless of apples and oranges class comparisons)."

Somebody help me out here........How does saying the man's airplane is a little slower but a better perfomer from an economic standpoint constitute an attack and make ME the d!ckhead? You can praise the guy all you want, nobody is going to attack you!........H3ll, I praise him! He's got an impressive background. He writes responses that are well versed and imformative. So I ask him for more specific responses and now I'm the D!ck? Maybe next time I should plod along, cattle style, and just take it all for gospel......
__________________

 

[enigma]

I should stay out of this, too, but wasn't it your inaccurate post that got him started?

Looks like he apologized to you, too.

Skygirl. First let me say that I harbor zero ill or hard feelings toward GV. I'm not continuing this in order to disagree with, nor attack GV. He did apologize to me, it wasn't necessary, but I appreciated it because I didn't originally understand that he wasn't attacking me. GV took something I wrote and used it as a spring board to showcase the Gulfstream. I guess that some others took exception to his passionate defense.

Second, my post was NOT inaccurate. Call it an overgeneralization if you will, but when Boeing agrees with me, I don't think that I'm inaccurate.

Quite frankly, GV took a simple little point that could use a little clarification (my statement that properly designed wings don't benefit from winglets) and took it a little too personal. I recognize that internet message boards are not the perfect form of communication, so once I realized that he wasn't attacking me, just zealously defending his baby, I moved on. Apparently others haven't, as is their right.

enigma