Thrust
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Most Efficient Wing In Aviation?

Thu Aug 25, 2011 7:05 am

Thought this would be interesting just because of all the new aircraft that have been popping up over the past 20 years. I would personally think it's the A380 wing or the 777 wing, but I'd like some input from others. Feel free to describe any aspects you think make it the most efficient. We're talking about commercial airliners here.
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Stitch
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 8:05 am

I'd expect it's the A380's wing at the moment, at least as it applies to commercial aviation.

I've heard amazing things about the 787's wing and then we have the A350's on the way.
 
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 8:40 am

Quoting Stitch (Reply 1):

I've heard amazing things about the 787's wing

If it is as good as it looks it's gonna be one extraordinary wing!  But the same goes for the A380 wing, head on those gull wings are really something.


If the OP meant Aviation in general I would think the latest generation of gliders would have the most efficient wing.

http://www.tcs-uk.com/dpye/images/Jaca%20Apr%202007_20070407_14-ed-web1.jpg

[Edited 2011-08-25 01:40:49]
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Starlionblue
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 9:54 am

Easily gliders or some of the Rutan designs for long-distance records like GlobalFlyer and Voyager.

When it comes to efficiency those beat any airliner hands down. Not very good for airliner speeds though.  
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ptrjong
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 10:37 am

The question was airliners. Does anyone beat the old Fokker F27/50's aspect ratio 12 wing?
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 11:35 am

Quoting ptrjong (Reply 4):
The question was airliners.

A bit ambiguous given the title:

Quoting Thrust (Thread starter):
Most Efficient Wing In Aviation?

But fair enough, airliners. If you're talking pure glide ratio, my bed is on a turboprop.
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 11:44 am

Hard question to answer I think...since the decisions that go into the wing design are dependent on so many other design decisions and external factors.

The 727's wing was pretty efficient if your goal is to cruise really fast and land really slow, and your airplane has the engines back on the tail, but obviously not the best choice overall (or for today's operating environment) or you'd see more aircraft with that kind of setup now.
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 11:48 am

Quoting ptrjong (Reply 4):
Fokker F27/50's
Quoting ptrjong (Reply 4):
turboprop

Forgive my ignorance. But from my un-informed perspective a turbo-prop wing doesn't seem to be very efficient just by the look of it. Square, low aspect ratio, not the sweeping aerodynamic shape of the 787 or 380. So what am I missing?
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Okie
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 12:56 pm

Quoting travelavnut (Reply 7):

Forgive my ignorance. But from my un-informed perspective a turbo-prop wing doesn't seem to be very efficient just by the look of it. Square, low aspect ratio, not the sweeping aerodynamic shape of the 787 or 380. So what am I missing


As with anything in aviation there are a lot of trade-offs and constantly evolving.
The question is about the most efficient wing and the answer is that it depends on application and operating regime.
As mentioned earlier the 27 wing was designed to operate in a speed regime of a straight pipe jet with operating speeds near .92 mach.
With the advent of high by-pass turbines then the operating environment dropped down to .84 mach or so. Wing designs were changed to take that into account.
As with say a ATR turbo prop operates down about 250 knots therefore you design a wing to operate in that speed range and you lose your swept design to stay most efficient in that regime.
So as a general rule the answer would be the latest design would be the most efficient for that application and time period.

I sure there a plenty of anomalies in the industry but probably one of the best known of inefficiency was when Dornier replaced the turbo props on the D328 and stuck turbines under the wing and did little to the wing. You ended up with a jet engine for power trying to push a draggy low speed turbo prop wing.

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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 12:59 pm

It might help the discussion if we could define efficiency as applied to wings. Is there a standard definition? I guess you'd want to normalize for wing loading somehow.
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 1:13 pm

In the bizjet world, the Citation Sovereign has a pretty impressive wing on it. It'll get a midsize jet off of a 4,000 foot runway, take it all the way up into the 40s, and then go 2800nm at .78 Mach or so.

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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 1:23 pm

I think you're going to find the Citation X hard to beat. Decent low speed efficiency and excellent high speed efficiency. As a comparison when I flew Lear 25s, at FL 450 I think we had around 20 kts between overspeed and stall. Check out the margin at FL510 in the X. It's somewhere between 90-110 kts.
 
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 5:53 pm

Quoting PITingres (Reply 9):
It might help the discussion if we could define efficiency as applied to wings. Is there a standard definition? I guess you'd want to normalize for wing loading somehow.

Probably L/D comes closest, although that's usually calculated for the whole aircraft, not just the wing. That does leave intended operating speed out of the equation, though - a Nimbus 4, for example, is certainly very efficient, getting better than 60:1 - but it does that at about 60kts. Airliners are mostly in the 15-20:1 range, although at closer to 200kts. If nothing else very high aspect ratio wings are structurally difficult at high speeds (and by definition lack internal volume).
 
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 7:35 pm

Concorde, obviously.
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 8:43 pm

Quoting Thrust (Thread starter):
We're talking about commercial airliners here.

If you read the OP's initial post, he clearly defines it as commercial airliners.

My vote would go to the 787, just my opinion.
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 9:19 pm

Quoting HaveBlue (Reply 14):
If you read the OP's initial post, he clearly defines it as commercial airliners.

He mentioned a couple airliners like they were candidates for "Most efficient wing in aviation". Maybe he meant to limit it to airliners, but he clearly never said so.

If efficiency means lift-to-drag, no jet will be a contender, will it? So this thread assumes efficiency means something else? Anybody know what?
 
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 9:36 pm

Quoting B777LRF (Reply 13):
Concorde, obviously.

Concorde was one of the most aerodynamically inefficient vehicles ever built.

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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 10:20 pm

Quoting okie (Reply 8):
As mentioned earlier the 27 wing was designed to operate in a speed regime of a straight pipe jet with operating speeds near .92 mach.
With the advent of high by-pass turbines then the operating environment dropped down to .84 mach or so. Wing designs were changed to take that into account.

The 727 wing was more efficient in terms of nautical miles per lb of fuel when operating at 0.84M as opposed to 0.92M. High speeds work when kerosene sells for $0.10 per gal as crew costs are the biggest component of operating costs. When the price goes to $1.00 per gal, you slow down.
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 11:11 pm

Wow. Well then. The posts above certainly have some wide ranging answers.

Given the vague nature of the question, I don't think there can be any truly right answer. Personally, I'd say an "efficient" wing would be a wing with the highest possible lift to drag (L/D) ratio, as a high L/D will allow the greatest distance traveled with the least power, which in my mind would be "efficient" flight.
Now, as a general rule, L/D is directly related to a wing's induced drag coefficient, which is directly related to the wing's aspect ratio. The higher the aspect ratio wing, the higher the L/D. Right there, that rules out the Concorde and other supersonic, stubby winged aircraft. If we assume Wikipedia's table of L/D ratios to be generally correct, a common tern (bird) is about 3x more efficient through the air than the Concorde at approach speed. A 747 is listed with an L/D of almost 4x that of the Concorde. Supersonic aircraft are designed with operation at supersonic speeds in mind, where reducing wave drag (a result of supersonic shockwaves) is much more important, and where lift coefficients start getting very convoluted. Even though aircraft like the Concorde and F-104 are capable of impressive speeds, they guzzle fuel at a tremendous rate to accomplish their missions. In a power-off scenario, I'd approximate the L/D of the F-104 to be about equivalent to that of a brick.

Assuming that aspect ratio is the primary driving parameter of efficiency, that leaves the contest almost entirely up to sailplanes. Since the focus seems to be on powered aircraft though, I'll narrow my investigation to rule out the super-high performance gliders (the German "Eta" glider probably holds the trophy for the most efficient aircraft in the world at the moment - it can achieve a glide ratio of 72:1 with its 51.3 aspect ratio wing.)

Unfortunately, L/D isn't directly related to aspect ratio, but also to an aircraft's parasite drag (where parasite and induced drag are a minimum, L/D will be a maximum.) Some of an aircraft's parasite drag will be due to the wing, so...it's not really possible to say the highest aspect ratio will be the most efficient. Herein lies the perpetual debate of vortex generators vs clean wings, wing tip fences vs winglets, and all the little trade offs which differentiate modern airliners. While vortex generators may increase drag, they also improve the performance of the wing, and so on. Based on whole-aircraft performance figures, I would have to say that the 787 and A350's wings are pretty close to state-of-the-art, but who knows, maybe the old Fokker pencil-thin wings would beat them in a glide...



Oh, and as an aside, I'm sure many of you are thinking "no way, the straight wing of a Fokker 50 can't be more efficient than the sleek swept 787 wing!!" Sweep has nothing to do with lifting performance or aerodynamic efficiency of a wing. Sweep will certainly affect drag to some extent, but its primary objective is to increase the critical mach number of the airfoil. A swept airfoil will delay the formation of shockwaves to a higher mach number, enabling the wing to still function closer to the speed of sound. At low speeds (less than mach 0.3ish) a straight wing will beat out a swept wing of equal wing area in a glide any day.
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RE: Most Efficient Wing In Aviation?

Thu Aug 25, 2011 11:56 pm

Quite impressive there DashTrash.
Particular looking at the AOA.

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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 12:00 am

Lift to drag ratio is one measure. Another is glide ratio unpowered.

Quoting travelavnut (Reply 7):
Forgive my ignorance. But from my un-informed perspective a turbo-prop wing doesn't seem to be very efficient just by the look of it. Square, low aspect ratio, not the sweeping aerodynamic shape of the 787 or 380. So what am I missing?

The sweep actually decreases lift and increases weight. The reason for the sweep is to delay shock wave formation at high subsonic speeds. It's there to allow higher speeds. Since the purpose of the wing is to create as much lift as possible for as little weight as possible I would argue this means sweep is an inefficiency.

If we narrow the question to "... at speeds over M0.85" then certainly a swept wing is more efficient. But if we're talking "best lifting device", a straight wing is more efficient. Turboprops take longer to get there, but they use way less fuel to do it.
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HaveBlue
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 12:03 am

Quoting timz (Reply 15):
He mentioned a couple airliners like they were candidates for "Most efficient wing in aviation". Maybe he meant to limit it to airliners, but he clearly never said so.

Um, no.

Again, he clearly stated.... and I quote:

Quoting Thrust (Thread starter):
We're talking about commercial airliners here.

Fairly simple, don't know why you're having trouble grasping it.
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 1:03 am

Quoting travelavnut (Reply 7):
Forgive my ignorance. But from my un-informed perspective a turbo-prop wing doesn't seem to be very efficient just by the look of it. Square, low aspect ratio, not the sweeping aerodynamic shape of the 787 or 380. So what am I missing?

Some of the guys above understand more about this stuff than I do. But building a sleek swept wing is difficult, and so when your definition of efficiency does not include speed, high aspect ratio straight wings are more efficient, more akin to a glider wing. Some turboprops, designed for STOL, have stubby wings, but the Fokker wing was designed for fuel efficiency in cruise. Have another look at it - it's not square and low aspect ratio at all. Its aspect ratio (span^2/wing area) is 12 and that is higher than for any other airliner that I checked, hence my question. Not that I think it's an engineering marvel.


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[Edited 2011-08-25 18:06:05]

[Edited 2011-08-25 18:06:25]
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 1:04 am

I would imagine that most of the STOL airliners would be in stiff competition for efficiency. Get off the ground as fast as you can, speed doesn't really count, and land slow.
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 3:29 am

Quoting timz (Reply 15):
Maybe he meant to limit it to airliners, but he clearly never said so.
Quoting Thrust (Thread starter):
We're talking about commercial airliners here

Seems pretty clear to me.

Quoting KPWMSpotter (Reply 18):
Personally, I'd say an "efficient" wing would be a wing with the highest possible lift to drag (L/D) ratio, as a high L/D will allow the greatest distance traveled with the least power, which in my mind would be "efficient" flight.

Since we're restricting discussion to commercial airliners (which the OP did clearly state), L/D isn't the right metric. You have to turn that into cost...something like $/nm normalized to weight, somehow, would be something like the right measure.

Tom.
 
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 6:42 am

The efficiency of a wing depends on how hard it's working and how fast it's going, so the context is important to figure out how much drag it will encounter in a certain regime under a certain load. A Q400 or Fokker 50 might seem more efficient in the low speed realm, but at Mach 0.89 a Citation X or Boeing 747 with a highly swept supercritical wing is going to win out.

One thing I am starting to resent more in modern aircraft technology is that the quest for fuel efficiency is producing slower and slower airplanes, which is way concepts like this one linked frustrate me. I'd rather see a supersonic A380.
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Thrust
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 6:58 am

Feel free to answer in both respects...i actually had originally meant in aviation in general, but then as I was typing decided I wanted to know about airliners in particular. Just out of curiousity, how efficient was Concorde's wing? Both the Concorde and shuttle had delta wings. And the F-18s and F-14s?
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Thrust
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 7:08 am

I'm also curious as to what narrow-bodied airliners like the 757, 737, and the narrow-bodied Airbuses tend to feature conservatively swept wings where as widebodies like the DC-10, L-1011, 747, and A380 feature more sharply swept wings. In fact, it almost seems Iike twins in general don't seem to have as sharply swept wings as tri-jets and quadra-jets. Does the drag and also thrust-to-weigh ratio play a factor in the decision for the degree a wing is swept back?
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rwessel
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 7:34 am

Quoting Thrust (Reply 27):
I'm also curious as to what narrow-bodied airliners like the 757, 737, and the narrow-bodied Airbuses tend to feature conservatively swept wings where as widebodies like the DC-10, L-1011, 747, and A380 feature more sharply swept wings. In fact, it almost seems Iike twins in general don't seem to have as sharply swept wings as tri-jets and quadra-jets. Does the drag and also thrust-to-weigh ratio play a factor in the decision for the degree a wing is swept back?

The A380 (33.5 degrees) has considerably less wing sweep than the 747 (37.5), a bit less than the DC-10s (35) and a bit more than the L10-11's (32). I think the A380's sweep is actually surprisingly high (compare the 777 at 31 degrees), but it certainly seems to work for Airbus.

Wing sweep exists solely to reduce the drag caused by supersonic flow over the wing. It's basically a bad idea in every other respect.

Some of the transonic drag reduction you get with swept wings can be achieved with supercritical airfoils. Most of the tri's and quad's are rather older designs, predating heavy use of supercritical airfoils. Add a willingness to give up a bit of Mach for efficiency, and a less swept wing is the obvious choice for more modern designs, which of course, are mainly twins. The older twins, like the 737, were designed for shorter router, making a lower operating speed easy to justify, often leading to lesser sweep as well.
 
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 7:52 am

Quoting KPWMSpotter (Reply 18):
(the German "Eta" glider probably holds the trophy for the most efficient aircraft in the world at the moment - it can achieve a glide ratio of 72:1 with its 51.3 aspect ratio wing.)

Good god that's efficient. I've always been a fan of the Stemme S-10VT myself and am amazed at how it can manage a 50:1 glide ratio with a side-by-side cockpit.



And how about a shout out for the A330? It's very efficient with its long wing span (I'm not saying the most efficient, mind you).
 
rwessel
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 8:42 am

Quoting KPWMSpotter (Reply 18):
Assuming that aspect ratio is the primary driving parameter of efficiency, that leaves the contest almost entirely up to sailplanes. Since the focus seems to be on powered aircraft though, I'll narrow my investigation to rule out the super-high performance gliders (the German "Eta" glider probably holds the trophy for the most efficient aircraft in the world at the moment - it can achieve a glide ratio of 72:1 with its 51.3 aspect ratio wing.)

Of course the Eta is self-launching, so it *is* powered.

http://www.leichtwerk.de/eta/en/gallery/photos.html

That's a lot of wing. 101.4ft to be exact (for comparison, 737 classics have about 94.75ft). The photo with a 15m ship nestled under its right wing is especially amusing.
 
hal9213
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 9:32 am

I would say the most efficient wing is having no wings and fly by thrust alone!!!!!
  
 
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 12:41 pm

Quoting rwessel (Reply 28):
Wing sweep exists solely to reduce the drag caused by supersonic flow over the wing. It's basically a bad idea in every other respect.

Well, not exactly. Wing sweep may reduce drag to a minimal extent, but generally sweep is designed into an aircraft to increase speed; specifically to increase the critical mach number of the airfoil. When air flows over an airfoil, the flow over the top surface speeds up. At some arbitrary airspeed, the flow over the wing becomes supersonic and forms shockwaves, which is a big problem for subsonic aircraft. The airspeed at which shockwave formation begins is called the critical mach number, and can be as low as 0.4 Mach for some airfoils. By sweeping the wing, the chordwise flow over the airfoil is effectively slowed down (the velocity of the aircraft is resolved into chordwise and spanwise components), so the aircraft as a whole can fly through the air at a higher velocity before the critical mach number is reached.

Unrelated to the topic at hand, but sweep can also contribute towards the stability of an aircraft. Look at the L-13 Blanik glider, it has a forward swept wing and won't be getting anywhere near the speed of sound. This is simply to shift the wing's center of lift forward while still permitting a cockpit big enough for two forward of the wing root. But I digress...

Quoting Thrust (Reply 27):
I'm also curious as to what narrow-bodied airliners like the 757, 737, and the narrow-bodied Airbuses tend to feature conservatively swept wings where as widebodies like the DC-10, L-1011, 747, and A380 feature more sharply swept wings. In fact, it almost seems Iike twins in general don't seem to have as sharply swept wings as tri-jets and quadra-jets. Does the drag and also thrust-to-weigh ratio play a factor in the decision for the degree a wing is swept back?

Again, all about speed. Narrow-body airliners aren't going to be used on the ultra-long-haul routes where a few knots make a big difference. It makes more sense for a short haul aircraft to have a straight wing which will get it off the ground and up to altitude as quickly as possible with the greatest payload possible. As a result, most narrow bodies are significantly slower in cruise. The 737 classic cruises at Mach 0.74, compared to the 747's Mach 0.85.

Quoting hal9213 (Reply 31):
I would say the most efficient wing is having no wings and fly by thrust alone!!!!!

I would call that the least efficient wing...  
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Rara
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 2:21 pm

Quoting DashTrash (Reply 11):
Check out the margin at FL510 in the X. It's somewhere between 90-110 kts.

Blimey, that's quite impressive. About how high would true airspeed be at that point?
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rwessel
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 3:55 pm

Quoting KPWMSpotter (Reply 32):
Well, not exactly. Wing sweep may reduce drag to a minimal extent, but generally sweep is designed into an aircraft to increase speed; specifically to increase the critical mach number of the airfoil. When air flows over an airfoil, the flow over the top surface speeds up. At some arbitrary airspeed, the flow over the wing becomes supersonic and forms shockwaves, which is a big problem for subsonic aircraft. The airspeed at which shockwave formation begins is called the critical mach number, and can be as low as 0.4 Mach for some airfoils. By sweeping the wing, the chordwise flow over the airfoil is effectively slowed down (the velocity of the aircraft is resolved into chordwise and spanwise components), so the aircraft as a whole can fly through the air at a higher velocity before the critical mach number is reached.

The problem with supersonic flow and its associated shock waves, is the resulting wave drag.

Quoting KPWMSpotter (Reply 32):
Unrelated to the topic at hand, but sweep can also contribute towards the stability of an aircraft. Look at the L-13 Blanik glider, it has a forward swept wing and won't be getting anywhere near the speed of sound. This is simply to shift the wing's center of lift forward while still permitting a cockpit big enough for two forward of the wing root. But I digress...

Several aircraft have done odd things like that to the wings, from the Me-262 to the Piaggio Avanti (although there they went for more of a biplane configuration to compensate for mounting the wings in an odd place) to F-4U Corsair (gull wings), for non-aerodynamic reasons.
 
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RE: Most Efficient Wing In Aviation?

Fri Aug 26, 2011 5:02 pm

If we re-open to non-commerical. I would say the latest Global Hawk.

Quoting rwessel (Reply 12):
Probably L/D comes closest, although that's usually calculated for the whole aircraft, not just the wing.

But one has to include the whole aircraft. For example, a lifting nose (1st implimentation the A380) will compromise the wing a tad, but far less than the benefit. Next generation will probably have lifting bodies. While longer aspect ratio wings are efficient, there is much to be gained at the wing root. Is that 'whole aircraft' or wing?

Quoting gigneil (Reply 16):
Concorde was one of the most aerodynamically inefficient vehicles ever built.

   A great design, but many areas to improve.

Quoting ptrjong (Reply 22):
so when your definition of efficiency does not include speed, high aspect ratio straight wings are more efficient, more akin to a glider wing.

  

So we have a topic no one will agree to. Wings are inherently compromized for takeoff/landing and for fuel capacity. Wings also need a body that can fly as high as the wing could lift.

Quoting KPWMSpotter (Reply 32):
The 737 classic cruises at Mach 0.74, compared to the 747's Mach 0.85.

Optimizing for the mission is critical. One wing that is great for 1000nm would be giving up fuel burn at 4000nm. While EK flies widebodies short haul, there is a tremendous 'weight of wing' employed in their airframes that doesn't help unless one is taking off with the fuel for a long haul mission.

In general, the design improves. Right now the 748 or the 787 have the long haul wings to beat (after the 747 reprofile). Soon it will be the A350. For shorter missions, I'm not sure if it is the superjet or the C-series...

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RE: Most Efficient Wing In Aviation?

Sun Aug 28, 2011 7:25 pm

Quoting Starlionblue (Reply 5):
my bed is on a turboprop.

How well do you sleep? I'd need a quieter place....  

Sorry - couldn't resist....   
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RE: Most Efficient Wing In Aviation?

Sun Aug 28, 2011 8:56 pm

Quoting Rara (Reply 33):

Blimey, that's quite impressive. About how high would true airspeed be at that point?

Answered my own question - about 467 knots...
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RE: Most Efficient Wing In Aviation?

Sun Aug 28, 2011 10:18 pm

Quoting KPWMSpotter (Reply 32):

That leads me to ask then, does the A340 have such a slow climb and acceleration rate solely because of it being underpowered, or is the degree the wing is swept back another factor?
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Thrust
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RE: Most Efficient Wing In Aviation?

Sun Aug 28, 2011 10:24 pm

I'm also slightly curious about the 727's wing, since it is one of the only narrow-bodies I've ever heard of to have sharply swept. It had a very high cruising speed. It also seemed to take forever to lift off the runway...I'm curious why it was given this feature and why it took so long to get off the ground....I'm assuming thrust to weight ratio plus the drag of having three engines aft were all contributors?
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Starlionblue
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RE: Most Efficient Wing In Aviation?

Sun Aug 28, 2011 11:02 pm

Quoting Thrust (Reply 38):

That leads me to ask then, does the A340 have such a slow climb and acceleration rate solely because of it being underpowered, or is the degree the wing is swept back another factor?

It is not underpowered. It meets certification and customer requirements just fine. It's just a bit of a Yugo in the thrust to weight department. 
Quoting Thrust (Reply 39):
..I'm assuming thrust to weight ratio plus the drag of having three engines aft were all contributors?

Compared to modern airliners, the 727 is a bit of a dog in the thrust to weight department.
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RE: Most Efficient Wing In Aviation?

Sun Aug 28, 2011 11:09 pm

Quoting rwessel (Reply 28):
The A380 (33.5 degrees) has considerably less wing sweep than the 747 (37.5), a bit less than the DC-10s (35) and a bit more than the L10-11's (32).

The L-1011 wing sweep angle is 35 degrees.
 
MrChips
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RE: Most Efficient Wing In Aviation?

Mon Aug 29, 2011 3:31 am

Quoting DashTrash (Reply 11):
I think you're going to find the Citation X hard to beat. Decent low speed efficiency and excellent high speed efficiency. As a comparison when I flew Lear 25s, at FL 450 I think we had around 20 kts between overspeed and stall. Check out the margin at FL510 in the X. It's somewhere between 90-110 kts.

The only thing that comes close in terms of efficiency would be a Gulfstream, specifically the upcoming G650.

The wings on most modern corporate jets are truly incredible these days; even straight-wing Citations are capable of some pretty impressive figures.
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tdscanuck
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RE: Most Efficient Wing In Aviation?

Mon Aug 29, 2011 3:58 am

Quoting Thrust (Reply 38):
That leads me to ask then, does the A340 have such a slow climb and acceleration rate solely because of it being underpowered, or is the degree the wing is swept back another factor?

It's not underpowered, it just gets used on long- and ultra-long haul flights a lot so it's usually taking off at a higher % of MTOW that most other airliners. A 747 on an equivalent length mission accelerates and climbs just as slowly. All quads have lousy acceleration relative to twins (and tri-jets) at equivalent weights because of how installed thrust has to be calculated.

Quoting Thrust (Reply 39):
I'm also slightly curious about the 727's wing, since it is one of the only narrow-bodies I've ever heard of to have sharply swept. It had a very high cruising speed.

It was a follow-on to the 707, built in a time where speed was a whole lot more important than fuel economy.

Quoting Thrust (Reply 39):
It also seemed to take forever to lift off the runway...I'm curious why it was given this feature and why it took so long to get off the ground....

It wasn't "given" that feature...the early turbojets and low-bypass turbofans have very high exhaust velocities and hence lousy acceleration (and terrific noise). That's why the 707 needed pretty long runways and why the 727 had to have an absurd flap system to meet the requirement to get out of La Guardia on a hot day.

Quoting Thrust (Reply 39):
I'm assuming thrust to weight ratio plus the drag of having three engines aft were all contributors?

The engine placement doesn't have much to do with it...thrust to weight, and thrust as a function of forward speed, were all huge contributors though. And it's a trijet so it automatically has worse acceleration than a twin.

Tom.
 
DashTrash
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RE: Most Efficient Wing In Aviation?

Mon Aug 29, 2011 1:50 pm

Quoting Rara (Reply 33):
Blimey, that's quite impressive. About how high would true airspeed be at that point?

Probably around 420-440. Normally we're at 520 in the high mach numbers.
 
OldAeroGuy
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RE: Most Efficient Wing In Aviation?

Mon Aug 29, 2011 3:29 pm

A good measure of efficiency is M(L/D).

This explains the differences between a wide range of aerial vehicles:

Powered sailplane: M=.15 L/D=50 M(L/D)=7.5

SST: M=2.2 L/D=5 M(L/D)=11.0

Commercial Transport: M=.85 L/D=20 M(L/D)=17.0
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Fly2HMO
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RE: Most Efficient Wing In Aviation?

Mon Aug 29, 2011 9:21 pm

I can't believe nobody has mentioned this:

http://www.wallpaperbase.com/wallpapers/military/b2/b_2_2.jpg

From what little I recall from aerodynamics class, flying wings were supposed to be by far the most efficient.

Please do correct me if I'm wrong.
 
tdscanuck
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RE: Most Efficient Wing In Aviation?

Tue Aug 30, 2011 4:03 am

Quoting Fly2HMO (Reply 46):
From what little I recall from aerodynamics class, flying wings were supposed to be by far the most efficient.

Please do correct me if I'm wrong.

Flying wings, in general, are very efficient. The B-2 has some severe aerodynamic compromises to protect the stealth features though. Split ailerons for yaw control are the most grievous example...they literally drag one wingtip backward.

Tom .
 
gigneil
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RE: Most Efficient Wing In Aviation?

Tue Aug 30, 2011 4:35 pm

Quoting Thrust (Reply 38):
That leads me to ask then, does the A340 have such a slow climb and acceleration rate solely because of it being underpowered, or is the degree the wing is swept back another factor?

As usual, utter crap. The A340 has a very competitive wing loading, and more than enough power to lift its heft.

Its just not overpowered, it just doesn't make a.net engineers happy.

NS
 
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Faro
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RE: Most Efficient Wing In Aviation?

Tue Aug 30, 2011 5:43 pm

Quoting gigneil (Reply 48):
As usual, utter crap. The A340 has a very competitive wing loading, and more than enough power to lift its heft.

True, although one must bear in mind that it was initially due to be powered by the SuperFan; I'm willing to wager that it would have had even better airfield performance if the SuperFan were installed vs the CFM's.

Another interesting tidbit: take the thrust-to-weight ratio at MTOW and divide it by wing loading to give a quick and dirty airfield performance indicator. The A343 has a comparatively low score compared to other airliners, though the difference is less with widebody heavies.

Faro
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