Lumberton
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Holes In Airplane Wings To Save Fuel

Sat Oct 21, 2006 8:30 am

Short article, title says it all.
http://www.dailymail.co.uk/pages/liv...id=411695&in_page_id=1766&ito=1490

Quote:
Markus Kloker and Ralf Messing, project leaders, told German newspaper "Der Spiegel" that a series of 50-micron-diameter (0.05 mm) holes in the wings reduce swirls and then also advancing resistance.

They are claiming a 15% reduction in fuel consumption!!!
"When all is said and done, more will be said than done".
 
474218
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RE: Holes In Airplane Wings To Save Fuel

Sat Oct 21, 2006 8:41 am

I think you may have the wrong link?
 
dw747400
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RE: Holes In Airplane Wings To Save Fuel

Sat Oct 21, 2006 9:51 am

There have been some studies done about using very small holes to manipulate the boundary layer. I believe most research has shown the systems are not worth their weight and complexity--but maybe that is changing. We do need the actual link of course! (Though I do find the picture of a regional jet in an article about a 777 amusing... not that I expect better from the press.)
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Bobster2
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RE: Holes In Airplane Wings To Save Fuel

Sat Oct 21, 2006 9:53 am

Found the correct link with Google:

http://www.avionews.com/index.php?co...d=66965&pagina_chiamante=index.php

It says they're talking to Airbus. I bet a 15% fuel reduction on the A380 would be a huge savings.  Smile
"I tell you this, no eternal reward will forgive us now for wasting the dawn." Jim Morrison
 
fr8mech
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RE: Holes In Airplane Wings To Save Fuel

Sat Oct 21, 2006 11:49 am

The problem, as I see it, will be maintenance and related costs. This will probably be a critical contour that won't play well if it is dented, scratched or deformed. I imagine hail will play havoc with the design. Not being a physicist: can water enter these holes and freeze? Will de-ice fluid be able to 'flush' these holes of ice? What will the adhering effects of Type IV do to the fuel burn?

Questions, questions, questions.
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kalvado
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RE: Holes In Airplane Wings To Save Fuel

Sat Oct 21, 2006 12:10 pm

Very hard to imagine manufacturing of 50-micron holes to be cost-effective whatever fuel saving would be. Even then, they will get clogged with dust very soon - not to mention any paint job.
I suspect, surface grooves were proposed, and idea lost in translation and communication. Patterned surface (some sort of shark-skin) would make some sense for me. But even then, how long are they going to last when exposed to real environment?
 
RichardPrice
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RE: Holes In Airplane Wings To Save Fuel

Sat Oct 21, 2006 6:09 pm

Sounds like a golfball design...
 
chksix
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RE: Holes In Airplane Wings To Save Fuel

Sat Oct 21, 2006 7:04 pm

Isn't this used already in the inlets of jet engines to control the boundary layer?
http://www.airliners.net/open.file/1090718/M/
See the inside of the cowling.

The F4 Phantom also had those "meshes" on the inlet ramps
http://www.airliners.net/open.file/1122681/M/
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troubleshooter
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RE: Holes In Airplane Wings To Save Fuel

Sat Oct 21, 2006 8:21 pm

Quoting Chksix (Reply 7):
Isn't this used already in the inlets of jet engines to control the boundary layer?
http://www.airliners.net/open.file/1090718/M/
See the inside of the cowling.

The purpose of the holes in the B737 air intake is to reduce noise.

I don´t think they do the same on the good old F4. It must be noisy Big grin!!!
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Starlionblue
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RE: Holes In Airplane Wings To Save Fuel

Sat Oct 21, 2006 8:29 pm

Quoting Kalvado (Reply 5):
I suspect, surface grooves were proposed, and idea lost in translation and communication. Patterned surface (some sort of shark-skin) would make some sense for me. But even then, how long are they going to last when exposed to real environment?

This has been tried on real airliners. I believe CX did some sharkskin experiments. But the cost of the paint job pretty much negated any advantages.

I'm not saying ideas like these should be discouraged, but often the proposals are made by people who know a lot about aerodynamics and not a lot about real world aircraft operations.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Bobster2
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 12:13 am

I found another article that explains it better. The key is that they apply vacuum suction to the holes that controls the shape and structure of the boundary layer. So it's not like a golf ball. They admit it's very expensive and would only be practical if fuel costs are high. There are links here to more technical info:

http://www.greencarcongress.com/2006/10/researchers_sta.html
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kalvado
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 1:39 am

Quoting Bobster2 (Reply 10):
The key is that they apply vacuum suction to the holes that controls the shape and structure of the boundary layer. So it's not like a golf ball. They admit it's very expensive and would only be practical if fuel costs are high.

Thanks for the link!
It makes much more sence now. What really confuses me, how would that work with all hardware (pumps, pipes) needed for all that - weight penalty would definitely be non-negligible. Overall, it looks more like some purely scientific research, which got publicity way before it really should.
 
aeroweanie
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 2:05 am

This is nothing new. The RAE and NASA have studied hybrid laminar flow control for years (about 50+). One huge problem is in-service maintenance. NASA flew a hybrid laminar flow control glove on a JetStar in simulated airline service to try and get the manufacturers interested, but the demo just showed up all the problems.


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BAE146QT
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 8:50 am

Quoting Starlionblue (Reply 9):
people who know a lot about xxxxxxxxxxx and not a lot about real world xxxxxxxxxxx operations.

They're called "middle management" and they usually have business school diplomas.
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LimaNiner
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 12:04 pm

Quoting Kalvado (Reply 5):
Very hard to imagine manufacturing of 50-micron holes to be cost-effective

I wonder if "drilling" these holes with lasers would be practical?

Quoting Kalvado (Reply 5):
they will get clogged with dust very soon

I would imagine positive pressure from the inside (e.g. by blowing in some warm air from the engines) would work (and avoid clogging the holes with freezing water, too), but then I saw that this technique requires *negative* pressure...

Quoting Bobster2 (Reply 10):
The key is that they apply vacuum suction to the holes



Quoting BAe146QT (Reply 13):
They're called "middle management" and they usually have business school diplomas.

Indeed!

I've always wanted to reply to some MBA clown "Hey, since we can replace an engineer with expertise X with an engineer with expertise Y, why can't we replace our CFO (who has an MBA in accounting) with an MBA with HR specialization?"
 
aeroweanie
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 1:01 pm

Quoting LimaNiner (Reply 14):
I wonder if "drilling" these holes with lasers would be practical?

That's how its done.
 
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jetmech
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 2:32 pm

Quoting Starlionblue (Reply 9):
I believe CX did some sharkskin experiments.

G'day Starlionblue  Smile. Was that an experiment only? I seem to remember that the fuselages of Airbus were covered in some sort of "micro-riblet" film  Confused
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chksix
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 6:52 pm

Quoting Troubleshooter (Reply 8):
Quoting Chksix (Reply 7):Isn't this used already in the inlets of jet engines to control the boundary layer?
http://www.airliners.net/open.file/1090718/M/
See the inside of the cowling.
The purpose of the holes in the B737 air intake is to reduce noise.

I don´t think they do the same on the good old F4. It must be noisy !!!

Hi,
I've read that those panels have suction or a low pressure behind them for boundary layer control. It can't be just noise reduction IMO.

I assume that the fan would lose a lot of efficiency if part of the flow was turbulent in the inlet.
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Starlionblue
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 8:00 pm

Quoting BAe146QT (Reply 13):
Quoting Starlionblue (Reply 9):
people who know a lot about xxxxxxxxxxx and not a lot about real world xxxxxxxxxxx operations.

They're called "middle management" and they usually have business school diplomas.

Hey, you're describing my wife  Wink You'll be glad to hear she works nowhere near the airline/aerospace industry. Big grin

Quoting JetMech (Reply 16):
Quoting Starlionblue (Reply 9):
I believe CX did some sharkskin experiments.

G'day Starlionblue Smile. Was that an experiment only? I seem to remember that the fuselages of Airbus were covered in some sort of "micro-riblet" film

By "experiment" I meant "in service trial". But I have no further info I'm afraid.
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troubleshooter
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 8:50 pm

Quoting Chksix (Reply 17):
Hi,
I've read that those panels have suction or a low pressure behind them for boundary layer control. It can't be just noise reduction IMO.

Definately not on the B737! They are "just" acoustic panels. Inside the small holes the airflow creates small vortices thus increasing static pressure resulting in a temperature increase. You can say that noise is transferred into heat. All this happens inside these holes. End of story.

As I wrote earlier I´m not sure if they serve the same purpose on the F4 air intakes. These intakes are designed for mach 2+ and are not comparable to those on the B737.
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aeroweanie
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 9:23 pm

Quoting Troubleshooter (Reply 19):
Definately not on the B737! They are "just" acoustic panels. Inside the small holes the airflow creates small vortices thus increasing static pressure resulting in a temperature increase. You can say that noise is transferred into heat. All this happens inside these holes. End of story.

The holes in the panels on jet engine inlets have tiny cavities behind them, tuned to absorb noise at the frequencies transmitted by the inlets. The cavities are called Helmholtz Resonators.

Quoting Troubleshooter (Reply 19):
As I wrote earlier I´m not sure if they serve the same purpose on the F4 air intakes. These intakes are designed for mach 2+ and are not comparable to those on the B737.

On the F-4 inlet ramps, the air is sucked into the holes to surpress boundary layer separation caused by the shocks used to slow down the flow into the inlets at supersonic speeds.

In the test panels, flown for example on the JetStar, less air is sucked into the holes. The idea there is to stabilize the laminar boundary layer and delay its transition to a much draggier turbulent boundary layer.
 
chksix
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RE: Holes In Airplane Wings To Save Fuel

Sun Oct 22, 2006 9:27 pm

Thanks for those clarifications.
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eatmybologna
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RE: Holes In Airplane Wings To Save Fuel

Wed Oct 25, 2006 6:34 am

Dennis Connor did this once with his America's Cup 12 meter racing yacht.

NF 203
October 1993
NASA RIBLETS FOR STARS & STRIPES

America has won an Olympic medal and the America's Cup thanks to the same NASA technology that is saving commercial airlines hundreds of millions of dollars annually.

On February 4, 1987, skipper Dennis Connor and his ten-man crew guided the Stars and Stripes racing yacht past the finish line at Fremantle, Australia, to recapture sailing's most coveted prize, the America's Cup. Representing the San Diego Yacht Club, Connor and Stars and Stripes scored a 4-0 sweep in the best-of-seven finals over Australia's Kookaburra III.

Stars & Stripes
The hull's underside was coated with a "riblet" skin
that helped the craft slide through the sea more smoothly.
(photo credit: Sally Samins - PPL MEDIALINK)

A key piece of NASA technology assisted in the win. Stars and Stripes design coordinator John Marshall disclosed the boat's "secret weapon" as the hull's underside, coated with a "riblet" skin that helped the craft slide through the sea more smoothly.

You can read the rest of it here..

http://www.nasa.gov/centers/langley/news/factsheets/Riblets.html
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prebennorholm
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RE: Holes In Airplane Wings To Save Fuel

Wed Oct 25, 2006 8:08 am

50 micron holes for boundary layer suction: Corrosion, crack development, paint, dirt, combine with anti icing heating, no, I don't see it happen.

And as AeroWeanie wrote, the idea is as old as fast flight itself.

NASA tested it on a special transport optimized wing mounted on an F-8 Crusader some 30 or 35 years ago. The results were inconclusive.

If the wing is not perfectly shaped, not polished as a mirror, if it it wet (rain, flying through clouds), if rivets are not completely flush, if the leading edge has collected dead insects, etc. etc... Then it all comes to nothing. Except for the weight penalty for the suction machinery, the vacuum tubing etc.

Anyway, one offspring from the idea has been used during the last 20 years or so with positive effect to energize the boundary layer on practically all competition glider aircrafts: Zig-zag tape mounted where transition from laminar to turbulent flow is expected. That at least minimized the size of separation bubbles.

That can hardly be copied with any effect on transport planes. They operate the wings at much higher Reynolds numbers at which separation bubbles are almost non-existant.
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aogdesk
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RE: Holes In Airplane Wings To Save Fuel

Wed Oct 25, 2006 9:13 am

Got so excited after reading the title of this thread that I ran out and drilled .125" holes all over the wing of a 737. Guess I should have read further huh?  Wink
 
787atPAE
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RE: Holes In Airplane Wings To Save Fuel

Wed Oct 25, 2006 9:22 am

Sounds like y'all are describing the "suck and blow" method of boundary layer control. I heard about this for my BS degree, and the prof let it be known that, although this is a great idea, and worked wonders, the implementation and maintenance on keeping the holes free of trash, dirt, etc, was a nightmare!!!
 
LimaNiner
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RE: Holes In Airplane Wings To Save Fuel

Wed Oct 25, 2006 1:02 pm

Quoting Eatmybologna (Reply 22):
Dennis Connor did this once with his America's Cup 12 meter racing yacht

Yeah, but: AC yachts are basically disposable (they have to last less than a year), and the "riblets" used on Connor's yacht weren't "active", i.e., not fluid was blown or sucked through the riblets.

Quoting 787atPAE (Reply 25):
"suck and blow" method of boundary layer control. I heard about this for my BS degree, and the prof let it be known that, although this is a great idea,

Careful about profs who tell you that "suck and blow" is a good idea, especially if it involves your grades!!  Wink
 
aeroweanie
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RE: Holes In Airplane Wings To Save Fuel

Wed Oct 25, 2006 1:41 pm

Quoting Prebennorholm (Reply 23):
NASA tested it on a special transport optimized wing mounted on an F-8 Crusader some 30 or 35 years ago. The results were inconclusive.

What NASA tested on the F-8 was a wing using the then-new supercritical airfoil. They actually first tested it on a T-2 Buckeye. The supercritical airfoil concept is now used on most modern airliners (777, A320, A330/340, etc.).

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The hybrid laminar flow via suction has been tested on many aircraft, including the JetStar I mentioned and a very hacked up B-66, the X-21A:
 
oly720man
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RE: Holes In Airplane Wings To Save Fuel

Wed Oct 25, 2006 5:28 pm

Our previous prof was looking at this over a number of years and, yes it works, but it's maintenance intensive as well as being marginal on efficiency, once you've taken the suction pump into account and pipework losses. It was shown that laminar flow could be maintained with simulated dead insects on the leading edge just by increasing the suction rate. But there's always the problem of blocked holes. As the holes get smaller, much higher pressure is needed to blow them clean.

Another problem with the laser drilling of the holes is that the holes aren't smooth and are more conical in profile than cylindrical.

Also it's not a system that can be easily retrofitted on wings. We had some involvement with RR on engine nacelles, looking at the possibilities there, but it's come to nothing so far.

As far as aircraft are concerned this technique would be a lot more effective on a flying wing than on a conventional aircraft because the wing area that could have reduced drag is a lot bigger. On a conventional aircraft there is little that can be done to reduce the drag on the fuselage, simply because it's so long, and that's about the biggest contributor to the drag of the aircraft.

And in the end there is the issue of safety. Will the aircraft performance be compromised if the system stops, or efficiency reduces?
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BAE146QT
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RE: Holes In Airplane Wings To Save Fuel

Wed Oct 25, 2006 8:30 pm

Imagine how much would be saved if they drilled holes all over the plane?

Better yet, make it out of chicken wire so we can test the theory about 100,000 pigeons taking off in the hold.
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HAWK21M
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RE: Holes In Airplane Wings To Save Fuel

Wed Oct 25, 2006 11:43 pm

Quoting BAe146QT (Reply 29):
Imagine how much would be saved if they drilled holes all over the plane

You'll end up flying it unpressurised then.
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MEL
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BAE146QT
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RE: Holes In Airplane Wings To Save Fuel

Thu Oct 26, 2006 1:36 am

Just kiddin, Mel.

There was a thread (or three) about what would happen to the weight (not mass) of an aircraft it it was full of birds, and all the birds took off... inside the plane. There was a sugestion that it would only make a difference if the aircraft was made of chicken wire.
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prebennorholm
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RE: Holes In Airplane Wings To Save Fuel

Thu Oct 26, 2006 2:12 am

Quoting AeroWeanie (Reply 27):
What NASA tested on the F-8 was a wing using the then-new supercritical airfoil.

Thanks AeroWeanie, my bad!

I totally mixed up the the NASA F-8 supercritical test aircraft and the Air Force X-21A laminar flow test aircraft.

As the decades flow by, the menory gets rusty.
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