EZYAirbus
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20 Years Til First Silent Plane Takes Off!

Fri May 28, 2004 1:38 am

Our skies in 20 years' time could be a lot quieter, if research by engineers on "silent aircraft" really takes off.

Cambridge-MIT Institute (CMI) engineers have been working on new styles of planes that would be barely audible.

No increase in noise around airports is a key requirement for expansion plans, particuarly at Heathrow and Stansted.

Prof Ann Dowling, CMI's Silent Aircraft Initiative (SAI) leader, said it was vital to take a fresh look at aircraft design to achieve quiet skies.

If [SAI] achieves what it is setting out to do, it will mean that aircraft noise will only be a problem for people within spitting distance of the airport

John Stewart, Hacan ClearSkies
"Our hope is to ensure noise is central in future designs, and to show in conceptual design what can be achieved if you give it really high priority," she told BBC News Online.

The research includes collaboration with key industry partners, like Rolls-Royce, to use some of its design codes to fundamentally alter a number of the elements of engine technology that contribute most to noise.

Noise at take-off is generated when engine exhaust air mixes with surrounding, calmer air. High-speed fans and compressors sucking air into the engines to produce thrust also make for unpleasant high-pitched whining.

And during cruising and at landing, noise is created by airflow over the body and other parts of the craft.

The ultimate aim of SAI is to make an aircraft with noise that is "barely perceptible", or equal to normal background urban noise, Prof Dowling says.

Anti-noise campaigners have welcomed the steps SAI has made since it started in late 2003.

Starting again

John Stewart, head of Hacan ClearSkies, a lobby group fighting expansion at Heathrow, thinks SAI is the most technological initiative he has seen in decades.


Partners like Rolls-Royce expect to see technological gains
"It is a genuinely interesting initiative and, in that sense, a little bit different from some of the vaguer promises we get from the aviation industry and the government about how technology will solve everything over the next 20 to 30 years," he told BBC News Online.

"The current technology just will not do that."

But the government has now accepted that the noise climate is getting worse, says Mr Stewart, and it is planning for it.

The UK government has estimated that there will be a 4% rise in air passenger traffic every year for the next 30 years.

That makes for very busy skies, and technological innovation developed now is crucial to coping with that demand. But making noiseless planes is hard.

SAI starts with the proposition of what an aircraft would look like if low-noise was a key design requirement.

"You can't just do it by incremental changes to current designs," says Prof Dowling. "So we have started again and said what will it look like? It needs much more integration of the air frame and the engine."

It takes a long time to develop a new aircraft in aerospace, so we can't expect instant fixes

Prof Ann Dowling
Under the UK government's 30-year aviation strategy, both Heathrow and Stansted would get new runways.

At Stansted, it is estimated that 14,000 people would be affected by noisier skies.

A recent report by the Civil Aviation Authority suggested that a third runway at Heathrow could mean that, by 2015, over 800,000 people would experience noise levels above those recommended by the World Health Organization.

The Heathrow runway will not get the green light unless there is no rise in noise.

Blended approach

One of the biggest challenges is reducing the noise of aircraft on take-off, as well as reducing emissions at cruising level. For that, the aircraft geometry has to be reconfigured.

One of the most popular concepts for future aircraft has been the "blended-wing body" design, originally devised by aerospace firm McDonnell Douglas. Prof Dowling believes a blended-wing concept is a strong contender for future craft.


How Stansted is set to expand


At-a-glance

"What looked like a better starting point for us was the flying wing, where you have a triangular shape of aircraft," she explains.

"If you put engines on top of the craft rather than underneath, the air frame shields some of the sound."

It is a starting point, and within the three years SAI has to run, the final result will be different. But already, SAI's designs mean there will be a requirement for radically different aircraft.

US manufacturer Boeing has been considering blended-wing bodies that can also be altered to balance good fuel efficiency with lower noise levels.

"It takes a long time to develop a new aircraft in aerospace, so we can't expect instant fixes," says Prof Dowling, who predicts we will not see really innovative, silent aircraft over our heads for another 15 to 20 years. "But if you don't start, you don't get there," she says.

One short-term option which is being examined by the Massachusetts Institute of Technology (MIT) in the US is to change the way aircraft approach a runway.

This means existing craft would fly differently on descent, at a fixed throttle setting. Tests on a method of approach developed by MIT have reduced noise by five decibels.

Silence is golden

The development of silent planes could have profound economic impacts, which SAI is also looking at in detail, especially for the viability of an airport's location.

If there are quieter planes, people may no longer object to having an airport in their region or neighbourhood, argues Prof Dowling.

Mr Stewart agrees, although he admits it is an ambitious goal and would like to see the planes working in the flesh - or metal - before being convinced.


SAI's developments look far beyond even the new planes about to come into service
His concern is that silent aircraft design will give airlines an excuse to bring in many more planes.

If the new technology produces planes as quiet as the engineers are now proposing, more planes may not be a problem in noise terms.

"If [SAI] achieves what it is setting out to do, it will mean that aircraft noise will only be a problem for people within spitting distance of the airport. That's a fundamental change."

While it is a vision groups like Hacan might well welcome, in the short and medium term, the problem of air noise remains, explains Mr Stewart.

SAI is a £4m academic and industry-supported project at CMI, building on previous research which developed computer models for noise reduction.

http://news.bbc.co.uk/1/hi/sci/tech/3749301.stm

Glenn
http://www.glenneldridgeaviation.com
 
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RE: 20 Years Til First Silent Plane Takes Off!

Fri May 28, 2004 2:23 am

and 20 years until the last drop of oil is sucked from the earth
 
cancidas
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RE: 20 Years Til First Silent Plane Takes Off!

Fri May 28, 2004 3:16 am

ok, so how do they plan on doing that?
"...cannot the kingdom of salvation take me home."
 
Rick767
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RE: 20 Years Til First Silent Plane Takes Off!

Fri May 28, 2004 3:19 am

"and 20 years until the last drop of oil is sucked from the earth"

They've been saying that for 20 years...
I used to love the smell of Jet-A in the morning...
 
MEA310
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RE: 20 Years Til First Silent Plane Takes Off!

Fri May 28, 2004 4:20 am

That would be a sad day,hearing a plane roar down the runway or another flying by is just awesome,a silent plane would suck all of the excitement.

MEA31-
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SSTjumbo
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RE: 20 Years Til First Silent Plane Takes Off!

Fri May 28, 2004 5:27 am

The ultimate aim of SAI is to make an aircraft with noise that is "barely perceptible", or equal to normal background urban noise, Prof Dowling says.


Then the urban rats surrounding the airports must revert to complaining about the background urban noise. We can't have that, can we?
I don't know, so this is my signature.
 
QantasA332
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RE: 20 Years Til First Silent Plane Takes Off!

Fri May 28, 2004 7:07 am

Why not focus first on very quiet aircraft rather than silent ones? In my opinion, it's not worth compromising other aspects of the design - and yes, I'm sure there will have to be at least a few - just for silence. The best bet would be to reach something in the middle, significantly quiter than modern aircraft but by no means absolutely silent. Most of us enthusiasts like a bit of noise, anyway!  Big grin

Cheers,
QantasA332
 
airplay
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RE: 20 Years Til First Silent Plane Takes Off!

Fri May 28, 2004 11:25 am

Someone here has never heard of "gliders"...

 Smile
 
BritPilot777
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RE: 20 Years Til First Silent Plane Takes Off!

Fri May 28, 2004 8:40 pm

Thats no fun, Hearing an aircraft coming into land out of the lands, and looking for her is the best part of visiting the airport!
Forever Flight
 
bsergonomics
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RE: 20 Years Til First Silent Plane Takes Off!

Wed Jun 02, 2004 10:41 am

It's a very nice concept. Unfortunately, the article (or the quotes therein) are contradictory. The turbulence due to a blended wing roaring (or should I say, "hushing") down the runway is not going to be much different to a 747 doing the same. On the same topic, mounting the engines above the wing is only going to make a difference once the aircraft is at altitude.

This dream of silent aircraft does not come close to reality, since the engines create thrust, which comes from air movement, which creates turbulence when it meets still air, which creates noise.

We can reduce noise levels, but we can't eliminate them using conventional methods. The only method that I can think of is using Active Noise Reduction (ANR) to blast the surrounding area with the 'opposite' noise - destructive interference. So we'll end up with 737s with 4 nacelles - 2 for the engines and 2 for the 500,000 watt JBL speakers...

(PS, there's nothing like accurate and realistic Journalism. And that is NOTHING like accurate and realistic journalism...)
The definition of a 'Pessimist': an Optimist with experience...
 
B727-200
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RE: 20 Years Til First Silent Plane Takes Off!

Wed Jun 02, 2004 12:54 pm


My simple theory = if aircraft silent, then better hope you are stationary at the gate.......
 
MITaero
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RE: 20 Years Til First Silent Plane Takes Off!

Wed Jun 02, 2004 2:12 pm

There's more to this issue - not all pressure waves create *audible* noise if the frequencies are outside a certain range. So don't be pessimistic about the future.

More on this issue: http://web.mit.edu/newsoffice/2004/planenoise.html
 
SEAPete
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RE: 20 Years Til First Silent Plane Takes Off!

Wed Jun 02, 2004 7:53 pm

I'm sure it's possible to reduce the noise of an aircraft from what there is now. They've done a wonderful job getting to stage 3 noise reduction. I always love acidemics who think that they have the answer especially with the blended wing body. Yea there's been studies on this and as efficient and noise reducing as it may be there's still problems with the concept.

Personally I think the NIMBY's should get a clue that airports are here to stay and BTW if you live in Seattle and are complaining about being near Sea-Tac maybe you should thik about the fact that when the airport was built in 1949 there were no houses near it...... Just my pet peeve.

Really there will be quieter aircraft... Silent is an good goal, but totally unreachable.

Cheers!

Pete
SEA No other place like it
 
buckfifty
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RE: 20 Years Til First Silent Plane Takes Off!

Wed Jun 02, 2004 8:31 pm

There is this article I read a couple of years ago, detailing how most of the propulsion from the B-2 bomber is used to drive generators that ionize the leading and trailing edge of the wings, which is actually then used to propel the aircraft, instead of using the actual thrust for that purpose. Almost like anti-gravitics, if I remember correctly, and extremely quiet.

If someone can find that article, that would be great.
 
QantasA332
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RE: 20 Years Til First Silent Plane Takes Off!

Thu Jun 03, 2004 7:15 am

Ah yes, electrogravitics and the B2. Apparently, the gravity around the B2 in flight is altered by positive and negative ions ejected from the leading and trailing edges of the wing, respectively, such that there is a "surfboard-riding-wave" effect and the aircraft surges forward in a way (that is, thrust is increased to a degree). I must admit that I'm pretty skeptical about this, especially because almost all the websites that came up with a search were sort of conspiracy sites...but hey, you never know...

Anyway, here's one of the articles I found. Note the articles on UFOs and their existence that can be found on the homepage  Laugh out loud...

Cheers,
QantasA332
 
buckfifty
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RE: 20 Years Til First Silent Plane Takes Off!

Thu Jun 03, 2004 7:50 am

Actually, I remember now, it was off Air International, when they ran a series on aircraft design (or something like that).

And I just did a search, and came up with a few rather serious attempts at discussing this issue. Doesn't really seem like a conspiracy...
 
QantasA332
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RE: 20 Years Til First Silent Plane Takes Off!

Thu Jun 03, 2004 7:57 am

I never said I thought it is a conspiracy, just that many (almost all) of the sites I found it on were that type of site. Myself, I'm just a bit doubtful at the moment  Big grin...

Anyway, I have sub'ed to Air International for quite a while, so if you can find out what issue it's in I'll look it up...

Cheers,
QantasA332
 
buckfifty
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RE: 20 Years Til First Silent Plane Takes Off!

Thu Jun 03, 2004 8:36 am

It was quite a while ago, I beileve it was a 'fundamentals of aircraft design' or something like that. As if I can remember the issue now, I can't even remember my mother's birthday.
 
QantasA332
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RE: 20 Years Til First Silent Plane Takes Off!

Thu Jun 03, 2004 9:23 am

I just flipped through the whole series ("Fundamentals of Airliner Design"), and I couldn't find anything on the B2's and its electrogravitics. Do you by any chance remember which general category of article it was in (aerodynamics, stability and control, propulsion, supersonic aircraft, etc...)?

Cheers,
QantasA332
 
buckfifty
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RE: 20 Years Til First Silent Plane Takes Off!

Thu Jun 03, 2004 9:30 am

No no, it wasn't from the 'Fundamentals of Airliner Design' series, but before that, there was a series on military aircraft.

Keep flipping.  Big grin
 
QantasA332
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RE: 20 Years Til First Silent Plane Takes Off!

Thu Jun 03, 2004 9:41 am

Oh okay, sorry. I think that's about as far back as my magazines go...

Cheers,
QantasA332
 
twr75
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RE: 20 Years Til First Silent Plane Takes Off!

Thu Jun 03, 2004 12:28 pm

I remember the article being discussed here. Sorry, but at the moment I don't know which issue it was in. I'll see it I can find it when I get home. If it's any help, the article mentioned a hypersonic vehicle using a laser spike to initiate a shock wave ahead of the vehicle. The shock wave produces plasma around the vehicle which the electro-hydrodynamic drive on board uses to propel the vehicle foward. The freakiest part of the article showed the ideal shape for the vehicle was a disc and that it was capable of tremendous speeds virtually silently (no sonic boom). Also, because of the EHD drive and plasma, the vehicle would have a tremendous static charge on the outside when it landed....  Wow!
Like a seagull on the MCG of life...

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