Airliners.net

http://news.bbc.co.uk/2/hi/business/6113418.stm

Quote: More and more of us fly every year. As we do so, the political pressure to act to curb greenhouse gas emissions from planes is rising.

Eh? Here in the US our conservative politicians couldn't seem to care less about emissions. I never hear about new measures for reducing plane emissions in the domestic news, and the US members of this forum tend to brush aside any suggestion that anything serious needs to be done. Too bad we have the largest airline market in the world.

Quote: The Silent Aircraft Initiative (SAI) team has succeeded in coming up with a radically quieter plane. Crucially, the SAX-40 is also 35% more fuel-efficient than any airliner currently flying.

I wonder how this compares to the expected increase in passengers numbers.

Quote: For manufacturers, it is much safer to develop new airframes out of what has gone before, rather than re-tool completely with a brand-new production line. Yet with increasing concern over climate change, we could see a radical shift in aircraft design. This would be more likely if airlines had to pay "green" taxes on their airliners' emissions of greenhouse gases. But the skies are not going to fill with radically new aircraft shapes any time soon. When an airline buys a new plane, it will keep it flying for decades in order to make it pay its keep. Which means even if this design gets the thumbs-up from the manufacturers, we won't be queuing up to board planes like the SAX-40 before 2030 at the earliest.

So, anybody want to guess that we'll have 35% more passengers by 2030, thus completely negating any possible benefit this design might have given us? The environment is a joke, a marketing tool, a bullet point on a brochure and nothing more. Trust me folks, the battle is over. The cronies won. You can vote with your ballot, you can vote with your dollars, none of it will change anything. We're all on a slow march to a more polluted planet and nothing can change our course at this point.

MIT/Cambridge To Unveil "silent" Flying Wing 11/06 (by Lemurs Nov 6 2006 in Tech Ops)

I know there will be people who think this has been tried. Research is not about producing a guaranteed profit and success, that would be prefered but not always the case. In the field of unknowns, nothing is proven, how else to see what works?

No, I am not stupid enough to lump all BWB studies together and think it's been tried and thus we know the result. Research is never discarded, someone with an idea always picks up after the other guy left off.

I think this design is already a compromise with earlier more radical BWB designs that have been floating around during the last decades.

An ongoing development I think is the fact many important airports have been pressured by their communities to restrict noise. So noisy aircraft are not forbidden just not welcome on some very important airports. That makes airlines demand manufacturers to come with more quiet aircraft / engine technology.

It s not hard to sum up disadvantages of BWB design (on board logistics, pressure cabin, stretches etc.) but theoretically is seems a way to substantially reduce fuel consumption.

As mentioned in the articles aircraft designers mostly cherry pick technologies from such design to make moderate improvements to existing design philosophies.

Quoting Keesje (Reply 2): It s not hard to sum up disadvantages of BWB design (on board logistics, pressure cabin, stretches etc.) but theoretically is seems a way to substantially reduce fuel consumption.

Yes, and the smallest size of plane where this would work is probably something along the lines of the A330 or B767, if not bigger. It's just not going to work with the A320/B737 types of aircraft because the "fuselage" will end up bigger.

It would certainly work as a replacement for the B747 and considering that the B747-400 does not come in stretched versions like the A340-3/5/6 it can't be argued that the fuselage is an issue. It's then down to either the regulators forcing the issue or the airlines biting the bullet and forcing 300 passengers to sit in 15x20 rows with no windows.

Quoting Keesje (Reply 2): That makes airlines demand manufacturers to come with more quiet aircraft / engine technology.

We've got a research student just started at our lab and he's looking at how to make the undercarriage quieter. All those circular cylinders, struts, etc are a great source of noise.

Check out this lecture (a video webcast) given by Dr Tom Reynolds at Trinity College entitled "The future of civil aviation - the approach of the silent aircraft".

http://www.sciencelive.org/component...encelive/task,view/id,35/Itemid,26

Got the link from the cambridge website.

Quoting TropicalSQ744 (Reply 4): Check out this lecture (a video webcast) given by Dr Tom Reynolds at Trinity College entitled "The future of civil aviation - the approach of the silent aircraft".

Looks interesting, but I can't get the audio to work.

Quoting SATX (Reply 5): Looks interesting, but I can't get the audio to work.

Worked on Quick Time, but not well.

Qoute from the brochure: "some of the aircraft boundary layer flow is ingested into the engines, increasing propulsive efficiency and reducing fuel burn"

Shouldn't it be the opposite since the boundary layer is low energy air?

While that is a nice BWB, its got a few flaws in the design. I'll just point to the most difficult part of BWB opperation: certification for evacuation. Due to the above fusalage engines, an overwing exit is certain to be not allowed.

Yes, a BWB cuts fuel burn over similar generation "cigar with wings" designs. I think we'll see one by 2025.  

But why replace the A380 this early? Quite bluntly, a BWB does not acheive its promised fuel savings until its a 500+ seater! Should one be built? Yes. But more 200ft wide runways are needed. Oh, did the article forget to mention they need wider runways?

I hope I didn't come across as too negative. We will have BWB's soon. But I keep seeing the "gee wiz" studies when what is truly needed at this point is an evacuation plan. Once a good concept for evacuating a BWB is arrived at, then its just an engineering problem to make one. Heck, McDonel Douglas had BWB designs. Its not a new concept.

Quoting TropicalSQ744 (Reply 7): Shouldn't it be the opposite since the boundary layer is low energy air?

Yes, sometimes research agencies get so obsessed with airframe aerodynamics that they'll kill the propulsion efficiency. The design shown was obviously done by military researches. For a stealth aircraft, the cut in radar signature is worth the hit in fuel burn.

Lightsaber

Quoting Lightsaber (Reply 8): While that is a nice BWB, its got a few flaws in the design. I'll just point to the most difficult part of BWB opperation: certification for evacuation. Due to the above fusalage engines, an overwing exit is certain to be not allowed. Yes, a BWB cuts fuel burn over similar generation "cigar with wings" designs. I think we'll see one by 2025. Smile But why replace the A380 this early? Quite bluntly, a BWB does not acheive its promised fuel savings until its a 500+ seater! Should one be built? Yes. But more 200ft wide runways are needed. Oh, did the article forget to mention they need wider runways?

I think the point is this was a design study done with its only goal to produce a "best-case" scenario in terms of both noise and fuel efficiency. The article does say this is a ways away from producing a "marketable" airplane.

I do agree that the concept of a blended-wing design is not new, and that to an extent it's not really all that helpful to come up with another one without regard to practicalities. But it seems that the difference here is that there were real aircraft and parts manufacturers involved, such that this design - while not conforming to safety standards or what passengers would demand in terms of comfort - *is* basically a practical design. It's not simply a wind tunnel model; it's got practical technologies built into it with the help of the real manufacturers that would be involved in producing it. That's a step beyond most BWB designs. The next step would be to try to adapt safety certifications and passenger amenities.

There are a lot of obstacles to making BWB designs acceptable to the airlines, the various airport authorities, and the public. Over time, though, new technologies will help overcome at least some of those obstacles. LCD displays could now simulate windows in interior compartments, for example. But yes, there are other obstacles that would be more difficult to overcome; no doubt that's why they estimate 2030 as the earliest date such a plane could debut. But I do think it'll happen at some point.

Quoting SATX (Thread starter): I never hear about new measures for reducing plane emissions in the domestic news, and the US members of this forum tend to brush aside any suggestion that anything serious needs to be done.

If I recall, the 787 incorporates features that would minimize emissions (as part of the better fuel efficiency, I would imagine). Likewise, manufacturing processes have greened. I don't have it on my fingertips, but there are Boeing references to that.

There is an old archived thread (last Spring?), I have bookmarked on my home computer, citing a Seattle newspaper story on Boeing's new energy efficient and environmentally friendly experimental designs (code named after Muppets, if that rings anyone's bell). Some way-out designs, not BWBs. I'd like to see them happen.

-Rampart

Quoting Spacecadet (Reply 9): I think the point is this was a design study done with its only goal to produce a "best-case" scenario in terms of both noise and fuel efficiency. The article does say this is a ways away from producing a "marketable" airplane.

Quoting Spacecadet (Reply 9): The next step would be to try to adapt safety certifications and passenger amenities.

If they take that 2nd step, I withdrawl any negative comment I made.  

Seriously, I am a huge fan of the BWB concept. But I keep seeing money thrown to improve the parts that are already way ahead of the "cigar with wings" aircraft. If governments really want to help, it will be to take that next step toward practical implimentation. There is a good decade of R&D ahead for that.

What I really like about the BWB:
1. Incredible aerodynamics. The required thrust at cruise is amazingly low.
2. Nice structural efficiency. Due to wider sections taking the wing root moment, tremendous weight savings.
3. Large hauling ability.

Another aspect that needs more research: Takeoff and landing performance. Why? BWB's tend to be engineered for cruise. However, its possible that since this study was highly noise focused that they addressed that portion.

Again, I love the idea of a BWB. This configuration doesn't place the engines where I would... but that's an easy change.   Its possible the best compromise might be an L1011 type inlet duct...    Or elevated engines with a "work platform" around the engine base... (Or seats in the nacelle a la MD-95/B717.)

Quoting Spacecadet (Reply 9): LCD displays could now simulate windows in interior compartments, for example.

Excellent point. In fact, wouldn't camera selection from your seat be better than a window? Put a camera pointing forward, down from the nose (perhaps the landing camera the pilots would be using or one placed next to it?), One pointing out and down from each wing and one aimed at the horizon from each wing.   Perhaps even a tail camera... I would love all of that!

Besides, I can only imagine LCD/display technology circa 2025!   

Now if they would just put a cupholder in the seats.  

Lightsaber

Quoting Oly720man (Reply 3): Yes, and the smallest size of plane where this would work is probably something along the lines of the A330 or B767, if not bigger. It's just not going to work with the A320/B737 types of aircraft because the "fuselage" will end up bigger.

And in the future (25+ years) we will more likely see an even higher proportion of A320/737 size aircraft than 767/A330 size aircraft (even more than in B's GMO).

Quoting Lightsaber (Reply 8): Yes, a BWB cuts fuel burn over similar generation "cigar with wings" designs. I think we'll see one by 2025.

But probably only as a strategic military aircraft and perhaps, eventually, as a civilian cargo aircraft.

Mike Bair addressed pax BWBs in one of his blogs and said that he didn't see pax versions in Boeing's future.

Quoting Lightsaber (Reply 11): 2. Nice structural efficiency. Due to wider sections taking the wing root moment, tremendous weight savings.

However, as materials science continues to improve, the weight saving differrential will become less and less. On the other hand, there is no such thing as a BWB "simple stretch or shrink" and engineering and manufacturing costs would be much, much higher for a family of BWBs vs tube and wing aircraft.

Aviation Week had a nice wrapup of the environmental issues titled "dishing the Dirt" in their July 17 issue. The article says that aviation historically improves engine efficiency about 1.5% per year, but traffic grows at 5% a year. Thus, while pollution per passenger-mile has been greatly reduced, total pollution by aviation has grown. Aviation's share of total greenhouse gas emissions is about 3%. A meaningful reduction of this number is very hard to achieve.

The best the industry can do is state that its pollution is modest compared to other sources. In the transportation sector, for example, aviation produces 12% of emissions while automobiles produce 80%.

Conclusion: while aviation is a minor source of the overall pollution problem, there is no easy way to reduce total aviation pollution based on current technology without grounding airplanes.

All of the above is from the article. Please don't shoot the messenger, unless you think I've misinterpreted the article.

The cabin design is just as crucial.

Pitch-friendly seats
Aggressive use of sleepers above/below the main deck
Eliminating overhead space in favor of berths

this can push existing frames up in efficiency.

Quoting MasseyBrown (Reply 13): In the transportation sector, for example, aviation produces 12% of emissions while automobiles produce 80%.

There is a lot more potential to reduce pollution per car than aircraft. Only now are we seeing that even large, powerful cars (Toyota Camry Hybrid) can get 40 MPG, a 100% improvement in efficiency compared to a 20 MPG car or SUV. So if push comes to shove, that's easy.

Electric cars are going to come out too. With 300 mi range per day, they can handle anything but long road trips. Or virtually all car duties. All with zero petroleum. According to Tesla Motors, their prototypes are 2x as efficient as hybrids, because electric plants are so thermally efficient compared to car engines.

Aircraft are so heavily optimized already, no big efficiency gains (+30%) are in the cards. Aviation regulations can't hope to raise aircraft efficiency. Instead, they can tax aviation for the pollution they cause, unlike today, when aviation pollutes without being taxed for it (unlike cars).

Aviation is important. That is why people will happily pay the relevant taxes in order to fly, and nothing bad would really happen - except slower growth. The same is true with cars - if we eliminate fuel taxes, growth rates would increase. But that is not what we choose to do.

I personally love the headline CNN used for the article "Silent plane would cut airport noise".

Who would ever have guessed that a lack of noise would result in a lack of noise?

Well, we have submarines that can displace thousands of gallons of water per second as they cut through the ocean at 20+ knots in absolute silence. Water even conducts sound better than air, and air is commonly visualized as a fluid in aerodynamics.

Over the next 20-30 years, I don't think it is an exaggeration to anticipate large commercial aircraft that don't produce noise significantly over background levels.

Quoting Supa7E7 (Reply 15): Electric cars are going to come out too. With 300 mi range per day, they can handle anything but long road trips. Or virtually all car duties. All with zero petroleum.

The next problem being: where do we get clean electricity for such vehicles?

Swapping an internal combustion engine for fossil-fuel electricity doesn't provide much more than a marginal reduction in pollution or energy dependence.

Quoting DfwRevolution (Reply 17): Over the next 20-30 years, I don't think it is an exaggeration to anticipate large commercial aircraft that don't produce noise significantly over background levels.

There are already landing approaches that have been experimented with would allow airliners to "glide" to a touchdown. There was a recent article about UA testing such a procedure on their Narita-SFO flight.

Quoting DfwRevolution (Reply 17): The next problem being: where do we get clean electricity for such vehicles?

Well, burning gas natural gas at a power plant to generate electricity for electric cars is still less wasteful and less polluting than using IC engines in the first place. However, as far as alternative energy sources to fossil fuel fired generating plants, a combination of solar, wind, bio-fuels, etc., plus increasing energy efficiency, will provide all the energy that will be required in the future.

Quoting DfwRevolution (Reply 17): The next problem being: where do we get clean electricity for such vehicles? Swapping an internal combustion engine for fossil-fuel electricity doesn't provide much more than a marginal reduction in pollution or energy dependence.

You are right, but look again. Coal plants are more efficient than your average ICE. That is where the magic happens. Electricity is just a means to get the power plant's energy into your car. The advantage being power plants can be nuclear, or indeed wind.

I am no engineer at all but coal plants are apprently very efficient compared to my car engine in terms of fuel, output and emissions.

In the 1960s we didn't have computers powered by batteries. Now we do. Apparently cars are going to do this soon.

Check out this amazing chart at Tesla Motors

Deep into the future I think it's possible we can see aircraft powered by stored electricity/energy. You need a way to dump let's say 10 megawatt hours of electricity into a plane and fly it. Given a storage technology that can handle that, we are in business. The problem remains, aircraft consume so damn much energy.

[Edited 2006-11-06 22:29:59]

Quoting Supa7E7 (Reply 19): Check out this amazing chart at Tesla Motors

FYI, there is another California company that is coming out with an electric car next year.

Quoting Supa7E7 (Reply 19): Deep into the future I think it's possible we can see aircraft powered by stored electricity/energy.

I know that you are referring to commercial pax aircraft but it is still interesting that Boeing carried out a research project 2 years ago that put an electric motor into a Diamond Katana!

Emission's can be cut significantly if the World wakes up , spends the billions and billions to develop nuclear power plants , Sets up IAEA to enrich Uranium for all nations ( therefore no dual use issues) . US can do with a lot more Nuclear Plants heck we havent build new ones since ages (although a couple are in the pipeline) . If we deal it through that front we are Ok , airliners are getting more eff. on accounts of burning less fuel , look at the Dreamliner it burns 20% less fuel then its Legacy competitor and the A350 will do the same , Between them they are likely to sell something like 3000-4000 Aircrafts , DITTO with the future aircrafts which have an even bigger market . The whole Packing in Fuel cells etc into planes is something way out into the future whereas Nuclear Power is something that exists today and is grossly underutilized.

Quoting Lightsaber (Reply 8): But more 200ft wide runways are needed. Oh, did the article forget to mention they need wider runways?

I don´t seem an automatic requirement for that. It seem they have choosen a kind of oval pressure cabin for this aircraft



There is also a video animation and more details on flight

http://www.flightglobal.com/Articles...e%2c+energy-efficient+blended.html

The silent aircraft initiative design as depicted is an academic pipe dream.

787/350 generation planes will produce less than 85dB noise with the noise footprint completely inside the airport perimeter fence.
85dB is about the noise level generated by the freeway surrounding your average airport. Not much use in making the airplane quieter than that.

As others have mentioned, the BWB isn't that great a passenger transport unless you have something to fill all the unusable volume with -> e.g. hydrogen tanks.

If the depicted scoop intakes are meant to supply the engines with sluggish boundary layer air, I'm afraid fuel efficiency won't be anywhere near what's claimed.

Good night...

Quoting Rheinbote (Reply 23): 85dB is about the noise level generated by the freeway surrounding your average airport. Not much use in making the airplane quieter than that.

Not necessarily true. There are several major airlines facing noise constraint issues with hundreds of yards from the runways their aircraft use.

Just one example of many: leaving DAL or MDW you are over populated areas just moments after take-off. At DAL, there is virtually no runway perimeter and we all know how narrow the runway margins are at MDW.

Noise reductions past 85 db would go a long way to improve community relations for these airlines and allow capacity growth without infrastructure development. Granted, the above example involves short/medium-haul aircraft and not the long-haul aircraft germane to this topic...

Quoting Supa7E7 (Reply 19): You are right, but look again. Coal plants are more efficient than your average ICE. That is where the magic happens.

Yes, I realize that:

"Swapping an internal combustion engine for fossil-fuel electricity doesn't provide much more than a marginal reduction in pollution or energy dependence."

There are gains to be made, but I haven't seen an analysis of electric vehicles tied to fossil-fuel powered grids are much more efficient than serial ICE/hybrid. Granted, no serial hybrids are in the showrooms, but it's a technology that could be implemented very quickly if either Toyota, Honda, or Ford so desired...

Quoting DfwRevolution (Reply 24): Granted, no serial hybrids are in the showrooms, but it's a technology that could be implemented very quickly if either Toyota, Honda, or Ford so desired...

For the latest info on PHEVs go to...

http://www.calcars.org/

Great info on 100+ mpg plug-in hybrid cars that are on the road now.

Quoting DfwRevolution (Reply 24): "Swapping an internal combustion engine for fossil-fuel electricity doesn't provide much more than a marginal reduction in pollution or energy dependence."

Natural gas is a much better fuel source than gasoline. And if you look at start to end pollution and energy consumption, the ICE isn't even close.

There's a lot of info at this site...

http://www.pluginpartners.org/

we just need a government - like the UK one which is loving the environment right now, to just invest money in it, in kinda like Concorde, but hopefully it would be more successful!

then maybe some people would buy it, and not just BA as a gimmic!

Quoting SATX (Reply 5): "The future of civil aviation - the approach of the silent aircraft". Looks interesting, but I can't get the audio to work.

That's ironic. You couldn't hear him talk about the silent aircraft. 

I hope you realize that this all based on work by NASA, Boeing, and MIT. You were wrong to bash Americans for not doing anything. This IS American. The British joined later.

Quoting Keesje (Reply 22): I don´t seem an automatic requirement for that. It seem they have choosen a kind of oval pressure cabin for this aircraft

Maybe... I scaled the model to a 70m wingspan (then noticed the article said 67.5m...) and thus it should be able to land wherever an A380 lands. So I'll take back my comment on 200ft wide runways. This is a smaller model BWB than I've seen before. I didn't realize (until your link) that this is only a 215 passenger aircraft.

Quote: each comprising a core engine driving three 1.2m-diameter fans, resulting in a bypass ratio at take-off of 18.3:1, compared with 9.5 for General Electric’s latest GEnx.

Umm... yea. I've seen some wicked off the shelf fan concepts... Nothing considered implimentable within the next 20 years had a 18.3:1 bypass ratio for teh thrusts we're talking about. In fact, judging how small the engines are in the model, I don't know of anyone who has come up with a concept to limit losses at the compressor blade tips enough to allow that. The leak back at the compressor stages alone disallows that bypass ratio. Will bypass ratios continue to increase? Yes. But not to 18.3 in that thrust class.

Why would you put on three engines on a 215 seater?!?
I'm used to 3 engine concepts of ~650 seater BWB's. Not 215... that's too inefficient. Smaller engines have greater losses as tip clearence is a function of the current level of compressor/turbine technology. Larger engines will always have a better TSFC due to this scaling effect. (engine flow area goes as diameter squared. Engine compressor and turbine losses due to tip clearences go as per engine diameter.) Thus, for 215 seats, two engines is much more optimal.

Definately a non-practical study... I'm sorry to keep nitpicking, but any experienced senior engineer from industry would have changed quite a few assumptions. But I really like the idea of a 787 sized BWB.   

Also... by my companies design standards, the gear is too close together. A nitpick, but long gear is heavy/expensive gear.  

Quoting DfwRevolution (Reply 17): air is commonly visualized as a fluid

nitpic:
air is a gas
water is a liquid
both are fluids.  
I think you meant to point out aerodynamic models are are run in water tanks/tunnels for simulation purposes and then simularity and non-dimensionalization are used to back out the performance in air (or another gas).

Lightsaber