Flying wings have been around since the 1950's and lifting body concepts for at least 30 years. The biggest problem is the same as the Concord - the lack of flaps means landing must be in an extreme upward pitched condition in order to achieve the same landing speed as an aircraft with flaps.

The Concord used a rotating nosepiece so the pilot can still see the runway but without that you either need a very high bubble cockpit or high landing speeds, which of course decreases safety and increases runway length requirements.

One of the other issues is for passenger comfort. Typically aircraft with conventional wings and a tail have higher wing loading and are less prone to getting tossed around in turbulance. A low wing loading design (as a lifting body, flying wing structure with a low landing speed would be) would tend to get tossed around by turbulance a lot more. People would very likely be willing to pay more just to keep from having to fly on something that will make them sick.

Lastly, take a look at the most efficient aircraft of all - gliders. None of those are a lifting body or flying wing design. Gliders are so aerodynamically efficient that they need no engine and can gain altitude merely through heat pockets over the ground. Gliders demonstrate there is great inherent efficiency to the "wings on a tube" style of aircraft.

Sid that was interesting to read. I thought that the whole point of flying wing or lifting body was that everything that produces drags is also part of the lifting system. Gliders are impressive, they often fly over the local ski area. But when an aircraft is really large and heavy exotic designs like this pay off. Turbulance on an aircraft weighing 6 digits is different than on small aircraft. That and the fact that aircraft cruise pressurized to 'get over the weather' makes turbulance less of an issue.

Here's how I read this one. The Airbus A380 is awsome. The A380 can carry more people/cargo farther than a Boeing 747-400 and be more efficient doing it. The Airbus A380 was designed with an aluminum wing to save money. Not having the more expensive composite wing made the aircraft heavier but still beat the current champ the Boeing 747-400. That left the door open for boeing to design a new composite 747-800 that is more efficient than the A380 and didn't break the bank designing an whole new aircraft. Boeing had already bought Northrup and hence the B2 Spirit bomber all composite technology. The B2 is a heavy bomber that cost more than it's weight in gold to build. Actually 90% was designing the technology. Now Boeing could adapt a composite wing with the new 787 Dreamliner and upgrade the 747 to the new 747-800 composite standard.

Airbus spent something like 10 Billion dollars on the A380 and that money saving heavy metal wing is biting them in the ass now. To come up with a new generation of A380 when this one isn't paid for yet... Now Boeing are spending there money and time getting the next generation of engineers to see their good work. As for ultra high bypass engines that's great. The more air pumped by fans the more efficient the emgine.

The article mentions that the SAX-40 will be about 25% more fuel efficient than comparable current aircrafts.
So maybe the figure of 201 passenger-miles per US gallon
(for current aircraft) is wrong ?
If the predicted fuel consumption for the SAX-40 is
124 passenger-miles/US gallon, then,
the consumption for comparable current aircraft is perhaps about 99 passenger-miles/US gallon ?

Sid made a good point that this new design does not necessarily reflect the most efficiently-possible design. Indeed, the article states that the estimated passerger-mileage for this new design is 149pmi/ImpGal, whereas the most efficient in this class (?Boeing 787?) can get 201pmi/ImpGal. Of course, in their research before building the Dreamliner B-787, the most efficient and best-selling new airliner todate, Boeing has looked at BWB concept, among others, and deemed that the conventional configuration still represents the most efficient possible.

The main advantage of this new BWB concept as stated in the article is noise reduction.

However, I see potential problem in the turbofan intake placed above the aft fuselage section. At high enough angle of attack, or with wind gust or atmospheric turbulences, there may be enough airflow separation in the aft fuselage area to stall the turbofan blades on the center engine, and that'll mean impaired takeoff performance. The two outer engines have intakes that could be behind the path of the vortices that would be formed at the junction of the wing to the fuselage at the angle of attack typically required for takeoff and climb. This is turbulent air and may not be good for the fan blades. Hopefully, the vortices would move outward enough as they move backward and will miss the engine intake entirely. Furthermore, if ice is formed in the front fuselage and breaks loose and travels on top of the fuselage to the back, some of it may be ingested by the turbofan blade, and that would be major bad news.

the passenger capacity of the B-787-9 and multiply by the max range and divide by the total fuel load reveals only 63 pmi/USgal for the B-787

That's assuming that all the fuel gets consumed, which it doesn't. Even so, at maximum seating, range, and fuel capacity numbers, the 787-9 would rate at 72.6 passenger-miles/gallon, not 63.

CNN quoted a Boeing spokesman giving a figure of 100 passenger miles per gallon for the 787.

Does anyone know what the equivalent passenger-miles/gallon are for various high speed rail systems around the world? I've seen something like 250pmpg for local rail, but the system is too small to be an effective alternative.

Of course a 1.5 hour flight is no longer a 1.5 hour flight. It's half an hour or more to the airport, half an hour to find parking (no rapid transit yet), 30 minutes to get checked in, another 30 minutes (or longer) to get through security, 15 minutes to board, 1.5 hours of flight time, 1 hour of luggage retrieval and then another hour by cab, rail of transit to where you're going. Trains are so civilized.

Boeing does not own Northrop

pose significant threat, mechanically, to the engine. I owned a slipstream genesis aircraft with a pusher propeller. The prop was in the most aerodynamically dirty position it could possibly be in, and the plane shook all over during taxi and ground roll (smoothed sid hoffman - The blended wing body is fantastic at stall recovery, I watched an engineer throw a small BWB mockup into a vertical wind tunnel, spinning it like it was a boomerang. The 3 foot wide mockup stopped spinning,aimed itself down at about a 60 degree angle and sat perfectly stable in the upward airstream.

BTW, there are alot of flying wing gliders out there.

roger pham- The engines being in an aerodynamically "dirty" location during rotation for takeoff doesn't out once you were in flight). It never had any effect on the reliability of the engine.

I agree with you on the ice though.

Northrup was aquired

I'm going to have to second Neil on the trains... while they aren't nearly fast enough for coast to coast travel, they would be really nice within the area east of the Mississippi, and they can take you right into city center instead of leaving you with a 1 hour journey after getting off the plane. Too bad Amtrak is so bad and there's generally no other options. Bear in mind that both airports and airlines are hugely subsidized, while Amtrak is weakly subsidized and has to make do largely with renting tracks owned by freight lines.

I too do not understand the reasoning behind having three engines. If either of them stops the control of the plane must be very difficult indeed. The best approach would be to use only one engine and to direct the thrust such that better control is achieved at lower speeds which will decrease the needed runways and the noise at take of and landing.

Regarding the danger associated with ice i think this problems boils down to inspection control and proper preparation. If this is done correctly ice will not pose a safety problem.

Turbulence at take of is also a minor risk since we are talking about a plane with considerable enertia. Never the less i would prefer directional thrust to exert greater control faster and i think the added cost is very well spent as this will provide access to smaller airports with shorter runways.

I find it strange that they even bother to put pilots up front. Cameras are far cheaper than cockpit windows and can provide better information, so in fact the cockpit could be anywhere.

Regarding power efficiency I think it should be considered to fly at higher altitudes which may imply that a Stirling engine should be considered because they increase thrust with altitude because of the wide temperature span between combustion and ambient temperature at high altitudes. Also their external combustion is super silent and vibration free.