Flying-V flying wing airliner

[Arjen]

Dutch Technical University Delft, partly funded by KLM airline, is to produce a flying prototype by October - most likely a subscale (unmanned?) demonstrator.
https://www.tudelft.nl/en/ae/flying-v/

The Flying-V is a design for a highly energy-efficient long-distance aeroplane. The aircraft’s design integrates the passenger cabin, the cargo hold and the fuel tanks in the wings, creating a spectacular v-shape. Its improved aerodynamic shape and reduced weight will mean it uses 20% less fuel than the Airbus A350, today’s most advanced aircraft.
In the Flying-V – originally an idea of TU Berlin student Justus Benad during his thesis project at Airbus Hamburg – the passenger cabin, cargo hold and fuel tanks are integrated in its wing structure. The design is not as long as an Airbus A350, but it has the same wing span. This allows the Flying-V to use the present infrastructure at airports, such as gates and runways. It even fits in the same hangar as an A350. The Flying-V carries about the same number of passengers - 314 in the standard configuration – and the same amount of cargo, 160 m3. Project leader at TU Delft, Dr. Roelof Vos: “The Flying-V is smaller than the A350 and has less inflow surface area compared to the available amount of volume. The result is less resistance. That means the Flying-V needs less fuel for the same distance.”
In October 2019, researchers will present a flying prototype that will be used to test whether the Flying-V can remain stable and reliable while being flown at low speeds – during take-off and landing.

 

[cluttonfred]

Neat, though I am not sure if the advantages will justify the innovation. Engines are also much harder to inspect/maintain in that position than under the wing.

 

[totoro]

What's with the unusually long landing gear? With that sort of clearance, they could've kept the engines under the wings.

 

[galgot]

Nice ! Only thing I don't like is that blunt nose.
Indeed wonder why they put the engines above the wings.

 

[merriman]

Likely the above-wing engine placement driven by the high angle-of-attack at take-off and Landing. Engine accessibility out can be achieved after some creative mobile platform design work.

David

 

[TomS]

What's with the unusually long landing gear? With that sort of clearance, they could've kept the engines under the wings.

The engine over fuselage position is typical of blended wing-body designs, which this is clearly related to. Putting engines under a BWB aircraft apparently does bad things to lift distribution and causes a bunch more drag.

 

[flateric]

...

 

[Sundog]

Putting the engines on the top allows the wing to shield the noise to meet noise requirements and probably aids with boundary layer control over the upper surface.

Also, while this design may be very efficient aerodynamically, it's not as ideal as a BWB structurally or volumetrically. It will be interesting to see how the trade studies pan out.

 

[Orionblamblam]

In the Flying-V – originally an idea of TU Berlin student Justus Benad during his thesis project at Airbus Hamburg –

I really liked Benad's entirely original and brand new idea when he was known as Harvey Chaplin of the Davis Taylor Research Center in the 1980's.

 

[Arjen]

Benad's own website shows some videoclips of a powered model in flight - this is one of them:

You may want to turn off the soundtrack, though.

 

[TomS]

I notice that his CAD drawing of the aircraft shows much shorter landing gear. Of course, they are older but it's possible the landing gear doesn't absolutely need to be as tall as the recent images.

 

[Arjen]

Image from Benad's site:

 

[galgot]

Maybe this config is also easier i term of pressurization ? I remember reading that could be a problem when designing a BWB pressurized cabin.
Here you basically have two tubes joining at the nose.

 

[flateric]

actually engines on top are all bad from the aerodynamics POV
second, combination of lateral and transverse G - the worse case for vestibular system - will make it vomit comet
of course it will never happen as KLM and TU Delft are just not aircraft builders and everything will end with models

 

[TomS]

actually engines on top are all bad from the aerodynamics POV

Then explain why every single study of blended wing body designs that I've seen says that engines under the wing on a BWB are bad for drag. And why I can't find BWB designs with low-mounted engines. BWBs are different aerodynamically from tube-and-wing airliners, which is why the engine location is consistently different.

 

[sferrin]

actually engines on top are all bad from the aerodynamics POV

Then explain why every single study of blended wing body designs that I've seen says that engines under the wing on a BWB are bad for drag. And why I can't find BWB designs with low-mounted engines. BWBs are different aerodynamically from tube-and-wing airliners, which is why the engine location is consistently different.

Even LM's HWB has them on top. (Did that thing finally die? Haven't heard about it in a while.)

 

[kitnut617]

That video was very impressive though, it shows it does fly (at least as a model). The stall looks a bit iffy ---- The CAD drawing shows the scale of the engines, is there really anything that big at the moment.

 

[flateric]

Then explain why every single study of blended wing body designs that I've seen says that engines under the wing on a BWB are bad for drag. And why I can't find BWB designs with low-mounted engines. BWBs are different aerodynamically from tube-and-wing airliners, which is why the engine location is consistently different.

not sure about 'every'
TSAGI DMS-LK WT tests had showh much better L/D with engines _under_ the wing (see graph), not talking about problems with balancing, servicing and sucking boundary layer.

 

[yasotay]

What about passenger acceptance? Didn't the Boeing Sonic Cruiser run into negativity about its "strange"design?

 

[sferrin]

What about passenger acceptance? Didn't the Boeing Sonic Cruiser run into negativity about its "strange"design?

I would think a bigger issue with a BWB would be the excitement when rolling and being far away from the centerline.

 

[Orionblamblam]

TSAGI DMS-LK WT tests had showh much better L/D with engines _under_ the wing (see graph), not talking about problems with balancing, servicing and sucking boundary layer.

How much more Russian-looking could a BWB get than by hanging eight different turbofans off it every which way? None more Russian.

 

[TomS]

What about passenger acceptance? Didn't the Boeing Sonic Cruiser run into negativity about its "strange"design?

I think that's highly overrated. Very few passengers even know what sort of plane they are flying on. And pax almost never actually see the plane they are boarding, thanks to jetways.

If there was an issue with passenger acceptance of Sonic Cruiser, it was that there wasn't much evidence that passengers would accept paying significantly more for shorter flight times.

 

[Orionblamblam]

I would think a bigger issue with a BWB would be the excitement when rolling and being far away from the centerline.

Doubtless there would be procedures put in place to fly maneuvers that limit that sort of thing. But that would only apply for pre-planned maneuvers like flyign a pattern. Sudden changes in course to avoid flocks of armored geese and the like, though, would not only make outboard passengers uncomfortable, it could also make them wet as their drinks go negative-g and it could rattle the flight attendants around like pinballs. And there'd damned well better not be outboard lavatories.

 

[sferrin]

On the other hand some might think it was a blast (myself included).

 

[yasotay]

What about passenger acceptance? Didn't the Boeing Sonic Cruiser run into negativity about its "strange"design?

I think that's highly overrated. Very few passengers even know what sort of plane they are flying on. And pax almost never actually see the plane they are boarding, thanks to jetways.

If there was an issue with passenger acceptance of Sonic Cruiser, it was that there wasn't much evidence that passengers would accept paying significantly more for shorter flight times.

Fair, but I think the 737 Max might argue differently.

 

[Orionblamblam]

On the other hand some might think it was a blast (myself included).

Sure. And if you were seat and belted in... hey, bring it on. But the poor attendants, and anyone up and about and the people who just happen to be near them, or anyone near anything loose, could be at some risk in the event of serious turbulence or the need to evade yet another errant Uncle Putey's HappyFunBuk.

I do wonder about the reaction of people stuck in what is essentially a vibrating auditorium for 12 or more hours. People clearly more or less can handle it while crammed into a narrow metal tube, so the hide open spaces of a BWB seem like they should be fine, but who can really say.

 

[sferrin]

On the other hand some might think it was a blast (myself included).

Sure. And if you were seat and belted in... hey, bring it on. But the poor attendants, and anyone up and about and the people who just happen to be near them, or anyone near anything loose, could be at some risk in the event of serious turbulence or the need to evade yet another errant Uncle Putey's HappyFunBuk.

I do wonder about the reaction of people stuck in what is essentially a vibrating auditorium for 12 or more hours. People clearly more or less can handle it while crammed into a narrow metal tube, so the hide open spaces of a BWB seem like they should be fine, but who can really say.

As you pointed out, probably not too fun if the can is outboard as well.

 

[FighterJock]

Anyone know how many passengers the flying wing plane would carry? Equal to or greater than the A-380.

 

[Arjen]

The design is not as long as an Airbus A350, but it has the same wing span. This allows the Flying-V to use the present infrastructure at airports, such as gates and runways. It even fits in the same hangar as an A350. The Flying-V carries about the same number of passengers - 314 in the standard configuration – and the same amount of cargo, 160 m3.

 

[FighterJock]

The design is not as long as an Airbus A350, but it has the same wing span. This allows the Flying-V to use the present infrastructure at airports, such as gates and runways. It even fits in the same hangar as an A350. The Flying-V carries about the same number of passengers - 314 in the standard configuration – and the same amount of cargo, 160 m3.

Thanks Arjen.

 

[Avimimus]

TSAGI DMS-LK WT tests had showh much better L/D with engines _under_ the wing (see graph), not talking about problems with balancing, servicing and sucking boundary layer.

How much more Russian-looking could a BWB get than by hanging eight different turbofans off it every which way? None more Russian.

I got excited about that... but I'm now pretty sure from the context that it is actually just the wind-tunnel model showing all of the possible attachment points for engines... the actual wind tunnel tests only looked at combinations of two or four engines...

 

[TomcatViP]

That video was very impressive though, it shows it does fly (at least as a model). The stall looks a bit iffy ---- The CAD drawing shows the scale of the engines, is there really anything that big at the moment.

That one flies too.

 

[Zoo Tycoon]

With this arrangement, bird strike will be a show stopper;- a conventional cockpit window glass is about 40-50mm thick laminated glass and it together with the frame is very heavy but there’s only a few of them. Normal pax windows are only 6-8mm thick lightweight plexiglass but can’t be impacted by a bird. With a conventional wing the leading structure, a bird will penetrate the leading edge but loose sufficient energy that its remains won’t penetrate the forward spar which is the fuel tank boundary.

With this Vee wing thingy every leading edge window/frame will have to be strong enough to take a bird without rupture or discharge of debris afterward;- all the front aspect pressurised hull will have to take a bird without breach;- doors, especially emergency exits will have to take a bird without loss of function. Hence any aero benefit will rapidly be negated by the extra structural weight. Good luck with that.

 

[Orionblamblam]

With this arrangement, bird strike will be a show stopper;-

A good point about the need to armor the passenger windows... but you'll also need stronger leading edge skins as well. We've all seen mashed-in aircraft noses due to bird and hail strikes. And more, even if the windows and skins are perfectly able to shrug off taking a condor at 500 knots... what about the *passengers?* A whopping great WHAM followed by a window covered in blood and gore might be the sort of thing that would disturb a couple people. This sort of thing is largely precluded from happening with windows along the sides of tubular fuselages

 

[galgot]

Years back, The train i used to take every day striked a deer. Was in winter, some of the windows of the car i was in where covered with frozen blood/red snow. It didn't stoped the train, once at the station , the frozen deer body sticked on one of the train bumper was a big attraction... Talk about gore. But people were more curious than anything.
Indeed seems the windows and leading edge resistance would be a big problem.
Oh well, we're not finished flying in tubes with wings...

 

[Orionblamblam]

But people were more curious than anything.

Now imagine that the train in question was moving at 500 miles per hour when it hit the deer. Granted, airliners rarely hit deer, especially since Putin shot down Santa Clause and blamed it on the Ukranilithuanians...

 

[steelpillow]

The point about birdstrike is a good one.
Another significant issue faced by the BWB with engines mounted above and behind is crashability. In a crash-landing the engines can break loose and would then be thrown forward to wreak mayhem on the passenger cabins.
Then there is the problem with the stall. In a conventional airliner the engines remain in clean air and help to pull the thing out of its stall. But in the above-and-behind BWB they are right in the turbulent dead zone and the thing will plummet like a ready-stuffed turkey.
And of course the engine-out condition. With no conventional surface, this has to be met by a drag rudder and a quick look at the moment arm suggests that it must create about as much drag as the whole airframe in cruise. That is some drag rudder! Moreover, with one engine out the other must now effectively drive two planes through the air.
When the safety regulators explained all this to Boeing, their ardour for their BWB project suddenly cooled.
But what about all these apparent claims about high drag for a BWB with a conventional engine position? IMHO that is rubbish, the BWB is no worse off than any other plane. What they really mean is that the high-aft position brings improvements. Sorry I cannot believe that either, or every modern airliner would look like a VFW-Fokker 614 with its engines shifted aft. The idea that the BWB somehow magically obeys different laws of aerodynamics is untenable. It is good for noise levels and short u/c legs but that is all.
Finally, I would draw attention to the sideways aerodynamic flows generated by steep sweep angles. These are crucial to the characteristics of sharply-swept and steep delta wings, even when flying subsonically. But they create inefficiency and the old Russian supersonic fighters with steep sweep angles resorted to huge wing fences to maintain adequate lift at low speeds.
These computer-modelled toys are all very pretty, but one must always reality-check the results against the real world.
You could actually enclose the same volume while drastically reducing the sweep, as it is determined by span, chord and depth, none of which changes with sweep angle. Indeed, this is basically just the Junkers 1930 design with its straight centre section drawn into a vee and the props replaced by a couple of jets.
Still, it is pretty.

 

[TomcatViP]

Bwb with turbo fan high in aft position = ejector.
Lift coef is improved and stall is delayed. But you are right that in case of hard landing the engine could eventually slam in top of the cabin compartment.
But then a turbofan is not a fire truck or a 32ft trailer...

 

[Desertfox]

There is a simple solution to windows on the leading edge. Just get rid of them... and replace them with TV screens. Simplifies the structure and most people shut their windows down anyways.

 

[FighterJock]

There is a simple solution to windows on the leading edge. Just get rid of them... and replace them with TV screens. Simplifies the structure and most people shut their windows down anyways.

Not me. Whenever I went on holiday abroad I always wanted the window's open to look out even if there was nothing to lookout at over the Atlantic Ocean.