Tubes are easy to make and handle pressurisation easily?

Wider is tricky to evacuate?

People like windows?

Runways are only so wide and its nice to have wheels wide relative to fuselage?

HTML5 might be Impolite...
 

Hi,

since HTMF:mad:U wiped out my explainful answer twice, all in very short manner:

Read through Ludwig Prandtl.
Galley won´t fit into wingbox.

Greetings,

Oh go on. Sounds like you actually know what you are talking about.

Ground Interface?
 

Interesting concept.
To fly, you are going to need some angle of attack, aren't you?
How does it rotate with all those wheels in ground contact including some well behind the C.G.?
Likewise, how do you land it?

You might need a variable incidence wing like the F-8 Crusader had. Either that or a whole lot of trailing edge flap and no leading edge slats.

I thought that there were some structural limits that dictate how big we can build something until it collapses under its own weight.
I'm not an engineer, so feel free to correct me....

AN225 is a bit like that with all it's rows of wheels.

Like a black hole?

Just another small point; when the B747 arrived, a number of airports struggled with the fact that their taxiways and parking stands were at a distance from the runway centre-line that meant a B747 tail fin would penetrate the obstacle limitation transitional surface while manoeuvering or on a stand. I don't remember the exact details, but it was a problem.

In your concept drawing the fin is 22.5m high, which I think is about 2.5m higher than a B747; maybe different variants had different heights.

All that shows is that trying to fit a revolutionary new aircraft into existing airport infrastructure is doomed to a degree of failure; fin penetration of the transitional surface is just one tiny detail.

If a team of engineers and designers were to take airport design and stand it on its head, imagine what they could come up with. It would take a decade or two to really change the industry globally as new aircraft design exploits the freedoms offered by a new generation of airports, and design changes must take transition into account, but it can and must be done.

Here's a starter; ever wondered why airport terminals exist? Is there any other way to design and operate an inter-modal hub; maybe doing away with private cars and taxis as a way of getting there or leaving, as well as forgetting any need to provide a shopping mall. If you start with a list of essential functions for the airport to provide, including 3000m of concrete runway, and put them together in a totally different way than is done at present, you begin to realise that there are better ways of doing it.

I'll go back to my previous remark in another post; is it not remarkable and shameful that 40 years after the introduction of the B747, and 50 years (I guess) since its design was first thought about, we are still building terminals that are so dysfunctional that while people can shop in them until they drop, when they board a B747, and get off it at the other end, they'll be lucky to do so through 2 doors instead of one. How utterly absurd is that?

Imagine building a railway station where to get off a train you need to walk down the whole length of it to get out through a single door, and vice versa to get on.

The challenge isn't to design new and better aircraft, it's to design a new and better airport system..

Yes, that's it! Or was it a worm-hole...? :suspect:

Seriously, though.
Is there no limit to how big we can build those things?

Yes, there is, and always has been.

That figure is constantly changing with engine/materials technology and I have no idea what it is at the moment.

I am quite sure that it is not the limiting factor in this case though.

I've not read his papers yet (in fact I don't think that they've been published), but gather on the professional grapevine that a well regarded professor at Cranfield is asking this very question at the moment.

He's apparently concluded that bigger airliners would be much more efficient, and that the limiting factor on airliner efficiency at the moment is the ICAO 80x80m box.

G

Sure there is: Firstly the budget, secondly the earth radius.

Sorry, not this evening.

Greetings,

That's very interesting and I would be interested to read about it. It makes sense for various reasons.
I am under the impression that the A380 is less efficient than 777 in terms of fuel per mile per passenger though despite being bigger and newer..

I should keep an eye on Aeronautical Journal - that would be my best bet on where he'll publish.

G

According to wiki you would be correct.

http://en.wikipedia.org/wiki/Fuel_ec...raft#Long_haul



Quick look on unverified websites for fuel cost confirms:


A380
$60.35 per nm
say 500 seats typical layout
$0.12 per nm per seat

B777
$38.99 per nm
350 typical
$0.11 per nm per seat


Never mind the vastly lower cost for the aircraft itself.


Probably why the A380 and B747 have been less popular of late with more orders for the wide-twins like the 777/787 and 330/350

The problem is not really how big the aircraft can be but more a case of how will the airport infrastructure cope? And then you have the human aspect. The weakest, most frail and unreliable things on an aircraft are passengers. Keep piling them on and after a while your HyperJumbo will be diverting all over the place because the buggers in the back keep popping their clogs. And then you have the marketing problem. Just how many people want to go from A to B? I am convinced that we are approaching saturation on some routes yet capacity keeps increasing. How long before the bloodbath? Do we need yet more capacity?

PM

To me the issue with getting bigger is how many massive planes are really needed in the marketplace for hub/hub movements. You have to sell so many aircraft to recoup the tooling and design costs. A good example is Concorde where operationally it made some sense but the marketplace was never large enough for the manufacturer to turn a profit. The A380 seems to be going the same direction (time will tell).

If you look at JFK<->UK and the number of flights there is no doubt that reducing to a couple A380's JFK<->LHR would be a lot cheaper as you would need less crew, ground, maintenance, etc. on the smaller fleet. The consumer though seems to prefer a lot more time slots and more point/point versus hub. Given the choice of flying 7hrs to LHR and then sitting around a couple of hours and connecting to MAN, I would prefer to pay more for a direct flight.

Now i am done with reading the .pdf in the first Post.

My Summary: Short Prandtl without mentioning key facts, Aeroelastics- the only mention in this Article, Missing parts of Computed Analysis, Computer coded Darwin-without Darwin, induced Drag is not Suitable for "classic" layouts @ M0.8, Overwhelming Conlusion without criticism.

The most disturbing fact is that he mentioned Aeroelastics only once in the whole Paper but is planning to include an forward swept Wing(part).
Thats also a Point of Criticism in the Openers Post. It is nice to get extra stiffness from installing the upper Wing nearly directly onto the Airframe. There are 2 things to obtain about this:

Firstly you get all the loads of both Wings directly into the Airframe which causes high stress.
Secondly you get in serious trouble with the aft wing when the plane has to ditch, it would be better if this wing would fall off at thus moment without big issues to the hull.

Thats why all BW concepts have thier aft wings installed on the Tailrudder.

P.S. The Wingbox is a highly stressed Part as you can see from Above. It has to be monitored on an regular Basis, no one wants to dismantle half of the Cabin for that.

The right conclusion in the Paper is that BW is a great concept for regional Airliners. To complete this thesis, slow flying regional Airliners, maybe fitted with RR Propfans. (Transonic Airfoils not needed for that)

P.p.S it is funny to see that aircraft designers use firstly CFD and then Euler, especially from a turbine point of view.

Greetings,

On the argument of the Hyperjumbo's business case:

As I said, I'm not here to argue about the marketability of such aircraft in today's economic climate. I think the A380 is overkill for most airlines except Emirates who seem to never be satisfied with the size of their aircraft. I was just curious about how big we can build airplanes with today's technology and standards.

On the argument of how airports will cope with the aircraft:

This would depend from airport to airport and how airport authorities are willing to accept this aircraft, which I believe boils down to the market demand for this aircraft, which is not the aim of this analysis. If there's a sudden change in the economic climate and an aircraft this size will be in hot demand, I think airport authorities will be more than willing to take action.

Renovating (which airports do all the time anyway) to make bigger pre-departure halls, immigration stands, baggage claim areas, etc. is not going to "rewrite airport infrastructure rules". Maybe in today's most modern airports, the biggest modification they will make is adding a 4th jetway that can reach the 3rd deck and that's it.



Some good points pointed out:

1. Pavement strength. I'm not too familiar with airport pavement standards. Is there a way around this with more wheels perhaps? Or, different landing gear configuration? I know Airbus made a variant of the A320 with 4-wheel bogies instead of two for it to be able to operate in weaker pavements.

http://cdn-www.airliners.net/aviatio.../0/1656061.jpg

2. Human aspect. It maybe true this aircraft may experience more diversions due to emergencies involving passengers going crazy or other health reasons. Is there an acceptable number regarding this. If so, how can this be improved?



Also, with so many passengers, how can they evacuate in an emergency? With slides of course!

http://s18.postimg.org/d0atia0vt/hyp...evacuation.png

Airbus did a study on how evacuation on the upper deck is compared to the lower deck. And the findings show that passengers on the upper deck may hesitate more. This could be a big blow to the design but we'll never know until more testing is conducted. Also the upper deck slides might need an upgrade to cope with the size. Possible solutions could be a slide design with taller handrails so exiting passengers feel more "cradled" upon sliding.

How does the AN225 undercarriage cope with the weight on touchdown? Does it land with no pitch? I can see the rear undercarriage collapsing on this mega-jumbo on landing. All the weight will be on the rear wheels.

Apart from that, it looks like a maintenance nightmare. You would need several cherry pickers on every transit just to check the engines and top up the oil. By comparison, the inboard engines on a 747-400 with RB211 engines can be serviced without steps.

One of the reasons the 777 is so efficient is because maintenance engineers had an input into it's design. If an aircraft is easy to work on, turnaround times are faster and it's inherently safer. Airbus didn't quite grasp this concept with the A380.

I see half the fuel supply is below the height of the engines (not so good when "gravity" feed is required).