Designing a very, very large airliner…
 

…yes it may not have much business sense right now but I had this nagging curiosity on how big airplanes can get since the flight of the A380. Yes you can say there’s no limit from a technical standpoint. As long as you have enough materials and power, a plane with a 10 kilometer wingspan carrying a million people can be built, right? But I’m not here to argue that.

It has been stated that the A380 (particularly the planned but undeveloped A380-900) maxes out the 80x80m box agreed upon by airports around the world. How can an airliner become even bigger without rewriting all the rules of airport infrastructure, without inventing extremely advanced technologies and without sacrificing comfort and performance big jetliners have today? The question is: what is the biggest airliner we can build and certify now?

I’ve taken a look at several concepts intended for large transport aircraft from flying wings to “sky-whales” until I found a design with huge potential for VLAs. It’s called the box wing.

Here’s a video of a box wing being tested in flight.

More about box wings here. Also see page 45 further explaining the potential of box wings for very large aircraft.

So here is my design solution:

http://s2.postimg.org/e3sxkqeh5/presentation_002.png

http://s29.postimg.org/r99dt3wdz/presentation_003.png


WINGS

More reasons why I chose a box wing:

1. In a forward-backward swept wing combo with enough vertical separation a box wing will have a huge lifting capability needed for a wingspan-constrained aircraft.
2. It naturally has very good vortex reducing wingtip devices.
3. It has a relatively strong structure compared to a single cantilever wing. This can allow for a thinner, lighter wing structure.
4. Box wings can eliminate the need for a separate horizontal stabilizer.
5. The brackets that close the wingtips can double as a vertical stabilizer and rudder.
6. The wing configuration can allow significantly more yaw, pitch and roll control options.
7. Engines can be mounted on the top wing giving them significant ground clearance to prevent ingestion of FOD. This also allows for space for ever expanding bypass ratios of aircraft engines.

FUSELAGE

Making the most out of the lift the wings are capable of, I found a triple-decker, multi-bubble to be the best design: 3-4-3 upper deck, 3-6-3 main deck and 3-6-3 lower deck giving the cross-section total of 34-abreast compared to total 18-abreast (potential 19-abreast) A380. This easily fits 1,000 in 3-class configuration. The design also eliminates the need for three or more aisles which poses hazards to emergency evacuation process.

FRONT CENTER WING BOX

To make this plane competitive in belly cargo capacity, I have placed the front center wing box through the lower deck cabin. This design makes for a continuous belly cargo hold that can accommodate 94 LD3 containers. There will be two corridors cutting through the wing box that will act as passage between the front and rear cabin. Instead of fuel tanks, the leftover space can be used for galley storage leaving the rest of the cabin for passengers.

PASSENGER/CARGO LIFT

Aside from the two staircases, the three passenger decks will be connected via lift. This is for the purpose of transporting persons with disability between decks as well as beverage trolleys, among many others. The lift will be located aft of the wing box.

ATRIUM & MEZZANINE

Since the curvature of the fuselage nose cone will cause the upper deck’s ceiling to curve downward, the space at the front will be of little use, so I decided to cut the upper deck’s floor short in order to create a mezzanine that overlooks a small atrium on the main deck. This is also where the main staircase is located giving an impression of a grand hall for passengers entering the aircraft. Due to this, the main deck atrium can only have limited overhead bins so this space can be used as a lounge or shop by premium carriers but it can also be used for more seats by LCCs.

I am not a certified engineer whatsoever and I have never formally studied engineering or aeronautics in my life. Compared to professionals, I only have a rudimentary understanding of aircraft design. I have a background though in architecture hence, some proficiency in 3D modeling.

Thank you for taking the time to read my post. I’ll post more detailed renderings soon. Anyway could it work? What do you think?


I have searched far and wide to find a place to share this where there are people with much expertise on the subject. I hope this is the right place to post this. If not, feel free to move this thread. Also I am inspired by keesje with his work with the Turboliner, Greenliner and the Ecoliner among many others.

Too heavy
 

I don't think many airports pavement would carry that load. A lot of airports needed strengthening etc for the A380.

It is a huge undertaking to make an airport usable for the A380. Very expensive and time consuming.The required space for runways, taxiways,clearways and gates is burdensome as is. To go even larger is probably uneconomical. Gate space is at a premium at many airports, larger gates mean less total available.

Your rudders "J"

They are at the midpoint-ish.

This means that they will not produce yaw. At best they would move the aircraft sideways, though if differential you could get some yaw as a secondary effect I suppose.

I can only imagine that ground effect must be a pig on landing w.r.t. pitch control in box configuration aircraft.

Why design an aircraft with 6 engines?
Plenty of room for 4 777 engines.

Less is better for efficiency, reliability (6 times more likely to have an engine failure than a one engined aircraft)

medviation,
Thanks for an interesting and well presented post.

On the subject of lifting surfaces, particularly of the box design, a distant relative of mine published a number of papers on the subject.
His research produced a number of interesting findings which significantly advanced aviation technology.

You might have heard of him - Lawrence Hargrave. :cool:


p.s. He later regularly corresponded with and advised a couple of Americans called Wilbur and Orville.
Thankfully, he lived to see his dream realised - powered and controlled manned flight.
.

I think it looks great. A clever way of fitting inside the 80m box while doubling capacity.

As the rudders at 'J' are split, I think they would work just fine for yaw control, using asymmetric drag.

One concern could be the position if the engines behind the front wing. At moderate angles of attack they may encounter disturbed air.

Why don't you send your ideas to the Royal Aeronautical Society? I'm sure they would be interested and have some well-qualified people to give constructive feedback, instead of the nit-picking you may encounter here.

A fascinating excercise from a drawing point of view! However I can imagine a number of downsides in terms of structural strength, center-of-gravity, air-flow, economics, efficiency, stability, undercarriage, etc.

How many aircraft can you think of that use asymmetric drag for yaw control eckhard?

it is just not an efficient way of providing yaw control if you already have vertical surfaces

Happened in Singapore last year. A number of arrivals left the terminal staff running very thin. There were only enough staff to allow us to board our A380 via one door. Delayed us an extra 30 minutes.

I'm thinkin' deep stall here... Other than that , it looks great. :ok:

Only one; the B-2. Are there others?

Not that I can think of, and the B2 does not have them because they are a good idea aerodynamically......

I can only add to the responses about airports.

It is much, much easier to design and build a very large aircraft such as this one than it is to create the environment in which it can operate at its full potential.

The airport industry has not really caught up with the B747, or any other later aircraft offering similar passenger loads. And the B747 first flew in the 1960's.

Most airports simply create parking stands for the large aircraft, and consider their job done. They might have to upgrade pavement strengths as well.

But the real problems with these aircraft start in the terminal, airdide and landside, where few if any airports are really designed to cope efficiently with the peak flows these aircraft generate. Just as a starter, think how long it takes to deplane a full B747, and then wonder why such nonsense happens. It's not set in the Holy Writ that you can only use 2 doors; but most airport managements and their architects believe that it is, which is why it is now a "fact of life" that no-one dares to challenge. Well, I do. (In BAA that meant a lot of unpleasant meetings, usually with a bunch of grocers talking about "footfall" and how to prolong passengers' misery so that they had more time to buy over-priced tat.)

Intermineable queueing in both directions, crowded discomfort, inability to handle massive disruption for reasons such as fog, are all the consequences of airport owners and managements failing totally to grasp their responsibilities as opposed to maximising their retail spend. The excuse that problems are exacerbated by security does not wash any longer. The industry has had 15 years to catch up with that, or rather the USA has had 15 years, the rest of the world 50 years.

My heart sinks when I see brand new, beautiful, modern terminals (eg LHR T5 and T2) which simply perpetuate the fundamental design flaws of their predecessors, wrapped up to look, but not to be different.

So, my suggestion is to put away the aircraft design, and focus on airport design. Bin all the received wisdoms that architects and layout designers hold so sacred. Start afresh. Use technology imaginatively, rather than as a means of just automating and consolidating existing processes and methods. Unless someone does that, the world's airports will always be the reason we cannot advance.

It looks lovely, BUT

As said above, there would be so many ground handling issues. Checkin, Immigration, baggage, you name it, plus You'd have all manner of PCN issues at that weight.

Maybe it might make a specialised freighter at some adapted airports?

Good luck though

Wow thanks so much for the many replies! :)

Good point. But I wasn't too familiar with airport pavement design. I thought if I added more wheels the distribution of weight will be spread out similar to an A380 or 747. Could you share some numbers?


I think you're missing the point. I'm trying to look at a design that would allow more payload than an A380 without going beyond the runway, taxiway, gate requirements of an A380.


I guess so, but well never know without simulation and testing.


I know, except 4 777 engines is not enough. An airplane this size may require 645kN thrust each compared to 514kN of the GE90. This would require a totally new engine technology.

Manufacturing the complex wing-joint sections would be difficult/expensive...

Curiosity not criticism - why did you go for that design rather than a Blended wing body with a much larger fuselage volume for the wingspan?


Weight is the limiting factor as much as size though, as mentioned, consideration to paved surfaces and undercarriage. Also wake turbulence for following aircraft... not all aircraft will be anywhere near as big, and something so big will limit approach/departure flow.

Also handling ability, something so big will have a massive turnaround time, not only will boarding/disembarking take forever unless airports utilise more aircraft doors, but also the time spent cleaning/prepping the cabin between pax.


It appears to make more sense for smaller more efficient aircraft, which is why 787/A350 seem to be the future rather than 747/A380

I've often wondered why the blended wing/lifting body concept hasn't met with much favour.
Vincent Burnelli's lifting body designs (1920s to 1950s) seemed to offer significant advantages in terms of safety, comfort,
economics and operation over conventional designs.

Could somebody enlighten me as to why the 'tin tube' concept continues to dominate?

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).