> They must carry huge payloads in order to make lots of money per flight from paying passengers. It would be great to have high aspect ratio wings on airliners, as the efficiency would slash fuel bills significantly. Unfortunately, it’s difficult to make them strong enough for such heavy-duty purposes. There simply isn’t room for the structure and material required.
Are they going to try and squeeze some more seats onto the trusses? I'm sure they could fit at least one on each strut landing.
Wing tanks keep the fuel from occupying the fuselage.
While in theory you could store things elsewhere, practically the logistics of loading and unloading a craft require containers that fit into the airplane. Which means those containers that fit into a cylindrical section.
A small amount of space used by the stewards for supplies or storing carryons might work in limited amounts, say for first class.
Spreading the load a wing must lift along the wing is an important way to be able to make a lighter wing, owing to the fact that part of its load is now distributed along where the lift is being generated.
Definitely. Liquid cargo has a really good property of being able to go around corners and through narrow passages, as long as the rates are reasonable. And they don't tend to jam, so you don't need to store them in human accessible locations.
Of course they also slosh, which means you need some tricks to keep the sloshing from causing issues.
This conversation does bring to mind the lifting body plane Boeing thought they were going to make. I wonder how they planned to load and unload that sucker? It would have taken multiple bays to do efficiently. And I don't know how you keep the crates from shifting. In a cylindrical craft the bulkheads and the ribs are right there to brace against.
> Throw on a brace for support, though, and suddenly the high-aspect ratio concept becomes plausible.
So, high aspect ratio is desired, but needs support... why not extend the trusses for a biplane design?
Not an aeronautical engineer, but from my armchair seems like high-aspect ratio and support are both gained by using a more familiar technology (I've seen pictures of real biplanes flying, have not yet seen a truss-braced like this concept in the air).
The reason why you use a biplane design is to get more lift per unit span, so you can keep wingspan within some arbitrary constraint.
As with all engineering, there is a tradeoff involved, and with biplanes you don't get double the lift because of the boundary layers of the wings interacting.
You also pay a drag penalty as you have twice as much skin area exposed to airflow, and it complicates the design because in the transonic région you can get interactions between shockwaves causing flutter and other not so fun effects.
Biplanes have twice the number of wingtip vortices, so lots more drag. I suspect the reason biplanes existed in the first place was due to materials constraints. We didn't know how to make the wings strong and light enough to be very long, so kept them short and added a second set. This caused both more lift and drag. The drag was compensated for by running the engine harder (or using more powerful ones).
We now have sufficient materials knowledge that we don't have a problem making wings long enough to lift the plane. We're instead working on reducing the drag, so we can make engines work less hard.
Biplanes have supports between the wings that add drag. Also, biplanes typically don't have swept wings; here, the truss sweeps forward while the wing sweeps backward.
I'm curious why they're using a MD-90, a retired design, as the basis for experimentation here. Wouldn't it make more sense to try it on something 737 Max derived where it's more reflective of Boeing's current airplane designs and where they have ongoing manufacturing of the hulls anyway?
- because the fuselage itself isn't important for testing
- older chunkier design is more amenable to bolting radical new bits on
- 737s still have market value
I've seen these designs floating around and I wonder where they are going to put the fuel. From a 737 MAX diagram and tank sizes, the wing tanks are nearly 1/3 of the fuel and the center tank is partially in the wings. I'd estimate well over half the fuel is spaces of the wing structure.
Why did we move away from high-mount wings like the B52? As a counter-example, the C17 is a bit newer and has high-mount wings, but is there a technical reason why aviation moved away from this deisgn?
Low wings work better for commercial airliners because the structure can go through the cargo hold instead of the passenger compartment. There are some other smaller benefits like easier refueling and ability to retract the main landing gear into the wings on many aircraft.
The structure between the wings is one of strongest parts are the aircraft. With low-mounted wings, the fuselage sits on top of that structure and only needs to support its own structure. The wings are pushing the plane up.
High-mounted wings, on the other hand, pull the plane up. This requires the fuselage to be stronger. Otherwise the wings would rip off the top of it.
High-mounted wings require the structure holding the wing to be suspended higher in the fuselage, requiring it to be stronger. Their main advantage is to avoid obstacles in the ground, which is desirable when landing in less developed airfields, but it's not a problem airliners have.
I find some of the graphics off-putting. This habit of putting random phrases on a picture, and then drawing a line to some random part of the subject (a plane in this case) is stupid, insulting, ignorant, lazy, oh I'm running out of adverbs it's so senseless.
'High lift system design' is apparently held entirely in the wingtip? 'Fuel volume' has something to do with the cabin? That particular part of the wing has '20% Increase' in something-or-other?
As marketing literature it's to be expected - just a junk graphic to catch your attention. But in an article on a bit of science? I find it unforgivable. But that's just me.
Anyway, my pet peeve.
Are they going to try and squeeze some more seats onto the trusses? I'm sure they could fit at least one on each strut landing.