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This comment on the article from 'Ted' says everything: "I’m highly skeptical. Drag is already very low on modern jetliners. You’re not going to achieve 70% fu

by 58x14 5y ago

This comment on the article from 'Ted' says everything: "I’m highly skeptical. Drag is already very low on modern jetliners. You’re not going to achieve 70% fuel reduction without a miraculous improvement in engine efficiency. A “once-through” air supply system would be inherently less efficient than current recirculating systems. No fuel in the wing? Then fuel weight is not distributed and the wing must be stronger.. thus heavier. I would love to be wrong about this, but with the information given, this design looks like vaporware."

dathinab 5y ago
> Drag is already very low on modern jetliners. It's so low that they have to add a bit of drag in the right place to prevent stalling (the small fins on top of wings). > No fuel in the wing? Then fuel weight is not distributed and the wing must be stronger.. thus heavier. It's also less secure in cases of emergencies, as far as I know. I forgot why but I think there where also some really good reasons (beside closeness to fuel) why turbines are now mostly below the wings. Aslo wouldn't building 3 wings more expensive even if they are smaller? And then I have very little experience with aero dynamics, but my intuition tells me that there are some tricky parts around the (forget name: movable parts at the back of wings) and additional failure cases as you now (likely??) have to have 3 sets off them on each side.
- albertopv 5y ago
  Engines are under the wings for easier maintenance, in case of pumps failure gravity could push some fuel to engines. Also, the farther engines are from the tail, the better, for safety reason in case of engine failure. And there are other reasons for sure, I'm no expert
jillesvangurp 5y ago
I wouldn't be so dismissive. I'm sure they ran some simulations on this. With 3 sets of wings, the plane would have much more flexibility with the center of gravity. With two wings this needs to be where the wings are. This is why fuel is put in the wings in such configurations. It's a good design if you only have two wings. With 6 of them and the engines mounted on the back, you can play around a bit with different weight distribution. I'm guessing that using fuel bladders on top of the roof would allow for flexible placement anywhere between the first and last set of wings. Also, you can pump fuel around as well to change the weight distribution (and possibly even trim the airplane's pitch). Drag of modern planes is quite optimized for their current designs. However putting the fuel in the wings and mounting the engines on them probably adds a fair bit of drag regardless. Also such wings have to be bigger and stronger. I've had a window seat next to the wings of an A380; they are massive. So, I can see how changing that configuration that could eliminate some drag. And using modern composite materials without seams is also going to help with both weight and drag. Less weight means more fuel savings. If it adds up to 70-80% will be interesting. IMHO the real issue is going to be getting rid of kerosene as a fuel. Synthesized fuels like hydrogen or methane could potentially be a lot more sustainable.
mcguire 5y ago
Fuel in the fuselage reduces usable interior space, meaning the fuselage has to be bigger for the same cargo capacity. As do the beams for multiple wings. Multiple wings along the fuselage put the after wings in the disturbed airflow from the forward wings. Many of the advantages they list would also apply to conventional designs, including fully-composite construction. The only advantage of multiple wings I can see is that the horizontal stabilizers on most planes generate downforce, which a multiple wing system could avoid. On the other hand, canard designs also avoid that and it seems the gains aren't so important as to get them adopted.

by 58x14 5y ago

dathinab 5y ago

> Drag is already very low on modern jetliners. It's so low that they have to add a bit of drag in the right place to prevent stalling (the small fins on top of wings). > No fuel in the wing? Then fuel weight is not distributed and the wing must be stronger.. thus heavier. It's also less secure in cases of emergencies, as far as I know. I forgot why but I think there where also some really good reasons (beside closeness to fuel) why turbines are now mostly below the wings. Aslo wouldn't building 3 wings more expensive even if they are smaller? And then I have very little experience with aero dynamics, but my intuition tells me that there are some tricky parts around the (forget name: movable parts at the back of wings) and additional failure cases as you now (likely??) have to have 3 sets off them on each side.

albertopv 5y ago
Engines are under the wings for easier maintenance, in case of pumps failure gravity could push some fuel to engines. Also, the farther engines are from the tail, the better, for safety reason in case of engine failure. And there are other reasons for sure, I'm no expert

jillesvangurp 5y ago

I wouldn't be so dismissive. I'm sure they ran some simulations on this. With 3 sets of wings, the plane would have much more flexibility with the center of gravity. With two wings this needs to be where the wings are. This is why fuel is put in the wings in such configurations. It's a good design if you only have two wings. With 6 of them and the engines mounted on the back, you can play around a bit with different weight distribution. I'm guessing that using fuel bladders on top of the roof would allow for flexible placement anywhere between the first and last set of wings. Also, you can pump fuel around as well to change the weight distribution (and possibly even trim the airplane's pitch). Drag of modern planes is quite optimized for their current designs. However putting the fuel in the wings and mounting the engines on them probably adds a fair bit of drag regardless. Also such wings have to be bigger and stronger. I've had a window seat next to the wings of an A380; they are massive. So, I can see how changing that configuration that could eliminate some drag. And using modern composite materials without seams is also going to help with both weight and drag. Less weight means more fuel savings. If it adds up to 70-80% will be interesting. IMHO the real issue is going to be getting rid of kerosene as a fuel. Synthesized fuels like hydrogen or methane could potentially be a lot more sustainable.

mcguire 5y ago

Fuel in the fuselage reduces usable interior space, meaning the fuselage has to be bigger for the same cargo capacity. As do the beams for multiple wings. Multiple wings along the fuselage put the after wings in the disturbed airflow from the forward wings. Many of the advantages they list would also apply to conventional designs, including fully-composite construction. The only advantage of multiple wings I can see is that the horizontal stabilizers on most planes generate downforce, which a multiple wing system could avoid. On the other hand, canard designs also avoid that and it seems the gains aren't so important as to get them adopted.