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Engineers are exploring radical new designs for commercial planes

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Re: Engineers are exploring radical new designs for commercial planes

#41

Post by dan_quixote »

VBprogrammer wrote: post #21
alexpotato wrote: post #5

Interesting historical note on the blended wing design: One of the main arguments against it was that designers weren't sure if people would be ok with sitting towards the center of the plane. The thought was that passengers wouldn't be comfortable without being able to at least see outside (even a little, looking at you 3/4/3 widebody planes). I mention this b/c there is a quote in Mary Roach's Flying to Mars. She m…

My understanding is that having to manufacture a different rib for each station along the structure is a significant challenge. It's possibly less of an issue with composites?

The ribs are already all different across existing commercial airplane wings.

Re: Engineers are exploring radical new designs for commercial planes

#42

Post by aclatuts »

VBprogrammer wrote: post #21
alexpotato wrote: post #5

Interesting historical note on the blended wing design: One of the main arguments against it was that designers weren't sure if people would be ok with sitting towards the center of the plane. The thought was that passengers wouldn't be comfortable without being able to at least see outside (even a little, looking at you 3/4/3 widebody planes). I mention this b/c there is a quote in Mary Roach's Flying to Mars. She m…

My understanding is that having to manufacture a different rib for each station along the structure is a significant challenge. It's possibly less of an issue with composites?

If the all the manufacturing techniques have to change, maybe 3d printing some parts or the whole plane would make sense and be viable.

Re: Engineers are exploring radical new designs for commercial planes

#43

Post by VBprogrammer »

dan_quixote wrote: post #41
VBprogrammer wrote: post #21

Earlier quoted context omitted.

My understanding is that having to manufacture a different rib for each station along the structure is a significant challenge. It's possibly less of an issue with composites?

The ribs are already all different across existing commercial airplane wings.

Across the wings yes but not across the majority of the fuselage.

Re: Engineers are exploring radical new designs for commercial planes

#44

Post by coredog64 »

jcampbell1 wrote: post #16
alexpotato wrote: post #5

Interesting historical note on the blended wing design: One of the main arguments against it was that designers weren't sure if people would be ok with sitting towards the center of the plane. The thought was that passengers wouldn't be comfortable without being able to at least see outside (even a little, looking at you 3/4/3 widebody planes). I mention this b/c there is a quote in Mary Roach's Flying to Mars. She m…

The main argument against it is that it increases fuel consumption. Plowing your cargo area through the air sideways is just idiotic. There is some crazy public belief that it is more fuel efficient because the public doesn’t understand physics. These things keep getting getting publicity because even Hacker News folks don’t get it. Long high aspect ratio wings and streamlined body are how you get fuel efficiency. Th…

It’s not that simple. Aerodynamic drag is made up of surface drag and induced drag. Given the same coefficient of drag, drag goes up as S-wet goes up (which is what you’re referencing). Induced drag is a consequence of how much structure is required to create a flying vehicle. IF (and it’s a big if) the BWB turns out to be more structurally efficient, then the total drag for the plane might be less than for a conventional design.

(Source: I have an aerospace engineering degree from Embry-Riddle)

Re: Engineers are exploring radical new designs for commercial planes

#45

Post by thot_experiment »

dan_quixote wrote: post #39
chrisBob wrote: post #23

Earlier quoted context omitted.

The issue isn't the bank angle exactly, it is the acceleration of the roll. Pilots will need to be careful not to throw people or drinks around, but I think it would be doable.

Pilots can control the bank acceleration, sure. They have much less control over acceleration due to uneven turbulence.

I'm not sure this tracks, I think turbulence powerful enough to cause passenger discomfort is usually so big that it affects the whole plane pretty uniformly. I think it's exceedingly unlikely that you'll spend enough time on a shear line to induce a large roll.

At least it's never happened to me, but I am only a passenger.

Re: Engineers are exploring radical new designs for commercial planes

#46

Post by coredog64 »

hotpotamus wrote: post #30
AlexandrB wrote: post #7

Earlier quoted context omitted.

Yup, I've been seeing these futuristic airplane concepts for most of my life, but commercial airframes seem to be converging to be more and more similar. Unusual elements like a third engine in the tail or horizontal stabilizers mounted above the rudder have largely disappeared. Given the thin margins in air travel, I suspect this is because this design is the most successful. It might be a local minimum, but when it…

My understanding is that tri-engine jetliners were actually more to fulfill a regulation than for engineering reasons. There are regulatory limits to how far a plane is allowed to fly on one engine called ETOPS - I forget what it really stands for, but the colloquial expression is: Engines Turn Or Passengers Swim. It used to be limited to around 2 hours I believe, meaning you've got a bit of time to divert and make a…

Extended Twin Operations.

Re: Engineers are exploring radical new designs for commercial planes

#47

Post by HPsquared »

thot_experiment wrote: post #45
dan_quixote wrote: post #39

Earlier quoted context omitted.

Pilots can control the bank acceleration, sure. They have much less control over acceleration due to uneven turbulence.

I'm not sure this tracks, I think turbulence powerful enough to cause passenger discomfort is usually so big that it affects the whole plane pretty uniformly. I think it's exceedingly unlikely that you'll spend enough time on a shear line to induce a large roll. At least it's never happened to me, but I am only a passenger.

In a typical plane in turbulence, you can see the wings bending up and down. Perhaps a blended wing would be stiffer, though.

Re: Engineers are exploring radical new designs for commercial planes

#48

Post by gauravjain13 »

chrisBob wrote: post #23
nicktelford wrote: post #15

Earlier quoted context omitted.

A bigger problem with blended wing designs is actually for the people on the peripheral. When the plane banks, passengers further from the axis of rotation will feel a more significant change in their altitude. You literally feel like you're "falling", as the plane banks to your side. This also applies to existing aircraft, but the amount you drop/rise is limited by the your distance from the axis of rotation, which…

The issue isn't the bank angle exactly, it is the acceleration of the roll. Pilots will need to be careful not to throw people or drinks around, but I think it would be doable.

True, but absolute bank angle would also matter (say endpoint of roll when roll acceleration is zero) because now there's a component of gravity pulling you sideways.

Re: Engineers are exploring radical new designs for commercial planes

#49

Post by inkcapmushroom »

shahbaby wrote: post #18

Who will be held accountable when this fails and people die?

Boeing has proven that you don't need a radical plane design to have it fail. So probably the same people that were held accountable with the 737 Max killing 346 people.

Re: Engineers are exploring radical new designs for commercial planes

#50

Post by dr_orpheus »

jcampbell1 wrote: post #16
alexpotato wrote: post #5

Interesting historical note on the blended wing design: One of the main arguments against it was that designers weren't sure if people would be ok with sitting towards the center of the plane. The thought was that passengers wouldn't be comfortable without being able to at least see outside (even a little, looking at you 3/4/3 widebody planes). I mention this b/c there is a quote in Mary Roach's Flying to Mars. She m…

The main argument against it is that it increases fuel consumption. Plowing your cargo area through the air sideways is just idiotic. There is some crazy public belief that it is more fuel efficient because the public doesn’t understand physics. These things keep getting getting publicity because even Hacker News folks don’t get it. Long high aspect ratio wings and streamlined body are how you get fuel efficiency. Th…

> There is some crazy public belief that it is more fuel efficient

There are a number of engineers at NASA and Boeing working on the X-48 who would disagree with you on this one.

The main advantage of the blended wing body is to reduce the skin friction drag [0] of the aircraft relative to the typical fuselage and wings. You have less surface area in contact with the air relative to the amount of internal volume. There may be some increase in the profile drag (i.e. the cross section of the aircraft) but is made up for by the reduction in the skin friction drag.

> The fuel burn of a B2 is far higher pound for pound than a 737.

This isn't really a fair comparison. They are two aircraft optimized for entirely different things.

[0] https://en.wikipedia.org/wiki/Skin_friction_drag

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