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.

Yes a blended wing would be stiffer, but wing stiffness isn't really relevant here. The wing bending isn't evidence of differential pressure between the two wings, it's only showing that the wings are the part of the plane that's most affected by turbulence while not accounting for the majority of the inertia.

The point is that air currents powerful enough to appreciably affect a large plane are large scale and therefore you're unlikely to have enough differential pressure from one wing to the other to impart much torque.

I'm not certain about this and I'd love to be corrected if I'm wrong.

Ah, so in other words the whole plane bumps up and down but doesn't rotate. Therefore the location of passengers doesn't matter much, as all locations experience the same acceleration. (Provided the cabin is stiff)

When I was younger, watching the wings flex up and down in turbulence was one of my favorite things about flying, like an amusement park ride. Over the years my perspective has changed.

I've been in turbulence with high roll rates and even as a pilot unbothered by moderate chop, it will cause me to sweat. I've been in the last rows of a 777 and watched the fuselage flex in chop. A blended body would be pretty rigid and have a very low wing loading because it's basically all a wing. So it would be pretty uniform.

It would work if all turns were managed via controls to be a 1/4g, otherwise riding the outside would be like a roller coaster.

I'd prefer to go back to the MD-80. Very high wing loading, fast and never broke down. Skated through turbulence.

The DC-9 and MD-[89]X were great airplanes. One of the great tragedies of unchecked American corporate consolidation/acquisition is that Boeing was allowed to borg McDonnell-Douglas. (Although some climed the opposite was closer to the truth...)

Anyway, the resulting company is too large to fail, and thus, too large to exist. We're at a point where we could really use the competition we had in aerospace companies back in the 80s, when there were enough competitors in both military and commercial aviation for competitive pressures to keep the players working to provide innovation and value. (Rather than milking the market with intentionally poor designs a la Boeing's 737MAX.) Modern airlines have only two vendors to choose from now that Boeing and Airbus have gobbled up even their second-tier competitors.

Personally, I'd love to see what the old Convair, LTV, pre-Martin Lockheed, or pre-McDonnell Douglas might come up with in this competition...

The problem is that, what airlines want, and what regulators want, is now too expensive to independently develop and start a new competitor for, even if you are well resourced like China, Japan or Russia (which all have attempted and failed to break into international aviation sales).

A new aircraft development is a $15B+ R&D investment, for the price and fuel efficiency and safety required. McDonnell-Douglass and more recently Bombardier messed up their bets and it cost them their independent existence.

can't speak to aeronautics of it, but from a pax perspective, the md80 was a fantastic jet. probably the last vestige of what flying "used to be like" since they were too old to retrofit for "efficiency". also its planform looked AMAZING; retro-futuristic even

closest modern aircraft to it is the 717/MD90, which Delta is still flying, but not for much longer iirc

md88 was shit as pax if you didn’t like cold and loud.

Good to know, I'm aware that high roll-rate turbulence is possible but presumably quite rare?

rareish but once was enough. After 5 minutes, people start puking and then it just gets worse.

Not a pilot, but I've flown in the MD-80 once, and I've found it much more unpleasant than most planes due to the engine noise in the cabin.

But on the other hand, I've never experienced turbulence that's made me more than barely uncomfortable in any plane.

Secret was to not sit in the back

depends on the flight paths for different airports. some require tighter turns.

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.

When roll acceleration is zero, the remaining acceleration (i.e., due to gravity) felt by a passenger on the wing edge will be the same as a passenger in the middle of the plane.

Not if the pilot did it right. The net force on you should always be directly toward the floor.

Even when the plane is tipped over at 15* (or whatever their max bank angle happens to be)? The floor is no longer directly underneath you.

The plane turns while banking which results in a force vector mostly straight down towards the floor. If the plane did not turn while banking what you wrote is true.

The ground is whatever you accelerate towards.

Balanced out by the centripetal force of the plane turning!

Underneath is a relative term.

It is called a coordinated turn and it is what one normally aspires to fly.

https://www.boldmethod.com/learn-to-fly/aerodynamics/the-aer...

A coordinated turn with 60 degrees bank should be achievable by any airworthy airplane (it requires pulling 2g), and the maximum bank angle for a steady-state coordinated turn depends on how many g you can pull before you run out of control authority, cause an accelerated stall, or reach the airframe's structural limit.

Next time you fly, get a beverage of your choice and observe how it behaves. Here's an example, courtesy of the great test pilot Bob Hoover:

https://www.youtube.com/watch?v=V9pvG_ZSnCc

If the turn is coordinated you can't tell the difference. I've been in small GA planes turning at 35-40 degrees and it doesn't feel like you're sliding at all, you're pulled back into your seat and "down" (relative to you) into the flooring.

?

I wonder if this could be solved by a rotating inner cabin that always maintain perpendicular to force of gravity when the plane banks?

I think that would be tough. Out in relatively empty airspace, sure, the pilot can make pretty slow turns. But major airports with multiple runways, other airports in the vicinity, military bases, etc, all put hard requirements on the flight corridor. Sometimes the pilot has no choice but to make pretty sharp turns, and that means a pretty fast roll acceleration.

How about... more rudder? Of course, more control surface area means more drag and less fuel efficiency. Wonder if a flying wing style craft that has enough rudder to match traditional cylinder fuselages bank-and-yank capabilities is still more efficient.

Lateral acceleration is less pleasant for passengers. You don’t want peoples drinks to fall off their tray tables for example.

That said there is a fair about of wiggle room so I doubt it’s a significant issue in practice.

Maybe they could try inventing a way of keeping drinks from spilling when the container is tipped over...

I even have a cool name word to describe it: "lid"!

μg coffee cup https://science.nasa.gov/science-news/science-at-nasa/2013/1...

Lid or no lid, it’s still a problem if your drink falls off the tray table. Which is one of the reasons they say to put your tray tables in upright an locked position.

But even beyond that feeling like you’re falling out of your seat is unpleasant.

Automakers solved this problem many years ago, by making cupholders that are deeply recessed instead of thinking that cups wills somehow magically stay in place with a very minimal indentation (see the "cup holders" on the backsides of glove compartments in 1970s American cars).

Airlines would rather have more people in economy than to include cup holders.

You do sometimes see cup holders on private airplanes, but in commercial aviation the efficient solution is to avoid needing them.

Adding decent cupholders to cars didn't make cars bigger.

Similarly, adding decent cupholders to airplanes is not going to reduce passenger space.

Commercial aviation could stick as many as 850 passengers on an A380-800 in it’s maximum configuration, but the most an airline actually gets is 538 because of business and first class passengers having more room. Increasing passenger space by even 1 inch or just a pound of weight per seat makes a real difference.

Better cupholders do not decrease space at all. Some (better) airlines even have them: they flip down from the seatback. They literally take no space at all. This is ridiculous.

Try really should just cut a sized a hole in the back edge of the tray tables.

People falling over is more of a concern, it would take significant lateral acceleration before drinks fell it’s just easy to visualize.

As to why no cup holders, people aren’t going to use them most of the time and they don’t even help that much in turbulence.

The issue isn’t the bank angle but pitch acceleration felt by the passengers when they pilot wants to bank for a turn. Which opens up several methods to compensate.

You could for example more slowly enter a higher bank angle to have an equally fast turn though passengers would feel more pressed into their seats etc.

Turbulence causing roll upsets seems like it could be a larger issue.

you could also put the passengers more towards the middle and the fuel / cargo on the tips. Doesn't solve the problem and balance would be tough I imagine.