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Comment by nicktelford | Hacker News Reader

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 is normally not very far. In blended wing designs, the distance could be considerably greater, making this sensation much more intense.

The workaround for this would be to simply use shallower bank angles, but I suspect that would require some pretty major changes to navigation rules, as it would drastically increase the turn radius.

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> 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 is a problem that a market can easily solve: make the more central seats more expensive than the outer ones. If the pricing is right, the demand for the various kinds/positions of seats will be balanced.

P.S. I can actually imagine that there do exist people who prefer the outer seats because they like the acceleration that makes the flight feel more like a carnival ride. :-)

Totally on board with flying in the outboard cheap seats, at least for any flight where I don't have to sleep. Flights are incredibly boring aside from takeoff and landing, and I love roller coasters. :)

I have a feeling there are enough of us to make it work in the market and still fill planes, just instead of first-business-coach going front-to-back it'll go center-out, like a theater.

Man you must like some adventure.

> This is a problem that a market can easily solve: make the more central seats more expensive than the outer ones.

There are risks to create a "vomit comet". Think about cleaning bills.

I mean, the rise of low-cost carriers has shown pretty clearly that passengers are willing to put up with a lot for cheaper tickets…

This "falling" feeling is my favorite part about flying

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.

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.

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.

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"!

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.

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

Cut a hole for cups to sit in on 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.

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.

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.

Balanced out by the centripetal force of the plane turning!

Underneath is a relative term.

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

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.

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.

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

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.

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.

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.

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

I wouldn’t want that on a red-eye, but it would add some entertainment to a one-hour flight.

Would legit pay extra for the fun ha

>This also applies to existing aircraft, but the amount you drop/rise is limited by the your distance from the axis of rotation, which is normally not very far.

When a plane is crabbing, as in coming in sideways towards the runway, when it touches down, and suddenly pivots to normal runway directions, even passengers in the rear of a normal plane, might be accelerated hard around the yaw axis.

Banking isn't a problem in practice or your coffee wouldn't stay in your cup while standing on the table.

That's called a "coordinated turn", and it's what airline pilots should be aiming at whenever possible. In a coordinated turn, "down" remains aimed at the floor, regardless of actual bank angle. There's even an instrument (the turn-and-bank indicator) designed expressly to help pilots execute coordinated turns, which are generally considered a mark of a capable pilot in any plane...

Does this mean if a blended wing plane banks hard and you stand up on one side of the plane you could potentially jump your way across to the other side a bit?

It might be good to have a disincentive for the peripheral window seats. Some also find that feeling of falling / turbulence enjoyable.

people in the center, cargo in the peripherals

makes evacuaion harder that it has to be

this issue is why the startup in socal is focusing on air freight for their flying wing design.

I'd image the biggest reason is that risk tolerance is lower for cargo companies than for passenger airlines, and that cargo companies are more inclined to run a subset of their fleet as an "experimental" model vs the consistency that passengers expect. They probably also have the biggest potential gains given there's only so tight you can pack people.

they don't have to be shallower, just bank angle increase should be slower than usual.

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