Flying-V: Flying long distances energy-efficiently
tudelft.nl
tudelft.nl
> "we’re looking into new options to having a rest or taking meals on a plane. Offering food from a buffet is one of the options we’re sinking our teeth in"
Based on the A380 "promises" of in-flight gyms/casino/salons/creches, I think we can safely call bullshit on this - we'll just get more seats crammed in as usual (in economy at least - perhaps first class will get these?). That is fine - I understand the economics - it is marketing I guess.
Simple. (UK resident.)
That's a scene... of a crèche. It's the same terminology.
It's possible to have a private shower and bedroom onboard an A380 flight, but you will pay dearly for the privilege.
There's room in the market for both extremes as well as in the middle. I doubt you'll get a buffet service on a round trip ticket that costs <$500 (trans-oceanic, at least) as it likely is not economical to offer that. That being said, there are airlines that are offering improved options even in Economy cabins... they just charge for it. An example is Air New Zealand's "Economy Skycouch" https://www.airnewzealand.com/economy-skycouch
So with the possibility that this design could save on fuel costs, maybe airlines will be able to sell upgraded experiences at prices that are today bare-bones. Time will tell.
Although in my experience, many companies that don't care that much about travel expenses pay most of the economy seats. At least on the transatlantic flights I've been on.
There has got to be more tiers
I do it all the time.
https://gyazo.com/1cfc5e5edb0aa4a9734138fce73c002e
Both American flights I'm taking in the next month. All have increased legroom, it literally says "Up to 6 inches".
Heh, I suppose I should mention these are out of Tulsa... :)
Are you really suggesting that airlines make a loss on economy seats?
I wonder if a paid shower pass system would work. You wait your turn, but you get to take a shower, for, say, something like $100. Just seems like it's kept to an all-or-nothing on purpose.
Put 1000 economy class seats into it and fly NYC-London, or Tokyo-SF till it falls apart. I otherwise have no idea how in the world can it make money.
I seriously believe that second hand A380s will eventually see this fate.
To make it truly profitable, you convert the plane to First class, but then you'll need to fill all those seats.
Wendover Productions had a great video on this a few years ago: https://www.youtube.com/watch?v=BzB5xtGGsTc
That video is very wrong compared to real life. For the first: it assumes a full plane. My experience is that economy tends to be full, business has a lot of available seats. For the second: it does not account for the cost of running lounges, fast track security and other complimentary services offered to business and first class passengers.
Look at the companies. Filling the plane with economy passengers and offering low service level is what brings profitability.
I can tell you there is a "saloon" on this thing, because at 37000 feet I stood in my Qatar PJ's with two other guys and drank cocktails in the bar.
surreal experience for me...
500 years ago it took Columbus and his crew of 88 men ten weeks to reach America in three 58 foot, 100 ton wooden boats pushed along the ocean by wind. They had no toilets, ate boiled food with cheese and salted meats.
Today, 525 of us can travel on a 230 feet long, 600 ton flying boat lifted above the clouds crossing over the north pole from Los Angeles to Dubai at Mach 0.8 in 17 hours. We can watch movies, special order a kosher or vegetarian meal, drink fine wine while wearing complimentary socks and PJ's. For a few thousand dollars each.
The rules are different for commercial aviation and for the military. The goal of commercial aviation is to get people to their destination, as safely and cheaply as possible, you don't have to fight against an enemy. As a result, commercial aviation is not very creative. They tend to use proven designs and incremental improvement.
Making a civilian flying wing aircraft will be a certification nightmare, which may involve several full-scale prototypes, a new kind of training for pilots, etc... It is a world where there is still a switch for the "no smoking" sign in the cockpit that doesn't do anything because all flights are non smoking now. Removing the button would require re-qualification and it is easier to leave it there.
The B737-MAX fiasco is another illustration. Just look at how far their went just to limit change...
I'm not saying that a flying wing commercial aircraft can't be done, but I have a feeling that the placement of passengers won't be the biggest issue.
RC flying wings are regularly flown by humans without any software in between the input and control surfaces.
As you might imagine, the scale and operating requirements of _actual_ aircraft introduces complex engineering challenges that aren't present in toys.
It may be difficult to achieve the required flight characteristics without software augmentation in a flying wing, even if RC hobbyists can usually fly them manually without crashing. The 737 MAX has raised the question of whether it's a good idea to approve transport category aircraft that require help from software to have acceptable flight characteristics.
MCAS (or another means to accomplish the same goal) was required for the aircraft to meet certification requirements, regardless of whether it was to share a common type rating with the rest of the 737 fleet (so long as it shared the landing gear with the rest of the 73' line, it was going to have this adverse aerodynamic raw result).
> 75 percent of maximum continuous power for reciprocating engines or the maximum power or thrust selected by the applicant as an operating limitation for use during climb for turbine engines; and
Wouldn't that give a stable pitch response because the thrust relative to the center of mass is constant? Also if the MCAS is always pushing the plane out of the given AoA (which seems to be what it's logic is, if AoA > x trim down until AoA < x) would that be considered outside the flight envelope anyways? The stick force curve goes screwy for every aircraft in a stall.
It is fine if a fighter jet crashes when the electronics fail. Much less so for a passenger yet.
I certainly hope not.
Technically this is definitely not true. Any modern RC wing will use software to do elevon mixing and get elevator/aileron input into the actual mechanical surfaces. It's possible to do this mechanically but software is so much simpler it's a no brainer to just have a servo per surface and do everything else in software.
It may be true in the spirit of this discussion in the sense that most RC wings just do fixed software mappings between inputs and outputs instead of having an on-board computer taking into account attitude/airspeed/etc and adjusting the inputs based on this. That's what's actually needed for aerodynamically unstable aircraft and RC wings generally don't need that, although similar kinds of hardware do exist in the RC world and are used sometimes.
The relevant question is whether there is an IMU providing feedback without which the plane would not fly.
[1] http://ardupilot.org/copter/docs/common-choosing-a-flight-co...
What kind of observations do you have to support your statement?
Ps. Most of them I have seen, and built, has been to play a game where you put a string on your tail and try to cut each others with the propeller. They were airodynamic stable.
However in RC gliders (slope especially) it's not necessary - the plane is made of foam and will bounce off any obstacle with minor damage, and they don't fly at long range. It's quite uncommon in this type of flying.
I've flown flying wing gliders that didn't have a flight controller - they work just fine. They're very aerobatic, though, which is less than ideal for carrying passengers.
The main issue I can see with this flying configuration is that the Centre of Gravity is extremely sensitive. You have quite a lot of leeway with a conventional airframe, but with a flying wing the CoG has to be spot-on or it becomes uncontrollable.
If your reference is simple foam planes this is true. But in high-performance applications like F3F people will run on-board accelerometer based control units that stabilize flight.
The whole discussion is a bit silly though. The standard for toys is clearly not the same as for a passenger carrying commercial airliner, even if sometimes they are very expensive toys...
> "everybody" puts a flight controller between the servos and the receiver these days
This was the point I was trying to address. It's definitely commonplace, but not essential, and the plane is aerodynamically stable without one.
The 737 fiasco was almost entirely because they refuse to allow new 737 designs to require a new type rating and therefore force weird aircraft/cockpit designs that would otherwise seem stupid.
Also, commercial aircraft aren't really certified based on how they handle stalls, spins and spirals. Swept wings already handle those situations very badly and therefore systems are designed to prevent the aircraft from entering those parts of its flight envelope.
The wing planform is passively stable without a tail, so there should be no issues related to certification as suggested upthread.
Source for both is this video from the designer: https://www.jbenad.com/news/2015/2/4/flyingv
Would the best seats still be in the front?
I think of riding a schoolbus... I know the rearmost seats were bumpier, but were the calmest seats near the center or the front?
where should you put the bathrooms?
Also, should the plane flex or should it be rigid?
Disclaimer: I am not an aviation expert, and don't know what I'm talking about.
Source needed
The Global Hawk has a wingspan over 50% as long as an A350, yet it weighs 1/10th as much. There is no comparison.
I agree that there is no comparison - in the sense that the two cannot be compared that way. For example: A childhood toy of mine (a compressed-air plane) needs a wingspan 1% as long as an A350, yet it only weighs 1/1,000,000th as much - and can still only stay airborne for 30 seconds!
This discussion [1] on the different most-aerodynamic plane shapes is fairly interesting, and certainly doesn't confirm the person above who claimed that a flying wing is the most aerodynamic shape.
[1] https://aviation.stackexchange.com/questions/17119/what-is-t...
Depends on the use case: for a feeder aircraft (regional to international airport) load, range and speed isn't terribly important, but fuel economy still is, for economical reasons (and for ecological reasons, which translate into economical by making the tickets an easier sell to a climate-aware population). In well developed regions, the main draw of feeder planes over ground transportation is not travel speed, but the convenience and piece of mind of checking in at your home airport.
Since a lot of regional (or effectively regional) airports are wildly overbuilt in hopes of attracting bigger connections there could be a market for a plane that fills the available width with a modern high aspect ratio wing to max out efficiency for small loads. If new aircraft designs weren't prohibitively expensive or fuel would be much more expensive this kind of plane would exist. Basically, put the wing of a Global Hawk on an ERJ-145.
Note 1: Boeing once toyed with a blended wing-body, a sort of flying wing, to produce dramatically better aerodynamics and fuel efficiency. Passengers would have sat in a wide cabin, rather like a small amphitheater. But tests with a mock-up produced such a negative reaction that the company dropped the technology, except for military refueling aircraft.
Although, I found an article from 2018 [1], quoting a Boeing VP of Product Development and Future Airplane Development, which basically says a blended wing design for commercial passenger aviation is unlikely because the required minimum height for passenger loading implies a minimum width that is quite large, and may not be very compatible with existing airports.
[1] https://leehamnews.com/2018/04/03/dont-look-for-commercial-b...
Aerodynamically the wetted area that generates drag without lift is undesirable. You need a wing generate lift, but everything else is there for something else like stability, handling, payload etc.
In conventional "tailplane" configuration the fuselage and tail are just providing drag and almost no lift (tail has little wings 'upside down' generating negative lift and trim drag). If you have canard or some more exotic wing configuration you can have all wings generating lift but there is still drag from the body. In clean flying wing, there is nothing else except the lift producing wing.
Swept wing in the Flying-V is clever way to get a optimal thickness-to-chord while keeping the total surface area in check.
(If I understand correctly, what is required is that its angle of attack is lower than the one of the main wing, or equivalently (if the wings have the same shape) its wing loading.)
See section 6.1 here, for example:
http://www.av8n.com/how/htm/aoastab.html#sec-basic-stability
But as the source you provides say: "indeed most aircraft operate with negative tail lift most of the time."
In practice all commercial aircraft have the center of mass so much forward that require negative lift for stability. If you look at the cross section of the horizontal stabilizer, it's like wing upside down.
See also:
https://aviation.stackexchange.com/questions/34963/is-a380s-...
https://aviation.stackexchange.com/questions/30400/will-opti...
In case of a crash, the seats will move forward and then spring back, if you have your body in between of the two seats in front of you while they do this, you can easily get crushed.
e.g. Billy Mays
Not that these are deal breakers, but it's generally safe to assume that at least economy passenger experiences are going to get worse, not better.
The thought experiment to play with is, swap out windows for computer displays, still with the air gap seen on some planes, but not for all windows and see what transpires.
Problem solved.
-Airline execs once economy passengers get used to having no windows on one side.
(A broken window still lets you see outside)
I could imagine seats facing "outwards", with a corridor along the windows. Kinda like a cinema but the screen is replaced by a row of windows. This way no one gets to "hog" the window seat (apart from the front row, and even then others can still see the windows on their walk along the corridors to the toilets etc). Bonus points for raised stadium-style seating with storage lockers under the rows at the back.
Also, the plane tilts by up to 20 degrees.
Acceleration was about 0.4 g with peak of 0.5 g. Second stage climb (5-10K) was 0.2g nose up. Rest of climb was 0.1g. Decel was 0.3-0.4 g also with a peak at 0.5 g.
On the big engine Lears, I’m quite sure the accel is higher than braking plus reversers. Airliners might also have higher accel rates on shorter runways as they often do power limited takeoffs on long runways in the interest of maintenance economy.
Related, we had a hold for weather at the destination, so I checked the pitch of the plane in the hold. It was 0.1 g nose up, which was quite noticeable when walking up the aisle to the restroom.
The same issue is for back facing seats on autonomous cars. I don't see it happening.
The flying-V solves that.
20% less fuel is huge, that's the real plus.
https://aviation.stackexchange.com/questions/65124/how-is-a-...
https://aviation.stackexchange.com/questions/12782/why-are-t...
A little more skepticism:
> Sadly for the Flying-V, it will probably fail like the blended wing body designs we've seen down the years. It's for the same reason, too: airplanes bank as they turn. That's not much of a problem in a conventional airliner design, where passengers are never that far from the plane's central axis. But as you move further out from that central axis the effect becomes a lot more pronounced.
https://arstechnica.com/cars/2019/06/radical-new-airliner-co...
There really is nothing new about a lifting-body design.
The A320 was the first all-digital plane in 1984, so it was unlikely anything before that could have been developed (and passed FAA/EASA standards).
Designers could reduce the problem to an extent by building a double deck passenger compartment and putting the baggage compartments out toward the wings, rather than the current standard design which places passengers on the upper level and bags on the lower level. But there are limits to how well that can scale. I'm skeptical that we'll ever see flying wing or blended wing body designs used for airliners. Cargo and military applications are probably more realistic.
What if the seats far from the axis of rotation faced sideways instead of forward? People don't seem to be as affected by pitch changes as they are by roll changes, probably because we are get a lot of exposure to pitch changes whenever we drive in a hilly area.
A last row width of 25m is much wider than the 5m of a conventional aircraft, but much smaller than 70m.
However, judging by the window placement, the passengers furthest aft are maybe twice as far from the center of rotation compared to a widebody? That's far better than any other flying wing/blended wing concepts I've seen to date.
[edit] Also the traditional place for first-class travellers will be no further than in a widebody aircraft, so the people for whom the airlines actually care about comfort will be unaffected.
It's entering an exiting the turn where you could have some greater effects. But again, so long as you use a slow roll rate, it shouldn't be too noticeable.
Disclaimer: I work at the same research group at the Delft University
Are people going to be bouncing up and down all the time?
I wonder how bad the odds would be even if an aircraft like this showed perfect flight safety characteristics (which is not a given).
> Passenger comfort is also taken into account.
That could mean just about anything, fwiw.
Then again there are only so many planes that can land on a given airport in the course of one day.
1. https://en.wikipedia.org/wiki/Blended_wing_body 2. https://en.wikipedia.org/wiki/Boeing_X-48
MIT also came up with D8 or double bubble (see: https://www.nasa.gov/content/the-double-bubble-d8-0) but that, too, was 9 years ago
It certainly seems as though we're stuck in a local minima w.r.t. commercial aircraft.
For one thing, while the split fuselage in the images appears similar to that of a conventional airliner, I expect it would actually be considerably shorter than that of a jet with comparable capacity, the reason being that much of the luggage and equipment that would normally be stowed below the passenger compartment could instead be relocated to the center of the 'v'.
You would still have somewhat more frontal surface though I would think. Perhaps this could be outweighed (no pun intended) by weight savings and lower surface area. Although I wonder if some of the savings would have to come from flying more slowly, which this design might facilitate.
I don't know anything much about aeronautics though, so would love input from someone who does!
IMHO interesting concept but the thing to be investing in would be electric engines (hybrid or battery) as that will cut fuel costs a lot more potentially. 20% is an incremental improvement and potentially not good enough by the time this gets productized and never mind the time when this gets retired a few decades later (in the best case). So, in short, I think this won't fly (bad pun, sorry) because it's not anywhere near good enough by the time it can reach the market (15+ years?).
This thing still takes about 140 tonnes of fuel. That's a lot of money to fly from A to B using a plane that is still a decade+ away. All I'm saying is that 20% cost reductions is not nearly ambitious enough for that type of long term project given the stuff that is already happening today and given the stuff that is likely to happen in the next decade.
Engines have taken out hydraulic control lines in the past.
However, for aerodynamic efficiency it is the lift/drag ratio that matters. And while in a normal airliner the body provides very minimal lift, here it's basically a wing and thus generates a lot of lift.
The end result is that while the drag is probably worse, lift is likely improved enough to compensate.
(Also, drag might not be that bad given you do not have a tail, which is pretty awful aerodynamically speaking)
"The aircraft is designed to be over 50% more fuel efficient[1] compared to aircraft currently under production."
There’s a good reason we don’t see any aircraft with a design like this today. It doesn’t work financially or aerodynamically.
I also wonder where would the fuel be stored. needs to be around the center of mass and lift, to avoid the com shifting around as the planes flies. and there aren't wings there conveniently placed near the com to store it, so, is it going to end up below the passengers? that'd be a huge safety hazard.
The last crash I saw on the news had something nasty going on with the engines hitting the tarmac, the above wing placement of the engines is a safety feature as I see it, even though that design choice is more out of consideration for noise - it should be quieter for those living under a flight path.
From the evolution of the bicycle to the mountain bike I can remember that a big, thin-walled tube is stronger and lighter than a narrow, thick-walled tube. I know planes are different, but bigger does not automatically mean heavier.
You could have all of the fuel at the back, behind the passengers and engines. The flight control surfaces and some thrust vectoring could accommodate that.
A U.S company called Boeing know a thing or two about making automatic systems for mitigating against a less than perfect centre of gravity. They went for less than ideally located engines rather than less than ideally located fuel. Allegedly there have been a couple of hiccups with this system but the general idea is that not even the pilots know that there is a computer accounting for changes in centre of lift/gravity, it just works.
On Airbus planes it has always been fly by wire. By 2050 - when this V thing is supposed to go into service - the idea that a human should fly a plane will seem daft, if the computer is doing it all anyway then the plane does not have to be dynamically stable or even balanced from side to side. It should be able to precisely balance out the shear forces no matter what the conditions. You could even turn the thing without banking.
Tongue in cheek criticisms aside, it is better than my student project and a nice thing for KLM's 100 year celebrations.
That would cause quite the difference in handling between takeoff and handling. The fuel tanks span the length of the fuselage in this design — and I'm sure that's intentional.
Is there greater surface area? One way to look at this design is to take an Airbus 350, take of the wings, bend the body in a V-shape and, finally, flatten it to make it generate lift.
That won’t be exactly correct (for example, flattening the body will decrease volume, and, likely, max # of passengers), but given that it has the same passenger capacity, I would think it’s a decent approximation. So, if you need extra material, the loss of those wings gives you some room before the resulting plane becomes heavier than a A-350.
Below: Engines can strike the ground. There is more debris ingestion, ranging from sand and burst tires to people and baggage carts. Noise regulations are harder to satisfy.
Above: Failure causes nose-up (as power is lost), which may lead to a stall. The aircraft sits lower in the water after a water landing. Being nose-up may put the intakes in slow turbulent air flow, killing performance and possibly stalling the intakes. Ice and rain may come off the body, to be ingested by the engines.
Some things could go either way. Maintenance is going to involve a crane or a jack to get the engines off.
"Flying Pinto".
That is such a meaningless claim.
The whole thing is a PR piece, calling the A350 the world's most advanced airplane must have satisfied some requirement for KLM.
> What’s more, the Flying-V will carry the same number of passengers – 314 in the standard configuration – and the same volume of cargo, 160m3.
https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#Propu...
See e.g:
https://en.wikipedia.org/wiki/Energy_efficiency_in_transpor
> The energy efficiency in transport is the useful travelled distance, of passengers, goods or any type of load; divided by the total energy put into the transport propulsion means.
I highly doubt that those numbers are trustworthy considering how closely we are scraping fuel efficiency numbers, unless there is some performance metric they aren't mentioned that has degraded.
If this design actually provides the claimed results, connecting 2 such wings (one behind the other) with a long fuselage (i.e. >---> which would incur almost no additional drag and twice the lift) would be even better, no?
The "---" portion of your idea provides no lift, only drag.
There are exceptions.
https://www.spangdahlem.af.mil/News/Commentaries/Display/Art...
In a flying wing, computer failure is a certain airframe and passenger loss. I don't know any engineers who write flawless code. Do you?
In a working cockpit, there should never be a question as to who is actually flying the plane...
For example:
https://en.wikipedia.org/wiki/2008_Andersen_Air_Force_Base_B...
> After the wheels lifted from the runway, which caused the flight control system to switch to different control laws, the erroneously sensed negative angle of attack caused the computers to inject a sudden, 1.6‑g, uncommanded 30-degree pitch-up maneuver. The combination of slow lift-off speed and the extreme angle of attack (and attendant drag) resulted in an unrecoverable stall, yaw, and descent.
This seems to support GP's assertion that "without very precise computer control they are uncontrollable" and "computer failure is a certain airframe and passenger loss"
I think it requires a little more careful design then traditional plane bodies, so there is some sense in which flying wings are less stable naturally. But the claim that flying wings are necessarily unstable without computer control seems to be false.
Not if you use an airfoil with an appropriate pitching moment, that's designed for flying wings. Look at all of the hobbyist models that fly just fine using very crude control inputs.
>In a flying wing, computer failure is a certain airframe and passenger loss.
No.
[1] https://en.wikipedia.org/wiki/Marske_Pioneer
The design in question is more of a flying dart than a flying wing anyway. There is no reason to think it would be particularly unstable in pitch.