World's Most Efficient Passenger Plane Gets Hydrogen Powertrain (newatlas.com) 59
Otto's Celara 500L -- "the most fuel-efficient, commercially viable business aircraft in the world" -- is about to get a hydrogen fuel cell powertrain. New Atlas reports: The Celera 500L is a truly remarkable design. Otto Aviation says its odd shape delivers an astonishing 59 percent reduction in drag, and a massive leap in efficiency and range compared to traditional plane geometries. [...] The whole thing is designed to maximize laminar flow -- smooth layers of airflow with little to no mixing of adjacent layers moving at different speeds. This avoids the swirls and eddies that lead to air turbulence at speed, causing aerodynamic drag and wasted energy. Laminar flow is by no means a new concept, but Otto says it's pushed the idea so far forward with the Celera design that it uses 80 percent less fuel than a traditional design. No, that's not a typo. [...]
Now clearly, an 80 percent reduction in fossil fuel use is an environmental win in and of itself. But if there's one sector in aviation that's crying out for brain-busting efficiency figures like the Celera promises, it's the emerging zero-emissions sector, which is currently struggling against poor range figures thanks to the low energy density of lithium batteries. Indeed, when we first wrote about the Celera 500L back in 2020, many questioned why the heck this thing wasn't electric from the get go. And it seems Otto is on board with the idea, as it's now announced a collaboration with hydrogen aviation pioneers ZeroAvia to develop a fuel cell-electric powertrain specific to the Celera's requirements.
This airframe's bulbous shape works well with a hydrogen concept -- hydrogen powertrains can weigh much less than battery-electric ones, but they tend to take up a bit of space. Still, ZeroAvia is being relatively humble with its ambitions to begin with, aiming for a range of just 1,000 nautical miles (1,852 km) of zero-emissions range for a hydrogen-fueled Celera. Still, that's a very useful distance, and pretty extraordinary for a clean electric passenger plane.
Now clearly, an 80 percent reduction in fossil fuel use is an environmental win in and of itself. But if there's one sector in aviation that's crying out for brain-busting efficiency figures like the Celera promises, it's the emerging zero-emissions sector, which is currently struggling against poor range figures thanks to the low energy density of lithium batteries. Indeed, when we first wrote about the Celera 500L back in 2020, many questioned why the heck this thing wasn't electric from the get go. And it seems Otto is on board with the idea, as it's now announced a collaboration with hydrogen aviation pioneers ZeroAvia to develop a fuel cell-electric powertrain specific to the Celera's requirements.
This airframe's bulbous shape works well with a hydrogen concept -- hydrogen powertrains can weigh much less than battery-electric ones, but they tend to take up a bit of space. Still, ZeroAvia is being relatively humble with its ambitions to begin with, aiming for a range of just 1,000 nautical miles (1,852 km) of zero-emissions range for a hydrogen-fueled Celera. Still, that's a very useful distance, and pretty extraordinary for a clean electric passenger plane.
No hard numbers (Score:3, Insightful)
Re: No hard numbers (Score:2)
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There aren't any actual numbers in the article to evaluate the claim of the most efficient passenger plane.
The headline says it is "the most efficient passenger plane."
The article says it is "the most efficient commercially viable business aircraft."
Re:No hard numbers (Score:5, Informative)
The article is lying. This aircraft is not in commercial use and it's commercial viability is a very big question mark.
It's also not upscalable. The entire point behind it is to get to absolute highest aircraft size while maintaining laminar flow among the fuselage to minimize drag. This isn't a new thing, P-51 used laminar flow in wing design to get to that excellent fuel efficiency that allowed it to escort bombers to Germany and back. This is WW2 vintage technology.
We don't really use that type of aircraft body because of extreme size limits involved. Largest actually in use is P.180 Avanti. It's a typical executive transport with less than 10 passengers capacity. Otto's design being talked about is just a prototype. It's viability is a huge question mark. Even it working as intended is a huge question mark because of extremely tight tolerances on everything involved as to not disrupt the laminar flow. Even if design flies as intended, how much more expensive the maintenance would be not to disturb the flow is another huge question.
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Even if it doesn't scale much beyond 6 passengers, that's still a pretty decent segment - all sorts of GA and smaller executive planes would fall below this size and I'm sure GA guys in particular would love to save some money on avgas.
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Like I mention above, there has already been an attempt at taking that niche with P.180 Avanti. It didn't really work. Too slow due to laminar flow requirements, too noisy because propellers have to chop into airflow disturbed by the airfoil.
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The P51, whilst having an early laminar flow airfoil, never actually did achieve large scale laminar flow on its wing due to imperfections from rivets etc. It took the arrival of moulded composite construction to get the smoothness required to have successful laminar flow. A peak to peak waviness of 4 thousands of an inch simply could not be done in riveted aluminium construction.
It did have a large fuel capacity though.
Further, this design uses a pusher propeller, to avoid the turbulent wash over the wings
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I explain history of discovering the technology in question, how it works, and what are its limitations.
I even reference a functional commercial aircraft built on this principle, that in fact does use pusher props for the reason of flow management. Which was a commercial failure to the point of bankrupting the company making it.
Meanwhile, you're literally talking about sail planes as examples of something that works, as if that is not a great example of "small and slow" in your other reply to my post. And t
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I complain about your usual bullshit Luckyo, its noted you dont actually respond to the points that make your inaccuracy clear, just resort to deflection. Sailplanes were the earliest users of successful laminar flow airfoils, and what applies at low speed only improves at higher Re.
You have a reputation for making shit up, and flat out lying, justly deserved.
Having done airfoil design studies using the eppler program since the 80’s I know a thing or two about the subject.your posts make it clear you
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In other words, you call people names when they point out obvious flaws in your arguments that you cannot address without conceding your point. As evidenced in this last post, where you still fail to address any of the points raised and instead bitch, troll, raise completely different points as new red herrings and finally make a desperate appeal to your personal authority. After you have already demonstrated both lack of knowledge in the subject and lack of ability to even comprehend the points being raise
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I guess I scared remains of your courage away, and you went AC. Good on you. At least you know your limits.
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There aren't any actual numbers in the article to evaluate the claim of the most efficient passenger plane. It's hard to believe that a small-scale vehicle can meet the efficiency of large-scale passenger jets which regularly get +100 mpg/passenger.
But TFA mentions a few stats for a the plane, with an implied comparison to others of its size:
Running on an efficient 550-horsepower combustion engine, Otto claims this thing will fly six passengers up to 4,500 nautical miles (8,334 km) at cruise speeds over 460 mph (740 km/h), challenging small business jets for top speed while more than doubling their range. An impressive glide ratio of 22:1 allows pilots to switch off the engine altogether and glide for up to 120 miles (200 km) completely unpowered. This monster efficiency factor, says Otto, should make the Celera some 5-7 times cheaper to run than a comparable jet.
And they note that it won't scale up to the size of a full-size airliner, but should be fine for smaller planes:
Mind you, it wont scale up to full-size airliner size, since the low-drag laminar flow model relies on a width-to-length ratio that'd be impractical in a bigger bird. But Otto says it'll scale up to take 19 passengers, and there are plenty of markets that could make use of an efficient airframe in the 6-19 passenger space.
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Obviously it is the most efficient in its class.
Only idiots compare different things that belong into different classes and then complain ...
Caravelle glided as well (Score:5, Informative)
If not better.
Jet Airliner from the 50s, more than a 100 passengers, with a glide ratio over 22:1.
https://en.wikipedia.org/wiki/... [wikipedia.org]
Original French wikipedia page has more data
https://fr.wikipedia.org/wiki/... [wikipedia.org]
Laminar Flow (Score:5, Informative)
Whilst a laminar flow boundary layer does offer great drag reductions, even early ones were at least a 25% improvement on the older turbulent airfoils, it is also extremely sensitive to small surface imperfections. Modern sailplanes get their great performance thru laminar flow sections, however, even small squashed bugs on the leading edge, or rain drops on the wings can cause significant losses, such that special bug wipers are fitted to clean the leading edge of the wings in flight. Newer airfoils are less sensitive than the early laminar flow sections, for example my 80’s DG 200/17m sailplane suffers a 30%+ loss of performance with bugs or rain. Unfortunately bug wipers cannot be used on the fuselage.
Bugs are of course seasonal, and mainly occur at lower altitudes, so if the plane can get above the lower areas without contamination, it will perform very well.
I call BS on "59 percent reduction in drag" (Score:3, Insightful)
Add hydrogen to that, and someone is playing buzzword bingo.
Charlatans, the lot of them.
Re: I call BS on "59 percent reduction in drag" (Score:2)
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You could've used the exact same argument against reusable first stage orbital rockets some years ago.
No, I could have used the exact same argument on the entire set of disruptively great innovation announcements made over that time period.
And I would have been overwhelmingly correct, save for the one or two extremely rare counterexamples that no one had the knowledge to identify ahead of time.
Re: I call BS on "59 percent reduction in drag" (Score:2)
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Re: I call BS on "59 percent reduction in drag" (Score:1)
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Yet if those who made the disruptions that do work and transform things often over the generations had listened to your naysaying, we'd still be picking up random rocks to throw at wild game for a living. Spears with sticks lashed to sharp pointy rocks? That buzzword-fest will never work! It will fall apart on the first throw.
Are you saying that criticizing deceptive marketing, is the same as not wanting anyone to invent anything?
Because if you are, that's trolling.
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You could've used the exact same argument against reusable first stage orbital rockets some years ago.
Reusable first stage orbital rockets have been done before so we know what they do.
Re:I call BS on "59 percent reduction in drag" (Score:4, Interesting)
The issue is that while the drag reduction might be decent, the body shape required to achieve it doesnt scale to large civil airliner sizes - too much dead weight involved, so once you are past the sweet spot in terms of size, you are hauling a lot more dead weight and that ups your fuel burn as a result.
So this might revolutionise small general aviation passenger aircraft but not thr large civil end of the market - and you cant replace a single large civil aircraft with many of these because then slot management at airports around the world and increased load on ATC would be insane.
The drag reduction is but one variable in many that has to be considered.
Re: I call BS on "59 percent reduction in drag" (Score:2)
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nobody is randomly going to do this.
Nobody is randomly going to do this while preserving the size, shape and passenger carrying capacity of a traditional plane. We are able to trade off a lot of things. This isn't sending shockwaves through the industry, you'd understand that just by looking at a picture of the thing.
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This isn't sending shockwaves through the industry, you'd understand that just by looking at a picture of the thing.
Which was precisely my experience with this puff post. Saw the headline, never heard of it, looked it up on Wikipedia and saw instantly "Oh, not a passenger plane, just as small business plan." Calling it a passenger plane is false - sure when certified it carries 6 passengers, but the term "passenger plane" is exclusively used for commercial airliners that carry commercial passengers. We don't call business planes, or civil light aviation "passenger planes".
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What do you call them, "cargo planes"?
If it's a single seater, or maybe a 2-seater with a copilot, it's not a passenger plane. But if it carries passengers, it's a passenger plane.
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We don't call business planes, or civil light aviation "passenger planes".
Errr yeah we do. But anyway point is that yes just because you made an assumption about size and shape doesn't mean that high percentage drag reduction figures are bullshit.
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Massive reduction in drag from designing around uninterrupted laminar flow is a known thing. First use in airfoils was in P-51, and it was in part responsible for that fighter getting range to cover bombers for trip to Germany and back.
We don't really build aircraft fuselage around this model for several reasons. First is the size limit. Largest of this body type actually in use is P.180 Avanti, and it has a payload of less than ten passengers. And that is pushing the size limit already and proved largely n
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The specific speed problem is fixed by flaps, that keep the fuselage aligned correctly to the airflow. Modern sailplanes get laminar flow to up to 95% of chord on the lower surface, and 60% on the upper surface over a wide speed range. Its a solved problem.
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Not at speeds needed for commercial flight. I once again reference P.180 Avanti, which is a flying aircraft with significant production numbers behind it and not some random prototype.
The problem "is solved" in that we understand that we cannot make it work beyond certain speeds and sizes. Remind me, what's Vne in those sailplanes and how does it compare to modern executive aviation tubrojets and turboprops? And how big are they?
There's your answer.
It's a prototype, not a passenger plane (Score:2, Redundant)
Give me a call once it's certified to carry passengers
Car is to train as regional air is to national (Score:2)
How many people would take a train to travel 100 miles instead of driving their car? Almost no one. But increase that trip distance to 1,000 miles, and that ratio would flip.
There are huge advantages to having a broader distribution of transportation hubs and routes. Traveling by national air service today can be a grit-your-teeth experience, and is enormously wasteful in terms of time and bother. Imagine if instead you could just drive your car to a parking lot near where you live, walk right onto a plane,
Re: Car is to train as regional air is to national (Score:3)
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The problem with taking a train is when you reach your destination, you don't have a car.
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That problem only exists in "weird countries".
Suppose you travel to London or Paris, what use would having your own car there have?
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I live in the Metro DC area of the US, and take the train daily for my commute. It just so happens that I am only 5 minutes away from where I need to go on both ends of that connection, so of course the train is much more efficient. For me.
And there's the rub. It's likely that only a sliver of the population of my area is in a similar situation.
We have been talking about adding more subway lines in DC, and even though I am a daily user, I'm not so sure that makes a lot of sense. The amount of money we're ta
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I lived in the DC burbs (both MD and VA) for 37 years. The Metro sucks ass. It's nowhere near as good a system as many others...Paris, London, NY, etc.
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How many people would take a train to travel 100 miles instead of driving their car? Almost no one. ...
You must be an American
This is meant to replace small corporate jets (Score:3, Informative)
This design will not replace jetliners. It cannot be made that big.
It is meant as an alternative to corporate jets.
If it gets the sort of fuel efficiency they claim, that would be a very big deal.
Most 6 passenger propeller airplanes get about 15mpg, and cruise about 215 mph. This is supposed to get about 40mpg, and cruise close to 400 mph.
A highly efficient 6 passenger corporate jet might get 5 mpg.
careful with terms (Score:2)
...like "commercially viable" considering all they've built of this wonder plane is a prototype and the "certainty" that "it must be attractive to the many (?) 6-19 passenger commercial operations that exist".
In my experience, no. Such operations are generally subsidised by local governments (and so technically aren't "commercially viable" in the first place. They operate on shoe string budgets, using extremely durable, easily repaired aircraft.
There are a lot - a LOT - of practical hurdles between "a cle
relevant (Score:4, Insightful)
I think this is curious because the efficacy of a diesel at the altitudes they need to reach to approach those performance numbers was always suspect. This may not be a green mine as much as a desperate effort to find power where they didn't have it...from someone almost infinitely more knowledgeable in the subject:
https://www.flyingmag.com/tech... [flyingmag.com]
Frankly, this just makes it smell more like investor-bait than an actual aircraft intended to ever exist.
Laminar flow used as snake oil (Score:5, Informative)
Now let's have a look how much laminar flow will be possible. Flight speed is claimed to be 205 m/s in maybe 25,000 ft = 7620 m. The Reynolds number per meter in these conditions is 7,314,000. Flat plate flow shows laminar to turbulent transition at about 400,000. With a stabilizing pressure gradient this can be shifted to maybe 4,000,000. So the first 55 cm of fuselage length will exhibit laminar flow but then turbulent transition is unavoidable. I cannot find dimensions for the Celera 500 L, but I think it is fair to say that laminar flow on the fuselage is insignificant. This corroborates well with other aircraft for which a lot of laminar flow had been claimed.
If the 22:1 L/D can be sustained up to cruise speed, the whole aircraft cannot weigh more than 3033 kg when using the given installed power and realistic assumptions about propeller efficiency. This is less than half of a Beechcraft King Air 350 which Otto Aviation uses for cabin size comparisons. The King Air, having a smaller cabin and lighter PT6A engines, still needs an MTOW of 6800 kg. Judge for yourself
The claimed L/D of the airframe is credible but that doesn't add up to the claims made regarding fuel consumption and speed relative to jets. Laminar flow seems to be used as the snake oil to sell this to gullible customers.
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Laminar flow will persist as long as the pressure over the surface is rising, and the air accelerating. Seperation and turbulent flow tend to occur at or after the start of pressure recovery.
Oops (Score:2)
Correction, got my pressure and velocity the wrong way round, too early in the morning.
Should have read tends to persist when the pressure is falling and the velocity rising.
Yeah. Sure. Right. (Score:2, Insightful)
> the most fuel-efficient, commercially viable business aircraft in the world
Except:
1) It's not commercially viable because it doesn't actually exist yet
2) It's not certified as a business aircraft
So literally none of that is true. There are of course also questions about if their claimed efficiency figures are true (or even possible) and if the efficiency savings will be enough to make it a viable alternative to other comparable but much cheaper aircraft.
wind (Score:1)
Looks interesting but there are some challenges... (Score:1)
Looks like an impressive prototype, with some reasonable honesty (quite good honesty as these things go) about the "built-in" limitations.
I'm a bit dubious about the speed claim, and note they have gotten nowhere near that in their test flights so far (740 km/hr claimed versus 400 km/hr delivered in testing so far - it's a long way from 400 to 740). But if they get there, that is seriously close to jetliner speed.
It's also going to be challenging to imagine that a single engine plane will be allowed to fly
Hydrogen is a terrible fuel. (Score:1)
Hydrogen is a terrible fuel for aircraft, or much of anything really. The one place hydrogen fuel once dominated, rockets to orbit, is now seeing this dominance threatened by methane.
We can't even make hydrogen work as a fuel for rockets any more, and these people think they can make it work in an airplane? This is kool-aid drinking and pipe smoking of the highest order.
I'd like to see someone run through the math on how an airplane powered by hydrogen fuel cells would work. I'd like to see things like h