That's not what they're claiming though. They're claiming that:
1. 20+ mpg
2. maximum speed of 450 mph
3. range of 4500 miles
are possible individually, not that 1+2+3 are possible all at the same time.
Edit: just to add a few numbers from the back of my napkin. To go 4500 miles, it would probably need to do 20mpg anyway. That’s 225 gallons of fuel. JetA is 6.7lb/gl, so ~1500lb. Not sure a small plane could carry a whole lot more than that without giving up all the useful load. And if it can only cruise at ~300mph in order to go 4500 miles, then we’re looking at a 15-hour flight in a pretty confined space with likely fairly basic amenities. It’s not exactly bringing back the glamour of aviation.
If you are interested this site gives a good overview of the routes and the legs involved http://220kts.com/ferry-flights/atlantic-ferry-routes.html
How would single-engine craft comply with ETOPS - the relevant standard for passenger flights, or equivalent?
So, without new regulation, this aircraft will not carry out "charter or scheduled flights in Europe" ?
If it can realistically do half of 4500 miles at 450mph, there are a lot of interesting routes (Gets you as far as Tel-Aviv from London, Boston to Phoenix, or Los Angeles to Miami).
Using that completely-pulled-out-of-my-ass number of half the range at 450, and assuming quadratic drag, the full range would be at about 300mph, so a roughly 12 hour flight from New York to London at a cost of $5k.
With these specs (which are completely fictional at this point), it's the size and cost of a light-jet with the speed and range of a mid-sized jet, which is a under-served niche with the increasing numbers of people in the "very wealthy, but not quite embarassingly wealthy"
Something like Garmin Autonomí might eventually allow for single pilot flights while maintaining a reasonable level of safety.
I have high hopes for the future efforts
Also, higher aerodynamic efficiency means lower HP requirements. Moving that weight savings to fuel can boost range even further.
PS: Winglets are actually really old technology. It’s making the trade offs worth it including significantly increased weight at the wing tip that’s new.
Which is why the jump in efficiency would be so extraordinary.
Props work better than jets at low elevation where the span of a propeller can work against a lot of high density air.
The engine company is German and so we can make lots of jokes about German companies' fuel efficiency claims I guess.
Nevertheless, it has been around since 2012 and is used in a few planes already, so presumably there is some measurable improvement there or they'd have taken the claim down by now?
For comparison, this engine has a Specific fuel consumption of 210 g/kW/h, while a P&W PT6A-6 (older, slightly more powerful: 431 kW vs 368kW) has 0.408 kg/kW/hr[2]
[1] https://red-aircraft.com/?lang=en
[2] http://www.all-aero.com/index.php/contactus/64-engines-power...
That doesn't seem completely unreasonable.
A Pilatus PC-12 (which is the turoprop competition here) NXG gets around 4.3 mpg.
And even if they somehow pull off that trick, that short skinny wing will make the MU-2 feel like a safe family minivan.
Basically this plane has the engine mounted on the back, which means center of gravity and wing position are quite a bit different. The nose cone looks very streamlined and crucially the wings are in front of the vortex produced by the prop. I'm guessing that that adds up to a bit of reduction in drag. The reason many planes have the engines mounted on the other side probably have to do with things like cooling, engine size, and other practical concerns.
However, they are claiming improvements across the board. 3x the range, significantly faster, flies higher, uses less fuel. It doesn't pass a sniff test.
Compare it to the Grob Strato 2c. Notice how long the wings are by comparison? This is a feature of nearly all subsonic high altitude aircraft. Also notice the how long the props are on the Grob, another feature of high altitude aircraft conspicuously missing on this aircraft.
Pusher aircraft are not new. In fact they are as old as powered aviation itself. They generally aren't significantly more efficient.
I think occam's razor applies here. Either the aerodynamics of reasonably modern aircraft designs leave a huge amount on the table or this startup is telling fibs.
There are other reasons to be suspicious, modern diesel engines rely on a large amount of turbo charging to achieve sea level rated power, it's difficult to believe they are able to maintain this rated power to 50,000ft or 60,000ft. (In the case of the TBM the engine is actually capable of about 1300hp at sea level but is "flat rated" to what it can maintain at altitude).
Finally, almost all high altitude aircraft have long wings (think the U2 as that is not far from what we are talking about here). Adding longer wings typically increases high altitude performance (there are aircraft with model variants where the wings got longer, like the twin commander). This aircraft appears to have borrowed a couple of surfboards.
Aerodynamics of reasonably modern aircraft designs do leave a huge amount on the table. Generally for good reasons, though. The 500L is clearly almost entirely a laminar-flow design, unlike conventional aircraft (including the one you linked). Experience from gliders have shown that a small laminar flow design like this can have less than a third of the drag of what a conventionally shaped design of roughly similar size.
There are two major downsides to designing like this:
Firstly, the shape is entirely determined by physics, leaving very little wiggle room for manufacturing or practical concerns. Without modern composites, cost-effectively manufacturing the frame is impractical.
Secondly, the great drag properties are very dependent on the properties of the skin of the aircraft. Laminar-flow gliders can have their glide ratios halved after accumulating a few too many insects on the leading edge. If you want to fly very high, (as this plane seems to want to), better hope you have an amazing de-icing system, or even a very small amount of ice will trash your aerodynamics.
There are so many places where the practically of this aircraft would fall down. Good luck fitting deicing boots to a wing which needs to be kept so clean polishing it makes a difference.
Also, good luck trying to get an clearence to climb to 60,000ft around any busy international airspace. Regardless of any aerodynamics miracles this aircraft pulls off I'm sure we agree that it's climb performance will be distinctly average. That means it's going to take well over an hour to get up there. 20 mins or more could be spent in the RVSM band (FL280+) where most of the airliners are, expect to be vectored all over the sky while this happens. This is already a problem in something like the CJ2 which like to cruise higher than the airliners but aren't quite as fast. It's climb performance is considerably better than you would expect from this aircraft.
It's optimized differently to the experimentals, and it's more useful commercially. Flying high avoids a lot of weather issues. You don't have to cancel flights because of weather.
The drag from the streamlined shape is very low. It's just a textbook minimum drag shape.
The cruise speed advertised does seem high still.
Why would you be shocked by flying at heights comparable to typical jet aircraft flying similar distances?
(Aside: the advertised range seems like drastic overkill for something designed to offer a cheap alternative to private jets--it's difficult to overstate how much it sucks being cooped up in a tiny plane for over 11 hours, even if you have the luxury of rich leather seats, can stand up in the cabin, and don't have to pee into plastic bags. Even if a family wants to charter a private jet from LA to the Bahamas for a long weekend, it'd be miserable trying to one-leg it.)
If an airplane like this meant being able to fly private, it's completely worth it. One other factor you have to consider is that this plane can probably use tiny airports which shaves a 4 hours of additional driving and security gates. I'd rather be in a slower flying plane for 7 hours than fly for 4 hours but spend 4 additional hours at security gates and car traffic.
Still, "low cost" is relative to a chartered private jet--which, emphatically, is not a service that people purchase because it's the most economical option--rather than a commercial airliner (although, if true, the SFC per passenger of the Celera would be in the same ballpark as modern commercial airliners, which is very impressive). The average domestic flight is under 1000 statute miles (https://www.bts.gov/content/average-length-haul-domestic-fre...), so this plane needs to offer compelling efficiency gains at ~500-1500 mile ranges in order to compete with existing services, unless they're strictly planning to fill the niche of one-leg, long-range flights that existing private jets don't have the legs for.
$300/hour charter price with 6 seats for a 5 hour trip (2000 miles) is about $250 per seat each way. This is pretty competitive.
[1]https://patentimages.storage.googleapis.com/3b/f3/9a/928c862...
A design cruising altitude of FL500 implies that they're seeing nearly all of their efficiency improvements due to the thin air at altitude (flying around 200 mph indicated, which isn't totally unreasonable for 20 mpg in a small-ish piston-prop), but I doubt they have the climb rate to actually reach that altitude in anything short of a transcontinental flight.
I like to think they crunched the performance numbers once or twice, but if they're off by the same amount they were with their initial SFC calculations, there's no way they'll reach an acceptable cruising altitude during an average flight.
I don't think many flights today are cancelled because of weather on the route there, it's the weather over each airport, which would still impact this aircraft.
Many other six seat planes are like that.
A second factor is the effect of a lifting body on stability, and the cost of compensating for it. Even in the case of nominally non-lifting fuselages, they tend to produce lift at high angles of attack, and that tends to be destabilizing, producing an increasing pitch-up moment as the angle of attack increases (ordinary straight wings do too, but the effect is proportionately less, as the wing chord is considerably less than the fuselage length.) This has to be corrected with measures (typically a larger stablizer) that also create drag. Having a fuselage designed to produce lift exacerbates this problem, commensurably with the amount of lift being generated.
Modern sailplane design is a case study in the persuit of aerodynamic efficiency, at least at low speeds, and lifting bodies have not proved to be useful. The fact is that, once you are flying, you do not need more lift; what you want is less drag.
Cost to repair and insurance is also a very significant part of the cost, so if this is difficult to land or costly to repair, it won't be very popular.
Other question is how safe the simplicity of the shape is, no front wing / canard with presumably very variable CG, or if they’ll have to sacrifice a lot of initial specs to make it work. Also if one should feel comfortable about the only semi-redundant engine over long stretches of water.
Hopefully it's not intended to do regular transoceanic flights, but it should be fine for shorter crossings (e.g. Great Lakes, Mediterranean north/south, etc.).
Amateur-built experimentals have achieved upwards of 50 mpg in realistic flying conditions, but they generally tended to be tandem-seat designs with minimal frontal area and low-powered engines.
More recently, the Pipistrel Taurus G4 (a highly modified sailplane with an electric motor between twin fuselages, designed to carry a pilot and three passengers) achieved just over 100 mpg at ~107 mph.
I eagerly await proof that the Celera--a significantly larger, heavier, and faster aircraft than Rutan's Catbird--actually achieves similar fuel economy. If true, it would be a pretty incredible leap for an industry that's been largely stagnant for decades, but these sorts of claims have a long history of being either sadly mistaken or outright fraudulent.