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For some perspective, the Scaled Composites Catbird (powered by a 210-hp V6) achieved just over 20 mpg at 200 mph with close to 1000 lbs of payload (it could ca
by scarier 6y ago
For some perspective, the Scaled Composites Catbird (powered by a 210-hp V6) achieved just over 20 mpg at 200 mph with close to 1000 lbs of payload (it could carry a pilot and four passengers) in the late '80s and early '90s.
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.
- deleted 6y ago[deleted]
- qzw 6y agoDefinitely some extraodinary claims that will require extraordinary evidence to prove. Especially getting 20+ mpg for 4500 miles, while flying at 450mph, which is near the top end of what piston/propeller aircraft are capable of. For reference, the P51 (one of the fastest fighters of WWII) had a comparable top speed. The Piaggio Avanti [0] has a somewhat similar design and top speed (460 high speed cruise), but has twin turboprops and a far shorter range and far lower claimed mpg. [0] https://en.wikipedia.org/wiki/Piaggio_P.180_Avanti https://en.wikipedia.org/wiki/Piaggio_P.180_Avanti
- Retric 6y agoThe Piaggio II (https://www.aircraftcompare.com/aircraft/piaggio-p180-avanti-ii/ https://www.aircraftcompare.com/aircraft/piaggio-p180-avanti...) is missing several modern aerodynamic and efficiency features like winglets and gets 15MPG and has a 1600 Mile range. Significantly beating it’s fuel efficiency at similar speeds seems reasonable just eyeballing the two designs. Getting the full 20MPG at 450MPH might be a stretch, but it’s not all that unreasonable. 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.
- brunooo 6y agoI’m not sure those mpg numbers are correct: the more fuel efficient Piaggio EVO update, with winglets etc, in the extended range version can hold about 450 gallons of Jet A and has a 1770nm range, so even with plenty of reserves that doesn’t get it anywhere above half of 15mpg (from what I can find IFR reserve comes out to 75 gallons, thus 4.72mpg nautical or 5.4 statute). Which is why the jump in efficiency would be so extraordinary.
- snovv_crash 6y agoTurboprops are less fuel efficient, they just have a higher power to weight ratio than piston engines.
- sunstone 6y agoI recall from the last time this plane hit the news cycle that it is designed to cruise at 60,000 feet where air density is lower and better fuel efficiency can be had.
- VBprogrammer 6y agoTo put that claim into context the manned single engine piston height record is held by a specially modified Rutan Long Ez and was around 35,000ft.
- mediaman 6y agoProp planes don’t work well at higher elevation. There’s nothing for the prop to work against. It’s why jet engines, with their compression, work better. Props work better than jets at low elevation where the span of a propeller can work against a lot of high density air.
- nl 6y agoMuch of the improved efficiency comes from the engine[1], which claims "50% lower fuel burn compared to turbine engines in the same power category". 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 https://red-aircraft.com/?lang=en [2] http://www.all-aero.com/index.php/contactus/64-engines-power/13099-pratt-whitney-canada-pt6 http://www.all-aero.com/index.php/contactus/64-engines-power...
- scarier 6y agoStill, a plane with half the aerodynamic drag and twice the BSFC is only getting 4x the fuel efficiency, not the ~10x they're claiming. Even if they're making a bit of "free" thrust from their cooling system (which has been a thing since WWII), I don't see what accounts for the rest, even ignoring that the Celera likely has a significant increase in frontal area due to the standing-height cabin.
- brunooo 6y agoRe “free thrust/WWII”: Real Engineering recently did a great summary of the P47 Thunderbolt intercooler and general craziness of the engine at https://youtu.be/IwqTN5fhMR8 https://youtu.be/IwqTN5fhMR8
- nl 6y agoThey are claiming slightly under 10x fuel efficiency compared to a jet (2-3 mpg vs 18-25 mpg). That doesn't seem completely unreasonable. A Pilatus PC-12 (which is the turoprop competition here) NXG gets around 4.3 mpg.
- desdiv 6y ago>Especially getting 20+ mpg for 4500 miles, while flying at 450mph 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.
- aidenn0 6y agoTFA did not say maximum speed 450mph, it said "maximum cruising speed of at least 450mph" Still doesn't mean it gets 18-25mpg at 450. 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.
- qzw 6y ago$5k plus pilots (I’d want two for a transatlantic flight). And you’d still be stuck inside a very small space for 12 hours, with what’s likely to be a porta-potty level lavatory and minimalist galley. Oh, and a single piston engine, which is less reliable than turbines, over a lot of very cold water. Not sure that would be the best use case for this plane.
- anovikov 6y agoWell, the size of aircraft certainly allows for fully enclosed, proper lavatory. CJ3 used for size comparison, has one.
- kristopolous 6y agoEverything deserves to have a Version 1.0 I have high hopes for the future efforts
- dzhiurgis 6y agoPlus airports, airspace, immigration, depreciation, insurance. So more like 20k.
- VBprogrammer 6y agoI'm calling bullshit. Compare it to the TBM900 which has a 900hp turbine engine and vastly similar layout. There is no way they can go 60 knots faster on 300 less horse power. And even if they somehow pull off that trick, that short skinny wing will make the MU-2 feel like a safe family minivan.
- asdfadsfgfdda 6y agoThe layout/payload may be similar to a TBM, but I'm guessing the wing loading and cruise altitude will be higher. So it's definitely feasible to go faster on less power.
- VBprogrammer 6y agoAerodynamic drag is a square relation so the difference in drag there is about 40%. With 65% of the power. 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.
- Tuna-Fish 6y ago> 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. 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.
- sgt101 6y agoI think that the evidence can be really simple (not extraordinary) - just gas it up, fly it for 4500miles in about 11hrs.
- aliswe 6y agoJust a nitpick, extraordinary claims normally do not require extraordinary evidence. For example, to gather evidence that, for example, there is a man who could run for 50mph in short bursts, it would require nothing but ordinary evidence. Have a nice day!
- brunooo 6y agoFeel the same, rooting for them but website is still a bit light on actual data and a lot of startup speak, wondering how they would get that big of an improvement vs similarly shaped (Avanti EVO) or powered (DA62) aircraft. 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.
- scarier 6y agoThe CG question is really good, but considering the very conventional tail on the prototype, I imagine it has about the same acceptable CG range as a similar passenger aircraft. The wing just looks like it's way too far back since the engine's in the back instead of the front. 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.).
- baybal2 6y agoWell, at least it's clear that they have no competition in piston powered niche because all pressurised piston aircrafts died out. Any remote equivalents are dual engine planes.
- NovemberWhiskey 6y agoPiper would like to please remind you that it is still selling the PA-46 Malibu / Mirage / M350 pressurized piston single.
- Gravityloss 6y agoI think this airplane is pressurized, flies very high and has a big turbocharger. And it has a diesel engine, so the MPG means a different thing - diesel is denser. 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.
- scarier 6y agoAll of that helps, but a pilot flying an unpressurized experimental can still get up to 17.5k' VFR on oxygen. Assuming the Celera cruises around FL250, you're talking the difference between ~300KTAS and ~350 KTAS at 200 KIAS. I'd be shocked if they cruise much above FL300, regardless of how high their service ceiling proves to be--for anything other than a really long-distance flight, they'll spend too much time climbing to altitude for it to be worth the effort.
- Robotbeat 6y agoThis is optimized for really long distance flight, thousands of miles. That’s the whole point. Cruise height of 30,000ft, I think. Why would you be shocked by flying at heights comparable to typical jet aircraft flying similar distances?
- scarier 6y agoI wouldn't be surprised by a long-range cruise altitude around FL300, but if it was FL450 I'd be extremely surprised. If the plane achieves the advertised 20mpg on a hypothetical 4500-mile flight at FL500, but only makes a small fraction of that on a more realistic 400-mile regional hop at FL210, it's not really a practical success. (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.)
- marvin 6y agoStands to reason that a modified glider will achieve the best efficiency characteristics. That is after all, practically speaking, the raison d'ètre for sailplanes.
- twic 6y agoHas anyone asked Rutan what he thinks about the Celera?
- chrischattin 6y agoMy RV-7 gets ~25 mpg depending on winds, power settings, etc. It’s been done before in private aviation. But, this is a very interesting design. Like you said, aviation does have a long history of new designs making big claims that don’t pan out in reality. I wonder what tradeoffs they made to achieve those results. It’s encouraging they’re into test flying phase, though.