The Celera 500L aircraft may fly soon(thedrive.com)
thedrive.com
The Celera 500L aircraft may fly soon
https://www.thedrive.com/the-war-zone/28409/the-mysterious-and-potentially-revolutionary-celera-500l-aircraft-may-fly-soon
118 comments
I don't have an aerospace degree, but I will nonetheless comment on a few of your comments:
Engine cooling: diesel engines need substantially less cooling than petrol engines, hp-for-hp.
Gearbox certification: you are generalizing from one example. Every turboprop has a gearbox. Most helicopters have a "complex" gearbox, coupling two (and sometimes three) engines.
Long propeller shaft: Not really a hard problem. Helicopter tail shafts seem more difficult.
Pusher efficiency: The propeller efficiency will be a bit lower for the reasons you mention, however the overall aerodynamic efficiency is likely to be higher. There are plenty of citations for this.
Pusher noise: Again, you are generalizing from one example (Avanti, in which the source of the noise is largely the turbine exhaust interacting with the propeller blades).
Forward visibility: I suspect they intend to use a camera. Other solutions are possible also. WW2 fighters had no forward visibility on landing.
Landing gear and door, tail strikes: yes, probably "prototype" stage engineering
Coffin corner: The potential problems are a consequence of specific airplane design. They are easy to avoid, though admittedly by sacrificing a smidgin of performance.
High altitude flight: I can't see that thing getting to 65,000 feet with that propeller and those wings... the number was taken from the patent, it seems, and may not have real world significance with the current design.
Overall, I think it is great to see a bit of innovation and experimentation happening in aviation again.
Engine cooling: diesel engines need substantially less cooling than petrol engines, hp-for-hp.
Gearbox certification: you are generalizing from one example. Every turboprop has a gearbox. Most helicopters have a "complex" gearbox, coupling two (and sometimes three) engines.
Long propeller shaft: Not really a hard problem. Helicopter tail shafts seem more difficult.
Pusher efficiency: The propeller efficiency will be a bit lower for the reasons you mention, however the overall aerodynamic efficiency is likely to be higher. There are plenty of citations for this.
Pusher noise: Again, you are generalizing from one example (Avanti, in which the source of the noise is largely the turbine exhaust interacting with the propeller blades).
Forward visibility: I suspect they intend to use a camera. Other solutions are possible also. WW2 fighters had no forward visibility on landing.
Landing gear and door, tail strikes: yes, probably "prototype" stage engineering
Coffin corner: The potential problems are a consequence of specific airplane design. They are easy to avoid, though admittedly by sacrificing a smidgin of performance.
High altitude flight: I can't see that thing getting to 65,000 feet with that propeller and those wings... the number was taken from the patent, it seems, and may not have real world significance with the current design.
Overall, I think it is great to see a bit of innovation and experimentation happening in aviation again.
"Pusher configurations - especially pusher turboprops like the Piaggio Avanti are noisy"
From a passenger perspective?
Why is this, Aerodynamics?
I would have thought that a pusher configuration would have been a net benefit from a passenger noise POV, and aerodynamics wouldn't make much difference on the ground, would they???
From a passenger perspective?
Why is this, Aerodynamics?
I would have thought that a pusher configuration would have been a net benefit from a passenger noise POV, and aerodynamics wouldn't make much difference on the ground, would they???
I've never been lucky enough to fly in an Avanti, but the noise comes from the turbine exhaust being interrupted at 2000 RPM times 5 blades per revolution. Other pushers I've heard, such as a Skymaster and Long-EZ also make that noise so it may have more to do with the prop being in turbulent air. It's very distinctive.
Honestly, who flies in class A airspace? Can you even fly IFR in that airspace? Class E ends at FL600. (I just do bug smashers, so not sure what the majors do up in the pressurized space)
I think you’re a little confused. Yes, you can fly IFR in class E airspace. The majority of piston airplanes flying IFR do so in class E (the portion below 18,000 ft). Class E is not uncontrolled.
I’m not sure about what you mean with “who flies in class A airspace?” Most airlines and bizjets cruise in class A because their fuel burn is ridiculous at lower altitudes.
The reason that class A becomes to class E above 60,000 ft is because hardly any planes can fly that high. This plane almost certainly won’t go that high, regardless of what the patent application says.
Edit for clarity on why helix’s comment doesn’t make a ton of sense- airspaces go like this:
FL600 (approx 60k ft) and up: Class E
18k ft to FL600: Class A, only IFR flight is allowed, no VFR (even if the weather is good).
below 18k ft to 700 or 1,200 ft above ground: Class E, except around airports, where it can be Class B (big airport), Class C (medium airport), Class D (small airport with control tower), or still Class E (small airport without control tower).
below 700 or 1,200 ft above the ground: Class G, except around airports. Class G is uncontrolled, but you still have to follow the law- no buzzing residential areas and such. You cannot file an IFR flight plan in Class G space, mainly because ATC can’t reliably see you and prevent collisions with other planes.
Class E is controlled airspace but you can fly VFR without filling a flight plan; you are required to fly at altitudes that are xxx,500 ft so you don’t hit planes flying IFR at the xxx,000 altitudes.
You would have to file an IFR flight plan to get to 65k ft because you would transit Class A airspace during your climb and descent.
I’m not sure about what you mean with “who flies in class A airspace?” Most airlines and bizjets cruise in class A because their fuel burn is ridiculous at lower altitudes.
The reason that class A becomes to class E above 60,000 ft is because hardly any planes can fly that high. This plane almost certainly won’t go that high, regardless of what the patent application says.
Edit for clarity on why helix’s comment doesn’t make a ton of sense- airspaces go like this:
FL600 (approx 60k ft) and up: Class E
18k ft to FL600: Class A, only IFR flight is allowed, no VFR (even if the weather is good).
below 18k ft to 700 or 1,200 ft above ground: Class E, except around airports, where it can be Class B (big airport), Class C (medium airport), Class D (small airport with control tower), or still Class E (small airport without control tower).
below 700 or 1,200 ft above the ground: Class G, except around airports. Class G is uncontrolled, but you still have to follow the law- no buzzing residential areas and such. You cannot file an IFR flight plan in Class G space, mainly because ATC can’t reliably see you and prevent collisions with other planes.
Class E is controlled airspace but you can fly VFR without filling a flight plan; you are required to fly at altitudes that are xxx,500 ft so you don’t hit planes flying IFR at the xxx,000 altitudes.
You would have to file an IFR flight plan to get to 65k ft because you would transit Class A airspace during your climb and descent.
It seems logical that if there was available on the market a large number of planes capable of flying between FL600 and FL900, the relevant authorities would simply extend class A higher. At present there's no civilian aircraft whatsoever capable of those altitudes for long duration cruises, so it has been a moot point.
For a lot of your questions, I think this thing is going to be marketed for defense purpose as a HALE (high altitude, long endurance) sensor platform that costs significantly less in purchase cost, and operating cost, than a global hawk. There's already companies flying retrofitted King Air and similar for this purpose for the DoD.
If it can carry 500 kilos at 65,000 ft for 24 hours without landing, and not cost a ridiculous amount in dollars per flight hour, that's something pretty unique.
In my totally non expert opinion the undercarriage and very low ground clearance also tell me it's intended to fly from paved strips in pristine condition, which is very different than the rough field capabilities of many single and twin airplanes powered by the PT6 turboprop or one of its derivatives.
If it can carry 500 kilos at 65,000 ft for 24 hours without landing, and not cost a ridiculous amount in dollars per flight hour, that's something pretty unique.
In my totally non expert opinion the undercarriage and very low ground clearance also tell me it's intended to fly from paved strips in pristine condition, which is very different than the rough field capabilities of many single and twin airplanes powered by the PT6 turboprop or one of its derivatives.
That doesn’t really line up with how defense aircraft (or defense anything, for that matter) are financed and designed. Aircraft designs are created as part of a response to a Department of Defense request for proposal and design details are kept highly secret (they won’t even file patents to ensure that no details about the aircraft are leaked). Then the craft are tested from military bases to prevent people taking pictures. Also, a defense craft wouldn’t be seeking FAA approval (the FAA isn’t authorized to regulate military aircraft)
Not all, necessarily, they may have created the design with a HALE market as one of several market possibilities. Companies have self funded r&d projects to build things and then try to sell them to defence markets before. Scaled composites did it with their Ares, and so has embraer with their turboprop ground support plane.
Here's an example of a retrofit of a COTS platform for bespoke sensor platform use.
https://www.thedrive.com/the-war-zone/19921/these-secretive-...
Here's an example of a retrofit of a COTS platform for bespoke sensor platform use.
https://www.thedrive.com/the-war-zone/19921/these-secretive-...
Maybe in the cold war, but these days there are plenty of repurposed civilian aircraft. They just swap out the avionics with some nicer things, add good cameras, and have a useable and proven platform. The airframe details are self-evident enough that they may not be worth keeping secret.
Do you think the engineers never thought of these things?
I'm sure they have. All of aircraft design is a tradeoff (cue that comic of if each different subteam had their way...). However, I'm not sure they've made the right compromises.
Some of that is due to the secrecy surrounding the aircraft. Especially the overall business strategy is in the shadows.
It's not even clear that this plane is close to the final size.
And to speculate about this strategy, those tradeoffs are valid input.
It's not even clear that this plane is close to the final size.
And to speculate about this strategy, those tradeoffs are valid input.
A piston engine at 65,000 feet? That’s unreal.
Which is probably part of the interest/mystique in this project.
At that altitude, the turbocharger is doing most of the work.
> The propeller is a pusher configuration, which isn't inherently bad, but causes efficiency losses from turbulent air coming off the fuselage.
Teardrop shape greatly reduces turbulent flow behind the fuselage compared to the mainstream tube shape.
Teardrop shape greatly reduces turbulent flow behind the fuselage compared to the mainstream tube shape.
I'd like to see how that stacks up and what the actual width of the turbulent flow is.
The gulf stream would be less efficient, require more passengers and may not be able to land at as many airports.
I think they aim for some kind of long-range air taxi. Small groups which want to travel a long distance from A to B but a very short distance to and from A and B's respective airports. Business trips, most likely.
And probably the plane is no slouch at medium or even short range if it is operated by a non-airline company. Just not "ridiculously efficient".
I think they aim for some kind of long-range air taxi. Small groups which want to travel a long distance from A to B but a very short distance to and from A and B's respective airports. Business trips, most likely.
And probably the plane is no slouch at medium or even short range if it is operated by a non-airline company. Just not "ridiculously efficient".
If it can show real efficiency gains on short travel, it could probably consume the market on flights from major hubs to local, just for being able to cut costs in an area where there's lots of room to do so
A slow plane is vastly quicker than any ground based transport so speed is not absolutely vital, 300 mph is not breaking the sound barrier but it is 100 times quicker than being stuck in a traffic jam.
I think the shape looks right rather than odd, in particular the bulbous rather than elongated body. Plus with the straight wings this looks well optimised for low skin friction.
Experience of VW rear engined vehicles tells me there are advantages in having the engine at the back when it comes to noise. I thought the reasons we had the propeller at the front was to have it cool the engine and have the centre of gravity 'right'. This just looks right compared to what has gone on before.
Looking right is not necessarily what you want, we have been stuck too long on what a fast plane should look like. But there is something in aesthetics when it comes to these matters.
Seeing the runway is not necessarily that important, I would prefer a plane that does all the landing itself with no assistance needed. It is not as if a regular jet pilot can see the wheels of the plane when landing.
I think the shape looks right rather than odd, in particular the bulbous rather than elongated body. Plus with the straight wings this looks well optimised for low skin friction.
Experience of VW rear engined vehicles tells me there are advantages in having the engine at the back when it comes to noise. I thought the reasons we had the propeller at the front was to have it cool the engine and have the centre of gravity 'right'. This just looks right compared to what has gone on before.
Looking right is not necessarily what you want, we have been stuck too long on what a fast plane should look like. But there is something in aesthetics when it comes to these matters.
Seeing the runway is not necessarily that important, I would prefer a plane that does all the landing itself with no assistance needed. It is not as if a regular jet pilot can see the wheels of the plane when landing.
65,000 feet from a plump looking single prop diesel powered (500hp?) plane seems surprising. For comparison jet airliners top out around 40,000 ft, a F16 fighter 50,000ft+, and a F15 at 65,000 ft with twin jet engines producing up to a few tens of thousands of horsepower.
I wonder how they get that much more perfomance, assuming they do.
I wonder how they get that much more perfomance, assuming they do.
I am sure the engineers who designed and built this aircraft know what they are doing, but as a pilot, I would be hesitant to fly this aircraft based on the very low level of forward visibility (especially when landing).
Also, the pusher prop concept was tested extensively many years ago, but seems to have disappeared off the radar of most aero engine manufacturers. I don't know the exact reasons, but I am presuming that they had problems with efficiency, or more likely issues with the blade tips reaching sonic velocity (which will be higher risk with this aircraft if it cruises at FL065).
Also, the pusher prop concept was tested extensively many years ago, but seems to have disappeared off the radar of most aero engine manufacturers. I don't know the exact reasons, but I am presuming that they had problems with efficiency, or more likely issues with the blade tips reaching sonic velocity (which will be higher risk with this aircraft if it cruises at FL065).
Really tiny 4k 60Hz cameras with surprisingly good quality are available now, I don't think it would be rocket science to integrate one into the nose and feed a low-latency view to flight deck monitors. Possibly intefrated with an overlay image for short range time of flight lidar to gauge distance to runway during landing.
A proper aircraft flare at the point of landing requires a fair bit of peripheral vision to judge sink rates etc. A camera tends to give you a flat picture without that advantage.
It's a workable solution, but most 'seat of the pants' pilots would eschew such things.
It's a workable solution, but most 'seat of the pants' pilots would eschew such things.
If this ends up being an airline aircraft, as opposed to a personal aircraft, that might not be a problem, at least business-wise.
I'd be reluctant to fly on anything of this level of redundancy where an electrical failure results in a 0/0 landing (or an abnormal that precludes the use of the system added to ensure normal landing visibility).
The Icon A5 uses a pusher prop.
We'll see what, if anything, becomes of the Terrafugia too.
We'll see what, if anything, becomes of the Terrafugia too.
Pusher props are fine for aircraft cruising, say, around FL020 and below.
But at higher altitudes, the speed of sound is considerably lower, and the radial velocity of the prop blade tips start to reach sonic velocity, with the corresponding significant increase in drag, thus requiring more torque to spin at constant RPM, resulting in decreased fuel efficiency.
The test bed pushers on commercial jets were a far shorter set of (more numerous) blades for that exact reason. This particular aircraft seems to have a standard sized propeller, with a greater blade length, and corresponding greater radial tip velocity.
But at higher altitudes, the speed of sound is considerably lower, and the radial velocity of the prop blade tips start to reach sonic velocity, with the corresponding significant increase in drag, thus requiring more torque to spin at constant RPM, resulting in decreased fuel efficiency.
The test bed pushers on commercial jets were a far shorter set of (more numerous) blades for that exact reason. This particular aircraft seems to have a standard sized propeller, with a greater blade length, and corresponding greater radial tip velocity.
> FL020 and below.
I'm assuming you meant FL200. (20000' MSL, not 2000' MSL.)
I'm assuming you meant FL200. (20000' MSL, not 2000' MSL.)
Goldschmied body shape. Propeller uses boundary layer air.
Could be efficient.
If center of gravity is far back with a really short tail moment arm and most of the big body is in the front, there could be control, stability and center of gravity issues. Is it possible to ealk around the cabin during flight?
Piaggio Avanti is somewhat similar on being an advanced concept with high efficiency. I think they just stopped the manufacture.
If center of gravity is far back with a really short tail moment arm and most of the big body is in the front, there could be control, stability and center of gravity issues. Is it possible to ealk around the cabin during flight?
Piaggio Avanti is somewhat similar on being an advanced concept with high efficiency. I think they just stopped the manufacture.
My impression was that jet engines are more efficient than turboprops?
And it takes a while to climb to 65000 feet. Especially if the engine isn't as powerful as jet engines usually are (yes, it's more complicated...).
Another point is safety. Bigger airplanes usually have fewer accidents, not just because the pilots are more experienced, but also because of higher robustness against weather, time to correct mistakes, and fewer dangerous actions (landings) per passenger. Basically fewer chances to screw up with pilots that have a very long track record of not screwing up.
And it takes a while to climb to 65000 feet. Especially if the engine isn't as powerful as jet engines usually are (yes, it's more complicated...).
Another point is safety. Bigger airplanes usually have fewer accidents, not just because the pilots are more experienced, but also because of higher robustness against weather, time to correct mistakes, and fewer dangerous actions (landings) per passenger. Basically fewer chances to screw up with pilots that have a very long track record of not screwing up.
Doesn't appear to be a turboprop, the engine is a multi stage supercharged v12 diesel. There's a Wikipedia article about it if you Google the engine manufacturer name.
When someone claims to have made a radical improvement in a mature field, It is reasonable to ask why other engineers have not thought of it before, at least if it is not based on newly-discovered science or a technical breakthrough.
The fact is that none of the features given in the article are novel, so why have they not been combined before? Some of them were, in fact, in the Republic XF-12 [1], and the idea of using a diesel with much more turbo-charging than is usual, as an aero engine, was seen in the Napier Nomad [2] (it was actually a two-stroke turbo compound, with, in one version, a sort of afterburner between the diesel and turbine stages!)
The usual experience of putting together several different incremental changes is that there are unanticipated problems, and the whole is less than the sum of the parts.
While I am skeptical that this airplane will deliver on its promises, I do not want to be entirely negative. It is possible that changing circumstances have produced an opportunity that was neither recognized or exploitable before.
Once gas turbines were developed, progress on piston aero-engines essentially came to a halt, but piston engines continued to be developed for cars, at least following the oil crises of the 70s, so that piston engines are now much more efficient, lighter and, importantly, reliable than they were (even diesels.) These developments have been making their way into aviation, but so far almost exclusively in the niches where piston engines were still being used.
Another development has been the use of composites, which permit the development of effective laminar-flow airfoils (several WWII-era aircraft nominally had such wings, but there is considerable doubt as to their effectiveness, as it is difficult to make metal wings to the stringent tolerances needed.) This capability has been used in sailplanes for decades, but is only slowly extending beyond that niche (more so now that electric airplanes are feasible.)
AFAIK, the Boeing Condor drone is the only piston-engined airplane to reach 65,000 feet, and the closest piloted flights have been some 15,000 feet short, but if this project can get a piston-engined, payload-carrying airplane cruising at that altitude without too many compromises, I think it has a chance of making a difference. The retro-futuristic appearance of this prototype is probably mostly incidental.
[1] https://en.wikipedia.org/wiki/Republic_XF-12_Rainbow
[2] https://en.wikipedia.org/wiki/Napier_Nomad
The fact is that none of the features given in the article are novel, so why have they not been combined before? Some of them were, in fact, in the Republic XF-12 [1], and the idea of using a diesel with much more turbo-charging than is usual, as an aero engine, was seen in the Napier Nomad [2] (it was actually a two-stroke turbo compound, with, in one version, a sort of afterburner between the diesel and turbine stages!)
The usual experience of putting together several different incremental changes is that there are unanticipated problems, and the whole is less than the sum of the parts.
While I am skeptical that this airplane will deliver on its promises, I do not want to be entirely negative. It is possible that changing circumstances have produced an opportunity that was neither recognized or exploitable before.
Once gas turbines were developed, progress on piston aero-engines essentially came to a halt, but piston engines continued to be developed for cars, at least following the oil crises of the 70s, so that piston engines are now much more efficient, lighter and, importantly, reliable than they were (even diesels.) These developments have been making their way into aviation, but so far almost exclusively in the niches where piston engines were still being used.
Another development has been the use of composites, which permit the development of effective laminar-flow airfoils (several WWII-era aircraft nominally had such wings, but there is considerable doubt as to their effectiveness, as it is difficult to make metal wings to the stringent tolerances needed.) This capability has been used in sailplanes for decades, but is only slowly extending beyond that niche (more so now that electric airplanes are feasible.)
AFAIK, the Boeing Condor drone is the only piston-engined airplane to reach 65,000 feet, and the closest piloted flights have been some 15,000 feet short, but if this project can get a piston-engined, payload-carrying airplane cruising at that altitude without too many compromises, I think it has a chance of making a difference. The retro-futuristic appearance of this prototype is probably mostly incidental.
[1] https://en.wikipedia.org/wiki/Republic_XF-12_Rainbow
[2] https://en.wikipedia.org/wiki/Napier_Nomad
It's hard to imagine a V-12 engine achieving Prius-level efficiency.
For some aspects, it looks quite similar to the Piaggio Avanti
Somewhat off-topic: the Prius isn't all that efficient in an absolute sense.
(That's because it's still a big and heavy car. Even with a conventional internal combustion engine, you can get a better mileage, if you are willing for a more European style smaller, lighter car.
Relative to its weight and size, a Prius is pretty efficient.)
(That's because it's still a big and heavy car. Even with a conventional internal combustion engine, you can get a better mileage, if you are willing for a more European style smaller, lighter car.
Relative to its weight and size, a Prius is pretty efficient.)
We detached this subthread from https://news.ycombinator.com/item?id=20130075.
It often makes me wonder, why especially Americans largely don't prefer to use the most economical to buy/own/operate vehicles, like European/Japanese small cars that give close to 20-25 kilometers per litre of petrol.
There are benefits to driving a larger vehicle for some people. It's fun, it's safer (for the occupant, less safe for others), there might be prestige?
Europeans would also drive bigger cars, if their petrol was as cheap as in America.
And you can see the Americans reacting to at-times more expensive petrol by buying smaller cars for a while.
Europeans would also drive bigger cars, if their petrol was as cheap as in America.
And you can see the Americans reacting to at-times more expensive petrol by buying smaller cars for a while.
> it's safer (for the occupant, less safe for others)
The data usually cited for this is studies showing that it is safer in given collision conditions. On the other hand, collisions are more likely, rollovers are more likely, and rollovers are disproportionately fatal for vehicle occupants compared to collisions.
The data usually cited for this is studies showing that it is safer in given collision conditions. On the other hand, collisions are more likely, rollovers are more likely, and rollovers are disproportionately fatal for vehicle occupants compared to collisions.
Interesting.
In any case, my argument is basically that some people prefer bigger cars; but Europeans don't get to act on that preference as much because their fuel is more expensive. So you'd see different cars, even if they preferences were exactly the same. (They are not exactly the same.)
In any case, my argument is basically that some people prefer bigger cars; but Europeans don't get to act on that preference as much because their fuel is more expensive. So you'd see different cars, even if they preferences were exactly the same. (They are not exactly the same.)
It's not only about fuel costs, but also about parking space. The extra half a metter matters in many situations ;)
"It's fun"
Why are larger vehicles inherently more fun? A go-cart is fun. A double decker not so much (I would guess anyway).
Why are larger vehicles inherently more fun? A go-cart is fun. A double decker not so much (I would guess anyway).
The trucks in question have outsized power for their size, it's part of their legitimate use as work vehicles. You get in these massive, comfortable vehicles and you accelerate, maybe not as fast as a sports car, but you're easily beating a Honda Civic and instead of a squeal from the transmission you hear a deep-throated roar from your engine.
That's power is fun, not size. A Honda Civic Type R is probably even more fun, and with less body roll.
I suspect Europe’s relatively narrow roads would prevent American-style cars ever becoming generally popular. One of the Smart Fortwo’s selling points is the small size making parking easier, not just the good-but-not-best fuel efficiency.
Parking bays are limiting the maximum dimensions of cars not so much the roads iirc
You still have a big, complex, expensive fuel engine to maintain. For short hops I think electric planes are going to be the better choice. Maybe they can have ground power connections or droppable capacitors for the burst of energy needed at takeoff without the extra weight.
Lies. 10x efficiency improvement is simply not possible. Or a gross misinterpretation.
Don't get why i am getting downvoted. What in particular can drive such a huge efficiency improvement? like, 100+ L/D ratio? Impossible. 10x more efficient engines (especially as engine is stock one and science of propeller design has been perfected in 100 years)? Clearly impossible.
This thing looks like the future. But not in an aesthetically impractical concept vehicle kind of way. It's actually beautiful.
I agree. Looks georgeous. Also looks believable.
If the claims about efficiency are correct, this aircraft has Prius-like levels of fuel efficiency. Incredible.
"The patent goes on to describe a notional aircraft that would cruise between 460 and 510 miles per hour at an altitude of up to 65,000 feet, yielding a fuel efficiency rate of between 30 and 42 miles per gallon. To put this in perspective, the Pilatus PC-12, a popular light, single-engine turboprop aircraft has a service ceiling of 30,000 feet, a cruising speed just under 330 miles per hour, and still burns, on average, 66 gallons of jet fuel per hour, for a fuel economy of roughly five miles to the gallon. Even going to a Learjet 70, which has similar speed performance to what's stated in the Celera patent documents, but still nowhere near as high a ceiling, we are talking about roughly three miles per gallon of gas at cruise."
"The patent goes on to describe a notional aircraft that would cruise between 460 and 510 miles per hour at an altitude of up to 65,000 feet, yielding a fuel efficiency rate of between 30 and 42 miles per gallon. To put this in perspective, the Pilatus PC-12, a popular light, single-engine turboprop aircraft has a service ceiling of 30,000 feet, a cruising speed just under 330 miles per hour, and still burns, on average, 66 gallons of jet fuel per hour, for a fuel economy of roughly five miles to the gallon. Even going to a Learjet 70, which has similar speed performance to what's stated in the Celera patent documents, but still nowhere near as high a ceiling, we are talking about roughly three miles per gallon of gas at cruise."
Why flying so high? Fuel economy?
Less drag (lower air density) but also slower winds. Cruising at such a high altitude avoids the strongest jet stream winds.
What are the downsides of higher altitude flights?
In addition to the other listed issues, it's above the altitude at which body temperature causes water to boil, commonly known as the Armstrong Limit. As you may imagine, this significantly complicates cabin depressurization incidents.
You are not joking.
> Exposure to pressure below this limit results in a rapid loss of consciousness, followed by a series of changes to cardiovascular and neurological functions, and eventually death, unless pressure is restored within 60–90 seconds.
> Exposure to pressure below this limit results in a rapid loss of consciousness, followed by a series of changes to cardiovascular and neurological functions, and eventually death, unless pressure is restored within 60–90 seconds.
For the curious: https://en.wikipedia.org/wiki/Armstrong_limit
Climbing that high takes time and fuel. Which you can recover somewhat on descent, but not totally, and under not-ideal circumstances like hiccups in the flight plan the plane even has to waste the potential energy.
I'd say that altitude is the reason for the focus on long distance.
I'd say that altitude is the reason for the focus on long distance.
That's what I was thinking, climbing up there burns some fuel, and only so much can be recovered into speed through a slow descent which airliners typically don't do, they hop between Flight Level.
So I suspect only long flights will be operated that high, and there will be some calculation for the optimal altitude for shorter flights.
So I suspect only long flights will be operated that high, and there will be some calculation for the optimal altitude for shorter flights.
Getting there … Especially if you are slow, you are causing issues for air traffic control.
Another issue is the survivability of incidents. If something goes wrong, for example with your pressure cabin or your oxygen supply, you have only seconds to start your mitigation measures.
Another issue is the survivability of incidents. If something goes wrong, for example with your pressure cabin or your oxygen supply, you have only seconds to start your mitigation measures.
The higher you go, the tighter your flight envelope gets as you approach the "coffin corner" and the more likely you are to stall. A stall is very bad (you lose lift and fall out of the sky).
https://en.wikipedia.org/wiki/Coffin_corner_(aerodynamics)
https://en.wikipedia.org/wiki/Coffin_corner_(aerodynamics)
Stalls are very bad when the aircraft is close to the ground. Stalls at about 5000 feet or more above ground level can be recovered from reliably by professional pilots, which is why (combined with the existence of autopilots and the fact that it is the cheapest way to cover distance) the majority of the thousands of airliners in the sky right now are right up against the coffin corner.
As long as you know you're stalling. Air France 447 stalled all the way from cruising to crashing into the Atlantic without anyone onboard realizing it.
Less drag.
Why do you compare miles per gallons to gallons per hour?
Unpacking the comparison:
Celera: 30-42 MPG Pilatus: 5 MPG Learjet: 3 MPG
Those figures are all in there, it's just maybe written kind of confusingly.
Celera: 30-42 MPG Pilatus: 5 MPG Learjet: 3 MPG
Those figures are all in there, it's just maybe written kind of confusingly.
I know that the answer is in there but it seems like he is trying to make it confusing... since it appears that he already did the math and didn't post the numbers with the same units. But thank you.
There's a distinct difference between time at indicated airspeed (which is what calculations based on fuel consumption per unit time are based around) and the ground distance you'd cover. Ground-dwellers - that is, most readers - are comfortable with miles per gallon (or, say, litres per hundred kilometres), but it's a useless number as an aircraft spec.
Aircraft account for 12 percent of all U.S. transportation greenhouse gas (GHG) emissions and 3 percent of total U.S. GHG emissions.
And yet, no EPA emissions regulations exist for aircraft at all.
I am glad to see aircraft efficiency improve regardless.
And yet, no EPA emissions regulations exist for aircraft at all.
I am glad to see aircraft efficiency improve regardless.
But the EPA does regulate aircraft emissions. You can see the regulations on their website: https://www.epa.gov/regulations-emissions-vehicles-and-engin...
There's huge economic pressure to make these aircraft as efficient as possible. What's the EPA going to do, crack the whip a little harder?
They might be responsible for global warming in a relatively unknown way.
When all aircraft were grounded the day of the WTC attacks of 9/11/2001 and the following few days, meteorologists noticed that the average US temperatures decreased a few degrees.
Since then there have been investigations into contrails reflecting and retaining heat in much the same way as the CO2 greenhouse effect.
search for "contrails global warming"
random article: https://phys.org/news/2011-03-airplane-contrails-worse-co2-e...
When all aircraft were grounded the day of the WTC attacks of 9/11/2001 and the following few days, meteorologists noticed that the average US temperatures decreased a few degrees.
Since then there have been investigations into contrails reflecting and retaining heat in much the same way as the CO2 greenhouse effect.
search for "contrails global warming"
random article: https://phys.org/news/2011-03-airplane-contrails-worse-co2-e...
This doesn't seem possible to me.
Do you live in a large city, or somewhere out in the country, not necessarily "off the grid"? If you lived for long times in
cities, you aren't used to feel the "normal" effects of weather and night-day differences of temperature anymore. The cover of buildings and streets dampens the difference. Out in the country during clear skies you feel how cold it can get. In a city not so much. I experienced this by mistake some time ago while riding out with a bicycle for about 80km in light shorts and a sleeveless shirt assuming i could take a train back. Which was wrong. I could even feel the difference in temperature different sorts of pavement made, or if i rode between open fields with just earth, or crops, or forest to both sides of the way. Anyways, as i finally got back near home i could see the haze dome from afar, and under it it wasn't so cold anymore.
Long story short: no clouds equals cold nights. Contrails are a form of cloud and contribute a little to the aforementioned dampening effects.
Long story short: no clouds equals cold nights. Contrails are a form of cloud and contribute a little to the aforementioned dampening effects.
Even in cities, cycle or walk through or around a park at night and you'll notice a drop in temperature compared to the blocks of housing close to it.
Except they are tiny compared to a cloud. The amount of sky they "cover" is a tiny percentage for a short time and even then they're not very substantial unlike regular clouds which can be que thick and dense. It just doesn't seem plausible.
Does it seem plausible though?
I wonder if we could tune them and use it to control the weather (minimize the effect during hot spells, maximize it during cold spells).
- https://www.nesdis.noaa.gov/content/do-contrails-affect-cond...
- https://news.psu.edu/story/361041/2015/06/18/research/jet-co...
- https://en.wikipedia.org/wiki/Contrail#Contrails_and_climate
I wonder if we could tune them and use it to control the weather (minimize the effect during hot spells, maximize it during cold spells).
- https://www.nesdis.noaa.gov/content/do-contrails-affect-cond...
- https://news.psu.edu/story/361041/2015/06/18/research/jet-co...
- https://en.wikipedia.org/wiki/Contrail#Contrails_and_climate
Ground them hot days, fly cold days... :)
Looks super optimized for low induced drag with the high aspect straight wing. Bubble fuselage probably handles the stresses for high altitude better than a tube, reducing weight. Nice work. Reminds me of a student design with what you get by just following design equations and going for a crazy mission profile.
I'm not a professional, but I had the impression that people generally don't want to fly in aircraft with shapes other than the current dominating design. For me that's a non-issue if I trust the regulatory procedures (737-Max 8 comes to mind)...
Rutan has a lot of great looking planes. Unfortunately they had limited success. People still try now and again to introduce flying-wings, but I guess the above is one factor why it doesn't seem to take.
Rutan has a lot of great looking planes. Unfortunately they had limited success. People still try now and again to introduce flying-wings, but I guess the above is one factor why it doesn't seem to take.
One problem with flying wings is that you typically have seats further from the plane's center line (roll axis). Those unlucky enough to be farthest from the center experience greater force during banking, causing dizziness and nausea.
I'd fly in something that looked ridiculous if it was a pleasant enough travel experience.
Likewise; honestly not sure why someone would have issue with the shape. Safety, cost, comfort, efficiency, sure - if it delivers on those, why would I care what shape it was?
It looks like a Bell X-1.
> Reminds me of a student design with what you get by just following design equations and going for a crazy mission profile.
This is the only thing that makes sense about this design. It's the result of optimizing some parameter at the expense of all others. Maybe the maths makes sense but it looks ugly and I've never seen an ugly machine that worked well.
This is the only thing that makes sense about this design. It's the result of optimizing some parameter at the expense of all others. Maybe the maths makes sense but it looks ugly and I've never seen an ugly machine that worked well.
https://en.wikipedia.org/wiki/Saab_29_Tunnan now you have
> Despite its rotund appearance, from which its name derives, the J 29 was a fast and agile aircraft for its era
So why do all modern fighters look similar and nothing like this?
So why do all modern fighters look similar and nothing like this?
The only reason I know - was hell to learn how to fly. Very unstable and it had quite the reputation for killings its test pilots.
There's something I don't quite get about the landing gear. The fuselage is about 10" - 12” off the ground (guessing by proximate shoes), unladen.
Coming in for a hard landing, wouldn't this low clearance potentially lead to gear down belly landings? They already look cambered and not even loaded and taking the impact of touching down.
I mean, I know they ordinarily touch down nose up, but still it looks like low clearance.
I mean, I know they ordinarily touch down nose up, but still it looks like low clearance.
On the ground the gear is compressed. It is extended as it hangs down before touchdown. https://aviation.stackexchange.com/questions/30583/how-much-...
What xvf22 said, plus, it may intentionally be designed to only operate from very long runways in good condition, allowing a long flare and very gentle touchdown. As compared to a turbo otter or something which can be put down fairly roughly.
But you never know when you’re going to have downdrafts or have a tire blow out. It’s not always pleasant breezes on approach.
Wouldn't that conflict with the stated goal "Such a transportation system requires a unique aircraft. It must be capable of operation from any current airfield,"?
(cited from the linked article)
Well, there's "capable of operating from a 3000 ft runway", which is a lot of things with turboprops, making a huge number of airports available. But if you bump that number up to 5500 or 6000 ft, there's less runways available, but still a huge number of airbases and airports. Think like, the difference between an airport you can land a twin otter at versus a 737-800NG.
When i saw the picture i compared that with Piaggio P180 Avanti and the Honda Jet 420, with the P180 because the fuselage looks similar in size, the Honda Jet because it claims to be efficient for a very light jet. By rule of thumb only, and they can utilize 3000ft/1kM easily. Anyways, all guesswork until further data comes in :)
Edit: Oh, i forgot: PRICE?
Edit: Oh, i forgot: PRICE?
Agreed. The main gear looks like it doesn't have much clearance to work with.
If it's not extremely stiff, I don't know how a hard landing would not result in fuselage contact.
If it's not extremely stiff, I don't know how a hard landing would not result in fuselage contact.
I am surprised I never see mention of http://synergyaircraft.com/ when aircraft efficiency comes up here. The designer/builder knows his stuff, and the models and tests have proven the double box tail is incredibly efficient.
I really hope they manage to finish the prototype and get it flying!
I really hope they manage to finish the prototype and get it flying!
One of the claims made here is "Synergy uses brilliant physics to achieve twice the expected speed for a given horsepower."
The power required to fly at a given speed is the product of that speed and the drag at that speed. If this is truly an apples-to-apples comparison, it implies Synergy is producing half the drag of the reference airplane at twice the speed. Drag of an airplane goes approximately (a good approximation, when we are talking about maximum achievable speeds) with the square of the airspeed, and therefore this is implicitly a claim that the these innovations reduce the drag coefficient of Synergy by (by, not to) 7/8.
Given the effort it takes to reduce sailplane drag by a few percent, and the enthusiasm within that community to adopt whatever it will take to do so, I will be skeptical until I see a quantitative explanation based on actual measurements.
It is claimed that the innovations mainly reduce the induced drag, but this makes the claim even more surprising, as induced drag decreases with speed, and so, therefore, do the benefits of reducing it.
The power required to fly at a given speed is the product of that speed and the drag at that speed. If this is truly an apples-to-apples comparison, it implies Synergy is producing half the drag of the reference airplane at twice the speed. Drag of an airplane goes approximately (a good approximation, when we are talking about maximum achievable speeds) with the square of the airspeed, and therefore this is implicitly a claim that the these innovations reduce the drag coefficient of Synergy by (by, not to) 7/8.
Given the effort it takes to reduce sailplane drag by a few percent, and the enthusiasm within that community to adopt whatever it will take to do so, I will be skeptical until I see a quantitative explanation based on actual measurements.
It is claimed that the innovations mainly reduce the induced drag, but this makes the claim even more surprising, as induced drag decreases with speed, and so, therefore, do the benefits of reducing it.
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That certainly looks like it pulls more aerodynamic tricks than this mysterious Celera, which is fairly conventional-looking besides the pusher prop and the non-cylindrical fuselage.
Looks very much like Piaggio Avanti
I'm not sure if there is a stated "breakthrough" in fuel efficiency. Slow, straight wing, glider-like airplanes with turbos and electronic engine controls were already better than some SUVs.
I'm not sure if there is a stated "breakthrough" in fuel efficiency. Slow, straight wing, glider-like airplanes with turbos and electronic engine controls were already better than some SUVs.
Long, straight wings resembling a glider and flying slower is a combination for better efficiency. Look at the wings on the long wingspan, 30 hour endurance version of an RQ9 reaper for instance. Or the wings on a U2, or Global Hawk.
The PC12 has speed to destination as a design criteria, and enough thrust to take off from runway length at small airports. If you remove those two constraints and say you don't care about raw speed so much, and it'll always fly from fields with 6500+ ft runways, that opens up new possibilities in design for long endurance.
Studying the design of the rutan Voyager, take a look at the wing length/shape and the 11,000 ft takeoff roll. That's one end of the extreme deep end of design possibilities. This is sort of a compromise somewhere in between.
The use of a diesel engine tells me that somebody cares about squeezing the very best kilojoule per kilogram ratio from a liquid fuel.
The PC12 has speed to destination as a design criteria, and enough thrust to take off from runway length at small airports. If you remove those two constraints and say you don't care about raw speed so much, and it'll always fly from fields with 6500+ ft runways, that opens up new possibilities in design for long endurance.
Studying the design of the rutan Voyager, take a look at the wing length/shape and the 11,000 ft takeoff roll. That's one end of the extreme deep end of design possibilities. This is sort of a compromise somewhere in between.
The use of a diesel engine tells me that somebody cares about squeezing the very best kilojoule per kilogram ratio from a liquid fuel.
The article mainly mentions kerosene-powered engines.
Is diesel more efficient on a per-kilo basis than kerosene? I always thought kerosene packs a bigger punch so you can carry less of it for the same distance.
Also if the plane is intended to fly both that high/slow and that low/slow that probably informs the wing choice. Less air resistance and lift up there.
Is diesel more efficient on a per-kilo basis than kerosene? I always thought kerosene packs a bigger punch so you can carry less of it for the same distance.
Also if the plane is intended to fly both that high/slow and that low/slow that probably informs the wing choice. Less air resistance and lift up there.
According to this, diesel is 45.6MJ/kg
Jet fuel is 43MJ/kg
https://en.m.wikipedia.org/wiki/Energy_density
A big part of it has to be how much is lost to heat, an internal combustion engine is far from efficient... But then again neither is a turbine.
Jet fuel is 43MJ/kg
https://en.m.wikipedia.org/wiki/Energy_density
A big part of it has to be how much is lost to heat, an internal combustion engine is far from efficient... But then again neither is a turbine.
Hydrocarbons have very similar energy/mole and therefore energy/volume, energy/mass ratios.
This relationship breaks down for very short HC (methane, basic alcohols).
Differences in effective energy density result from the combustion cycle used: Otto is better than Diesel for the same compression ratio, but you can’t easily get high compression ratio w/ Otto. Therefore Diesels are, typically, more efficient.
However, if you use methane (high compression) in an Otto cycle with turbo compounding, you’ll probably beat diesel. But then you have NOx emissions
This relationship breaks down for very short HC (methane, basic alcohols).
Differences in effective energy density result from the combustion cycle used: Otto is better than Diesel for the same compression ratio, but you can’t easily get high compression ratio w/ Otto. Therefore Diesels are, typically, more efficient.
However, if you use methane (high compression) in an Otto cycle with turbo compounding, you’ll probably beat diesel. But then you have NOx emissions
Kerosene, diesel, jp8, etc. are all basically the same from a power density point of view. It's what you burn them in and how you burn them that matters.
Hydrocarbons have very similar energy/mole and therefore energy/volume, energy/mass ratios.
This relationship breaks down for very short HC (methane, basic alcohols).
Differences in effective energy density result from the combustion cycle used: Otto is better than Diesel for the same compression ratio, but you can’t easily get high compression ratio
This relationship breaks down for very short HC (methane, basic alcohols).
Differences in effective energy density result from the combustion cycle used: Otto is better than Diesel for the same compression ratio, but you can’t easily get high compression ratio
The speed envelope discussed is much faster than i thought straight non-swept wings could manage. Same for propeller thrust.
What am I missing? Aircraft are such illustrative examples of the whole concept of tradeoffs.
What am I missing? Aircraft are such illustrative examples of the whole concept of tradeoffs.
I assume its a function of altitude? Not much air at 60, 000 feet. Although the same goes for the propeller I guess. The altitude would certainly be where the efficency comes from, but it's such a simple solution, there must be very good reasons commercial don't already fly that high.
A CitationJet can reach ~420 knots cruise with straight wings. For propulsion, seems that they become a "hybrid" with propeller thrust and some jet thrust from their exhaust nozzle. This is similar to a P51, which generated some thrust with radiator exhaust.
Doesn't say how many passengers it can take. That's a weird thing to not mention when you are talking about efficiency.
- Who is going to want to take the time to climb to 65,000 feet in this? People going transatlantic? They'll probably still take a Gulfstream.
- Does it still get reasonable range economy at lower altitudes and true airspeeds?
- Nobody will be able to see the runway over the nose on landing.
- That door doesn't look like it'll hold up to pressurization.
- The landing gear looks very light.
- The engine is going to have very tight thermal and mechanical constraints based on its position in the rear of the fuselage.
- I'm assuming it's a turbine engine in here? Trying to turbocharge something enough to get to 65,000 feet is going to be awful and very maintenance intensive.
- Update: Nope, at least one V-12 with multiple turbochargers. If there is more than one engine the complex gearbox to drive the propeller will be difficult to get approved. See the Learfan aircraft [0].
- The propeller is out on a long shaft, may cause issues.
- The propeller is a pusher configuration, which isn't inherently bad, but causes efficiency losses from turbulent air coming off the fuselage.
- Pusher configurations - especially pusher turboprops like the Piaggio Avanti are noisy.
- Update: It's a piston engine. May not be as noisy because it appears that the exhaust is farther upstream than usual. However, cooling everything will be difficult.
- High altitude flight introduces the possibility of coffin corners in the envelope and very little room between overspeed and stall.
- That big engine (for high altitude flight) will reduce room in the cabin considerably.
- Everybody and their mother will probably have a tail strike.
Source: pilot and an aerospace engineering degree.
[0]: https://en.wikipedia.org/wiki/LearAvia_Lear_Fan