
The Celera 500L aircraft may fly soon - bookofjoe
https://www.thedrive.com/the-war-zone/28409/the-mysterious-and-potentially-revolutionary-celera-500l-aircraft-may-fly-soon
======
skunkworker
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."

~~~
dorfsmay
Why flying so high? Fuel economy?

~~~
asdfadsfgfdda
Less drag (lower air density) but also slower winds. Cruising at such a high
altitude avoids the strongest jet stream winds.

~~~
usaphp
What are the downsides of higher altitude flights?

~~~
DuskStar
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.

~~~
semi-extrinsic
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.

------
inamberclad
A few things off the top of my head that look odd:

\- 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](https://en.wikipedia.org/wiki/LearAvia_Lear_Fan)

~~~
briandear
A piston engine at 65,000 feet? That’s unreal.

~~~
bayesian_horse
Which is probably part of the interest/mystique in this project.

------
aedocw
I am surprised I never see mention of
[http://synergyaircraft.com/](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!

~~~
mannykannot
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.

------
walrus01
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.

~~~
bayesian_horse
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.

~~~
walrus01
According to this, diesel is 45.6MJ/kg

Jet fuel is 43MJ/kg

[https://en.m.wikipedia.org/wiki/Energy_density](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.

------
tim333
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.

------
mc32
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.

~~~
walrus01
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.

~~~
LargoLasskhyfv
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)

~~~
walrus01
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.

~~~
LargoLasskhyfv
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?

------
cyberferret
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).

~~~
walrus01
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.

~~~
cyberferret
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.

~~~
dmos62
If this ends up being an airline aircraft, as opposed to a personal aircraft,
that might not be a problem, at least business-wise.

------
starpilot
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.

~~~
bayesian_horse
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.

~~~
PopeDotNinja
I'd fly in something that looked ridiculous if it was a pleasant enough travel
experience.

~~~
GordonS
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?

------
baybal2
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.

------
e40
Doesn't say how many passengers it can take. That's a weird thing to not
mention when you are talking about efficiency.

------
banku_brougham
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.

~~~
gwicks56
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.

------
Gravityloss
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.

------
new_realist
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.

~~~
m463
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...](https://phys.org/news/2011-03-airplane-contrails-worse-
co2-emissions.html)

~~~
eloff
This doesn't seem possible to me.

~~~
LargoLasskhyfv
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.

~~~
pmontra
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.

------
bayesian_horse
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.

~~~
walrus01
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.

------
cairo_x
This thing looks like the future. But not in an aesthetically impractical
concept vehicle kind of way. It's actually beautiful.

~~~
DEADBEEFC0FFEE
I agree. Looks georgeous. Also looks believable.

------
mannykannot
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](https://en.wikipedia.org/wiki/Republic_XF-12_Rainbow)

[2]
[https://en.wikipedia.org/wiki/Napier_Nomad](https://en.wikipedia.org/wiki/Napier_Nomad)

------
PopeDotNinja
It's hard to imagine a V-12 engine achieving Prius-level efficiency.

------
lormayna
For some aspects, it looks quite similar to the Piaggio Avanti

------
eru
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.)

~~~
billfruit
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.

~~~
eru
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.

~~~
dragonwriter
> 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.

~~~
eru
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.)

~~~
nottorp
It's not only about fuel costs, but also about parking space. The extra half a
metter matters in many situations ;)

------
Creationer
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.

------
anovikov
Lies. 10x efficiency improvement is simply not possible. Or a gross
misinterpretation.

~~~
anovikov
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.

