Celera 500L -- A much more efficient private aircraft

[Vanadium 50]

Their claims of cruising at high altitudes are contraindicated by the engine type certificate, which states that the engine is certified for a maximum altitude of 25,000 feet

Yeah, but they have two of them and 25,000+25,000 = 50,000.

 

[cmb]

A cruising speed of 450mph (odd units) 'and' 25mpg seems quite a claim.

Be better to know the full operating profile first.

I tend to think we've been making and optimising aircraft for a long time, unclear where such a massive improvement comes from.

I recall when I was learning to fly in the UK, there was a guy based there who owned a 'motorised glider' and commuted back to his home in Netherlands every weekend in it (weather permitting, presumably) and he said it delivered 120mpg. I see no reason that could not be done similarly on a larger scale, but 450mph with that sort of efficiency seems slightly on the wild side.

I mean, sure, if you want to 'potter along' at 80 kt and you get "25mpg" (ground distance?), or maybe there is an efficient climb out and then engine-off for a glide decent, etc., sure. I'd like to see the claim for 25mpg + 450mph made together.

Rarely do you get something for nothing, especially on the delta between existing aircraft and a new one.

 

[gleem]

That is also what I have been thinking. One usually would expect an improvement in design would result in an increase in fuel economy of maybe 5 to 15% considering aircraft have been evolving for over a hundred years. A new design resulting in an 800% increase in fuel economy can only be considered as astonishing. One would have thought that the concepts used for this aircraft would have already been discovered and implemented long ago considering everybody has available the same development tools, knowledge, and education. Was something fundamental in aircraft design overlooked all this time?

 

[gleem]

I did some quick calcs to check the HP and thrust needed for level flight.

450 kts

22 nm/gal ---> 20.5 gal/hr
Fuel --=> density = 6.7 lbs/gal
Energy content of fuel used = 5220 Kcal/lb
wgt of fuel used per hour = 137.4 lbs./hr
Energy used per hours 717,230 kcal/hr
If 1 kcal/sec = 3600 kcal/hr = 5.613 HP
Then the rate of energy use is 1118 HP. If the efficiency is 40% then the useful HP delivered is 447 HP

How much thrust is needed?

F⋅v = power = F ⋅ 450 ⋅(6076/3600) lbs ft/sec = f ⋅760 ft/sec = 447 Hp = 245,850 ft lbs/sec
F = 323 lbs of thrust.

Does this seem reasonable?

 

[boneh3ad]

You see them in the photo in #13. They are not under the wings. That raises yet another stability question; tipping during taxi or crosswinds while parked.

The fact that fuel isn't stored in the wings would tend to make it more stable in this instance since so little mass is located outside the width of the gear.

 

[etudiant]

What do you mean by "Mach effects?" That's not a technical term. If you intend that to mean "compressibility effects," then we've long since passed that threshold. That's roughly Mach 0.7 at cruise. Be that as it may, that doesn't necessarily introduce any control issues. Long gone are the days of believing there is a sound barrier.

Long straight wings at altitude with speeds in the Mach 0.8 class can be nasty, so it does not take a big excursion from cruise to bite.
Afaik, the U-2 at cruise has only about 5 knots of margin between buffet and stall. Admittedly, that is at 70,000 feet, rather higher, but the same caution applies here imho.

 

[mfb]

There is not much mass located outside the main body, but still some torque from the wings if it is windy.

F = 323 lbs of thrust.

Does this seem reasonable?

~2m height of the cabin, the width seems to be similar, so we get pi square meter cross section of the main body. WolframAlpha says the air density at 50,000 ft is 190 g/m³. Assuming an amazing tear-drop shape with a coefficient of 0.04 we get 1.0 kN of drag from the main body. 323 lbs = 1.4 kN. That difference needs to cover everything else in the aircraft. Is that plausible?The company claims $328 hourly operating costs. How much of the overall cost of a flight is included in that? Can you just fly for three hours for $1000 plus whatever a pilot might cost? Probably not, but how much else is there as extra cost?

 

[boneh3ad]

Long straight wings at altitude with speeds in the Mach 0.8 class can be nasty, so it does not take a big excursion from cruise to bite.
Afaik, the U-2 at cruise has only about 5 knots of margin between buffet and stall. Admittedly, that is at 70,000 feet, rather higher, but the same caution applies here imho.

I am not sure what your point here is, as you seem to have ignored my question. What do you mean by "Mach effects?" My point was that this is already a highly compressible flow. It flies at Mach 0.7 at cruise, while compressibility becomes important at Mach 0.3. The issue when you start pushing Mach 0.7 and above is you start reaching the regime where transonic effects become relevant, i.e. the flow can locally turn supersonic over the wing or fuselage and form shocks when slowed. Either way, the term "Mach effects" is ambiguous at best.

 

[etudiant]

I am not sure what your point here is, as you seem to have ignored my question. What do you mean by "Mach effects?" My point was that this is already a highly compressible flow. It flies at Mach 0.7 at cruise, while compressibility becomes important at Mach 0.3. The issue when you start pushing Mach 0.7 and above is you start reaching the regime where transonic effects become relevant, i.e. the flow can locally turn supersonic over the wing or fuselage and form shocks when slowed. Either way, the term "Mach effects" is ambiguous at best.

You're quite right, I was sloppy in my terminology.
I'm not sure what formulation would be much better though.
The combo of near jet speeds and a straight wing has hidden risks, even when all is nominal. Flying is a guarantee that sometimes things will not be nominal, but Chuck Yeager will not be at the controls in most cases.

 

[Algr]

Electric planes don't have wings that small. Do they stuff the batteries in the wings?

 

[mfb]

This aircraft will probably fly slower, and at lower altitude as well.

 

[jrmichler]

The N number, N818MW, was originally assigned to a BAE 125 business jet. That jet was deregistered 6-4-2013 and the jet exported to Russia. Otto Aviation registered that number to their Celera 500 on 3-30-2107, and the Experimental category airworthiness certificate issued 2-15-2019. The Experimental airworthiness certificate gives the owner permission to fly the airplane.

Flightaware.com lists the most recent flight as 4:55 PM CDT to 4:55 PM CDT on 6-Oct-2015 from Houston, Tx. I don't know how to reconcile the Flightaware.com report with the lack of an airplane assigned to that N number on that date. Flightaware lists all flights in the U.S., except where the owner has filed a request with the FAA to not report their aircraft, in which case they state that the owner does not want their airplane tracked. If they flew it with the transponder turned off, Flightaware would not know about it.

An ADS-B transponder is required at all times when flying above 18,000 feet.

 

[member 656954]

10x the fuel economy at similar performance is quite a claim.

I am wondering about the operating cost comparison, too. The website claims $328 hourly operating costs but without details. My favorite business jet that is comparable, the Phenom 300E, runs to about $1,800 / hr but that's fully loaded with engine refurb, crew, landing / parking fees, etc.

Given that variable costs are dependent on hours operated and nautical miles traveled, and that Otto is still testing prototypes, there numbers may be on the optimistic side!

Still, even if it is double that, the incumbents in that segment will be facing stiff competition.

 

[etudiant]

The main difference is that turbine engines are brutally expensive.
So if Celera can get the needed performance from an intercooled and supercharged diesel, they are almost home free.
I'm still unconvinced, as I fear that the airplane will be demanding to handle at low speeds and possibly subject to real excursions at cruise if mishandled. But the basic aerodynamics, a clean high aspect ratio wing with a laminar flow fuselage do make sense.