Otto Aviation "Celera 500L"

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https://www.thedrive.com/the-war-zo...PnCICVh9TpRQvDaSiR2o2xKUKAQlqDd5s4uOYn8o

Quote: "the Otto Aviation Celera 500L, is definitely focused on potentially game-changing high-efficiency flight that has the potential to disrupt the aerospace marketplace"

"It is unclear from the available information whether the Celera 500L uses one or two A03 engines. The FAA's profile describes the aircraft as a "single engine," but patent documents had described two engines driving a single propeller. Of course, they had also said these would be diesel engines with multi-stage turbochargers and intercoolers, the latter of which redirect heat to improve efficiency and keep the entire system cool while the former would theoretically provide enough power even at very high altitudes where super-efficient flight can be realized"

"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"





Powered by (possibly 2) 500HP diesel engines, although it looks like just one engine. I have to wonder...... It's a neat shape, and clearly there is a bit of drag reduction by having such a clean shape. However, the twin pusher Piaggio Avanti is similarly configured and achieved little in the way of better efficiency.

The thing that always comes up is that we've done remarkably well optimizing shapes for low drag. Today's modern aircraft have incredibly low Cd

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Originally Posted by Driz
If the old adage " if it looks good it will fly good" has any truth to it they're in trouble....


It's funny you bring that up. There is no question that form follows function in aviation. Clearly the guys building this thing believe a teardrop fuselage is a functional shape.

What's interesting is that the conventional tube is incredibly hard to beat, with a Cd so low (0.022 for example) , there just is not much to be gained by changing fuselage shape.

The G650ER, a true high altitude performer, it's form looks like you'd expect for a 51,000 foot, Mach 0.925 aircraft.

[Linked Image]





Brings another thing to mind. Diesel engines are more efficient and will result in better MPG. However diesel/jet fuel is heavier. Aircraft carry fuel by weight/mass. Miles per gallon is simply economic criteria, when comparing piston engines. Today's piston aircraft engines have fantastic BSFC numbers (consumption by weight) . Gas powered engines burn more fuel than diesels when measured by gallons, but when measured by weight, the numbers are quite close.

Piston airliners were very efficient and achieved passenger MPG that rival the best jets today. The diesel has some serious disadvantages, including reluctance to re-start at any altitude above 14,000 feet. Compression ignition is funny that way.... Another distinct aero diesel disadvantage is the requirement to carry power during descent, as they tend to flame out when driven by the prop in a common high altitude descent.
 
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I think it looks okay.

Seems like a lot of airplane for one V12 that is probably derived from an automotive V12 - hard to imagine developing one from scratch for aero application in this age.

Wonder what the coffin corner / envelope is at 55,000 to 65,000 feet with those little wings and engine?
 
No kidding. Diesels consume a LOT of air. I guess if you have compound turbos sucking and compressing enough of it, there's enough oxygen to get by?

Is is going to be a true diesel burning diesel fuel, or one of those "diesels" burning JP on the diesel ignition process?

No matter what, Chuck Yeager is going to to be livid that they repainted his plane and are taking it for joyrides.
 
Of note, liquid cooled, turbocharged, intercooled, piston engines have a LOT of cooling drag. One look at those huge ducts on top is all you need to know with regard to the prospect of actual high speed flight.

This drag issue presents a problem in high altitude, high speed flight. With coolant temperatures around 200-220 degrees F, the surface area required for heat transfer is roughly triple that of equivalent air cooled engines. Before you bring up the P51, it's cooling radiator and Meredith effect, the very same effect works even better with the higher temperatures of air cooled engines.
 
With those thin small chord wings, where will the fuel go?
While the thing has obviously been taxied, will it actually ever fly?
The fin looks awfully tall for an aircraft that'll never see asymmetrical thrust.
Overall, this looks like an intriguing concept, but I don't see how its performance claims can be met.
There are other very fast prop aircraft actually flying, but they have lots more installed power and high fuel consumption at speed.
What here merits a patent?
 
Originally Posted by fdcg27
I don't see how its performance claims can be met.


In a nutshell, the performance claims cannot be met using the chosen propulsion system.

There are some interesting tricks that can be employed to optimize performance. The very first item of note is the choice of prop style. Any conventional prop becomes incredibly inefficient at higher speeds. While there are some reasonably fast prop planes, the Piaggio Avanti for example, they are pouring 1600 HP into each of the well designed pusher props. Even so, the practical limit seems to be 400Kts TAS maximum speed and a cruise speed of 318Kts.

The other is to eliminate cooling drag entirely.

This can be done by the use of gas turbine engines or by mechanically forcing air through the radiators and intercoolers.

Here is a prop design that can achieve near jet speeds:

[Linked Image]
 
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Reminds me of the Bell X1... and it probably has about the same chance to make it in general aviation as the X1... I see more hope in the RED V6 and V12 Diesels...

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We both know that there are piston propeller aircraft that can operate at near jet speeds and they were flying more than seventy years ago.
Not very efficient and not offering long engine life, but they could do it.
There is also the Soviet era but still in service swept wing Bear bomber, which uses contrarotating props to absorb the power of its turboprop engines.
It was built and operated as an airliner as well.
The UDF engine you depict has an unacceptably high noise profile for operations from any airport one might consider operating from.
 
Originally Posted by fdcg27
We both know that there are piston propeller aircraft that can operate at near jet speeds and they were flying more than seventy years ago.
Not very efficient and not offering long engine life, but they could do it.
There is also the Soviet era but still in service swept wing Bear bomber, which uses contrarotating props to absorb the power of its turboprop engines.
It was built and operated as an airliner as well.
The UDF engine you depict has an unacceptably high noise profile for operations from any airport one might consider operating from.


I love the idea of UDF propulsion. One potential way to reduce noise on UDF designs is to stagger the blades. Eurocopter/Airbus has used this method with their tailrotors for 25 years now. It's very effective.


You are correct about some very high performance piston engine'd, prop driven aircraft being capable of near jet speeds. But it's good to understand that they are not operating in the same environment. No piston props operate at high mach numbers. Piston prop record holders do so at rather low altitudes, where the speed of sound is higher, and achieve modest mach numbers. A flight profile comparison (climb, cruise, descent) really illustrates the differences. Our Gulfstream G650ER climbs at M 0.87 and max cruise is M 0.92, which it will do easily at any altitude below FL490. A FL to NY trip takes roughly half the time of typical turboprops. It's not just cruise speed that matters. It's climb and descent speeds too.

It's also good to note that gas turbine powered prop driven aircraft achieve significant jet thrust from the engines. In some high speed record setting cases, most of the thrust comes from the core engine and not the prop.



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Watch the airspeed indicator on the P51 during takeoff and climbout. It's in MPH and it remains in the mid 100's. Prop speeds.
 
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Otto-Aviation-Celera-500L-16x9-1.jpg


I thought I'd update this thread, as the Celera 500L has (according to some sources) now performed over 30 test flights. It is good to see it fly and I truly hope the realistic engineering goals have been achieved. Some of the numbers (originally copied from their website) in the OP were wildly optimistic, and may have simply been part of the sales pitch for investors.

Suggestion: Change the playback speed of the video to 0.25. Doing so provides more viewing time to see interesting details.

Observational notes: The two empennage mounted cooling pods are huge and are very likely to be responsible for significant cooling drag in some aspects of flight. They do seem to be designed to recover the heat energy and convert it into thrust by utilizing a variable outlet area. While this can and has been done in the past (P51 Mustang for example), the alternative of fan forced cooling may in fact provide advantages. I can't imagine the airflow the prop operates in is smooth.

Also, the pitch up on takeoff and climb out was about 2 degrees. That's unusually low and can indicate caution on the part of the pilot, lack of excess thrust (my guess) or design parameters that include very high takeoff and cruise-climb speeds.

The 750 pound Red A03 engine, ( https://en.wikipedia.org/wiki/RED_A03 ) a 550HP 80 degree diesel V12 used is quite interesting and provides a BSFC number of 0.35 pounds of fuel per hour per HP produced.

RED_A03_side_view_with_gearbox_%28cropped%29.jpg


As I mentioned above, the Piaggio Avanti, a very similar shape and slightly larger size requires 3200 HP (and significant jet thrust from it's 2 PT6 engines) to achieve it's near 400Kt cruise speed. I question the ability of 550 HP to push the Celera 500L to similar speeds and altitudes.

800px-LotniczePogotowieGDN.jpg
 
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Originally Posted by fdcg27
I don't see how its performance claims can be met.


In a nutshell, the performance claims cannot be met using the chosen propulsion system.

There are some interesting tricks that can be employed to optimize performance. The very first item of note is the choice of prop style. Any conventional prop becomes incredibly inefficient at higher speeds. While there are some reasonably fast prop planes, the Piaggio Avanti for example, they are pouring 1600 HP into each of the well designed pusher props. Even so, the practical limit seems to be 400Kts TAS maximum speed and a cruise speed of 318Kts.

The other is to eliminate cooling drag entirely.

This can be done by the use of gas turbine engines or by mechanically forcing air through the radiators and intercoolers.

Here is a prop design that can achieve near jet speeds:

[Linked Image]
Just like todays engines we see on the commerical air liners cept the fan in in the front of the engine and ducted
 
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