New Alice Starts Taxi Testing

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Aesquire

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Victor Bravo beat me to it. Looks like a turboprop design. The electric is for investment.

Po!itical Rant deleted.

It's pretty smart to plan for the failure of the promised power plant with a design that can use an existing, proven, one in case the promised engine is cancelled.

I point to entire programs in the 1930-40s that failed because the engine designed for never reached production or promised performance.

The British Avro Manchester.
The German Bomber B program.
The American "request for data" R-40C programs.

And so many early jet airplanes...
 
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tspear

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@Aesquire

Not likely. What I think is likely is economics will beat policy first, but eventually expect bans on certain kinds of EV tech. Such as LiOn NMC batteries will be banned from EVs (only after LFP or Sodium whatever are viable).

Already you are starting to see discussions about making customer charging cycles more aware of when excess power is available. By the fact this discussion is occurring now, you will see changes in pricing which will eventually drive consumer behavior.

Tim
 

Monty

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Trivial to have differential thrust for yaw control if they're not designing for motor out. This is part 23, not part 25, so if they can substantiate sufficiently high motor reliability they don't necessarily need to design for motor out.
That doesn't have anything to do with the Htail.....and the props are just as likely to fail as any other prop. Controllers fail too. Short coupled design with a long forward fuselage. Engine nacelles and wing wake, likely to block both tail surfaces at high alpha.....Tail too small....
 

Aesquire

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To fill in the reason for tspear's response above, I deleted a political rant that predicted the banning of electric vehicles for environmental concerns.

It was only partly tongue in cheek/hyperbole. Consistent isn't a requirement for politics or scams.
 

BJC

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Am I the only one who just happened to notice that those electric motor nacelles look like they're the perfect shape, and you could just reach up and swap out that electric motor out for a PT-6

If you zoom into the photo and squint, you can see they have sump drain ports under the present location of the batteries.:)
Forward thinking, these guys are.

Victor Bravo beat me to it. Looks like a turboprop design.

Is it my imagination, or do those cowlings look about perfect for a PT6 turbine?
Probably your imagination. And VB’s, and V1’s, and Aesquire’s too.


BJC
 

addaon

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Certification doesn't usually consider the odds of power plant or prop failure. You have to demonstrate continued flight and control after a failure of one motor/ prop/ battery/ controller.
This is a simplification, and for some current designs it's an over-simplification. Essentially, you have a target FIT rate for each category of failure -- catastrophic may be 10^-7 (one failure in 10^7 hours), hazardous 10^-6, major 10^-5, minor 10^-4. (These numbers depend on the category, size, and type of aircraft -- a commercial airliner may target 10^-9 for hazardous, and go from there).

If you demonstrate that failure of one power plant is minor, then you also have to show that the chance of this is 10^-4 or better -- which, if you have ten power plants, means that the rate of any one failing is 10^-5 or better. This is very achievable, so this is a reasonable approach, which is approximated as "demonstrate continued flight after one failure." But there's two ways this can vary -- the first is to have a more serious impact of a failure, but show that the failure is less common; this is viable for example an eVTOL that will be forced to make an immediate landing after one failure (which is probably "major") due to, say, motor thermal limits, but can substantiate a 10^-5 failure rate for power plants. The other way this can vary is if the chance of two failures starts to matter. If each motor fails at, say, 10^-5, then twelve motors have one failure at near enough 10^-4, but have two failures at worse than 10^-9. If you need to reach 10^-9 for catastrophic, this means you have to either show that two failures is not catastrophic, or improve reliability per motor. (Or make an exposure argument -- if you escalate single failure to major with a "land within five minute" restriction, then the chance of a second failure in this time window is reduced per flight hour.)

Sorry to go deep on this stuff, I just find that it's super interesting, and one of the most reasonable things about the FAA regulations. The rules-of-thumb that I use are (1) electronic components (including motors) have a failure rate of 10^-4 individually; therefore (2) continued operation after single failure can reach 10^-7 (which is permitted for catastrophic for small Part 23); so (3) dual redundancy is sufficient for detectable failures, and triplex is sufficient for undetectable failures. It's important to know when these rules of thumb don't work, but they're a great start.
 

rv6ejguy

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Since there are no certified electric passenger carrying aircraft at this time, the onus will be on the first few to prove reliability of these new motors, batteries and controllers to the FAA/ EASA. Also a big one will be thermal and smoke mitigation from a thermal runaway event. If you've watched videos of battery fires in EVs (lots of them) you'll see how serious this could be in flight. The FAA will remember the 787 battery fiasco and this will be X 20 if one ever lets go. Theory and probabilty won't apply much here initially since this is all new hardware. They'll have to prove it and that will take a long time if no shortcuts are made in the process (737 MAX).
 
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addaon

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Yep. Been involved in doing exactly that. I'm confident that this is pretty well understood in the space right now. I will say that there's a reason that eVTOL batteries tend to have a lower energy density than you'd expect -- there's a lot of size and weight going to preventing a single cell's bad day from spreading. That's the primary approach -- design for isolation -- but testing definitely does apply. It's not terribly hard to get 10^7 hours on cells (a thousand cells for a year), which starts being significant. One challenge is that the failures we've seen in the field for pouch cells (see, e.g., Samsung) tend to be lot-specific manufacturing issues (a bad fold, sharp edge, etc), which means that you either have to substantiate per lot or just acknowledge the uncertainty and mitigate in other ways.

The motors and controllers are honestly less interesting here -- testing is well understood, and while SiC FETs do tend to burn up when you use them at the edge of their performance envelope, if you stay within it they're pretty consistent and reliable.
 

BBerson

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I guess Arlingtons 6000 feet of runway was inadequate for taxi testing. Moved to 13,500 feet runway at Moses Lake according to;Eviation's Alice Completes High-Speed Ground Test, Receives 50 Aircraft Pre-orders – TransportUP
From TransportUP email: This past week in aerial mobility, Eviation completed lift-generating high speed taxi tests at Moses Lake in Washington State and announced a pre-order for 50 aircraft, Honeywell hosted their 2022 Air Mobility Summit, Kittyhawk announced its impending closure, and SkyDrive announced its exhibition at GITEX GLOBAL 2022.
 
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Dan Thomas

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Not enough elevator authority to rotate until 300 mph....
Who knows. The CG on their first iteration was obviously off; why would they turn it into a taildragger (started out as a trike) if it wasn't? And even that doesn't fix a CG problem, just the optics for the naive investor. A trike sitting on its tail doesn't look quite right even to the newbie.

To be fair, I'd want a long runway too for testing such a novel design.
 

addaon

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He said Eviation needs still-to-be-developed advances in battery technology to make its planes commercially viable.

“Are the batteries on the prototype aircraft capable of propelling the certification aircraft, capable of providing sufficient energy? The answer is no, absolutely not,” Davis said.

I might not like how it looks, particularly, but it's a real aircraft, flying, with a realistic and pragmatic approach to the business side of things. Impressive.
 

rv6ejguy

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I like the looks but since it doesn't meet any mission requirements of a viable passenger carrying aircraft at this time, it's like all the others out there- still waiting for much higher energy density batteries. No surprise to anyone with a working brain and a calculator. What were they telling investors though?

Kudos on the first flight. That's always reason to celebrate. Lots of time, money and thought went into building this.
 

addaon

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They're telling investors that they're going to have the only certified electric design ready to go when the batteries arrive, I'm sure. A ten year moat is pretty sweet to investors.
 
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