News ESA hosted electric powered aircraft.

[Notebook]

6 May 2016
A start-up company hosted in an ESA business incubator is developing the world’s first vertical takeoff and landing aircraft for personal use. The electric two-seater will open the door to a new class of simpler, quieter and environmentally friendly planes available from 2018.

http://www.esa.int/Our_Activities/S...al_aircraft_aiming_to_take_off_from_your_home

http://lilium-aviation.com/

Nice website, not much info. We'll see if it takes off.

N.

 

[Loru]

So 36 RC motors, some carbon fibre, plexiglass, battery and android device to run it?

Ok running the numbers gives me ~9kW per motor. Is it possible with such small motors? My drill looks similar size to this motor yet it's only 750W.

Also according to numbers provided by website I estimate endurance at 100 minutes (500m range at 300km/h) and that gives me ~520kWh of electricity you need to take with you.

I like multiple motor design though. Lots of redundancy it case of emeregency.

 

[Notebook]

Early days, I suppose. Though they do have a 1/2 size prototype. Strange no videos of it?

Looking at the graphics, it appears the fore-plane retracts/extends, wonder why they did that?


N.

 

[Loru]

Improve aerodynamics in level flight?

 

[RisingFury]

Ok running the numbers gives me ~9kW per motor. Is it possible with such small motors?

Yes. RC heli guys commonly use four 6 cell LiPo batteries in parallel for 100A, 50V or 50A, 100V circuit. You can easily squeeze large power out of small electric brushless motors.

Also according to numbers provided by website I estimate endurance at 100 minutes (500m range at 300km/h) and that gives me ~520kWh of electricity you need to take with you.

Right, battery storage is the key problem here. Best LiPo batteries store about 300 Wh / kg, where fuel stores about 14 000 Wh / kg. That said, the conversion efficiency for the battery-ESC-motor can easily be 80%, while the conversion efficiency for fuel is in the 20 to 30% range. So that brings us down to 240 Wh / kg for batteries and 3500 Wh / kg for fuel. We can see batteries still need to advance an order of magnitude.

There's another thing working in favor of electric design - the motors are much lighter per unit power than an internal combustion engine. Smaller weight means smaller wings, which lower drag and reduced energy consumption. However, this doesn't offset the aircraft an order of magnitude.



ESC = Electronic Speed Control

I have an issue with the aircraft's aerodynamics. The wing is way in the back and no canards at the front. Not sure that's gonna fly. I highly doubt the wing at the back could provide enough counter torque to prevent the aircraft from being too nose heavy to fly.

 

[Ravenous]

It looks like... the Shuttle PB!

I think it looks a bit nose heavy too.

Just think, the sky full of Sunday Drivers...!

 

[Notebook]

To Loru above. Yes it will reduce drag, but what if it can't extend for low-speed flight?
As RisingFury points out, its a canard, sort of...Looks very short-coupled compared to a Vari-eze type configuration

https://www.youtube.com/watch?v=cSstlRdoG7g

N.

 

[Hielor]

I'll believe it when I see it.

 

[Urwumpe]

First flight

The Lilium aircraft has done its first flight over Bavaria:

https://www.heise.de/newsticker/mel...ich-ersten-Testflug-ueber-Bayern-3689946.html

The video looks pretty convincing to me that at least the most energy demanding phase of take off and landing works... once cruising the aircraft should do much more kilometers per kWh. But I don't see a full transition to horizontal flight yet, the maneuvers look like transition phase at most (or blown flaps)

They calculate that a flight from Manhattan to JFK would take 5 minutes and cost $36 at the current technology, they expect that the price could drop to $6 for the same flight with improving technology.

I would not go so far to claim that electric cars are already obsolete... but looks like longer ranged electric cars have now a serious competition with some advantages (faster and more efficient at the same battery technology).

English article about the event here:

https://www.wired.com/2017/04/lilium-jet-first-flight-test-flying-cars/

 

[RisingFury]

As far as forward flight goes, the nose-heaviness of the aircraft still worries me. If they're planning to keep the nose of the aircraft up by having the front EDFs running, that's an immediate safety issue: What if the EDFs go out?

Planes and helicopters can both survive non-powered landings. Planes because they can glide and helicopters because they can auto-rotate. But this thing would nose dive out of the air.


Another few things I have to challenge here:
- The cost of the flight is not only the vehicle and energy, but takeoff and landing fees and other aviation fees.
- Electric cars aren't obsolete until they're actually obsolete. This thing isn't selling yet and is just a prototype.

Don't get me wrong, I look forward to the day when these flight pods zip us around with their own computer guidance. But until it happens, it's just a prototype.

 

[Urwumpe]

As far as forward flight goes, the nose-heaviness of the aircraft still worries me. If they're planning to keep the nose of the aircraft up by having the front EDFs running, that's an immediate safety issue: What if the EDFs go out?

As far as I can tell, they first of all calculate with the redundancy of having multiple motors. From the article, it seems like one or two motors failing is not bad, just like one electric circuit with its own battery set failing is not a problem.

Also, this is just a smaller prototype, the real version looks more like a Scaled Composites VariEze

 

[RisingFury]

Yea, if you don't run each motor on full power, you have some leeway for some to fail, but motor failure isn't the only mode of failure.

There are two things in particular to worry about:
- Running out of energy. If that happens, you're just done for...
- ESC heat damage. ESCs are nasty and heat up a lot. If one overheats, one motor fails, but the heat can affect other ESCs. You can end up with a cascade failure.

I also don't know how bird strikes would affect this aircraft. This is an entire unknown...

 

[Urwumpe]

Yea, if you don't run each motor on full power, you have some leeway for some to fail, but motor failure isn't the only mode of failure.

There are two things in particular to worry about:
- Running out of energy. If that happens, you're just done for...
- ESC heat damage. ESCs are nasty and heat up a lot. If one overheats, one motor fails, but the heat can affect other ESCs. You can end up with a cascade failure.

I also don't know how bird strikes would affect this aircraft. This is an entire unknown...

Well, you can also fix many problems there. Running out of energy is a problem, but if you have a clever battery management, you should know when you are running on reserve and be able to perform an emergency landing. If you get the plane avionics to the same level as a Volkswagen E-Golf (2017 model) has on-board, your flight planning system should already tell you at the start how unlikely you are to reach your destination and optimize the trajectory.

Also the heat damage problems for ESCs is also no constant. Its plain stupid high power solid-state electronics. If you buy your ESC cheaply from a Chinese ISO container with real design power being 20% of the value stated on the product sheet, you should not be surprised. Especially cheap ESCs that operate with square voltage signals to the motor are a problem - those are cheaper to build, but turn a lot of power into heat during switching. I know that the electric racing cars build at German universities invest more into a good ESC than into a good motor, because a mediocre motor with a good ESC is much better than a good motor with a mediocre ESC - and little investments into the ESC have more effect than the same investments into more sophisticated motors - a BLDC is after all, technically not much different to a synchronous AC motor with DC electronics.

 

[MaverickSawyer]

For safety, I have three words: Ballistic Recovery System.

 

[Artlav]

For safety, I have three words: Ballistic Recovery System.

AKA ballast from the seller's point of view.

 

[Urwumpe]

AKA ballast from the seller's point of view.

I know nobody who calls a BRS ballast. A few hang gliders still live because of it.

 

[MaverickSawyer]

Call it ballast if you wish. I call it life insurance of a more energetic form.

 

[Artlav]

I know nobody who calls a BRS ballast.

Call it ballast if you wish.

Oh, i don't doubt it's efficiency.

It's just that these days things are made by removing parts until it stops working, then adding the last one back in and selling.
Obviously, this thing would still work without a BRS, so it would be removed/won't be added.

 

[Urwumpe]

Oh, i don't doubt it's efficiency.

It's just that these days things are made by removing parts until it stops working, then adding the last one back in and selling.
Obviously, this thing would still work without a BRS, so it would be removed/won't be added.

Well, Hardware is not Software....

 

[Hielor]

Oh, i don't doubt it's efficiency.

It's just that these days things are made by removing parts until it stops working, then adding the last one back in and selling.
Obviously, this thing would still work without a BRS, so it would be removed/won't be added.

Then why are so many modern small aircraft fitted with them?

I wouldn't be surprised if they become required safety equipment if these kinds of "flying cars" become common.