PPRuNe Forums

PPRuNe Forums (https://www.pprune.org/)
-   Rotorheads (https://www.pprune.org/rotorheads-23/)
-   -   Lilium vertical take off "jet" (https://www.pprune.org/rotorheads/578979-lilium-vertical-take-off-jet.html)

Ian Corrigible 26th Apr 2017 11:50

Bell is now also getting into the electric VTOL game: Bell Helicopter, Embraer partner with Uber for electric VTOL taxis (Bell microsite here).


Originally Posted by IFMU
I don't believe the Firefly ever flew.

Correct, though someone did manage to get a battery-powered R44 airborne: Electric Boogaloo part 2: R44 Edition

I/C

SansAnhedral 26th Apr 2017 15:08


Originally Posted by mickjoebill (Post 9752441)
So who is digging a deep hole for themselves, Ppruners or Lilium?

Mickjoebill

So what is the gross weight?

EDMJ 26th Apr 2017 21:52

Have never, ever seen a "real" aircraft prototype flying in Germany without a registration. Which begs the question which class they're going to register it in..

A clever, modern version of "The Emperor's New Clothes".

Anyway, Germans are suckers for these things. Does anyone remember Cargolifter and the amount of money the German state sunk into this....

mickjoebill 26th Apr 2017 23:08


Originally Posted by SansAnhedral (Post 9753084)
So what is the gross weight?

No idea.
Have a guess, a 6 meter wingspan, canopy, electric motors and a battery long enough for one of the test flights, let's say 1 minute.


I wonder how it taxied from the hangar to the runway?
Perhaps the same way a helicopter get to the pad?
Maybe those square things under the bed springs are part of a dolly?


But if it is an air vehicle of significant size and mass (larger than the germa large RC model rules would cover) it would still require the airfield and surrounding area to be notam'd - it should be easy enough to find that notam to add some substance to the claims.
Perhaps someone familiar with dragging Notams from the archive on the Notam website could have a look.
It is a great point that there was no registration. What is the max weight of the large agricultural drone in Europe?


Mickjoebill

Thracian 27th Apr 2017 06:25


Originally Posted by EDMJ (Post 9753374)
Have never, ever seen a "real" aircraft prototype flying in Germany without a registration. Which begs the question which class they're going to register it in..

A clever, modern version of "The Emperor's New Clothes".

Anyway, Germans are suckers for these things. Does anyone remember Cargolifter and the amount of money the German state sunk into this....

Careful ;-)
We germans donīt have the slightest trace of humor ;-)


You have to distinguish between state investments and private ones. Look at the Volocopter guys (building a Heli-like looking electrical 18 rotor multicopter with battery exchange system). They are already doing manned flights with a registered aircraft. Their first manned takeoff was a year ago.
And theyīre doing it in Germany.


They just have presented their "2X" model for certification in 2018.


In my humble opinion this will be the first electrical manned aircraft being commercially available.


Of course, itīs not fast, but itīs a beginning


Thracian

XV666 27th Apr 2017 07:39


Originally Posted by ShyTorque (Post 9752635)
I wonder how it taxied from the hangar to the runway?

Really? 1:05 in the video clearly shows a trolley under the machine as it lifts.

aox 27th Apr 2017 08:10


Originally Posted by mickjoebill (Post 9752483)
The airfield in Tussenhausen Germany can be viewed on Google Earth.
According to google earth the taxiway the craft lifted from is around 6.5 meters in width.
Video from a few angles indicates the wingspan of the lilium craft is a similar width to the taxiway.

So an extraordinary achievement if the craft has a wingspan of over 6 meters yet weights only 25kg:)

Mickjoebill

And the pictures in the Daily Mail a year ago really are of it flying amongst some mountains and across some sea quite low.

May 2016: on sale in 2018.

April 2017: first manned flights in 2019

What will next year's update say?

mickjoebill 5th Sep 2017 11:35

$90 million more into coffers
 
Lilium have just raised $90 million to continue development of the lilium jet.
70 staff, recent senior hires from Airbus, Tesla and Gett, co-founders of Twitter and Skype on board.
The team continue to look impressive on paper and social media:), but endurance v payload yet to be well defined, other than one hour endurance at 300kph mentioned in the press release.
https://lilium.com/news/

"The Lilium Jet will be able to travel at up to 300 km per hour for one hour on a single charge - meaning an example 19 km journey from Manhattan to JFK Airport could last as little as five minutes. The jet’s economy and efficiency means flights are predicted to cost less than the same journey in a normal road taxi."

Here is one way to increase payload and range:)
https://www.facebook.com/CivilWork/v...2061358200167/
Mjb

Ascend Charlie 5th Sep 2017 21:59

MJB, did you read the comments on that clip? Astounding how many rockapes thought it was real.

mickjoebill 6th Sep 2017 10:40


Originally Posted by Ascend Charlie (Post 9883356)
MJB, did you read the comments on that clip? Astounding how many rockapes thought it was real.

Potential Lilium investors!

Mjb

Hot and Hi 8th Sep 2017 08:04

More recent 'artist's impressions' on their website https://lilium.com/technology/ now show a big canard (span maybe half of the wingspan of the main wing).

https://lilium.com/images/press/reso...-with-gear.jpg

Ascend Charlie 8th Sep 2017 10:39

OK, so now those canards appear to have lost their swivelling hinges and are now looking very fixed?? Now it is just the engines that swivel to the vertical, but no hinge or actuator is visible - under the wing must be some very strong actuating arms. And the early "design" where the front canard retracted into the nose has been dropped. Obviously they paid attention to the constructive criticism here on Proon.

cattletruck 8th Sep 2017 11:07

I hear it suffers from the dreaded 35 engine approach.

(someone wants their computer cooling fans back).

Rengineer 8th Sep 2017 12:24

Mmmh, let's at least try and guesstimate if this thing has a chance.
To lift off, those fans will need to create more lift than its mass, at least including ground effect. I did a quick calculation based on comparison with known aircraft and found that if it had a mass of say 2 tons and the fans a diameter of 0.6m, depending on propeller efficiency, ground effect, and some more esoteric things, it should require between 700-1200kW total power; let's say 25kW for each of those 36 engines. That doesn't appear totally out of the question for me.
Then, for cruise flight, power would obviously depend on the lift/drag ratio and on speed. For some reasonable assumptions, I find it would need only a fraction of the T/O power (as one would have expected); again depending on assumptions, this could be 5-15% of the take-off power.
Then, with decent batteries, say between 150-300 Wh/kg, there really is a corner of the design space where this vehicle might just potentially be realizable. I'm not saying it will necessarily be successful or reach any of the advertised performance goals, but just from looking at the energy and mass budget, it doesn't seem to be quite out of the question. Obviously that's before we've talked about controllability, failure tolerance, minimum reserves, and all that stuff. We'll see.

riff_raff 9th Sep 2017 03:10


Originally Posted by cattletruck (Post 9885805)
I hear it suffers from the dreaded 35 engine approach.(someone wants their computer cooling fans back).

That's funny. Except it should be "the dreaded 36 motor approach".

Unfortunately, there are quite a few practical issues with this concept that they do not seem to have fully resolved yet.

First, relying solely on differential thrust produced by speed changes of (36?) small diameter fixed pitch rotors to provide satisfactory pitch/roll/yaw control authority, plus the required lift in hover, is a very inefficient approach for VTOL operation.

Second, their claims of "simplicity" and "high redundancy" may be rather optimistic. Having 36 individual motor driven fans does not make the propulsion safer or more reliable if there is some single point in the motor control/power system which if it fails would disable enough motors to cause loss of lift/control of the aircraft. This means several isolated/separate systems for power/control of those 36 motors.

Third, using 36 electric motor-driven fans does not reduce the maintenance requirements or increase reliability versus a conventional commercial helicopter drivetrain. In fact, the most failure prone part of this system will be the high-power motor control electronics. A good helicopter gearbox and turboshaft engine will last >2000 hrs. But an air-cooled aircraft-weight electric motor and high-power control system will likely have an MTBF of a couple hundred hours at best. Consider how worse the situation gets with 36 motors.

mickjoebill 23rd Apr 2018 23:51

Frank Stephenson joins the Lilium team.

Mjb

Ascend Charlie 24th Apr 2018 00:36

If it was Frank Robinson it might gain a little credence.

Aluminium Mallard 24th Apr 2018 05:27


Originally Posted by mickjoebill (Post 10128189)
Frank Stephenson joins the Lilium team.

Mjb

It's just what they need at this stage... a designer to polish the turd a bit more and suck up some more investment. Can't wait for the shiny new video complete with inspiring music.

Rotorbee 25th Apr 2018 08:34

I clicked trough the website a bit more in depth and I am not sure, but somehow I have the impression the team isn't the same as in the beginning. I think to remember on the old site that the founders where entirely non-aviation.
It looks like the new toy has not a lot in common with the first idea, even with the one in the video. That swivelling canard wing is gone. It does not retract. That makes it a fairly normal canard configuration, except for the straight main wing. The arm of the winglets as vertical stabilisation devices seems awfully short. I wonder how effective they are. Anyway, I think reality got them. It looks much more feasible than 3 years ago.
It is hard to judge the extent of the fail safe system approach for the FBW, but let's assume, that they know what they do.
But it does have a parachute now. Either because they want to certify it as some kind of VLA/UL and not in a completely new class as they said on the old page (EASA wasn't amused, probably) or they don't trust the thing as much either. But it swims, too.
While I still don't like the 38 motors configuration (entry to the minimum equipment list, at least 36 must be working), let's see how far they get. My bet is, that the "flap actuator" mechanism will be the biggest problem. Four heavy control "surfaces" (planks with a lot of fans on it) which have to move constantly to keep things at bay. Make it three times redundant, that adds to 12 fast and very light electric motors probably with gear boxes, constantly working back and forth.
I don't see how they want to get yawing under control while hovering. Not with those winglets. I think they make things even worse.
Imagine a gust of side wind close to the ground while hovering. If you "lean" into the wind with these wings, they will suddenly become a nice big sail that wants to push down. I wonder if the fans are speeding up fast enough to counteract this. Or I see one wing suddenly wants to fly and the other not. Now the fans of the not flying wings have to produce lift like hell and yawing, on the other wing they must be virtually stopped, which will disrupt the lift over the wing ... I think they have even worse aerodynamic problems than helicopters.
And we haven't even touched the word flutter with those heavy and wings and vibration producing fans.
The fans compress the air like jet engine, without heating it. I don't get the point of that. Only probably that they need more thrust but the size of the fans is fixed. Is this very efficient as a propulsion system?

The Lilium Jet engines have only one moving part - the central shaft of the rotor holding both the fan in the front and the magnets of the electric motor. This ensures highest reliability in operation and low maintenance costs of the propulsion system. The high redundancy of the system allows large inspection intervals to keep costs much lower than for helicopters or reciprocating engines
Where is the redundancy in a single electric motor. I don't think EASA would let you go flying with even just one motor broken. I think you get even higher maintenance because out of 38, one is bound to fail.

mickjoebill 6th Jun 2018 04:03

Not a lot of new here... a video of a Lillim Presentation made in May by Daniel Wiegand at WORLD.MINDS MOBILITY 2018
Has an apparently unedited video of the 90 second test flight of full scale prototype from 2017.
(curious that they didn't use one of the edited videos that had higher production value and the air to air shot from a drone)

https://lilium.us13.list-manage.com/...7&e=85cc7af9ad

Hopes/claims/design
JFK to Manhattan, same price as a taxi.
60-70% stripped away from the complexity of previous designs.
300 kilometer range in cruise at 300kph
Same energy consumption per kilometre as a electric car but 5x faster
Any component can fail as there is redundancy to every part.
Plus parachute.
ect


All times are GMT. The time now is 03:16.


Copyright Đ 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.