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)

SansAnhedral 24th Apr 2017 18:56


Originally Posted by etudiant (Post 9749415)
The ESA web site so helpfully referenced says the concept has been 'validated ...with several scaled prototypes weighing 25 kg'.
It goes on to say that Lilium is now developing its first product, a two seater ultra light...
I think that settles the matter, the video is of one of the prototypes.

Indeed, the slow speed flight dynamics certainly do indicate that this scaled prototype in the video was 25 kg

aox 24th Apr 2017 20:57

Some great pictures of it in a British newspaper site about a year ago.

And apparently it will be on sale in 2018

Lilium the world's first electric vertical take-off and landing jet | Daily Mail Online

One thing occurs to me - are those front pods or whatever they are called retractable into the front fuselage sides, as one photo implies?

If so, where are your legs?

Ascend Charlie 24th Apr 2017 21:33

Yeah, been asked before - when the "pods" retract;

1. Front seaters' legs get crushed;
2. Retractable front wheel assembly gets mangled; and
3. Machine pitches nose down due to the whole structure c.g. being in front of the lifting surface.

PDR1 24th Apr 2017 22:52


Originally Posted by Ascend Charlie (Post 9751245)
Yeah, been asked before - when the "pods" retract;

1. Front seaters' legs get crushed;
2. Retractable front wheel assembly gets mangled; and
3. Machine pitches nose down due to the whole structure c.g. being in front of the lifting surface.

Well you don't get all that innovation without some downsides...

PDR

PDR1 25th Apr 2017 07:03

So in summary what we are seeing is a "scaled prototype" (ie not full size) weighing 25kg (not something with a 200kg payload or a 300 mile range).

So it's an RC model aeroplane, as we said. Its power system, energy storage and structure will not be representative in any way. Its control system might employ similar general principles, but won't use the same hardware. As such it matters not whether it's a model of the 2-seater or the 4-seater; it's still just an RC model.

And more to the point it's only shown in jet-borne flight; there is no video of it in wing-borne flight (whether with the front fan units deployed or retracted) so it does nothing to address the fundamental questions we have been asking about how it is to work aerodynamically.

I believe our scepticism is growing rather than receding.

PDR

WillyPete 25th Apr 2017 11:03


Originally Posted by Ascend Charlie (Post 9751245)
Yeah, been asked before - when the "pods" retract;

1. Front seaters' legs get crushed;
2. Retractable front wheel assembly gets mangled; and
3. Machine pitches nose down due to the whole structure c.g. being in front of the lifting surface.

Reminds me of the old Tucker automobile, where he originally planned for front wheel fairings to turn with the wheels and thus have the headlights mounted on them follow the direction of travel, but had to settle for a single headlight in the centre of the bonnet that turned with the steering wheel.

Slatye 25th Apr 2017 11:28


Originally Posted by SansAnhedral (Post 9751102)
Indeed, the slow speed flight dynamics certainly do indicate that this scaled prototype in the video was 25 kg

That seems like a reasonable number, which should be quite achievable using the foam (either sheet or carved from a solid block) construction used for millions of RC planes. If you wanted to do a mock-up to show to potential investors, as well as having the ability to do demo flights, that would be a good way to start.

Stick a couple of big-ish (110 - 130mm) electric ducted fans in there (up to around 8kg thrust each at 6kW; 5kg would be more common in the cheaper models) and you should be able to fly that around very nicely - at least when there's no wind.

mickjoebill 26th Apr 2017 00:51


Originally Posted by SansAnhedral (Post 9751102)
Indeed, the slow speed flight dynamics certainly do indicate that this scaled prototype in the video was 25 kg

So who is digging a deep hole for themselves, Ppruners or Lilium?


Lilium Facebook post from co-founder Patrick Nathen,
"As a founder, I can guarantee on behalf of our amazing investors and all you people out there, we did NOT use CGI or a size scaled model. This is the original size of our previous two-seated concept."

Email from Marketing manager in response to edited video.
"I can confirm that it is the full scale 2-seater.
We are running a test flight program, which means, we are testing it more than once.
We can start and land anywhere, doesn´t have to be exact the same spot, right?
Best, Mareike

Mareike Mutzberg
communications manager"


A remote test flight, apparently not above 100 feet, on "private" property of a fly-by-wire craft, backed by ESA and funded by the founder of Skype is not far fetched. Especially since they were test flying several scale models throughout 2016, videos of which are on u tube.

The thing is just a drone on steroids so remote control is embedded in its DNA.
They plan for it to be autonomous, so there is less to be converted.

Sure, they have shot themselves in the foot by labelling the video a "maiden flight" when it is a glossy compilation of several flights. They seem reluctant to release a continuous unedited shot of a flight which would adress the scepticism that scale models were used.

But it would be very silly of lillium to further mislead the public by making the statements quoted above if they were not true.

Has anyone found a report from a journalist who eye-witnessed the test flights?

Ppruner scepticism up to a point (!) is encouraged, given the radical design and the "forward looking" specification and performance of the craft and the unsatisfactory presentation of the test flights.

Mickjoebill

Terry Dactil 26th Apr 2017 01:33


In regard to the forward fan array not being retractable without crushing front passengers legs, it's apparently a moot point as the two seater was a concept not necessarily meant to go into production.
It's a bit of a worry that the design team did not notice that small problem right at the start.
I expect the next announcement will be something like
"Yeah, that one was just the concept. The production version will have extra wings... and wheels.... and a big engine... and...err, lots of other stuff" :E

mickjoebill 26th Apr 2017 02:24


So in summary what we are seeing is a "scaled prototype" (ie not full size) weighing 25kg (not something with a 200kg payload or a 300 mile range).
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

ShyTorque 26th Apr 2017 07:03

I wonder how it taxied from the hangar to the runway?

PDR1 26th Apr 2017 07:25


Originally Posted by mickjoebill (Post 9752441)
A remote test flight, apparently not above 100 feet, on "private" property of a fly-by-wire craft, backed by ESA and funded by the founder of Skype is not far fetched. Especially since they were test flying several scale models throughout 2016, videos of which are on u tube.

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.


The thing is just a drone on steroids so remote control is embedded in its DNA.
They plan for it to be autonomous, so there is less to be converted.
Stunning! I must try that as a safety case argument:

"Certification, design standards compliance and range airspace sanitation/segregation not required because remote control has been embedded in the vehicle DNA".

Yep, I can see the airworthiness authorities signing off on that!


But it would be very silly of lillium to further mislead the public by making the statements quoted above if they were not true.
Making unsupported and expansive claims to attract inward investment is hardly a novel practice.

PDR

PDR1 26th Apr 2017 07:26


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

Indeed - that was one of the many as-yet un-answered questions asked in the preceding pages.

PDR

PDR1 26th Apr 2017 08:23

The whole "retractable forward lift motors" thing seems to be a feature of this "flight test model" only. The other concept picture show a large and blown foreplane, so I'm confused. Are they saying that this sample is ONLY for jet-borne flight, and the one that does wing-borne flight will have a foreplane? Why build two that are different?

The CG issue perplexes me. It is claimed that the final product is a 4-seater, with all the seats forward of the mainplane. That's a load which could be anything from (say) 100kg to 400kg. Now if there is a large foreplane it's conceivable that the CG lies somewhere in the cabin area and this variable load could be accommodated.

But if it is flown with no foreplane then the CG will need to be somewhere around 15% MAC (typical stability point for an unswept "plank" tail-less with a reflexed wing section to give the favourable pitching moments). That means that the occupants will all be ahead of the CG. Now if we assume there is a vast battery weighing more than a brace NFL quarterbacks which is mounted right at the "back end" (please stop me if this techie jargon is getting too complicated) that would balance the occupants. But how would it cope with the massive variations in occupant weight? This doesn't stack up.

The website talks about the final vehicle will charge overnight form a normal mains outlet, and then defines a mission profile of just over an hour's duration. So let's be generous and say a 12:1 charge/use ratio. In the UK/Europe the most you can take out of a mains socket is 13A, which gives you a smidge under 3kW. So if we ignore charging losses that tells us the average power consumption across the mission would be no more than 36kW - 47bhp.

Does it sound reasonable that a vehicle could carry 4 people and luggage at 180mph for 200 miles with vertical take off and landing on an AVERAGE of 47bhp - less than a typical VW conversion in a Turbulent?

There are other techie howlers on the website as well, but the man's down so I'm stopping the kicking.

PDR

pettinger93 26th Apr 2017 09:50

Well, either it will fly or it won't. If the above sceptics are right, and nothing beyond a scale model ever flies, we won't hear much more about it. If, on the other hand and in the fullness of time, a full size airworthy aircraft surprises us all with new and astounding technology, the above pruners will all have to eat humble pie. Stranger things have happened and time will tell.

Ascend Charlie 26th Apr 2017 10:06

This one looks a bit more like it will ... ummm ... take off?

Aurora Unveils New eVTOL Aircraft at Uber Elevate Summit

IFMU 26th Apr 2017 10:43


Originally Posted by riff_raff (Post 9378367)
Compare this to a battery-electric 2 seat rotorcraft that was actually built and flown. It was a modified S-300C helicopter which already had a well developed rotor system and lightweight airframe. The electric motor was rated at 141 kW which was the same power produced by the original Lycoming piston engine. The lithium ion battery pack weighed 1100 pounds which was limited by the S-300C max GW capability . This allowed around 15 minutes of flight with a single pilot on board.

I'm sure the engineers that designed the Firefly were competent, and the motor/controls/battery were all based on current technology. So it would be fair to use the Firefly's demonstrated performance as a baseline to evaluate concepts like Lilium.

I don't believe the Firefly ever flew. Sorry for the response to an old post, I'm behind here.

I will say that anything will fly if you get the disk loading low enough. Asking about size and weight are entirely appropriate.

oggers 26th Apr 2017 10:44

So a year after their claimed date for a manned flight they have managed instead to fly a large drone that looks like the concept but cannot carry out the functions of the concept. Certification in 2018? :rolleyes:

Electric drones doing VTOL is decades old news. The concept was for this thing to carry people and also the wings to fold away so it could drive along the highway. This "first test flight" was actually an RC model aircraft that could do neither. Boring.

Thracian 26th Apr 2017 11:12


Originally Posted by oggers (Post 9752843)
So a year after their claimed date for a manned flight they have managed instead to fly a large drone that looks like the concept but cannot carry out the functions of the concept. Certification in 2018? :rolleyes:

Electric drones doing VTOL is decades old news. The concept was for this thing to carry people and also the wings to fold away so it could drive along the highway. This "first test flight" was actually an RC model aircraft that could do neither. Boring.

According to their new timeline, first manned flights will take place in 2019 now. Well, I do remember the old one you´re referring to ;-)
Additionally, the new pictures don´t show the slightest chance of retractable "wings". Maybe they came across some serious physical issues with CG? On of the founders being an (inactive) glider pilot, I would have expected this encounter a few years earlier ;-)
What remains, is an electrical driven VTOL aircraft.
A five seater Lilium will presumably be bigger (in terms of wing span) than a comparable 5 PAX classical Heli in rotor diameter. I wonder, how they will get their "Lilium Pads" in downtown Manhattan...


But hey, the´ve got their investors, they seem to have some App (or at least some true image manipulation geeks).
Isn´t that all you´ll ever need in modern business?
:E


Thracian

Nige321 26th Apr 2017 11:19

For those that can be bothered, there's a different video on Liliums Facebook page which shows a couple of different camera angles and some extra detail.

As certain posters seem to be utterly convinced the whole thing is a scam, I'll leave them to find it themselves...


All times are GMT. The time now is 01:30.


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