Will the Lilium Jet Work? A detailed analysis by an independent expert.

[@GeorgeOu]

Great to see KZbin recommend a small channel like this. I'm sick of the fluff click-bait videos. Thanks for your work.

[@frankyflowers]

its recommending it? thats great.

[@raj61091]

This was one of the best lectures on electric aircraft design and certainly the principles explained can be applied to other vtol aircrafts. Very comprehensive.

[@paulbrouyere1735]

As an RC aviation modeller and pilot in the 1980’s I am perplexed these engineers started this project from a top-down approach. (First some calculations, then a model). In an RC modellers mind you start with a general concept, then you start adapting until it works. Low cost development, high return. Make it crash and build better. I designed a canard glider with a special wing design in the 90’s, first model were flat balsa surfaces to have a rudimentary proof of stability of the design. It worked. Then you can start upgrading. Due to life’s duties that project is still on my shelf. What I remark in your analysis is that a designer drew a manta-like flying object, but I wonder if he realizes how aerodynamics work. By the way, VTOL can save lives for short distances, but it’s not suited for long flights. Best in between choice would be STOL then, but also requiring a lot of power. VTOL electric is quite crazy if it consumes 10 times more to go up or down.

[@TecTrends]

Some interesting information for you to consider: Building an aircraft is not close to building RC planes when it comes to processes. I have experience at Airbus. One of the biggest cost eaters is design changes, increasing with time within the process. Thus, its the complete opposite to your RC planes with the slogan "high developtment cost, low probability of failure or big design changes". About Lilium: changing their design shows uncertainty and is a cost eater. The top down approach is also common at Airbus aircraft design, and with my experience id like to say that you are making the wrong argument. But as a Startup Lilium makes something completly different than Airbus: There is no fixed mission assigned before building the plane. The argument you make is about the order in which they calculate which is actually fine. What is not so much fine is: 1. As stated in the Video, after the first theoretical calculations there is yet lack of confirmation by proof of 1:1 scale flight test (lets see what this year brings). 2. The first theoretical calculations are used as data for investors, which is very risky. 3. The biggest risky thing to do in my opinion, there is no fixed mission. For example at Airbus, you would define the whole mission(s) of all possible customers, then do some basic calculations if those missions are even possible in theory, and if confirmed, THEN you would proceed. Lilium just changes their performance in the process, before having a fixed mission. The argument you make is in my opinion worthy, but not factually correct. You are saying Liliums design process is risky and uncommon in the industry. Comparing RC planes to real planes is wrong on alot of levels, but your point in the end is valid in my opinion due to different facts then what you stated. Lilium takes alot of risks. LILIUM HAS TO TAKE RISKS. None company would develop such a design otherwise, which would maybe not push battery suppliers on the huge scale (you could argue with automobile here). So they are not "stupid", they are risky. Lilium is a Startup. Lets see what happens.

[@paulbrouyere1735]

@@TecTrendsThank you for your answer, I appreciate it, after all, I know RC modeling is in no way to be equaled with real planes. I agree you need a top down approach for production, but you need a bottom up approach for development

[@grasuh]

@@TecTrends Small scale flying model prototypes have been used in industries since the dawn of aerospace development. It is just that such works are not well published and tend to be company internal information.

[@TecTrends]

@@grasuh Considering what I already said, here my opinion which I try to express neutrally as an aerospace engineer, Airbus insider and privat pilot: You did not understand what I said. Small models are used in different scenarios to get some information, eg at same Reynold Number windtunnel testing. But what I said is something completely different then what you inferred, even tho I have been more then clear. I was talking about processes on how aircraft are developed. A model aircraft is, as the first commenter stated, built up by big radical steps, to cite him „make it crash and built it better“. It doesn’t fly straight, so you change the rudder. Airplanes are NOT designed this way. Development changes are getting more and more expensive as development state rises. Thus, there are first made (even in times before computer) heavy calculations, which get iterative more and more advanced. A clear mission is defined and the physics need to align, meaning from that definition comes the powersystem, the wing design and everything else. After the physics align in some kind of calculated model, every single part is being optimized, BUT NOT YET BULILT as a WHOLE AIRPLANE. This is the huge difference which I was talking about. And trust me, I’ve seen Liliums early designs. Shown at a local conference, not allowed to talk about it. Like for everything it’s just to display the general form. A model airplane is BUILT and then OPTIMISED holistically by big changes. Opposed to airplanes which develop after the „physics fit model“ after heavy calculations in tiny steps. That model approach is what we see from Lilium, which as a startup they kinda have to do but I still don’t think it’s optimal as stated. Because it’s a cost, time eater and high risk. Please read all my lines carefully, it all makes sense. Thank you.

[@grasuh]

@@TecTrends Here is an example of a scale model usage. Search Google for "ADAPT Scaled Demonstrator" and read the paper through ResearchGate, called "System Identification and Stitched...".

[@kingplays5369]

This is a 12/10 analysis

[@denisw398]

Interesting and highly professional analysis of this concept and somewhat inline with my gut feeling after 40 years in the industry - good job

[@robitwhisperr]

Lilium successfully passed their 4th & final DOA audit. It fully disproves John's lies about Lilium. Don't always go for the gut when Germans are engineering hm?

[@denisw398]

​@@robitwhisperr Good for them, and as might be expected from German engineering diligence. We can learn most from being proved wrong, so lets see if it passes the real World usability test.

[@ratherbeflying101]

This is a death trap.

[@rezasaba1602]

@@denisw398 can this plane handle the weather, such as wind gusts working at high elevations I notice it to be always windy. massive gusts of winds at high altitude most likely is even more

[@Triple_J.1]

@@rezasaba1602 wind is surprisingly a non-issue for aircraft, it only becomes a problem with crosswind landings. But crosswind landings are only performed because its physically impossible to reorient a paved runway to align with the prevailing wind. A VTOL aircraft can easily along itself into the wind and therefore doesn't need to perform a crosswind landing.

[@amazingdiyprojects]

Love the detail and analysis, thanks for taking the time making this video and posting it, very interesting.

[@zhihenglou]

Thank you!

[@alfonsod.287]

Such a great video material! The best is that with your high-level technical work on this video, you attracted a really knowledgable crew of commentors that only enrich more this. Please continue doing these analysis at this level or even higher. I loved to see the technical details, the backed-up data, and conclusions. I just discovered your channel and I am subscribed now

[@ettrike]

Dear John, nice video, nice work from your side, keep this ongoing, I will just add a remark to what you said: In 2017 i sent an email to Lilium telling them that this eVTOL will never fly, (they announced 2019 as a first fly), I explained to them that they should reduce the number of EDF and increase the diameter, guess what, after millions of € and 5+ years, they increased the diameter of the EDF (also the number is reduced). But after all this is a new startup, they should keep iterating the design/system, maybe it will fly.

[@zhihenglou]

Hi there! Thanks for sharing this story and your comments. Sadly, I did not discuss the change from 36 to 30 EDF's in this video. But I have analyzed this change in my previous video. In hindsight, I should have included this detail for completeness...

[@Wordsmiths]

@@zhihenglou Hey, you did yeoman's work in this long video. Don't worry about that one change. You can mention it, and its expected impact on the flight/range performance, in a follow-up video. (Which I will watch. Duly subscribed, so I won't miss it)

[@zhihenglou]

Thanks for your positive feedback, Nicolas! This video analysis is based on the 7-seater with 30-motors (see Chapter 2), so the video's conclusion regarding flight performance should not be impacted by this change from 36 to 30 EDF's. But I should have explicitly mentioned this change in the timeline (Chapter 3). Thanks again for your comment and your sub! What would you like to see in my next video?

[@jankeller5061]

Great Video, Keep up the good work!

[@williamzk9083]

A ballistics parachute is certainly possible. A ballistics parachute with rocket extraction and pyrotechnical instant inflation is possible to allow inflation at zero speed and zero altitude. A ballistics parachute with a high speed ribbon drogue is possible. I would argue only a plain simple parachute designed for low speed deployment at a modest altitude is required. Ilium now has designed the Lilium Jet to land n a runway. This may mean that the aircraft no longer needs a ballistics parachute so long as it is in flying distance of a runway. Ballistics parachute might be very expensive to develop and the weight will detract from other more important sofety factor.

[@xjet]

An excellent calm, objective and factual evaluation of the hype that surrounds this project. As someone who's spent a lot of time using electric-power propellor and ducted fan model aircraft I can tell you that in "the real world" there's just no way an electric ducted fan can come close to a traditional propellor in terms of efficiency when you've got high disk loadings such as those proposed by Lilium. Also, how convenient that one of the requirements for their promised performance is battery tech that is not yet readily available. It was also very interesting to note that their prototype self-incinerated because one thing very rarely discussed by eVTOL companies is how they plan to mitigate the risk of in-air fires caused by battery malfunction. Multiply redundant power systems and ballistic parachutes do *nothing* to save passengers from a fiery death in such an event.

[@EverynyanSan]

in the case of vertical flight, really large propellers have an advantage, while this vehicle is supposed to fly like an airplane to make optimal use of the engines.

[@xjet]

@@EverynyanSan The concept of using many small EDFs as opposed to a lesser number of fan-units with a larger diameter is still flawed. The "wetted area" of the ducting on those fan units is much greater per area of cross-section than would be the case with one or two larger-diameter fans producing the same amount of thrust and that means increased drag hence lower efficiency. There's a reason we're seeing a lot more twin-engine commercial airliners than four-engined ones and some of that is down to the greater efficiency of larger fans over multiuple smaller fans. In the world of electric flight, efficiency is *everything* so this concept is immediately flawed through its use of many, many small (and thus less-efficient) fan units. There's a very good reason that all the other players are using lower disk-loadings than the Lilium -- they've prioritized efficiency over gimmicky styling.

[@EverynyanSan]

@@xjet I guess lilium wanted to add extra lower pressure to the top of the wings to increase lift. I have no illusions that this project has no chance of success without a new type of batteries. I am not an aviation engineer but it seems to me that propellers powered only by electricity have certain limits that cannot be overcome compared to internal combustion engines.

[@alanhilder1883]

The theoretical batteries and the theoretical motor bearings. "we will get it working when reality catches up with our fringe science" ( get Walter Bishop onto it ( Fringe ))

[@gilbertanderson3456]

@@alanhilder1883 Walter would have it solved yesterday.

[@harryseagar]

Stoked to see you get the recognition you deserve mate! Such refreshing and well delivered analysis/information. Let's see how battery technology over the next 24 months impacts the sector. Thank you!

[@zhihenglou]

Thank you, Harry!

[@harryseagar]

@@zhihenglou Pleasure man, really love this type of work and sometimes wish I was more an engineer than a marketer! It's pretty wild how all this new and increased battery density news is coming out a week after the release of this video. Let's see how long it takes to play out in reality for the leaders, I also think I've got the topic/title of your next analysis! aha.

[@zhihenglou]

Yes, I've been reading the news on CATL's 500Wh/kg battery. I haven't found any useful resources that describe the batteries in depth; I only found a few short news articles thus far. I'm still very intrigued about this new battery. What's your topic/title idea for my next analysis?

[@tenlittleindians]

It's the same old story; design an airplane that's needs power that's currently beyond what's on the market! Even military aircraft get caught in this cycle. One of the most famous experimental kit planes that did this was the BD-5 in the 70's. They sold lots of kits but most were never complete because a reliable, affordable and available motor never happened. Here we are 50 years later and there's still no motor that really checks all the boxes as a powerplant for those airplanes.

[@robitwhisperr]

​@@harryseagar He deserves egg on his face at least. Lilium passed their 4th & final DOA audit from EASA. If verifies their battery tech & wing flight fully. So John here spent an hour successfully fooling you all. This 2 mo video didn't age well 😂

[@SuryaSarav_]

What an amazing 100+mins of content! Can't wait for your future analysis

[@Lazarov_Tweevles]

I want to buy the first unit that rolls off the production line .... and park it next to my Moller Skycar and Aptera solar car (trike). I'll then be able to look at them through my Echroma color-blindness-correcting glasses.... I wanted to include a Titan carbon submersible to my collection... but circumstances prevented that. ** outstanding analysis b-t-w

[@JoeyBlogs007]

Very much look forward to watching this in full a bit later today. Looks great and like a much needed report.

[@frankyflowers]

im goings to let the video play through without watching it again because i don't want the algorithm to think i got bored and bailed. i never care about that stuff but this video deserves it.

[@ralphpanhuyzen7861]

The Lilium founders have been talking for years about its potential... but there's where it stagnates: talk. Still no decent let's say 20 minute test flight with 4 passengers incl. vertical takeoff and landing.

[@TheBagOfHolding]

You are completely justified. Lilium is gone.

[@NikoWeify]

The financial failure of a company doesn't proof the claim that it's technological not working.

[@TheBagOfHolding]

@NikoWeify it never worked

[@TheBagOfHolding]

@NikoWeify they are going to get sued and maybe even criminal charges, so maybe we will get proof.

[@northsure]

I welcomed your very candid, clear and uninhibited analysis. I hope that you will continue your efforts to educate the public. I hope that lilum will take your service to heart. Better yet, I hope that they seek you out as an advisor and advocate. Thank you.

[@yagwaw]

Very good and calm analysis, thank you very much. It’s hard to believe that so much money can be raised for a quite obviously flawed concept.

[@khayangoma9064]

Exactly my thoughts😂

[@jo21e6]

Is it a flaw? Why should 175km not be possible?

[@charlesblithfield6182]

Nice work. I like how your analysis sticks to the applied science. The company’s analysis seems biased by fundraising and marketing concerns.

[@robitwhisperr]

He fooled you I'm afraid. Lilium has been issued their long awaited DOA license from Europe. If John Lou was correct about anything he disparaged Lilium for, EASA would never have given them their DOA. It verifies everything from their battery to wing flight. It also allows them to scale up their craft without further approval because they have proven their engineering competency. It in turn proves John Lou is incompetent and a pathological liar.

[@rezasaba1602]

I eagerly watched the report by John Lou. Although difficult for me to understand the technical language and calculation, It was informative for me as a potential investor, and want to say Thank You for taking the time and review it for all of us. Not sure it was stated what the weight of the batteries are, and how long it takes to recharge them, Just as an observer the wing span length to the fuselage length. Planes need long wing span for lift to happen. If it is Li batteries, they weigh a lot, The Lilium looks more like a Drone than a plane from what I have seen

[@ChrisFu7]

Excellent video and analysis. If only we had one of these for each of the other eVTOL concepts, as the vast majority of them are hiding mountains of "bad news" data from their investors as well. This is precisely why Beta suddenly shifted to marketing Alia as CTOL.

[@williamzk9083]

There are no doubt technical challenges. I've seen ilium go from being described as impossible by 'professors' in learned papers, to full fore and main plane transition (also said to be impossible). Aeronautical engineers are no more qualified to talk of battery tech than civil or mechanical. The batteries to make Lilliium achieve its performance goals already exist. Lilums economic success will depend on battery tech that allows much more than 600 cycles and battery tech scientists should be asked and they will probably say its a matter of when not if. It's eaither 3 years or 10 years.

[@rezasaba1602]

What kind of battery exists today that can produce enough current for 10 turbine-looking motors? and how much do these batteries weigh?@@williamzk9083

[@frankyflowers]

this video was so good i watched it again. i don't even bother arguing about lilium anymore i just link this and they quit.

[@jonstevenson5831]

This is a very good evaluation. However, I don't quite understand the overly negative reaction to Lilium in the comments. The evaluation concludes that Lilium is viable, but the 7 seater version is overly optimistic with current battery technology, with a simple solution - exchange passengers for additional batteries. Alternatively, keep 7 passengers, but take much shorter routes in the initial years of service (sub 100km). Most of the initial business is likely to be for sub 50km routes, in any case. Initial business is likely to be aimed at the semi-luxury market, so having more expensive tickets to cover the loss of passenger numbers, is viable. It is likely to be competing with helicopter services initially, which it should still be able to undercut by a pretty solid margin. I do think that we're looking at the (mid) 2030s before this, and other EVTOLs, become regular means of transport for the general public. A big advantage of Lilium is that it can perform short running landings, if necessary, reducing the essential need for hover duration during the landing phase. Initial trips could be carried out where there is sufficient space for a short running landing, in the unlikely event that this is required, if the trip is long enough to be pushing the maximum range.

[@Secretlyanothername]

Exactly. 300km might be highly optimistic, but smaller fractions of this are absolutely possible with today's battery technology (which is pushing into the 300Wh/kg range). This can be commercially successful without hitting all the named goals.

[@幸运男人]

You are amazing, what you said become the reality today. Kudos

[@XPLAlN]

They have quietly slipped the in service date back another year, to 2026. And for a company that issues a press release claiming a watershed moment every time they so much as partner with a new supplier of widgets, the lack of candour about the slipping timeline speaks volumes. Reality is they have not even built the conforming prototype for evaluation test flights so no way will they be in service in 2026. Joby and Vertical have both had catastrophic failure of their full size prototypes, so EASA and the FAA are bound to take a most cautious approach to certification of this untried technology for which no prior operational data exists. In my view, few if any of the eVTOL start ups can meet the exacting requirements of certification with an aircraft that will still deliver their bold performance claims.

[@jo21e6]

Which one could keep up with the EASA or FAA do you think?

[@Ozbird-72]

For an urban aircraft to be usable, it needs to be able to safely handle strong, gusty winds, rain and snow and turbulence due to low level operaration. Density altitude is also a huge issue. All tests seem to be no-wind tests in calm sunny weather. If you have ever done a rooftop landing in a helicopter, you know how tough that is

[@rezasaba1602]

yes, I noticed that too planes just like cars need to have some weight for basic stability, how much? am not sure ? more questions than answers came up after this review

[@XPLAlN]

That is an astute observation. What is most noteworthy about the Lilium YT channel is not what they show us of a big r/c model flying about with agility that would be underwhelming on the bridge of a super tanker, but the absence of a single flight in so much as a moderate wind. There is not one example of it performing a spot turn, nor even so much as a ground taxi. And yet they cling to the line that they are on track to have a 7 seat version certified and in commercial service within 2 years. It is deluded. We are seeing a version of ‘The Emperor’s new clothes’ fable play out in front of our very eyes, and it is apparent that most of the people watching are the idiots of that tale.

[@jo21e6]

​@@XPLAlNSo what's the point of the flaw? Just that they are too late with the first flight and have 175 and not 300km?

[@XPLAlN]

@@jo21e6 the point here is that Lilium have not demonstrated the essential manoeuvres critical to VTOL operations. Range and and being 7 years behind their own service entry date are a whole other problem.

[@BrendanAus]

Have been watching Lilium. Started on this but skipped through. Its looks to be 'German' comprehensive and well delivered. I note the many positive comments below, well done! For a potential (not yet) investor, in between the marketing hype and your comprehensive analysis (and also for the math, physics, areo competent), a 5 minute, compelling, executive summary would be awesome - though certainly not demanded. Thank you for your great work.

[@zhihenglou]

Hi Brendan, I am not doing further work on my project about Lilium, except for some light maintenance work, like replying to comments. Because I have other exciting ideas and projects coming up! You can find a summary in 'Conclusion' (see 1:41:51). You can also find a PDF version of this video, which might help (see drive.google.com/drive/u/1/folders/16IEpl-tQwd244ZVuoIncWn4l8evGRIwH ). Lastly, I must remind you of my disclaimer. I am not giving investment advice, so please read the disclaimer in full. Best, John

[@BrendanAus]

@@zhihenglou Thanks again John. Great content. Disclaimer noted and understood. Will look for your other content.

[@MrDschubba]

Well said and great analysis. It is insane the capital that these firms like Lilian generate from people and companies that do no due diligence

[@octavicolom4562]

Tencent, tech company and one of the top 10 biggest in the world and biggest in China does no due diligence? But you do right? Lol

[@frankyflowers]

@@octavicolom4562 why don't they take the lilium out for a fight and record it? they only show short clips of a short flight a couple of times a year.

[@ahmetmehmet9686]

@@octavicolom4562 Tencent is an IT company not an aviation company. It should be easy to attract non aviation investors with tiktok videos.

[@MC-yb5le]

@@frankyflowers I've read the LILIUM can only fly for 15 minutes, thus the Lilium is a piece of junk. JOBY has already flew 1,000 of times and 150 minutes at up to 200 mph. JOBY is the West leading EVTOL. Thus JOBY is the world leader, and copy cat Archer is not far behind per my research.

[@andypughtube]

A better comparison than the Tesla would be a Sea King. It can definitely achieve VTOL and can definitely carry 5 people, and it does that with 2000kW.

[@marcjohnson4884]

Good analysis, that kind of reminds me of the concept of the 80% solution being much easier than the the 100%. I read down below, pilots are pointing out some failure possibilities which seemingly don't have "autorotation" or glide to landing fall backs.

[@davidantill6949]

Ballistic parachutes will also increase in quality and fall in price. Wright's Law will prevail...it's quite predictable

[@jo21e6]

​@@davidantill6949Not everything has that much potential...

[@n1vca]

Your analysis it really amazing and I admire the way you diplomatically avoid saying that this is utter BS. I also agree that it can not be more absurd to blow though hundreds of millions of dollar for last 8 years, employ tons of people when they can barely make a small unmanned empty weight version carefully go from vertical to horizontal flight mode while flying in the near vicinity of the airfield. Now believing in catching all that wasted design work up in one year is totally ridiculous. I find it just as absurd that you can win awards for things that don't exist/don't work at all as long as you can present nice images of a model. Our world makes it easy for cheaters of all kinds to gain public visibility and create completely wrong impressions. We should overthink the concept of giving awards, because they are supposed to highlight excellence, which in this case they just don't. Your analysis and presentation is so great that I instantly subscribed - fantastic work 👍

[@jo21e6]

I haven't understand why it can't work. Building an airplane from scratch does take several years and much money, if it's the first one, one will make false assumptions. And of course they won't make 300km, but maybe 80,100km with the first battery, and in a few years they'll have better ones.

[@kennyskyun]

Excellent video with comprehensive investigation. Great work!

[@randxalthor]

An excellent summary of the state of Lilium's technology. I ran the numbers in 2018 as well. That was less thorough, but I also used Leishman's standard analysis techniques and results from modern ducted fan research from projects like the XV-24. A crucial pin in Lilium's (and Joby's) forward flight L/D was the NASA research leading up to their founding regarding blown wings and distributed propulsion concepts. Joby pivoted away from this concept for a number of reasons, and I am not aware of any full-scale demonstrator that has flown at relevant Reynolds numbers. An L/D of 18 could be legitimate if and only if the promises of distributed propulsion drastically increasing stall C_L are true, but this has yet to be proven out at scale. For their sake, I hope investors are taking note of your analyses. They are in line with my previous estimates and with what I'd expect of my colleagues at the University of Maryland. The "marketing" of Lilium expecting huge leaps in technology to improve their business cases only seem, based on my knowledge, to be borne out in the event that a new battery chemistry matures in the very short term. Work has been in progress on Lithium Sulfur batteries for years as an eVTOL energy storage mechanism, but I have not heard of the chemistry problems drastically shortening the cycle life at high specific energy being solved as yet.

[@TecnamTwin]

Check out Jeff Dahn's research. He's actively working on relatively high energy density batteries with a lifespan over 10,000 charge cycles. An actual test cell is demonstrating nearly zero degradation after thousands of cycles with a projected lifespan of a whopping 19,500 cycles!! The secret sauce is silicon carbide that allows for high energy density and long battery life.

[@williamzk9083]

The Lilium demonstator has flown with full transition of main and fore-wing now. Batteries are improving to allow the necessary performance and economics.

[@TecnamTwin]

@@williamzk9083 Lilium has a design that potential customers far prefer to the likes of the Joby S4, Archer, Vertical VX4, etc. with their many exposed props flailing the air. Pass. The efficiency and performance disadvantages are forgotten when the customer experience is superior. That's why regional jets are preferred over much more efficient turboprops. Batteries are only getting better and will make longer range flights a reality. It really is just a matter of time.

[@wolfgangpreier9160]

@@williamzk9083 "Batteries are improving to allow the necessary performance and economics" Practical examples please. Or are you telling us your wishful thinking?

[@williamzk9083]

@@wolfgangpreier9160 There are laboratory devices available in small quantities and excess 400 what hours per kilogram. This is above the 300 watt hours per kilogram that Lilium needs to get its ranges objectives. In fact 500 hours per kilogram laboratory devices. Why don’t you spend some time researching batteries maybe take a positive mindset to things and stop listening to nonsense speculation by some aerodynamics Proffesor unqualified in the area of batteries, who wrote stuff five years ago.

[@PuLSe980]

Great video. Please keep up the good work. Very much enjoy you videos, John!

[@frankyflowers]

this is a great video. i was worried that you deleted it when i couldn't find the original. its as good as a video can be.

[@tomapc]

Dayumn! This was very detailed, great work. One small addendum, small fans=very, very low efficiency That is something no amount of money or buzzwords can change, ever. When i first saw this, i just dismissed it as another CGI money grab for the uninformed.

[@jo21e6]

But aren't they nessessary for the lift on the upper side of the wing?

[@rossnolan7283]

Looks like it is kaput. Their 'stretched,' developments with yet more seats and yet higher disc loading were even less feasible. Good job on calling it out early on.

[@huibu8987]

Liliums latest test flight range was over 13 km. Thanks for the in depth video. Pls more content about lilium :)

[@amazingdiyprojects]

Not sure they were carrying any payload at all at the time?

[@zhihenglou]

​@@amazingdiyprojects From my observation and analysis, Lilium has not flown a full-scale prototype to date. As the video explains, the current prototype, the Phoenix 2, differs significantly in weight and the variable nozzle. The variable nozzle is critical for aircraft performance, as shown in Lilium's paper. Yet, the absence of the variable nozzle in Lilium's current prototype is seemingly missed by many other commentators.

[@knabbagluon]

So short the stock and get a billionair @@zhihenglou 👍

[@ahmetmehmet9686]

Finally an engineer published a rational analysis for that lil jet!

[@aalaal171]

Many also laughed at Hunter Kawald's e-hover board for being engineering impossible but there he rode it in Times Sqr, and every where. So as many big auto makers laughed at Tesla when its inventors came up with a prototype... saying engineering impossible. The SECRET sauce is the trick to supply enough consistent electric juice and software energy planning.

[@jo21e6]

Who said Tesla is impossible? There are electric cars on the road since decades

[@MrGunderfly]

i would love to see actual test data. this should be continuously published. Such transparency would be better than the question of "techno-scam?". Even if this data might have a negative impact on fund-raising, it could nevertheless keep the company alive for longer, due to confidence in the reality of the product. could it be so bad that they would want to hide it? i remember hearing that the hover efficiency of this duct configuration was better than expected, given lift produce by the rigid portion of the wing with ducts pointed at angles downward. i did not hear that mentioned in this analysis.

[@faluffel]

Also curious on this. In Liliums last test flight, you could definitely see that the air "attached" to the wing in the last part of the vertical descent, so that would suggest that some lift might be generated by the fixed wing part.

[@jo21e6]

​@@faluffelvery interesting. And are ducted fans better for hovering because of less induced drag or is a big prop better because of lower speed?

[@KaZaProduction]

I believe that it’s really profitable to focus at cities transportation, for example carrying 16 persons with 30 KM distance is better than carrying 7 for 175 KM ? Serving like a bus stations from one block to another

[@zhihenglou]

| References | (Adams, 2016) www.wired.com/2016/06/lilium-electric-personal-jet-concept/ (Anonymous, 2020) www.aerokurier.de/static-download/8/3/7/8/5/9/6/aerokurier_Konzeptberechnung_Lilium_Jet.pdf (Bogaisky, 2021) www.forbes.com/sites/jeremybogaisky/2021/02/10/lilium-evtol-spac-air-taxi/?sh=6d11a7f8627c (Crunchbase, 2023) www.crunchbase.com/organization/lilium-aviation (DLD Conference, 2018) kzbin.info/www/bejne/lWXFn6ZpeK-NaMU (EASA, 2022) www.easa.europa.eu/en/downloads/136701/en (ecosummitTV, 2016) kzbin.info/www/bejne/nqXElnSIrNiYZ9k (Gapper, 2023) www.ft.com/content/87b1ee8b-e856-40a5-aa57-62340ff3d8c8 (Goldstein, 2023) aviationweek.com/aerospace/advanced-air-mobility/aam-ceo-spotlight-klaus-roewe-lilium (Gollnick, 2022) iceberg-research.com/2022/08/31/liliums-misrepresentations-over-its-technology-keep-mounting/ (Gudmundsson, 2022) www.sciencedirect.com/book/9780128184653/general-aviation-aircraft-design (Hello Tomorrow, 2017) kzbin.info/www/bejne/fonOh4mwrNl4mrs (Hodgetts, 2017) edition.cnn.com/travel/article/lilium-electric-vtol-jet/index.html (Iceberg Research, 2022) iceberg-research.com/2022/08/31/liliums-misrepresentations-over-its-technology-keep-mounting/ (IEEE, 2023) spectrum.ieee.org/room-temperature-superconductor (iF, 2023) ifdesign.com/en/winner-ranking/project/lilium/309667 (ILT, 2023) cgi.tu-harburg.de/~iltwww/en/institute/staff/volker-gollnick.html (Leishman, 2006) www.cambridge.org/9780521523967 (Lilium, 2018) web.archive.org/web/20180309094606/lilium.com/mission/ (Lilium, 2019a) kzbin.info/www/bejne/a6bOnoZvj6-gapI (Lilium, 2019b) lilium.com/newsroom-detail/meet-the-founders (Lilium, 2019c) kzbin.info/www/bejne/nqmQo6mVirl6pZY (Lilium, 2019d) lilium.com/newsroom-detail/from-the-oceans-to-the-skies-the-inspiration-behind-the-lilium-jet-design (Lilium, 2019e) lilium.com/newsroom-detail/lilium-jet-awarded-prestigious-red-dot-best-of-the-best-design-award (Lilium, 2019f) twitter.com/Lilium/status/1130493391412899844 (Lilium, 2019g) lilium.com/newsroom-detail/youve-never-seen-anything-like-this-an-introduction-to-the-lilium-jet (Lilium, 2020a) lilium.com/newsroom-detail/lilium-architecture-design-principles (Lilium, 2020b) lilium.com/newsroom-detail/linkedin-top-startups-2020 (Lilium, 2021a) investors.lilium.com/static-files/c355ba0f-662c-466c-aa6a-43072b3d34c3 (Lilium, 2021b) lilium.com/newsroom-detail/technology-behind-the-lilium-jet (Lilium, 2021d) ir.lilium.com/static-files/25ae9d1d-7ed2-43eb-918f-983c17ae6f0c (Lilium, 2021e) kzbin.info/www/bejne/mmi7fmqbgbpsgNU (Lilium, 2021f) lilium.com/newsroom-detail/Lilium-intends-to-list-on-Nasdaq-through-merger-with-qell-and-reveals-serial-aircraft (Lilium, 2021g) lilium.com/newsroom-detail/Tom-Enders-joins-Lilium-board (Lilium, 2022a) kzbin.info/www/bejne/r6itiJ6XZsqpfpo (Lilium, 2022b) investors.lilium.com/static-files/ddddaf2f-e33e-4115-8fa4-7a0779b28301 (Lilium, 2022c) kzbin.info/www/bejne/p4uaZIOcqaeZfMk (Lilium, 2022d) lilium.com/newsroom-detail/liliums-battery-strategy (Lilium, 2023a) lilium.com/patrick (Lilium, 2023b) investors.lilium.com/ (Lilium, 2023c) investors.lilium.com/techfaq (Lilium, 2023d) kzbin.info/www/bejne/qYKtnHt6rLOpoc0 (Lilium, 2023e) lilium.com/news (Lilium, 2023f) lilium.com/jet (Lilium, 2023g) lilium.com/careers (Lilium, 2023h) kzbin.info/www/bejne/qYKtnHt6rLOpoc0 (Lilium, 2023i) lilium.com/ (Lilium, 2023j) ir.lilium.com/management/alastair-mcintosh (Lilium, 2023k) ir.lilium.com/corporate-governance/management (LinkedIn, 2020c) lilium.com/newsroom-detail/lilium-comes-second-in-linkedin-top-startups-of-2019 (LinkedIn, 2022) Potentially available upon further request (LinkedIn, 2023a) Potentially available upon further request (LinkedIn, 2023b) Potentially available upon further request (MAF Suomi, 2019) kzbin.info/www/bejne/sGeYh3ign7FoiKc (Michell, 2017) cities-today.com/german-start-receives-us90-million-build-flying-taxi/ (Nagel, 2023) www.tytorobotics.com/blogs/articles/what-is-the-average-efficiency-of-an-electric-motor (Raymer, 2018) arc.aiaa.org/doi/book/10.2514/4.104909 (Reinhold, 2020d) www.aerokurier.de/lilium-artikel-ausgezeichnet-aerokurier-erhaelt-hugo-junkers-preis-des-lpc/ (Rheinhold, 2020a) www.aerokurier.de/elektroflug/lilium-jet-dossier/ (Rheinhold, 2020b) www.aerokurier.de/elektroflug/lilium-fragen-an-das-unternehmen/ (Rheinhold, 2020c) www.aerokurier.de/elektroflug/lilium-fragen-an-investor-frank-thelen/ (SMG Consulting, 2023) aamrealityindex.com/aam-reality-index (TEDx Talks, 2013) kzbin.info/www/bejne/moamd4mOptShmrc (Tesla, 2023) www.tesla.com/en_eu/models (The Real Life Guys, 2018) kzbin.info/www/bejne/e4KuaqCVhKeJnbs (Wikipedia, 2023a) en.wikipedia.org/wiki/Glider_(aircraft) (Wikipedia, 2023b) en.wikipedia.org/wiki/P-factor

[@unclewerner]

Another glaring problem with Lilium's concept is the ballistic parachute they were initially envisioning to employ. A damn heavy vehicle spinning very fast on top of a forward speed of 300km/h will be difficult to rescue and it is not easier when in low-level hover, in which a chute cannot be used but adds weight. Furthermore putting the thrusters directly on top of the wing also disturbs the airflow over the wing once the thrusters stop to operate (or operating no well in sync with environmental factors). Therefore after a safety-shutoff the wings become ineffective and just add as dead weight.

[@zhihenglou]

Hi there, This detail regarding the ballistic parachute is something I have genuinely forgotten about! Thank you for bringing it up. I think other viewers will find your comment helpful in building a comprehensive picture of this story. I have not worked with ballistic parachutes before, so I cannot comment on the technical details, but I read your comment with great curiosity and interest. Thanks again! Best, John

[@unclewerner]

@@zhihenglou I'm just a light sport aircraft enthusiast and probably not qualified to comment on the technical details. But Lilium once stated they want to certify their vehicles as LSA. But whatever happened since then they never produced a prototype that could carry a test pilot (being it only for a short hover flight). That parachute issue just comes to my mind when I go through my everyday pre-flight checklist. That said I really enjoyed your technical analysis. I used to write software for the aircraft maintenance world and I always wanted to switch to engineering the other side that actually flies. In so far thanks for providing your educational outreach here.

[@zhihenglou]

When I was researching Lilium's history, I also found that the company wanted to certify its vehicles as LSA (see this German webpage: webarchiv.typo3.tum.de/AR/ls-id/id/design-fuer-startups/project-showcase/lilium-aviation/index.html ). I believe the initial concept was intended as a personalized air vehicle: an airplane with wings but also a ground vehicle that can be driven like a normal car. The wings could be folded to create a more space-efficient geometry (see this picture: kzbin.info/www/bejne/nqXElnSIrNiYZ9k ). I know nothing about light sport aircraft. I assume you use a parachute there because you mentioned it in your checklist? Thanks again for your comments!

[@Triple_J.1]

Ballistic whole-airframe parachutes are utilized on several aircraft that wouldn't make much sense unless you understand the philosophy of use. E.g. Cirrus Jet has a parachute that has a maximum deployable airspeed so low that the aircraft would be well below its operating speed to utilize the chute in an emergency. It is completely and totally inadequate for most high speed scenarios. But its there for one specific scenario that kills many private pilots. That is departure from controlled flight after exceeding the critical angle of attack while performing the base-final leg turn to landing at low airspeed and low altitude. Being high wing loaded and rather fast, that mistake will absolutely be fatal at traffic pattern altitudes. If the pilot is able to deploy the recovery parachute in time, it probably will be survivable. The most likely scenario is deploying the chute at an altitude of 500-1,000ft AGL, at a velocity of around 150ktas. Also, the vertical descent velocity in a fully developed spin is likely right around the parachutes maximum deployment speed, so in the case of a spin, it is recoverable with less risk of injury to passengers. Also, at high-altitude long range cruise/loiter velocity, the Dynamic Pressure may well be low enough to safely deploy the chute in the case of rapid cabin depressurization or pilot incapacitation being a single pilot certified aircraft. If one slowed down to a low indicated airspeed at 37,000' just above stall, the chute might work fine for that. Same with this Vtol. Its not meant for maximum speed. Its meant to save lives if the power fails in a hover between around 250'-1,000ft AGL. An automatic deployment on power failure such as the F-35 ejection seat would be ideal.

[@arturoeugster7228]

@@zhihenglou Thanks to your reference, some details become clear. The propulsive efficiency of these small electric driven fans is rather poor due to Reynolds scaling, (Ackeret efficiency scaling formula) I have analysed solar cell powered aircraft like the Swiss one that did fly in sections around the world ( Piccard) If you carry 2 persons , with today's storage batteries (4 kg/kwh) reaching 500 km seems inadequate or the reason, that a sufficient minimum reserve flight time must be provided any less requires a mayday call , that forces ATC to give priority. Even flying at altitude, the flight time with reserves is less than 2 hrs. Without a substantial increase in span, laminar airfoils, and optimal design, the range is not achievable. New developments in boundary layer suction may overcome this problem . See University of Delft research. Have a tail dōng fēng in tropical latitudes.

[@doughamblett5204]

The real value here is your airframe and thruster design. To get on with the goal of commercialization: Why don't you dispense with the battery altogether, and create the electric power required with either a turbo-generator or an ICE-generator, using available high-energy-density fuels. It is also quite obvious by now that the energy-density of batteries will never compete with other developing technologies, like hydrogen fuel, or possibly power cells . An aircraft is the last place to consider battery-electric propulsion despite the "popularity" of the subject.

[@travelbugse2829]

Recharging times are going to be nightmare with lithium batteries. A modern fossil-fuelled commercial aircraft can achieve turn-round in half an hour.

[@LarryKeck-qq1ms]

Ilike the overall concept. I am an inventor and an eVTOL reseacher. With newer battery technology this concept could be viable.

[@derkatzenfuerst6077]

Watching this in 2024, CATL has just introduced 500 wh/kg batteries. Might be an interesting option if they can mass produce them.

[@jo21e6]

​@@derkatzenfuerst6077do you have a link to a video where catl shows it's tech?

[@papparocket]

I would be very interested in seeing what the power requirements of a STOL take-off and landing of the Lilium would be when a short ground roll is possible. By taking off with the propulsor arrays at an angle that is somewhere around 45 degrees the upper surface suction at low speed would result in a very large lift coefficient. As such most of the force necessary to lift the aircraft then comes from lift on the wing and canard with a lesser portion from the vertical component of the thrust from the propulsors. With such a high lift coefficient, the stall speed is correspondingly low. The result should be a very short take-off distance (~50-100 m?) along with a very steep departure and approach angles at a power level that is likely 2-3 times that of cruise as opposed to 10 times. With less energy used during take-off and landing, more remains available for cruise, and so increasing cruise distance. So I would hope that anywhere the Lilium can avoid take-off and landing vertically it probably should do so.

[@jirimarek112]

Velice přínosné dokumentární video. Fandím lidem, jako jsou ti ve společnosti "Lilium".

[@harshavardhanbose]

I have done some drag analysis and optimization for canard plane like Lilium as a personal project . The drag of the canard was significant.

[@jasoncrandall]

I love VTOL but……. If one still must utilize and airport for takeoff and landing….. just buy a Cessna 182. All this effort and money spent on VTOL but nobody wants to talk about all the noise and prop-wash you’d have to deal with landing one of these at your house or the mall. Great video. Thank you.

[@ddavideo]

I have no academic qualifications whatsoever in design nor aviation but just a hobbyist. When I first saw this concept I have already had a few doubts about the project. 1. The "over-the-wing" multi-turbine fans design has already compromised hugely on "flying" efficiency as that is the area that a plane would generate its lift. 2. Multi-fan design...regardless how efficient each motor can be, the design required a housing assembly that creates more frontal area hence reduced overall efficiency. 3. Mult-fan design...the more parts the more lost in power efficiency, as simple as that. Apart from Mr. Lou's detailed analysis, the above is my personal observation on the failure of Lilium Jet.

[@Ozbird-72]

Your key finding is that if you overstate every point in the list by only 3-5 %, the end result will be 30% off

[@goodcitizen9827]

He's a terrible con artist

[@rossnolan7283]

I just sought out some better data on the lilium - hopefully dimensioned drawings but had to settle for a screen grab and scaling that -the paper "Architectural performance assessment of an evtol etc.." (Lilium) gives a duct diameter of '.295 metre' which is 11.6 inches -my guess of one foot/ 12 inches was not too bad . The length of the ducts varies greatly on different crosssection sketches and looks to be more like 2.5 feet than three -less on the canard but still in the ballpark ( the velocity through the ducts is much higher than freestream and varies non linearly with flight speed but will cause MUCH greater skin friction drag on the scrubbed internal area -likely at least three times higher in cruise .- the drag estimates will be higher than calculated. ) The transition from hovering to level flight has to rely on the forward component of thrust as the ducts tilt forward (there is no other propeller like the Wisk Cora say ) and those ducts are part of the 90 degree deflected flaps that are 'barn door' drag producers that have to be pushed broadside through the air whilst trying to accelerate --and the forward compnent of thrust is tiny to begin with --the 'flap 'creates little lift past 45 degrees deflection (and flight test tufting shows massive intermittent separation ) - this means that power requirment will not drop as rapidly as might be thought during conversion to level flight - it might even increase - and hence the surplus thrust only gives slow acceleration to cruise configuration (this is typical of all VTOLs that have enormous installed power and hence are heavy but have little excess or useful power - sluggish and ponderous controlability as if in 'slow motion'. This 'arthritic' take off and landing phase slows down the potential turn around time for 'taxi' use and severley limits the productivity --the uber Elevate figures needed thousands of movements per day per pad to be remotely economic and elaborate means to clear the landing area between operations . The cost of the sophisticated infrastructure essential to non roadable flying vehicles is going to be a primary constraint on any expansion (incidentally evtol.news/lilium-jet-prototype-eagle/ records the 'roadable' wings folded original Lilium design and intention -with the retracting 'dustbins' even shown fully retracted in cruise - with only the body lift intended to hold the nose up --this not even remotely feasible 'feature' should have raised alarm flags about their credibility at the start..... Everyone is aware of the extremely fast launch of a naval fighter using ATOL (and the rapid arrested landing -seconds only between stationary and 'full speed' and ready for the next - all conducted in a very restricted space nothing like an airport . Glider winch launches are similarly rapid at much lower forces - witnessing a 'snatch' launch of a small glider is virtually instantaneous -but you can stand right behind the aircraft and not even move a hair --there is no hurricane force wind like VTOL , no noise at all and a rate of climb that not even a fighter can match -- with a ground roll (if any in a breeze) measured in tens of feet - for landing gliders use airbrakes for approach control and precise positioning and all 'fail safe; by being always above the glidepath. For arrested landing a simple tailhook and tranverse cable similar to an aircraft carrier is sufficient ( I have done one , 'inadvertent' cable arrested glider landing in a standard Cirrus sailplane into an invisible smooth cable 'emu fence' on a dry lake bed - in 1978 during a wave camp - no significant damage to the glider (tore off a gear door ) but an unforgettable experience like hitting a force field and stopping in mid air with no float or roll . This gave me the clue to eliminating the landing space problem and coupled with take off assistance solves the use in built -up or congested areas (ie suburban precincts ) together with the necessary raising up ABOVE the ground clutter -that 'fifty foot' distance that covers most vegetation or structures and is best located in the vacant space over roads - giving both free real estate and direct access to the road network to access the air and carry on as a vehicle to the real destination ( a cable 'array' acting like a conveyor belt in effect supports the aircraft below flying speed and arrests or accelerates as required . The design of ATOL aircraft imposes parametric and geometric constraints and requires morphing (as do. most VTOL and carrier aircraft even if only being wingflaps )but has none of the diseconomy,danger and undesireable side effects inescapably associated with VTOL. When the VTOL 'fad' has played out but the 'vision' of airborne personal mobility and perhaps some of the air traffic management protocols and paraphenalia has been developed to allow mass air movement remains the public will be still looking for an affordable and benign means to enjoy the benefits of air 'wandering **' -ATOL will be there to satisfy the new 'demand' . it turns out that a suitable ATOL compatible aircraft will be eminently soarable and with a dribble of power can even simulate the best current sailplanes opening up a whole new world of adventure and recreational use far beyond a mere replacement for the bus ride to work or whatever 'pedestrian' use a taxi can provide (pilots refer to passengers as 'self loading cargo' and most people who fly by airline regularly have long forgotten the once romantic vision of the freedom of flight if they ever entertained it ) Note;** AeroPLANE or AirPLANE refers to the Greek word for "wanderer' - PLANET -since the planets 'wandered' amongst the fixed stars --the idea of moving at will through the air was adopted for the new flying machines . The rigid, ticketted passive passenger 'service' offered by air 'taxis' is the antithesis of the concept of aerial freedom of movement and indeed the long wished for ability to 'fly like a bird' in dreams or as realized in sailplanes or hang gliders ,most closely ,can be granted by the properly conceived and designed 'Aircar' or 'Aircycle' type vehicle together with the mundane task of jam free commuting to work or such just as a motorcar can do both to a lesser degree -- private ownership and operation is key to the value of the automobile and will be so for air vehicles not only from the economic viewpoint (rideshare is a misnomer for taxi or Uber but works for gliding clubs and shared ownership even of luxury jets ) Taxis form around 1/300 of the road vehicle fleet according to one source but certainly cannot form a basis for mass operation or production and neither can expensive elaborate 'infrastructure' needed by eVTOLs - to do any good thousands of take off and landing 'places' -henceforth "ATOLS" will be needed across an average city -not a mere handful as for Uber plans. Perhaps this was a 'long winded; answer to the question put "Will the Lilium jet work?" but I believe the trite answer or guesswork ,prejudice etc is not adequate to even indicate the nature of the 'problem' to be solved let alone a solution (just as hovering 'gets you nowhere' and is the root of much of the drawbacks and an unrealized assumption that complicates the issue enormously - not having a ground roll or obviating airport dependance is the real aim and not to flog the air with great violence ) Apologies for the length but this response only scratches the surface in reality but hopefully might help to rescue the 'dream' from the nightmare it could easily become or even just another false start along with SATS, HITS, AGATE, Eclipse, EU 'initiatives' and the 2000 plus stillborn attempts to date to provide the everyman's airplane ,an 'airplane in every garage' or even the fond hope of Sir George Cayley that one day we may be able to set sail upon the 'ocean of air that laps at every man's doorstep'.

[@jefferyzhang1851]

I completely agree, and this is my personal view as well. A cheap/compact ATOL/arrested landing ground module is much more feasible than all these VTOL concepts. If you are willing to accept aircraft carrier take off acceleration (3.5G), and Piper Cub take off speeds (14m/s), you can take off in under 10 ft. Relaxing the constraints a bit, you can take off/land in 20-40 ft, which would make it feasible to pack an entire ground module into a 20 or 40 ft container and install these ground modules anywhere where you have 1-2 cars worth of empty parking space and clear approach.

[@rossnolan7283]

Nice to see someone is reading my commentary . The length of take off and landing runs need not be as short as you suggest and getting to such lengths imposes it's own energy demands which can be much lowered by relaxing the distances and minimum speeds somewhat more - at too low minimum speeds gust effects,wind gradient ,crosswind etc become more problematic also . Glider operational experience is the closest analog in my view , -the acceleration on a typical winch launch is not noticeably violent unlike aircraft carrier figures . Until the eVTOL 'rush' has played out I don't think the flaws in the whole eVTOL concept will be realized , if commercial operations do begin there will be pressure to operate in 'inclement' weather and the dangers of hovering in wild gusty winds with something having large exposed wing surfaces subject to blusters and 'upset' will become apparent. Helicopters can hover in 'weather' by not having fixed wing and tail surfaces -- normal aircraft have momentum and aerodynamic control - winged eVTOLs have the worst of both worlds.. The 'clear approches' issue is crucial and requires an apparatus to be above the local ground clutter of trees and buildings --ie elevated (ATOL should be EATOL -"Elevated Assisted T O L but putting "e" in front of something would be taken as "Electric' (even so eATOL is still much more doable than eVTOL and much safer quieter and more efficient ) cheers.@@jefferyzhang1851

[@evkienlin]

Thank you for this highly interesting and impressive in-depth analysis. It seems that the Aerokurier paper is too conservative, but the Lilium paper is (far?) too optimistic. I was surprised to hear that no results from the test flights have yet been included in the published papers. If too many uncertain parameters actually have to prove realistic for the concept to fly, the risk for investors increases considerably. A first manned test flight is now announced for end of 2024 - let's see how it goes.

[@XPLAlN]

…first manned flight has quietly been slipped back to 2025. Service entry 2026, but that won’t happen either.

[@jo21e6]

​@@XPLAlNwhy do you think that? What's so complicated to fly 5 more kilometers then they did at the first flight?

[@XPLAlN]

@@jo21e6 I think the first manned flight has been slipped back to 2025 because Lilium have now quietly admitted to it. Sorry if this does not answer your question but I don’t understand your reference to 5 km?

[@jo21e6]

@@XPLAlN They flew a few meters a few years ago with no people on board, maybe a little mass. It couldn't bee toooo complicated to make a short flight (5 km), why do you don't think that's possible?

[@XPLAlN]

@@jo21e6 I am not saying they can’t in theory fly 5 km in the certification prototype they are supposed to be building. I am saying they have already failed on the timeline, it isn’t built yet, they have delayed the first piloted flight to next year. The boss was “100% certain” that they would be certified and in service by 2025. When the guy with every single piece of information about this aircraft is 100% certain, and turns out to be 100% wrong, it should sound alarm bells with investors about the competency and/or credibility of the organisation. The first in service date was 2019. Lilium were quite insulting toward skeptics of that claim, and yet here we are with them 7 years behind their own schedule, so skepticism of all the failed projections so far has been been vindicated.

[@AlJay0032]

Lilium could solve this whole problem if they just dropped going purely electric and used a hybrid approach. Then it could run long distances using a small gasoline engine providing enough power for horizontal cruise flight and perhaps a bit more to top off the batteries for landing. This nonsensical green approach is destroying the whole progress. Also the second part of self flying is also highly problematic and I doubt that it can be solved by the current team which has no clue of the complexities of autonomous flight. Neither of the software required, nor of the hardware.

[@XPLAlN]

I watched the whole video and think it is very good. However, there is a small elephant in the room here called final reserve energy. I don’t know what it will end up being for this new class of aircraft, but it is most likely going to be the same as for helicopters. So minimum 20 minutes VFR. I did not see this discussed in the video. This is going to have a big adverse impact on the range/weight. What I am saying is, it is not even going to be able to achieve the performance estimates seen here, given it will be lugging about a 3rd more battery deadweight as a legal contingency. One other point. I find it very odd that the mission profile is for a climb and cruise at 3000 m. In the helicopter world you would typically be in the 150 - 1000m range above ground level. Obviously it offers a modest advantage in terms of true airspeed to be higher. Maybe cooling of the electrics. Against that you have the adverse effect of low temps on battery. There is much that could be discussed from the technical POV. But in the end it just isn’t a good operational fit with short to medium range VFR hops across Northern Europe and the like. And if they think this thing is going to be doing IFR work for a living then they will certainly need a bigger battery

[@zhihenglou]

Hi there, Thanks for leaving so many detailed comments - I have read them all! The final reserve energy, to which you are referring, is honestly a big elephant in the room, even for someone like me who is generally supportive of eVTOL development. There is no doubt that this problem will require changes to the regulation. Because removing 30 minutes (I do not think it is 20 minutes; I could be wrong here) from an eVTOL's cruise flight means there is essentially no battery energy left for revenue generation. I think most eVTOL proponents are working on the assumption that battery technology will improve and regulations will change favourably. Whether these assumptions are realistic is another discussion (for example, if I am honest, battery improvement has been more sluggish in the last 5-10 years than I hoped). Opinions change over time, often in light of new information. So you might see me change my mind about eVTOL, in one way or another! Thanks again for all your comments. It is clear to me that you are very knowledgeable in this field. Best, John

[@XPLAlN]

@@zhihenglou thank you John. It has been refreshing to watch a video that does a rigorous and objective analysis. And I learned a thing or two which is the reason to watch.

[@jo21e6]

The reserve energy has to be much enough for a 1) landing approach 2)go up when landing is not possible 3) go a certain distance further (I don't know how much) 4) make a second landing approach. That could easily take about 50% of the energy of today's batteries

[@XPLAlN]

@@jo21e6 hi, thanks for the reply. I am talking here about final landing reserve. For VFR, which in truth is the only realistic possibility for this concept, it is simply 20 minutes for helicopters. You need the amount of energy to fly to your destination, land and retain a nominal 20 minutes of energy at the ‘normal cruise’ consumption. For IFR you require the reserve energy to: carry out a missed approach at the destination; cruise to the alternate; approach and land; plus xx final landing reserve. I don’t believe the final landing reserve has yet been specified for IFR EVTOL. It will not be less than 20 minutes but is a moot point because there is zero likelihood of any battery that could provide useful range plus IFR reserve. Note, no reserve “distance” can be specified, it just depends on how far away is the nearest suitable airport with forecast weather conditions compliant with regulated alternate minimums. Given that all the nearby airports to the destination are likely to have similar forecast conditions, the IFR reserve will, in practice, often end up doubling the energy requirement of these short range missions. “50% more” is unlikely to be enough anytime the forecast weather at destination requires the IFR reserve. None of the start ups in this sector will admit to this elephant in the room.

[@jo21e6]

@@XPLAlN How does other electric Airplanes deal with that? At example the Pipistrel Velis. It can fly about 40-45minutes with one charge. I don't think there's enough capacity for 20 minutes flight time

[@XPLAlN]

Another thing that has not been discussed is spillage drag. If this thing is meant to be only using 10% of maximum thrust in its cruise condition, there will inevitably be a great deal of spillage drag over the large array of ducted fans. It makes the claimed L/D ratio of over 18:1 seem all the more implausible.

[@williamzk9083]

18:1 is about normal for a modern jet airliner. A B787 perhaps 21:1.. The small wing area means parasitic drag is reduced.. The suction across the top of the wing ensures laminar flow.

[@XPLAlN]

@@williamzk9083 18:1 is in the region of a modern airliner but therein lies the issue, it is a bold claim for any eVTOL to achieve drag as low as an airliner. Saying “small wing reduces parasitic drag” is beside the point as the area reduction also reduces lift in the same proportion as drag so you cannot improve L/D that way. The key parameter for good aerodynamic efficiency in the subsonic regime is high aspect ratio. The Lilium jet appears to have an aspect ratio that would be unremarkable on a typical light airplane (where 15:1 L/D would already be exceptionally good). They claim distributed thrust is going to make all the difference, but it is a stretch, and given the lack of evidence to back this rhetoric everyone should treat this number with great skepticism. The large array of ducted fans is extra drag. The bottom line here is those fans need to increase lift by 18 pounds, for every pound of nacelle drag, otherwise the airframe L/D ratio is degraded rather than enhanced. Nobody is denying that blowing the wing will increase lift - that isn’t new - but is that going to net you 18 pounds extra lift for every extra pound of drag? Particularly given it is meant to cruise at only 10% of rated power so high spillage drag is implied. It would be futile to try and estimate nacelle drag, suffice to say that those EDFs are likely to spill a lot of air in the cruise.

[@XPLAlN]

⁠​⁠@@williamzk9083….if 18:1 is normal for an airliner cruising with optimal spillage drag, how is the Lilium going to be able to match that with the extremely sub optimal spillage drag? The answer is it won’t. And why do you say “the suction across the top of the wing will ensure laminar flow”? The rhetoric rolls off the tongue easily but it requires a theoretical basis that may or may not be credible…

[@williamzk9083]

@@XPLAlN I don’t think there is any spillage drag as the Lillium jets electric ducted fans as there is no compressor that will need to reject excess air. It’s a fan and doesn’t have spillage drag.

[@XPLAlN]

@@williamzk9083 You get spill drag with or without a compressor. It depends on mass flow through the fan, airspeed and inlet area. The Lilium mass flow is 158 kg/s according to their white paper. They don’t state inlet area, but based on fan diameter they will need to spill 30 kg/s in the 300 km/h cruise. That is over 30 000 litres per second. The extra drag is anyone’s guess, which is effectively all they do. Coefficient of drag of the nacelle is, quote, “set at 0.017 because it is a lifting surface”, a number dropped into the paper without explanation. Just calling the nacelle a flap won’t make additive drag go away. But that isn’t the biggest problem. The entire drag analysis of their white paper is full of holes. The claimed cruise L/D of 18.26 leads to an L/D max exceeding 20. Just no way is that credible with fixed gear at the aspect ratio of the Lilium. The Cirrus Vision Jet is a similar sized modern composite airframe with L/D max of 15 - gear up. The canard is not included in the profile drag. Only its ‘flap’ is included. A plan view photo on their blog shows the flap is only 70% of the area of the canard assembly. Why is the rest not included? The estimated ‘flap’ area is itself bogus. They simply multiply fan diameter by duct length and number of fans. But that ignores the nacelle surrounding the fan! Hence the ‘flap’ area used for the drag estimate is a clear and wilful underestimate. I can get their induced drag estimate from the theory they cite. However, Lilium claim a span efficiency factor of 0.83 and I cannot get this without including the area of canard that is missing from the profile drag estimate. In other words, there is some real estate ignored to the benefit of the profile drag estimate that is then included to benefit the induced drag estimate. Dodgy. Cooling drag is overlooked but will likely be significant. The all electric Pipistrel Velis has a 13% deficiency in L/D max to its piston sibling - due in all likelihood to the extra cooling air scoops. Lilium estimate induced drag is only 36% of total drag in the 300 km/h cruise. But L/D max occurs when induced drag is 50% of total drag, so using Lilium’s claimed Cdo and efficiency factor the L/D max ends up being an astonishing 20.4! We are expected to believe this thing with its fixed gear is going to be more slippery than the best airliners out there. A favourable estimate of the wetted aspect ratio is around 2.4 which suggests an L/D max of about 14 based on extrapolation from the known L/Ds of fixed gear airplanes (re Raymer’s Aircraft Design fig 3.6). With a modern composite airframe they may exceed 14 but getting to 20.4 is fantasy land. The white paper in no way validates the suspiciously low drag count claimed for this concept. On the contrary, it shows all they did was ignore multiple sources of drag. Nonetheless, the elephant in the room remains the battery specific energy.

[@simonbowden8408]

This is all about Physics & Chemistry and with current Li-ion battery tech & many small fans (which are less efficient w high disc loading than larger fans) 300km & 5 ppl isn't happening. Lillium has no incentive to be honest & fair as they need to raise money. It looks cool but won't work as advertised. Excellent video. Lillium using calculated thrust not tested is mad! And using battery mass ratios from Kittyhawk (which is bust) misleading.. And the lift to drag ratio nuts. Basically Lillium are using best case models, not experimental data. Inexcusable. They will likely go bust without a battery revolution. Test. Test. Test!!!! Not numbers numbers numbers!!!

[@TheBagOfHolding]

If there was a battery paradigm shift then we wouldn't need lilium because could make one.

[@jamesclerkmaxwell8020]

I would like to fly a machine that can -at least theoretically- glide safely to the ground in case of power loss. The current VTOL propositions seem to be riddled with too many "death zones" in case of power loss. I like your first principle analysis and style. What do you think of e-STOL hybrid proposition like Electra ? Thanks

[@travelbugse2829]

Has anyone tried an e-gyrocopter yet? Still think they are the cinderella of the rotor aircraft industry. The other issue for me is, how much do we want vertical takeoff? There is a case for first responders, but for the rest of the world a 100 metre runway would be fine. Take offs from skyscraper roofs may still be possible, but I don't think apartment owners or office workers would want large amounts of traffic coming and going. Electric vtols are going to be noisy. OK for busy high income earners only, IMO.

[@sUASNews]

@@travelbugse2829 There are several unmanned ones

[@travelbugse2829]

@@sUASNews I will try to check them out - tks!

[@MC-yb5le]

Add a parachute.

[@maxbootstrap7397]

Conventional small airplanes can land safely without power. For example, airplanes like Cessna 150, 152, 170, 172, 182 and so forth. Typically they need 300 feet or so ... but that can be a dirt or paved road, often even a road with traffic on it, since you can lower yourself between cars to just above the road while flying at typical traffic speeds, then land between cars. Better is a school with a baseball or football field. In a message above I suggested that a better configuration for eVTOL (or other) "flying cab" aircraft would have the entire wings and canards capable of being rotated, which would make landing them in small places even easier ... a lot easier in fact, and in a much shorter landing area.

[@XPLAlN]

The first manned flight is no longer going to happen this year, according to Lilium. The pattern of quietly slipping back tangible results continues. This latest failure should surprise no astute person who has been following the PR of this company for these last 10 years.

[@jo21e6]

Isn't the speed more realistic with the Airbus manager?

[@XPLAlN]

@@jo21e6 sorry but it took me a while to figure what you meant. Here I presume you are referring to the former Airbus guy who became the boss of Lilium. This is referenced in the video but we are more than another year on from that now. The short answer is no. The reason is: as of March 2023 that guy was, quote “100% confident of service entry in 2025”. And yet 18 months on this has officially been superseded by the estimate of first flight in 2025 and the estimate for service entry in 2026. And yet still no prototype rolled out. “Realistic” is subjective but dates are objective. The fact is that guy’s timeline from 2023 has been proven wrong. Imo, this delay could be seen as poor judgement but not inconsistent with “75% confidence”. But relative to “100% confidence” it is an abject failure and therefore the timelines provided by the ‘airbus manager’ have to be treated as unrealistic. I don’t think he even believes his own timeline, it is just what he has to say to prevent the stock market from cutting away. It is the ‘fake it til you make it’ mindset, it is ‘full self driving next year’ - every year for the last 10 years, it is right out of the Elizabeth Holmes ‘book of engineering the future’.

[@JMurph2015]

The ironic thing is that they were so close to a blown-lift wing design which would allow them to use slotted flaps to achieve ultrashort horizontal takeoffs, but they went "screw that" and put the motors in the wrong place and designed the thing for VTOL.

[@Ozbird-72]

Yes, SUPER STOL is a lot better to handle and achievable than VTOL

[@Ozbird-72]

Engines to the front, high lift design, some sacrifice in cruise but a totally valid and safe concept. 30 ft take-off and 50 ft landing.

[@ardaricus1566]

​@@Ozbird-72Its electric Motors, you can probably program them for reverse thrust. Even shorter landing!

[@jo21e6]

They want to takeof from a helipad, that's a big difference in usecase

[@JMurph2015]

@@jo21e6 a lot of super STOL aircraft could take off in the width of a helipad.

[@akayarda]

Amazing work, very detailed presentation! Thank you for the effort given

[@UweKlingauf]

Congratulations on this very sound analysis!

[@Caleb-qr6lo]

Would love a deep dive into why evtol systems don’t use PEM fuel cells or a hybrid approach to reduce battery weight.

[@AlJay0032]

Green politics and delusional denial of basic facts of physics as things scale. Dunning-Kruger ignorance coupled with wishful thinking. Just look at current German politics, they want to electrify transportation plus heating which would require about 500GW additional power plus large amounts of minerals and materials like copper, lithium, neodymium etc but instead of expanding electricity production they are reducing it. And no one even thinks about securing the minerals. No one is investing and building the new mines except for the Chinese. They don't care that solar output in the winter is low and sometimes PV might even be covered in snow when most power for heating will be needed. They don't care that wind power is negligible for weeks in the winter months in some years. They don't care that the storage needed will be gigantic if they don't use fossil fuel power or nuclear but they are neither allowing nuclear nor working on backup storage. Green and electric is sexy and clean in the minds of the willfully ignorant woke left-green fascists and their sheep. The consequences will be great destruction of wealth. But in the end they will blame capitalism for their impoverishment and demand even more socialism and government intervention in the markets.

[@_Dibbler_]

Because thats way more complicated. Hydrogen is a beast that is hard to tame. Batteries and electric engines are easy, as long as you stay below a certain power consumption and range

[@nicklockard]

Me too. I've also wondered if these concepts could use spring loaded legs to help leap into the air?

[@plorks445]

Good job on the analysis. I think they ran into the same issue all other air taxi ventures have. They thought hover stability was the difficult part until they got off the ground and found that electric power doesn't keep you airborne for very long. The one thing they have going for themselves is looks. It looks more futuristic than most other designs. Doesn't perform any better and is arguably worse than a propeller design, but it sure looks purty. Just like all other air taxies, they will delay and delay as long as they can until the electric power plants get to where they need to be. Like most others, they will eventually go with a hybrid approach in the mean time.

[@stefano1844]

Thank you so much for this clear and helpful analysis!

[@stevenbalderstone709]

Your thoughts on Lillium now they've successfully completed hover to aerodynamic flight to hover test flights? It seems the question of range viability comes down to battery power density and aero drag. It seems entirely reasonable that Lillium anticipate further enhancements in battery chemistry and design the aircraft well ahead of current battery technology - so long as their investors are patient. It also seems reasonable that they develop multiple models of aircraft over time, waiting for battery technology to catch up.

[@Secretlyanothername]

This seems to be the approach that Eviation are taking, even though they're not an eVTOL company. Iterate the design, allow battery technology to mature.

[@rossnolan7283]

Another 'contender' in the same category as Lilium has surfaced - "Nazzeni' - identical 'flapducts' on three surfaces in a staggered triplane layout , doubtless inspired by Lilium . The bandwagon must be just about ready to collapse (830 projects on the VFS directory) and max hype . It helps to take an overview of the whole rapidly mushrooming eVTOL "thing" as well as a forensic detail examination of specific designs and to detect generic trends (who can spare the time to examine ,in detail ,each of the over 800 'offerings' anyway ?) Lilium can, justifiably, claim (as @2.00 ) to have been misunderstood or misrepresented by several 'analysis' but also tries to infer that ALL examinations have been 'flawed' on the basis of the couple of ill researched ones . Specifically the first paper by Sripad and Viswanathan used dimensions scaled off a photograph with a person whom they arbitrarily took to be 1.5 mtr tall (short for a westener but likely average for an Indian ) hence their figures for disk area were way too low and the errors compounded from there . The highly non linear effect of discloading on power makes small errors magnify the inefficiencies -- nevertheless , the figures in the main paper referred here by John (Lou) arrive at an installed power figure that equates to 3343 HORSEPOWER - a stunning figure for so small an aircraft with so few seats and a 'modest', at best, performance . Other papers critical of Lilium quote 2200 KW in hover (near enough the 3000 HP in my rounded estimate ) - cf. Bjorn Ferhm in "Bjorn's Corner" . Even if the Lilium can hover and transition ,be controllable and stable etc etc -how can it possibly be said to "WORK" when the overall objective was to be environmentally 'pure' -and received government funding as a 'solution to the climate crisis' but the FACTS are that it is an obscenely wasteful and profligate example of virtue signalling that is, literally, orders of magnitude short of being any sort of energy saving transportation nor any possible replacement for existing mass commutting by car or anything else eg trains buses . Even if it ran on fairy--burps, and really required no electricty there is no possible way these things can perform the same sort of door to door personal mobility service that the existing modes do (and recall that Lilium DID set out to be roadable -- a car not a taxi , and by abandoning that intent it's economics left only a high cost 'chauffered' model requiring expensive interchange air terminals ; they then changed the business model yet again to be more like a shuttle bus - up to 19 seats with apparently very little more disc area . (!) This is piling absurdity upon absurdity in a vain attempt to amortize the sunk costs and pilot cost over more 'seat miles' but defies every physical constraint . Another offering claiming to be VTOL AND roadable (almost a certain engineering impossibility ,within any reasonable limits ) is the ASAKA A5 - possibly the most ill conceived and ugly/cartoonish contraption in this field -ever. It has been constructed and is being promoted as yet another competitor /contender to Lilium et al in the 'advanced air mobility' area. Whilst engineering analysis of these misbegotten projects is essential and required there is another analysis needed -namely by a psychologist or social scientist to analyze the phenomenon underway in the 'eVTOL space' (if that even exists in reality) which is reminiscent of the earlier 'south sea bubble' or the 'tulipmania' craze that erupted in the speculative stock markets of yesteryear -- the DotCom or real estate bubbles in more recent times and the SPAC /IPO fever with money being showered where it was never before known to fall - in the small personal flying machine field - otherwise still building 'legacy' designs from the 1950s or earlier . There was a brief 'boom' just after WW2 that busted in 1947 leaving only a handful of 'boutique' light aircraft building firms operating at low levels of production and high costs . The 'eVTOL boom has all the hallmarks of a mania and as such is the 'irrational exuberance' of Greenspan and reasoned debunking will be like water off a duck's back . Need to clarify what is the reason for analysis and the aim.

[@saturnomega768]

Absolutely one of the best debunking videos I know!

[@RalphEllis]

The Lillum’s MD is confident that his engineers know what they are doing. But forgets he is paying them to not be critical of the Lillum jet. Rolls Royce made the same mistake with their EfanX hybrid aircraft. Rolls said this new propulsion system would reduce fuel consumption by 70%. I said the design was stupid, and would never get airborne. Too heavy, too bulky, too hot, and too inefficient. Guess who was right - the engineers paid to keep silent, or the independent? I won, and won in the first round. The EfanX actually increased fuel consumption by 400%, And was unable to get airborne. R

[@RichSpeculation]

In hover those wingflaps canted vertically are going to introduce a horrendous gust response dynamic. Control logic can probably be figured out(space x can land rockets with millisecond control response challenges after all). But i expect for certification the weather maximums will be very very low

[@forest42821]

The aircraft design is definitely valid, the remaining question is range, which undoubtedly will keep increasing with higher battery power density. I believe in it, but for sure I’ll take longer to achieve 200-300 miles range.

[@ziad_jkhan]

Ducted fans are known to be inefficient which is why the competitors don't use it. The test data is poorly documented so I'm not sure how you figured out the design is valid.

[@forest42821]

@@ziad_jkhan it is flying and looking functionally beautiful. That’s a valid design to me. may not be the most efficient yet, but they’ll improve it. May be they could strap 2 rockets on the top to get to 300 miles range :D

[@ziad_jkhan]

@@forest42821 It's a company that focuses on creating hype, hence the emphasis on beauty, not the actual science behind which, btw, has not been duely documented thus far. There is no mention concerning the load during the tests so nothing yet confirms it's validity. If you have to believe in it then it's basically just a religion.

[@forest42821]

@@ziad_jkhan I still have lots of doubt but yet I don’t want to count it out. Will it work if they can use a Quantum Scape or better battery?

[@christopherpardell4418]

Its not “valid” if it does not do what was promised to the folks who put up the cash as an investment. That is, Transport 5 people 300 km in 1 hour. Theranos’ ‘concept’ of doing multiple blood tests from a small sample of blood was a valid ‘concept’ given what CAN be done with small samples… but there is a wide gulf between a great concept, and something that is actually doable with the technology we have or can develop within the scope of a return on investment.

[@henrimilo1]

Lilium is designing a Vtol for Future energy sources, and they shall continue. It is obvious that today’s energy density of latest batteries are not meeting the expectations, we all know it, Lilium knows it too. Sirius came out with a copy of Lilium‘s design with a significant change : hydrogen fuel cells.

[@zyzyzx3352]

Impressed, prof, very well presented

[@JoeyBlogs007]

I'm not an engineer of any kind, but am enjoying this video very much. I only used to fly model aircraft when I was young. I see this as university quality lecture material. I would suggest perhaps consider breaking future videos up into 30 minute segments, to increase your KZbin rankings, by more frequent uploads etc... however I'm not a KZbin expert either. However that simply might not be important to you and that's fine. I'm 30% through this video and expect to have a few questions by the end of it. I'm taking some notes.

[@JoeyBlogs007]

I have an early hypothesis that 4 motors with variable pitch mounted in the inner wing areas ( two on each side ) might be worth considering. That covers your 224 kW for cruise plus a bit extra to help cover drag inefficiencies of the other rotors. Possibly 6 motors if you want a bit more redundancy for variable pitch. That still leaves the bulk of motors for VTOL.

[@JoeyBlogs007]

NOTE: There are claims out there that CATL claim just released a 500 Wh/kg battery. Even if that were true, I remain a bit sceptical of this Lilium Jet.

[@JoeyBlogs007]

Agree that hover capability should be the higher priority.

[@patrikwihlke4170]

Sad to see these aggressive startups that cannot respond maturely to criticism. I wish it was feasible, and I think it could be in other hands (and a much longer timeline) but it simply is not going to happen. I think many cases like this come out of a genuine will to innovate but a dream is not enough and hyping the potential up with lies for investors is not acceptable, and potentially illegal.

[@einzeln00]

Good review. Funny thing is some guy asked me for making a duct fan to work on both static and high flow conditions, and they said they were with ... and we both agreed the spec required is impossible 😂

[@kwrddudi4882]

😂

[@allanborzel4442]

John, it would be great to see a similar video on the Jetoptera from the US.

[@frankyflowers]

with a canopy like that it will get hot in there and it can't have air conditioning if it can't even cover its connectors to save weight.

[@Dynamic_Flyer]

Very good analysis. The true range and payload capabilities, with realistic and reasonable values, are probably significantly higher than the Aerokurier paper but not as high as Lilium postulated in their paper, which should have been far more robust in its calculation and validation of key parameters. I suspect a 5 person version of the design would have a range closer to that demonstrated by Joby, probably nearer 100-150km, and cruising at more like 150-200km/h, not 300km/h. As for the 450km/hr and 500km range estimates put forward in 2015, they were fantasy. So were the project timelines. One elephant in the room the video did not mention is battery cycle life. Even if a battery with sufficiently high specific energy (Wh/kg) and specific power (W/kg) is produced, its cycle life is likely to be low (maybe a few hundred cycles). Cycle life has a huge effect on operating costs because short life = more battery replacements, which are very expensive. This has the potential to wreck the business model and leave VIP transport as the only market sector. Difficult to see how it can be a mass-market “Uber like” proposition.

[@frankyflowers]

joby never demonstrated its range just said they did. where is the demonstration of the range? they are both scams and vaporware

[@XPLAlN]

…yes, battery life is a big problem (I think he did touch on it). It is most likely that EASA will impose short battery ‘TBO’ based on the 700 hour limit they slapped on the Pipistrel with its relatively tried and tested battery technology. Compared with the equivalent piston engine, that battery replacement costs more than the 2000 hr engine overhaul and needs done 3 times as often. So even if a new type of battery becomes available for Lilium that can provide the performance, there will be no operational experience to prove its safety and longevity. They will have the devil’s own job trying to convince the powers that be to certify it, in this post 787 Dream-burner battery fiasco and post 737 MCAS debacle certification environment.

[@pauljmeyer1]

Let's get an efficient power package that has the power-to-weight ratio to do this eVTOL stuff before we try to harness it.

[@huibu8987]

59:00 back then lilium didnt achieve full transition yet. Spain test-flight campaign started later. In germany located flight test they on tested hover flight.

[@zhihenglou]

I fully accept your point that Lilium did not achieve full transition at the time stamp you mentioned. This is a fair comment, thanks for raising this point!

[@barryscott6222]

Wouldn't touch this project with a barge pole. The whole thing starts at the end point (an aircraft design) - and tries to work backwards towards fitting in the critical engineering/development into a design envelope. They never proved out the various subsystems first, had an initial basic design knowledge deficiency, and hoped that they could engineer solutions to fit within physics limits. When that proves impossible, they are increasing the size, weight and complexity to attempt to squeeze scale efficiencies into the design limits. This is classic design run-away.

[@supervolant]

I have watched the whole video with attention. You have displayed an extraordinary well done showcase for an independent engineering review, yet I can assure you there are many things hidden to you in terms of design architecture. As an Lilium insider I would suggest to you to apply, come to Munich find out for yourself. Ps: Allow your self to think again about if performance data really does not give something away in this stage of EVTOL as a whole?

[@alfredspijkerman]

I agree with you. I am an innovator myself: I design electric yachts. Now 4 years of development and coming jan 2024 to market. We are very very careful about sharing any information and for very good reasons. At this stage, you really don’t want competition to look over your shoulder. Like with $TSLA high end customers first, then early adopters, then mass market. Currently huge battery investments worldwide. Biggest supplier CATL recently announced 500 WH/kg in mass production soon.

[@zhihenglou]

Hi there, Thanks for viewing the video in depth and leaving a comment. I see you are making two points: 1) information for predicting aircraft performance is hidden from me, 2) performance data may give something away. So allow me to respond to each point in turn. The first point uses the same reasoning by Frank Thelen (see 44:00). When making this video, I considered this argument, and precisely because I respect its merits, I have based my analysis solely on Lilium's technical paper. The majority of Chapter 2 is a review of Lilium's technical paper called 'Architectural performance assessment (...)'. Therefore, my analysis is wholly aligned with Lilium's own description and explanation of its design architecture. Furthermore, according to Lilium's investor relations website, Lilium's paper offers 'a more thorough and transparent technical explanation of the Lilium Jet' (see 56:34). So unless Lilium has hidden critical information from its own paper despite the purpose for thoroughness and transparency, my analysis is whole and withstands your first point. Regarding your second point, Lilium has already given theoretical performance data via the technical paper. So I do not understand your concerns. For example, Lilium's paper uses theory to calculate a hover power of 2570kW. However, theory is just theory. Hence, a concept demonstrator is used to collect test data and thus demonstrate a concept's performance feasibility (e.g., range). This intent was explained in Lilium's investor relations website (see 54:40). Therefore, why are you concerned if the hover power comes from test data instead of theory? If that is not the case, what are you concerned about? Best, John

[@supervolant]

@@zhihenglou Let me try to give you some further food for thought. If the whole industry believes, based on the current baseline understanding of aviation technology, that Lilium is on the wrong path, who would actually profit from proving the validity of the Lilium jet concept other than the rest of the industry itself? The moment Lilium has truly proven itself is the moment you will see companies comming up with design imitations and separate R&D projects. Isn't it better to further separate and gain a few years in advance by having a technological advantage? That is why the only people Lilium has to prove anything to at this point of time are big budget investors. These investors and Lilium employees are the only people gaining full transparency while having to adhere to tight NDA agreements. One might understand from this viewpoint why the same investors keep on investing and talent keeps on joining. Business is war, strategies will only make sense after the war has been fought out. I wish we could discuss this in depth and truly look forward to the day we are releasing our actual performance data (if we ever), as I can fully understand the industry wide frustration towards our secretive nature. However, due to the contract agreements that are set in place for me I am unable to go into further detail, and frankly speaking, rightfully so. Edit: a spelling mistake.

[@zhihenglou]

@@supervolant Thanks for the reply and the civil discussion. Let me respond to your last comment. "(...) who would actually profit from proving the validity of the Lilium jet concept other than the rest of the industry itself?" Comment: Besides the industry, government institutions and universities have been researching aircraft concepts for decades. Due to their experience and funding structure, these institutions can be considered the most knowledgeable in aircraft design while also being independent in this business competition. So, what are their views on Lilium's concept? "The moment Lilium has truly proven itself is the moment you will see companies comming up with design imitations and separate R&D projects. Isn't it better to further separate and gain a few years in advance by having a technological advantage?" Comment: I see little merit in this reasoning. There are already legal systems and mechanism to protect innovations, namely patents. Patents are designed to protect your technological advantage and lead. Hence, I am still left wondering: what is concerning about demonstrating the hover/cruise power with test data instead of theory? "(...) look forward to the day we are releasing our actual performance data (if we ever)" Comment: Video footage of the aircraft flying and achieving its performance targets would be even better (i.e., achieving maximum payload-range). If this cannot be produced, then the next best thing would be sharing hover/cruise power test data from the demonstrators. If those cannot be produced either, then the third best thing would be to produce component ground test data. I look forward to your results, too. Best wishes, John

[@ALC656]

Even after so many flight test videos, they have yet to disclose any payload info. What’s up with that? I’ll be convinced once I see that they can lift a payload equivalent to two passengers or whatever that flight test vehicle is suppose to do…. Based on my observation (mostly from landing) I can see that the flight test vehicle is pretty light weight

[@Guitar6ty]

The Lillium concept is a brilliant idea but VTOL is very wasteful of energy so short take off and landing would be a better route to follow.

[@andrewburbidge]

People might pay to fly in it because of the fine design and the fame. To have a Lilium arrive at a ski resort and fly down to Innsbruck airport would be special for wealthy people. It's a long descent down the valley from St. Moritz, for example, which would help with the battery problems. There is a stream of videos about new battery technology that is going to change everything. In the meantime, to have something providing such a service would help further the dream.

[@XPLAlN]

…a stream of videos about batteries isn’t going to get this thing certified.

[@andrewburbidge]

@@XPLAlN That's true. They expect it can be certified with existing battery technology. New batteries may open up more possibilities.

[@customraspi]

I cant wait for 2019

[@Jonah100]

Why not incorporate ground powered air assist from take off? Upward air forces under the wings from a ground based launch pad could dramatically reduce battery drain during the lift off.

[@cinmay2000]

I wish John would do a video about the "Alice" electric passenger plane. Seems like there is a similar start-up pattern of over-promising and under-delivering. There is a ton of online content about the "Alice" project, but the images seem to all be AI or CGI renderings, yet the associated language refers to a seemingly real thing.

[@codetech5598]

Bankrupt. Who didn't see it coming?

[@eriktempelman2097]

More people need to see this type of level-headed analysis. Then we would see more emphasis on proven technology (like HS trained) and less on these ducted pipe-dreams.

[@goodcitizen9827]

It's a low brow attempt at exaggerating his low brow concerns. They passed all 4 DOA audits and passed 3 before he posted this video. He should have known better

[@maddemon1385]

Even a significant reduction of the range would still make the Lilium jet very attractive, especially for early adopters in more niche markets. There are plenty of places around the world where even very short hops make a lot of sense, for example places where a mountain or a body of water is in the way. It seems that they will initially sell the aircraft to high net worth individuals, who will also most likely not care about having 7 people on board. Of course this market is much smaller than the mass market, but it is likely big enough to give them an order pipeline for several years with a less price sensitive customer base. With these profits and future generations of batteries, they will likely be able to eventually achieve and even surpass their stated goals.

[@frankyflowers]

like 100 yards? how many people can it carry 100 yards? they should try that.

[@frankyflowers]

where are places like that? if there were rich people there then there are bridges.

[@maddemon1385]

If you have only a few people on board, a range of >100km is very realistic, even according to Iceberg researches report. There are not that many bridges in the world that are longer than 10km. It becomes prohibitively expensive to build bridges at a certain distance. In any case, their order pipeline seems to be filled for several years. So there is definitely demand for the initial product. They will also be able to upgrade the batteries once more advanced ones are available. If the aircraft flies several times a day, they will have to replace the battery after a few years anyways.

[@frankyflowers]

@@maddemon1385 they should have no problem lifting the weight equivalent of passengers and going 100 yards. the passenger compartment has a big forklift battery in it where the people should be so they can't fit people in there. i doubt it would lift off.

[@zhihenglou]

You have made excellent arguments. I think your logic is solid, and you explained your case very well. I followed all your reasoning and have no objections to their qualitative value. Where I differ from you is how I weigh your points with respect to the arguments I made in the video. Among many other arguments, my opinion is formed by the observation that Lilium has yet to show a full-scale prototype (with variable nozzles). Thanks for your high-quality and objective comments! I think they add value to the discussion, and other viewers will find your comments insightful, too.

[@gogo22976]

Best Regards from Theranos' Board

[@gyrocopterkai]

What a fantastic and deep evaluation of the Lilium Charade. I wish I could somehow interest Germany's Secretary of Transport, Mr. Wissing in this video. He still wants to throw millions into the blazing fire. By the way, are you German? Or do you just live here?

[@chrispratt6064]

Excellent analysis. Thank you.

[@zhihenglou]

Thanks, Chris!

[@rossnolan7283]

Thanks John -it seems that any 'lengthy' response gets treated as spam from what I can work out . My laptop is pretty ancient and has some other quirks like 'striknig out' text at random. The whole eVTOL scene is like the wild west at present and has been driven by irrational exuberance fueled by cheap money and ignorance plus the easily exploited desire for flying cars in the public mind . The vertical flight society seems to have taken a hands off policy with Darwinian selection expected to winnow out the 'unfit' but those included in the directory also claim the imprimatur of the organization just by being listed ; it is hard to know what else could be done but at least some sort of disclaimer might be made ( it might have been but if so I am unaware of it ) The situation is reminiscent of the ultralight boom of the 1970s that was a free for all with predictable results and bad publicity from fatal accidents (maybe moreso in Australia since we had had a total ban on local experimental aircraft design ,only imports, and thus a dearth of engineering experience -- the hiatus in VTOL activity for many years after the burst of new designs in the 1960s (the tri service competition etc ) and failed experiments leading to the 'wheel of misfortune' of VTOLs created a similar 'know how'/ ' know-how-not-to , gap. ( I think it was a Lockheed engineer who dubbed it as such - a similar thing could be done for unsuccessful flying cars of any type ,including VTOL which bridges the new field of 'air taxis' . Just substituting battery power and computer software is not enough to solve the inherent defects in basic design. The tilting lifting duct was pioneered by Alexander Lippisch and adopted by Dornier in several drones and later again by Paul Moller (with a caveat - he expected that FIXED ducts with venetian blind flaps in the duct exits would give him VTOL -- look at the first depictions eg popular Mechanics covers . After Martin Cole ,then vice president of the Australian institute of engineers, extoled the great promise of the Moller Skycar in an editorial in ~1993, which was brought to my attention (he wanted Australia to get behind Moller ) I advised him of the NACA research that debunked the possibility of so much flow turning ( I had access to the complete set of NACA/AGARD etc research reports while working for our aeronautical research organization DSTO ) The tilting duct 'aerodynes' had to hover about 45 degrees nose up -- soon after Cole visited my home/design office he advised Moller and then Moller 'redesigned' his design with - you guessed it- TILTING ducts . And commenced to make his usual claims as if the thing had flown successfully - by tilting, the fans did not interfere as previously - (just as the Joby now does in forward flight) Ignorance of the findings from vast amounts of prior research means that all the old mistakes are being repeated . The staggering diseconomy built in to the lippisch concept as adopted by Lilium is matched by the shortcomings in contollability in gusty conditions that will become apparent (the induced airflow is inadequate to negate gust effects on the fixed surfaces and is not comparable to slipstream blown wings /tails - the fixed wing areas are a big liability in hover but are needed to support the huge hidden mass in batteries -unlike earlier gas turbine VTOLS that had much smaller wings sized for cruise .... enough for now . regards,

[@huibu8987]

There are plenty of usecases for 100-200km air transport. Going for more passengers is than more range is the right decision in my view.

[@zhihenglou]

Hi Huck, In your view, how much time can an aircraft save (compared to a regular car) for a 100-200km range? We must consider that the aircraft must land at airports (or other designated areas). So passengers would need to spend time to get to their departure airport. And they need time to get from their arrival airport to their final destination. There will likely be a security check at the airport, too, costing more time. Cars do not have these time costs. Lastly, airspace is regulated, so we often cannot fly from point A to point B in a straight line. We might have to take less efficient air routes. How would you weigh these factors in your estimation? Thanks for your comment and the constructive discussion!

[@zhihenglou]

Another point that we should consider is the travel price. For an aircraft, we will need a professional pilot. Is it worth hiring a professional pilot for a 100-200km trip range?

[@user-fj9yy7xt3w]

@@zhihenglou Valid concerns. Lilium is targeting inter city vs intra city in order to increase time savings. Many other operators believe they can make money even flying within a city, Ehang, Joby, and Archer, for example. They plan to fly initially where there is already heavy taxi demand from downtown to the airport. Back to Lilium, a rough estimation of a 100 mile trip in a car to a nearby city could take 1.5 hrs with good traffic conditions. Flying you could make it in 40 minutes + time to-and-from airport/vertiport on each end. So, roughly a half hour of time savings based on some assumptions of how long the ground piece takes which we don't know for sure. If you add in that you can work while you fly, you're getting the experience of flying, and time savings could be greatly amplified in the case of heavy traffic, or water/mountain obstacles for example, the proposition gets better. A lot of these aircraft operators have preliminarily agreed to purchase the 640 Lilium Jets will have to work out appropriate pricing and pilots pay. Definitely will be challenges though in terms of infrastructure, atc, demand, pilot training, and pricing, but they should be solvable. Also, what I really want to see is what announcements Lilium makes in the coming months about closing the funding gap as they were down to 206 million Euros to start this year I believe.

[@JiriTuma-vd5lq]

@@zhihenglou Hello John, with newly released battery with energy density up to 500 Wh/kg from CATL can be operating range doubled (to 350km).

[@liskajp]

@@zhihenglou in a mountainous country, a lot!

[@carlosortega7888]

We all want Lilium to be the Tesla of aviation. Anyone who contributes ideas and suggestions and transfers them to the Lilium engineering team is appreciated. For the good of humanity and for defending investors. We all want to see Lilium fly in 2025! Thank you.

[@rossnolan7283]

Speak for yourself sport, I hope they are exposed as the conmen they are and don't end up crueling the entire idea of personal airborne mobility as it was originally conceived ...

[@ejrupp9555]

So that guy deleted his reply? If it was censored, I'd be sniffing for the BS. I'm not one of your we ...or INVESTORS. It's got Theranos written all over it.

[@faluffel]

@@rossnolan7283 Hey Ross. I've seen multiple people voice this opinion and I'm curious to what the main points are - obviously some optimistic targets were set forth, but they are testing, and brought some pretty serious people on board, but what are the other things that make you call them out like that?

[@rossnolan7283]

@@faluffel A summary of my reasons is in 'comments 'here -below (curious that the offhand comment on 'we all want ... for the good of humanity " has reappeared mysteriously - the reply I made to that is what you refer to I am assuming ..yes ? OK, the first thing to sort out is WHAT are they trying to do and judge their 'progress' against that AND then to evaluate what their aim is . Many of these eVTOL start ups are making sweeping claims to be working to solve the ('humanity's) ground traffic congestion problem (eg JoeBen Bievert's 'mission statement' "To save a billion people a billion hours a day' and talking about having 'millions' of his Jobys (shouldn't they be :Bievert S4s" - how many other aircraft are named after the designer's First -and in this case, baby -name ? - Chance Vought might be the only one incorporating it - just an aside. What have ' Lillies' got to do with aviation ? The 'lilium' (latin) is a symbol of purity and innocence, -google it - a bit of a misnomer in this case ,like 'pedophile' means 'lover of children' ) The guff from Lilium purports to be about not just solving this problem but being environmentally pure -they have even received large government 'clean technology' monetary grants and tout the ZERO (operating...) emissions .-- isn't it absurd to make claims for 'saving the planet' with something using an unheard of amount of power in a civilian aircraft ? Terrafugia made a simlarly baffling statement about it's ,aborted, VTOL (TFX) quote "A MEGAWATT lifts you !" (746 Watts is a HP - a megawatt is 1340 HP -not quite in the Lilium league but similarly profligate whilst seeming to hope that by extoling this figure it was seen as a plus. Using 36 or even 30 roughly 100Horsepower motors on anything hardly seems destined to be either energy efficient or economical -especially when using 'second hand' energy --electricity,- realistically produced by some distant thermal power plant using, most likely 'fossil fuels' or even imported 'biomass' (Canadian wood chips) -- that extreme mismatch and deceptive language might be the first reason why I call it a 'conman' job. Since I have studied and concluded that there is NO imminent ,or ever, global crisis involving runaway global climate calamity due to mankind's CO2 contribution I find their 'raison d etre' to be nonsensical in itself - they are 'saving' nothing but profitting mightly from selling ,indirectly ,fear and a brute force 'solution' that cannot possibly address either environment or public road clogging (saturation of the electromagnetic spectrum related to CO2 absorption rules out any 'tipping points' and the scale of the traffic volume vastly dwarfes any contribution that something flying between two points ,both needing another ground vehicle on the roads to pick up and deposit each passenger at and to their respective home'/start point and their destination - with probably 'dead head' trips by the taxis to pick up Lilium pax. Even Mark Moore has commented on the idiocy of lilium's approach . Larry Paige had some big names on his payroll also and just as cocky (Sebastian Thrun ...) but ended by just closing the doors - the Wisk /Cora abomination is still blundering on with endless test flights - in New Zealand of all places - hoping to get some sort of certification on the cheap (as did BEDE) .Assuming that having a line up of 'names' can somehow make up for basically flawed design conception is a curious thought -- your question ends with a- "BUT" what else....' - that being the 'nuts and bolts' engineering deficiencies of their CONCEPT - no matter how well embobied which I and others have detailed already , the earlier 'but' in your question implies that by 'testing and having pretty serious people involved -or 'on board - on THE board - they must be above question (it seems in context) The Titanic lesson or maybe the Bristol Brabazon in this field suffered the same presumptions -can 800 eVTOL projects be based on a false premise . You bet.

[@ALC656]

@@faluffel simple… these guys don’t know how to design an airplane. This airplane is aerodynamically unstable. And the earlier concept if you ever saw…(with canards retracting into the fuselage or bs), tells a lot about their experience. Also their current flight test vehicle wings (and canards) structurally looks very week. And I highly doubt that this flight test vehicle has enough power to even take off with two passengers (or equivalent payload). Just flawed designs everywhere

[@EarnestKaraoke]

Thank you for in-depth insight. 👍🏻👍🏻👍🏻

[@whawdotca]

Fantastic analysis. Specific energy capacity of 320 Wh/kg is an extraordinarily optimistic value for high power lithium ion battery applications. Currently 250-260 Wh/kg is the leading edge for commercially available batteries and ever 250Wh/kg can only be obtained with creative manipulation of system mass. These values are only obtainable without any supporting structure, electronics, or cooling systems. Realizable high power systems (C Rate > 1) will require heat management systems and structural integration which will likely reduce specific capacity from 250 to 190-200 Wh/kg (which now in line with realizable specific capacity estimates). Either they are including all peripheral material within the total vehicle weight allowance or they have massively over predicted their ability to source and implement commercially unavailable lithium ion batteries. Either way not a good look for a published white paper. Side note, if you are able to find commercially available 320 Wh/kg batteries I would like to know haha Edit: @1:30:13 A battery fire is great evidence that proper wiring and cooling systems were likely scrapped rather than accept the weight penalty of proper high power battery design. Just a guess!

[@alanhilder1883]

Ah but the battery fire can be used as the "afterburner" for more thrust... Obviously I'm joking. Too much of this sounds like fraud.

[@samreciter]

60s of high power hover flight is nothing for those batteries in terms of heat management. i don't know, why everyone still tries to downplay the batteries - i mean - it's nothing exotic anymore... bzw. China-based Amprius has their 320Wh/kg and 350Wh/kg since last year - Zenergy launched it's 320Wh/kg high density aviation battery last month and that's only what i've seen lately...

[@Secretlyanothername]

And these companies are moving slowly enough to let the battery technology mature enough to be commercially useful.@@samreciter