Lilium down the gurgler

[GregLocock]

old thread

Lilium eVTOL - Aircraft engineering

Interesting news that both EASA and FAA have determined their basis of certification. It'd be nice to see this if anyone can access. I've been trying to see Lilium specs, but seems to be very difficult. It appears that their marketable version is their 7 place plane (6 pax plus a pilot), so...

www.eng-tips.com

New news

Out Of Options, Lilium To File For Self-Administered Bankruptcy | Aviation Week Network

While the company has made significant progress in development and was nearing first flight of a production-standard aircraft, it has run out of time and money.

aviationweek.com

 

[Ng2020]

Analogous to Reason's swiss cheese model: for a project to be truly successful - from concept through first flight through to production and market acceptance- there are many holes in the swiss cheese which require concentricity.
I am doubtful of the technical integrity of most urban air mobility projects, one only need look at the configuration and detail design.
Of those that are more convincing, the operating economics, market demand, and societal acceptance are big question marks.

 

[3DDave]

Lilium seems like one of the worst aerodynamic schemes. There was an article about it: https://www.aerokurier.de/elektroflug/lilium-jet-dossier/

 

[GregLocock]

Google translation, not too sure if the link will work (you need to select german not French!)

Urban Air Mobility: Liliums Scheinwelt

300 Kilometer in 60 Minuten mit fünf Personen an Bord – und das rein elektrisch: Der Lilium Jet wird den Versprechen seiner Entwickler zufolge die Urban Air Mobility revolutionieren. Doch was bleibt vom Hochglanz-PR-Image übrig, wenn man das Projekt mal durchrechnet? Spoiler: viel ist es nicht...

www-aerokurier-de.translate.goog

pretty damning stuff, and no real surprise. When has anyone ever said 'we want lots of tiny ducted fans'?

 

[GregLocock]

Here's their investor presentation

https://investors.lilium.com/static-files/c355ba0f-662c-466c-aa6a-43072b3d34c3

 

[3DDave]

Google translation, not too sure if the link will work (you need to select german not French!)

Urban Air Mobility: Liliums Scheinwelt

300 Kilometer in 60 Minuten mit fünf Personen an Bord – und das rein elektrisch: Der Lilium Jet wird den Versprechen seiner Entwickler zufolge die Urban Air Mobility revolutionieren. Doch was bleibt vom Hochglanz-PR-Image übrig, wenn man das Projekt mal durchrechnet? Spoiler: viel ist es nicht...

www-aerokurier-de.translate.goog

pretty damning stuff, and no real surprise. When has anyone ever said 'we want lots of tiny ducted fans'?

The Chrome browser asks if I want it to be in English.

 

[GregLocock]

Yes I'm using Opera for random reasons!

 

[GregLocock]

Effect of ducted fan diameter on ducted fan performance

 

[rb1957]

bad ideas tend to have a common fate. all of these "air taxis" are just awful, IMHO. Most are trying to do the most energy dense operation (VTOL) with the least effective fuel/drivetrain. sigh

I wonder how well "gurgler" translates ? (I understand it, but I wonder about those who are ESC ... English as a Second Culture)

Then there's this "gem" ...

 

[IRstuff]

Then there's this "gem" ...

That's a boatload of propellers for someone to walk into; if it's not safe as a prototype, it would have needed to be redesigned from the ground up to be safe, and thereby nullifying any certs and qualifications.

 

[3DDave]

People walk into propellers already; they get sucked into turbojet engines as well.

 

[WKTaylor]

3DDave... Have You ever investigated a GA prop-Acft or a helo crash? Rotating blades are punishing.

After years

BUT YEAH significant numbers of props/motors are individually and collectively high maintenance and increase the chances for multiple/cascading failure combinations and asymmetries and a host of other negative factors.

Bird strikes, lightning strikes, dust/rock/ramp-FOD, snow, rain, slush, static charge build, FOD etc... to name a few.

This photo... was of a helo that landed safely after a lightning strike on it's 4-bladed helo tail rotor... think about it...



"If it's not there, it costs nothing, weighs nothing and is 100% reliable.” –POPS, forum member, homebuiltairplanes.com

 

[3DDave]

Not sure what need there is to investigate - it's not a requirement to shield people from propellers.

 

[WKTaylor]

3DD... all...

Look closely at the photo.

It is of a 4-bladed tail rotor after a lightning strike... which simultaneously failed ['liberated'] 2-opposing blades... and the aircraft flew to a safe landing on these 2-remaining blades... unknown to the crew.

Miraculously the 2-separated blades did not collide with the main rotor blades... nor the aft side of the forward fuselage or landing gear... which, alone could have caused devastating damage.

 

[Lou Scannon]

I saw that. Definitely a freak event, unless somehow the design ensured or promoted such a blade shedding mode.

 

[3DDave]

I was referring to investigating a multi-rotor aircraft designs to keep people from walking into propellers, not the particular accident.

As to the loss of opposing 2 of 4 blades, that cannot realistically be a design point, particularly in departure direction. If such things were then the many crashes due to ordinary use failures of tail rotors would never happen, having been so thoroughly analyzed.

---

I do have some interest in aviation accidents; I would not say I investigate them, but I read the investigation reports and pay close attention to reliable data.

 

[rb1957]

yeah, but Will means investigating why the tail rotor blade exploded in the first place, and why did the second blade fortunately depart.

Thee was a Mayday episode about a helicopter struck by lightning (in the tail rotor as I remember) over the North Sea, Luckily everyone got out ok. There was 1 guy in the CAA (maybe, or in industry) who felt that this event showed that the lightning standards were way too low ... but the combined voice of the CAA and the FAA ruled the day. In twenty plus years we might see who was right (given the amount of composite primary structure there is these days) ?