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

mickjoebill 12th May 2022 20:30

New test flight video
 
Two videos.

45kts test flight

Interview with engineer
Mjb

mickjoebill 7th Jun 2022 02:18

Houston, we have transition
 
Lillium state this is the first transition from hover to wing-borne flight for a full scale, all electric aircraft.

130Kmh, 1200fpm climb.
Transition occurs at 1:30 in the clip.

Mjb

Lonewolf_50 8th Jun 2022 12:13

mjb, as I watched the video, I wasn't sure if there was a person in the aircraft. Was that whole flight accomplished remotely?

CTR 8th Jun 2022 13:01


Originally Posted by Lonewolf_50 (Post 11242711)
mjb, as I watched the video, I wasn't sure if there was a person in the aircraft. Was that whole flight accomplished remotely?

All Lillium flights to date have been remote. This is due to both pilot safety and pilot mass. They have barely enough battery energy to fly, a pilotís mass on board would make it almost impossible to leave the ground.

mickjoebill 9th Jun 2022 23:07

Specs announced
 

Originally Posted by CTR (Post 11242742)
All Lillium flights to date have been remote. This is due to both pilot safety and pilot mass. They have barely enough battery energy to fly, a pilotís mass on board would make it almost impossible to leave the ground.

Latest video today from CTO Alastair McIntosh, states the range and power density. They apparently have confidence these specs can be achieved, a range of 250km empty operational and 175km max take off weight. They state with a run-on landing the range will increase ( as the hover landing phase uses more juice)

This is the most revealing video thus far, they outlined the finalised design of the production model.
As CTR states, the battery density of existing commercially available technology is a hurdle. In this video they claim new battery tech will deliver the stated range and a full payload, presumably full payload is a person in each seat?
In other videos they mention the production model will have 7 seats and 30 engines (The prototype is full scale 5 seater with 36 engines)
The engine guru states there will be a mechanical connection to adjust flow to optimise energy use between landing and cruise. (10x more energy required for the hover) This is a repeating theme with electric aircraft, hover phase is a means to an end, gas powered helicopters will rule slow orbit tasks until battery density is improved.


WillyPete 13th Jun 2022 08:55


Originally Posted by mickjoebill (Post 11243660)
Latest video today from CTO Alastair McIntosh, states the range and power density. They apparently have confidence these specs can be achieved, a range of 250km empty operational and 175km max take off weight. They state with a run-on landing the range will increase ( as the hover landing phase uses more juice)

To put it in perspective, this is almost the same range as our VW ID4 Life model. (Shorter range battery, less tax)


Originally Posted by mickjoebill (Post 11243660)
They state with a run-on landing the range will increase ( as the hover landing phase uses more juice)

What about take off?
I don't foresee these ever taking hold as rooftop delivery for pax, but on shorter controlled fields in well regulated air corridors.

A short takeoff could be assisted with a cable tow, similar to gliders, but may not be what passengers might appreciate.

Petit-Lion 13th Jun 2022 17:31

My take-away is: 9 times more power to hover than to cruise. A conventional helicopter is close to 1:1. It starts to worsen with tiltrotors. Then there are those oversized multicopter drones. Did Lilium chose the worst way to hover?

widgeon 13th Jun 2022 20:41


Originally Posted by Petit-Lion (Post 11245537)
My take-away is: 9 times more power to hover than to cruise. A conventional helicopter is close to 1:1. It starts to worsen with tiltrotors. Then there are those oversized multicopter drones. Did Lilium chose the worst way to hover?

https://aviation.stackexchange.com/q...-when-hovering
i don't think there is a helicopter that burns same fuel in hover as fwd flight ,I am sure ratio is much better than 9 to 1 though
.



Non-PC Plod 14th Jun 2022 19:53


Originally Posted by Petit-Lion (Post 11245537)
My take-away is: 9 times more power to hover than to cruise. A conventional helicopter is close to 1:1. It starts to worsen with tiltrotors. Then there are those oversized multicopter drones. Did Lilium chose the worst way to hover?

You are looking at it the wrong way - It has fixed wings , which is makes it much more efficient in the cruise than a helicopter. So, its not that it is inefficient hovering, it is instead more efficient in forward flight.

Mee3 15th Jun 2022 03:50


Originally Posted by Non-PC Plod (Post 11246137)
You are looking at it the wrong way - It has fixed wings , which is makes it much more efficient in the cruise than a helicopter. So, its not that it is inefficient hovering, it is instead more efficient in forward flight.

Rotors are wing surfaces. You'd be surprise how much lift they produce in forward flight.

Ascend Charlie 15th Jun 2022 05:43


Rotors are wing surfaces. You'd be surprise how much lift they produce in forward flight.
They are quite inefficient. The retreating blade is the limiting factor, with only around 40% of it producing useful lift, and at a high AoA with resultant drag.

The advancing blade has to throw away all that beautiful lift it gets from the added forward airspeed, to match the poor old retreating blade.

If both blades were advancing, lotsa lift both sides, no need to worry about retreating sides, hence the ABC test aircraft and Hokums and intermeshing tandems.

mickjoebill 15th Jun 2022 08:06


Originally Posted by WillyPete (Post 11245317)
To put it in perspective, this is almost the same range as our VW ID4 Life model. (Shorter range battery, less tax)



What about take off?
I don't foresee these ever taking hold as rooftop delivery for pax, but on shorter controlled fields in well regulated air corridors.

A short takeoff could be assisted with a cable tow, similar to gliders, but may not be what passengers might appreciate.

They only quote the run on landing in the context of flight endurance for certification for commercial flights.


Mjb

Mee3 15th Jun 2022 08:38

Dissymmetry lift is not 0 lift at retreating side and plus with multi blades also gets the benefit of multi wings instead of a pair. And rotorcraft limits 150kt Vne not only preventing shock wave but also to make sure retreating blade still plane air faster than relative air flow.

Powered flight always been dealing with dilemma of disproportion power requirement between MTOW and cruise. Compound design like lilium is one of those went physically challenged approach to this. If they resort to running takeoff, might as well venture into extreme STOL dropping the expensive vector thrust part. I predict first 10 years into the market operation will be limited from airfield of some sort instead of helipad. And a super STOL might even be a winner.

Ascend Charlie 15th Jun 2022 19:19


Dissymmetry lift is not 0 lift at retreating side and plus with multi blades also gets the benefit of multi wings instead of a pair. And rotorcraft limits 150kt Vne not only preventing shock wave but also to make sure retreating blade still plane air faster than relative air flow.
Never said it was 0 on the retreating side, just that the limit to the aircraft's lift generation is the retreating blade.

Be nice to have an advancing blade on each side, and not have to worry much about the retreater.

Petit-Lion 19th Jun 2022 18:09


And a super STOL might even be a winner.
Or a conventional helicopter... With these much-awaited (still non-existent) great batteries, right-sized motors... ground effect, translational lift, well-understood flight regimes...
And what about the very high nozzle velocity of those tiny fan-jets? Ultraclean FOD-free Lillipads?

Winemaker 19th Jun 2022 23:06

Endurance seems, to me, to be the big problem. With the much bigger power demand with a vertical landing and take off, a go-around would see to be a real deal breaker for certification. As for the machine(s) as extreme STOL, that seems to totally destroy the entire concept of their potential use as some sort of city air taxi. How did the New York rooftop helicopter flights turn out? Probably a good reference. I suspect their business case with the huge number of passengers is a bit off the mark....

Ascend Charlie 20th Jun 2022 02:36

Does their claimed range include 30 mins reserve? If not, why would CA$A approve them to operate with less reserve than a real aircraft?

Silver Pegasus 20th Jun 2022 16:28


Originally Posted by mickjoebill (Post 9378315)
Is this achievable if applying the specs of Tesla batteries of 5kilos per 1kWh? The Tesla modules themselves in an 85 kWh Model S are about 900 lbs. The other ~300 lbs is everything else for the pack.

Previously, the battery pack was 157-watt hours per kilogram in the 85kWh Model S, and in the new 100kWh Plaid it is 181.5-watt hours per kilogram.


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