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 Post subject: Re: Lilium "Jet" flies
PostPosted: 29 Oct 2019, 09:16 
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I think that the timeline is around 3 years before it happens on a large scale. Is is coming, absolutely.

Will we be better for it? Absolutely, I'll be able to ride my bicycle with worrying about being flattened by someone texting in their car.

As of my last count I think that there are over 25 companies working on this now.

Remember when everyone thought we'd be in flying cars by 1997?


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 Post subject: Re: Lilium "Jet" flies
PostPosted: 30 Oct 2019, 00:16 
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Username Protected wrote:
I think that the timeline is around 3 years before it happens on a large scale. Is is coming, absolutely.

Will we be better for it? Absolutely, I'll be able to ride my bicycle with worrying about being flattened by someone texting in their car.

As of my last count I think that there are over 25 companies working on this now.


I think you are wildly optimistic on this. I am sure they will have a useable vehicle in 3 to 5 years, but solving all the other problems is going to take much longer. Think how long it took to certify SF-50, and that's a simple conventional jet. Now imagine how long it will take for FAA certify something for which they don't even have the rules to certify it under. Not to mention airspace usage rules, landing pad infrastructure, scheduling/boarding logistics, pilot training, weather contingencies, and of course the economics of operating all this profitably.

As for this reducing ground traffic congestion, that's just funny. On any given day, there are probably 50,000 taxi/uber cars roaming around Manhattan, and 5 times as many private cars. You think we gonna get 50,000 of these flying things up in the air to replace them?

My blood pressure goes up when I see 5 traffic targets while flying around Manhattan. You want to put 50,000, or even 5,000 up there and hope there won't be mid-airs? Granted, one day we will have the technology where these things will zip around safely under positive computer control with 50 ft separation. That technology is not there yet.


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 Post subject: Re: Lilium "Jet" flies
PostPosted: 30 Oct 2019, 06:21 
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Noise is what killed this very similar idea 60 years ago.

[youtube]https://youtu.be/dkJOm1V77Xg[/youtube]


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 Post subject: Re: Lilium "Jet" flies
PostPosted: 18 Dec 2019, 13:28 
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Making progress.

https://lilium.com/newsroom-detail/watc ... est-flight

Still a long way to go of course.


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 Post subject: Re: Lilium "Jet" flies
PostPosted: 10 Jun 2022, 15:52 
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I really think this design has a lot of potential.

36 ducted electric motors providing ample redundancy. Yes, small disc size reduces efficiency in vertical mode but the whole concept revolves around spending minimum time in vertical flight mode.

However, one of the biggest obstacles to widespread urban use of these aircraft is the noise they produce in the landing/takeoff phase. This aircraft is supposedly one of the most quiet of the crop of electric VTOL's.

This video purports to show the noise profile on landing but it seems they've greatly reduced the audio level on the video. I'd be a bigger fan (no pun intended) if they'd be more candid about the noise profile.

[youtube]https://youtu.be/8FK79N3TWEQ[/youtube]

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 Post subject: Re: Lilium "Jet" flies
PostPosted: 10 Jun 2022, 16:45 
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Username Protected wrote:
I really think this design has a lot of potential.

36 ducted electric motors providing ample redundancy. Yes, small disc size reduces efficiency in vertical mode but the whole concept revolves around spending minimum time in vertical flight mode.

However, one of the biggest obstacles to widespread urban use of these aircraft is the noise they produce in the landing/takeoff phase. This aircraft is supposedly one of the most quiet of the crop of electric VTOL's.

This video purports to show the noise profile on landing but it seems they've greatly reduced the audio level on the video. I'd be a bigger fan (no pun intended) if they'd be more candid about the noise profile.

[youtube]https://youtu.be/8FK79N3TWEQ[/youtube]


The small disc size reduces efficiency in ALL modes.

The electric aircraft designs that work will be ruthlessly efficient. Someone's going to win this race, but it ain't this horse.

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 Post subject: Re: Lilium "Jet" flies
PostPosted: 10 Jun 2022, 16:48 
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Yeah, that video is meaningless without some numbers to it. How far is provided. Now show me a DBa meter.

It's a cool concept. No idea of how practical it will be. It is certainly complicated.

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 Post subject: Re: Lilium "Jet" flies
PostPosted: 10 Jun 2022, 17:20 
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I’ve wondered about these startups, Especially the VTOL types. Since they are flying unmanned couldn’t the weight of passengers and baggage be simulated with batteries to make up a bit for the low capacity of current battery technology.

Then they could make longer test flights with all the transitions and testing needed. All weather. Hot cold etc.

When battery technology advances then the airframes, power systems (and software) would be well tested in all conditions with some real world time on them.

Unmanned testing is fine. You could push harder to test with no risk to test pilot or crew out in an open area.


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 Post subject: Re: Lilium "Jet" flies
PostPosted: 10 Jun 2022, 18:40 
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I seem to hear the same great music when I take off in my Bonanza -

NOTHING like a Bo

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 Post subject: Re: Lilium "Jet" flies
PostPosted: 11 Jun 2022, 14:12 
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Does anyone not have a good idea why Textron and Cessna aren’t introducing clean sheet light aircraft designs to market?

Yet, all the startups are introducing not only clean sheet based on proven technology, but clean sheet aircraft built with clean sheet (expensive) technology? What do they see that Cessna doesn’t. Or, better yet, how do the same economic realities that hold Cessna back not hobble these folks?

It’s obvious they think the same rules don’t apply to them. But…..there’s nothing in the FAR that suggests a 1,500 lb electric powered even remote piloted aircraft have different rules than a 1,500 lb traditional aircraft. So, how do we reconcile the differences? FAR 91, 121, etc aren’t meant to protect us, they’re meant to protect the public. So, unmanned, manned, piloted, remote, how does any of that matter from a regulatory perspective? Either we hold everyone to the same current rules, or we admit they’re archaic and we free up the traditional manufacturers to compete fairly and take the cost burdens off the shoulders of pilots having to pay for all the testing, etc that goes into a new product IN A CERTIFICATED AIRCRAFT these days.


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 Post subject: Re: Lilium "Jet" flies
PostPosted: 11 Jun 2022, 15:11 
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Username Protected wrote:
Does anyone not have a good idea why Textron and Cessna aren’t introducing clean sheet light aircraft designs to market?

Yet, all the startups are introducing not only clean sheet based on proven technology, but clean sheet aircraft built with clean sheet (expensive) technology? What do they see that Cessna doesn’t. Or, better yet, how do the same economic realities that hold Cessna back not hobble these folks?

It’s obvious they think the same rules don’t apply to them. But…..there’s nothing in the FAR that suggests a 1,500 lb electric powered even remote piloted aircraft have different rules than a 1,500 lb traditional aircraft. So, how do we reconcile the differences? FAR 91, 121, etc aren’t meant to protect us, they’re meant to protect the public. So, unmanned, manned, piloted, remote, how does any of that matter from a regulatory perspective? Either we hold everyone to the same current rules, or we admit they’re archaic and we free up the traditional manufacturers to compete fairly and take the cost burdens off the shoulders of pilots having to pay for all the testing, etc that goes into a new product IN A CERTIFICATED AIRCRAFT these days.

Older, established companies have lower risk appetite and are not going to "bet the farm" on a radically new technology.

Startups almost by definition are betting the farm. Or, more accurately, someone else's farm.

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 Post subject: Re: Lilium "Jet" flies
PostPosted: 11 Jun 2022, 17:47 
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Because the FARs are written in blood from lessons learned over many years. New designs seem to be ignoring these lessons. The new clean sheet designs from engineers and companies that have never built an airplane before will need the most testing. Do many current rules apply to a electric VTOL? Thats up to them to negotiate if they can prove a better way. I have not seen any progress that is even close to that point.

Without a large amount of accelerated service testing in all conditions it will be a long road to acceptance. The airframes, components and control software are just are not getting enough hours on them to identify weak points.

Right now would be the time to be doing drop tests, seat survivability for the new crash angles, service testing of motors and propellers in cold, hot, rain, icing. Testing of prototypes in wind, dust, dirt, lightning etc. Identify failure modes and how to survive them. 5 min flights will take a long time to test to a 1500 or 2000 hour service life.

Remember once you are flying in the highest time example every flight you are the new test pilot. Unknown conditions who wants to be the first?

I don’t see any of that yet other than hover and slow forward flights in perfect conditions.
If they can fly unmanned then it’s time to be aggressive with testing so they are ready when the main limitation (batteries) are improved.

Moller Skycar sucked development money for years with not much to show for it.

Here’s a good description of how it was done at Cessna. https://www.avweb.com/recent-updates/bu ... st-flying/

Even as far back as the Cessna 120 they flew day and night to get 1500 hours of service testing before releasing it.


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 Post subject: Re: Lilium "Jet" flies
PostPosted: 12 Jun 2022, 15:54 
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Older, established companies have lower risk appetite and are not going to "bet the farm" on a radically new technology.

Sure they do. See: Cessna Citation and Beech Starship. For both of those projects, they thought they had a reasonable chance of success.

Today's most advanced batteries carry less than 1/10th of the energy per kilogram that liquid fuels do. Until you fix that problem, the math just doesn't work. Period.

The physics for successful electric aircraft as transportation just aren't there yet, and Cessna, Beech et al have plenty of experienced engineers on staff to tell them so. It doesn't matter how much money you throw at Bernoulli, Maxwell and Newton - their laws are the same as they were 100+ years ago.

It's not an aviation design problem, it's a battery design problem.

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 Post subject: Re: Lilium "Jet" flies
PostPosted: 12 Jun 2022, 23:54 
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Older, established companies have lower risk appetite and are not going to "bet the farm" on a radically new technology.

Sure they do. See: Cessna Citation and Beech Starship. For both of those projects, they thought they had a reasonable chance of success.

Today's most advanced batteries carry less than 1/10th of the energy per kilogram that liquid fuels do. Until you fix that problem, the math just doesn't work. Period.

The physics for successful electric aircraft as transportation just aren't there yet, and Cessna, Beech et al have plenty of experienced engineers on staff to tell them so. It doesn't matter how much money you throw at Bernoulli, Maxwell and Newton - their laws are the same as they were 100+ years ago.

It's not an aviation design problem, it's a battery design problem.

The Citation wasn't radically new technology for Cessna. It was based heavily on their existing T-37 military trainer.

Beech already was producing twin turboprops. The Starship was a twin turboprop with some new aerodynamic and construction ideas. But at the end of the day, it's still a twin turboprop.

For sure electric aircraft are not going to compete with liquid fueled aircraft for medium to long-range missions in the foreseeable future. But the Lilium's success is predicated on short-range missions.
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 Post subject: Re: Lilium "Jet" flies
PostPosted: 13 Jun 2022, 08:31 
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The Citation wasn't radically new technology for Cessna. It was based heavily on their existing T-37 military trainer.

Beech already was producing twin turboprops. The Starship was a twin turboprop with some new aerodynamic and construction ideas. But at the end of the day, it's still a twin turboprop.

For sure electric aircraft are not going to compete with liquid fueled aircraft for medium to long-range missions in the foreseeable future. But the Lilium's success is predicated on short-range missions.


The market was radically new for Cessna, and the construction methods were radically new for Beech. It wasn't the propulsion that was new, it was the airframes. They took massive, huge risks to bring them to market. One worked, one almost sank the company. If next year's electric airplane technology could be used to build something that would sell, I promise you Cessna and Beech would be breaking ground on new factories right now.

The reason these small startups are aiming for short range is that's all they can do. And right now, short range electric aircraft are a solution in search of a problem. If we REALLY wanted short-range limited payload VTOL aircraft buzzing all over our cities, the sky would be dark with R22s. There just isn't a massive need for 30-50 mile two seat aircraft, no matter what you see in the pitch deck from the electric airplane company.

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