VTOL On Demand Mobility


An interesting critical analysis of Joby's long term projections of building thousands of evtol's versus the reality of what they're telling local authorities. Here are 2 relevant quotes :

"Joby tells investors it will soon have many aircraft coming off the production line. However, local government files obtained through a public records request show that Joby seems to have massively overstated its production plans to investors. "

"Joby is telling local authorities that its initial plan “is to build up to 10 planes per year in the next couple of years, and up to 30 planes in about 5-7 years.” Joby has told investors it will manufacture over 100 planes in 2024."

So basically they are flat out lying to their investors. This video was posted previously, but it analyzes Joby's evtol project in great detail and points out some problems with it.


View: https://www.youtube.com/watch?v=a717YZnhQ-s&ab_channel=AVweb
 
This is one aspect of electric aviation that is never addressed.
Yes. The other aspect that is never addressed is the energy efficiency of these electric solutions (in kWh per seat-mile) against the appropriate alternative.

Aircraft are extremely weight sensitive by nature… perhaps it is actually better for the environment to fly with weight-efficient kerosene/SAF powered turbines rather than heavy batteries that lead to poor energy efficiency. Instead put those batteries in land based applications such as cars, buses and trucks.

And once you start comparing kWH per seat miles I’m pretty sure the entire eVTOL industry’s environmental claims fall down like a house of cards compared to electric cars already on the road today.
 
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And once you start comparing kWH per seat miles I’m pretty sure the entire eVTOL industry’s environmental claims fall down like a house of cards compared to electric cars already on the road today.
There's a German Prof doing this in a few papers. The appropriate comparison point is an IC powered supercar. Evtol is massive energy use per seat mile.
 
The specific disk load needs to be more than twice as high, this surly can"t be done with half the tip speed. You might increase the pitch angle for a fixed geometry rotor somewhat (it would help), but twice the disk load with less wing tip speed is surly impossible. Please note, the rear rotors have only two blades.

A starting noise of 45 db is incredible low, you could stand next to it and having a conversation by whispering.

Please correct me, but "lower rotor spin" sounds more like lower rpm to me.
Noise is to the largest extent a function of tip speed. I have heard a NASA acoustics guy claim it varies with the fifth (!) power of tip speed. If you can successfully tackle that, then lower down the list of priority there's noise deriving from the thickness of the blades, and blade vortex interaction.
So yeah, the biggest measure to control noise is to limit tip speed. Unfortunately for a given rotor diameter, this means lower RPM, which turns into higher torque, which turns into more motor mass.
Anyway, you are correct in stating that these eVTOLs likely have higher disc loading than your run of the mill helicopter. This doesn't mean that you can't get the thrust; it simply means you have to pump more power through the rotor to get it. As a matter of fact, for a given power, thrust will vary with the square root of discloading. The blades might be designed with more solidity (i.e., chord, or number of blades) to absorb the increased power.
 
That's not very different from what I wrote. A higher disk load will require higher tip speeds which might be partially compensated by a higher "pitch angle" (to quote myself). But even with more soldity (that what I ment with an higher pitch angle), I doubt, that this could compensate the two times higher disk load.

For reducing the tip speed, using more blades would also be helpfull, but the rear rotors here have just two blades (for turning them out of the wind at level flight), this will require higher tip speeds than a rotor with three or four blades.
 
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At least they're smart enough to go with a hybrid propulsion system instead of only relying on batteries. But even then, this project seems very ambitious for a tiny startup.
 

This is one aspect of electric aviation that is never addressed.
Ammonia. More exactly ammonia mixed with a little hydrogen to get more energy. Can't see any other solution for non co2 air transport.
 
 
Excellent news! Just what the aviation industry needs! Another eVTOL start-up... Anyway, for those who are interested, here's the usual and somewhat predictable headline -

Alef Aeronautics launches eVTOL flying car​


The all-electric composite Alef Model A has a 200-mile driving range, a 110-mile flight range and fits within existing urban infrastructure for driving and parking.

Taken from - https://www.compositesworld.com/news/alef-aeronautics-launches-evtol-flying-car

Attached is a picture but frankly, does it matter? It'll hardly get built but hey, if you're still reading; here it is.


(too cynical? Nah ;) )
 

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This is another major problem with Evtol's flying commercial services that isn't being discussed by these startups, the fact that these machines might not have enough reserve range to fly in bad weather due to the limitations of battery tech.
 
Wow, that is a shockingly low figure. I guess analysts are now starting to take things like certification hurdles and infrastructure development into account. Not that long ago you had sensational reports like this one that were projecting a global market of 30.8 billion by 2030.


Even Morgan Stanley is still projecting a 12 billion dollar global market by 2030. They famously said back in 2018 that by 2040 the UAM market would be worth $1.5 trillion.


I know I've brought this up before, but to me this feels like the Very light Jet bubble all over again, but on an even bigger scale.

 
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Infrastructures are gonna drive this market. There will be so much money to make in re-orienting (upside down in effect) city access from low dow to roof top as of today to roof top down to ground level that inevitably investors are going to poor money in.

IMOHO, the 100% EV idea is just a concept that will gradually be tuned down to more practical mode of operations. So, let's not be discouraged by the decreasing market projections. Those are not taking into account the variety of solutions for on-demand mobility.
 
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I've seen this morning that EVSTOL are coming to Paris next year and in time for deployement for the 2024 Olympic Games.
 
Infrastructures are gonna drive this market. There will be so much money to make in re-orienting (upside down in effect) city access from low dow to roof top as of today to roof top down to ground level that inevitably investors are going to poor money in.

IMOHO, the 100% EV idea is just a concept that will gradually be tuned down to more practical mode of operations. So, let's not be discouraged by the decreasing market projections. Those are not taking into account the variety of solutions for on-demand mobility.

I agree. I think what will happen is that some of these designs will enter service, but not in the large numbers so many analysts are confidently predicting. So the air taxi revolution that companies like Joby are counting on will not happen on the scale that they are hoping for. And that is a big issue because the business plans of many of these start ups depend on building these machines in large volumes in order to make a profit. So there will definitely be a bloodbath down the line with many of these companies either going out of business or being bought out by stronger rivals. However the low noise profile of these aircraft will help ease acceptance in many potential markets. But cranking these things out in large numbers at an affordable price point is going to be a massive challenge. Icon tried to do this with their A5 which was a much simpler aircraft to build and flopped badly.





Once the limitations of battery density become fully understood, I think there will be a transition to hybrid designs to solve the range issues. Rolls Royce is already preparing for this by developing a lightweight turbogenerator.

 
 
https://www.thetimes.co.uk/article/...ke-off-over-home-of-the-dam-busters-k6d5cxhmr (subscription or registration may be required)
Elstree, home to the film studios that spawned The Dam Busters and Star Wars, is to play host to something new: flying taxis that are expected to be criss-crossing city skies within the decade.

An aerodrome on the outskirts of the Hertfordshire suburb north of London is set to be used as a test bed for “urban air mobility”, becoming a base for two- to five-seater electric aircraft that take off and land vertically.

Elstree Aerodrome, close to the M1 and abutting Haberdashers’ independent schools, is understood to be the favoured location for the development of a “vertiport” for plug-in air vehicles.

[snip]
 
I still struggle somewhat to see the extra value of this eVTOL vs. a 25 year old H120, AW009 or a newer B505 that do the same or better while weighing half as much.

Especially with the possibility of developing a hybrid electric backup system to make single engine operations safer.
 
Me too. I don't understand why would eVSTOL succeed where classic helicopters failed in the 1950-1970's.

I mean: point-to-point flight from a city rooftop to another city rooftop (Pan Am building disaster 1977, cough cough).

Bottom line "hey, look, a flying taxi cab !"

What are eVSTOL advantages, compared to classic helicopters ?
- pollution ? ok, they are electric when helicopter use kerosene turbines that stink and emits CO2
- noise ? ok, rotors are noisy. But won't eVSTOL be noisy too ?
- more compact shapes ? less dangerous ? because the rotors are smaller and enclosed in tubes ? not sure about that.

Something else ?

The more I read about that eVSTOL thing, the less I understand the ongoing craze. Wait until the first eVSTOL falls from the sky like a led brick and makes a carnage on the pavement. Helicopters were banned from New York (and aircraft from flying over Paris) for that reason alone.
Sooner or later, this will happen to an eVSTOL. What will happen next ?
 
Not a fan of Archers landing gear fairings. They make it look very massive and not really sleek and fast.
 
Wait until the first eVSTOL falls from the sky like a led brick and makes a carnage on the pavement. Helicopters were banned from New York (and aircraft from flying over Paris) for that reason alone.

That’s the genius of the first route that Archer & United have chosen for their pilot. Newark to the Downtown Manhattan heliport is one of those magical unicorn routes that doesn’t require flying over any residential areas, mostly overwater and about as safe as you can find in any big city. (Ignoring snow, icing, summer thunderstorms, other aircraft and a few “small” risks).

True urban taxi ops will be a lot more complicated.
 
EVTOL has following potential advantages:
1. Noise: distributed propulsion enables greater design space than those limited by mechanicals
2. Operating Cost
- Trade mechanical complexity with electrical system complexity, which should be cheaper
- Wings
- Electrical operation when applicable, means low cost for amount of energy used
3. Safety: Distributed propulsion redundancy

I see hybrid EVTOL eating the helicopter market far before (decades) general flying taxis stuff. If the point of the helicopter is VTOL transport, EVTOL would be better, since helicopter is a poor configuration and only used because more efficient configuration has too much mechanical complexity, a lesser issue with electrical architecture. You'd only want helicopter if the point is to do things while hovering.
 

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