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Author Topic: VTOL On Demand Mobility  (Read 14977 times)

Offline Grey Havoc

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VTOL On Demand Mobility
« on: August 20, 2016, 04:22:32 pm »
Airbus is apparently getting in on the act, with a project called the CityAirbus Vahana. Via Gizmodo: http://www.airbusgroup.com/int/en/news-media/corporate-magazine/Forum-88/My-Kind-Of-Flyover.html

Quote
A3, the company’s innovation group located in Silicon Valley, said it is working on a project called Vahana—stemming from the Sanskrit word that means “that which carries.” The vehicle, being developed under the title CityAirbus, would have “multiple propellers and also resemble a small drone in its design.” It would be an alternative to regular land-bound taxis, that would cost just as much. The company apparently has been working on this since February of this year and hopes to test its first prototypes by the end of 2017.
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Offline CammNut

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Re: VTOL On Demand Mobility
« Reply #1 on: August 21, 2016, 10:16:44 am »
CityAirbus and Vahana are two separate projects. Vanaha is an A3 (Airbus Silicon Valley) project to develop a single-passenger autonomous VTOL aircraft, CityAirbus is an Airbus Helicopters project for a multi-passenger VTOL air taxi.

Offline Grey Havoc

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Re: VTOL On Demand Mobility
« Reply #2 on: January 17, 2017, 02:58:44 am »
Airbus is apparently getting in on the act, with a project called the CityAirbus Vahana. Via Gizmodo: http://www.airbusgroup.com/int/en/news-media/corporate-magazine/Forum-88/My-Kind-Of-Flyover.html

Quote
A3, the company’s innovation group located in Silicon Valley, said it is working on a project called Vahana—stemming from the Sanskrit word that means “that which carries.” The vehicle, being developed under the title CityAirbus, would have “multiple propellers and also resemble a small drone in its design.” It would be an alternative to regular land-bound taxis, that would cost just as much. The company apparently has been working on this since February of this year and hopes to test its first prototypes by the end of 2017.

R&D for VTOL personal transport seems to be fashionable these days  ::)

http://www.businessinsider.sg/airbus-air-taxi-uber-of-skies-2016-11/

https://electrek.co/2016/10/24/airbus-unveils-concept-autonomous-electric-vtol-aircraft/

"The vehicle program is called ‘Vahana’ and it is being developed by Airbus’ subsidiary (pronounced “A-cubed”) based in Silicon Valley. A³’s CEO, Rodin Lyasoff, was formerly a Lead Engineer for Flight Software and Simulation at Zee Aero, one of the electric aircraft startups financed by Page."

http://www.reuters.com/article/us-airbus-group-tech-idUSKBN1501DM
http://www.digitaltrends.com/cool-tech/airbus-test-flying-car/
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Offline Grey Havoc

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The sole imperative of a government, once instituted, is to survive.

Offline Grey Havoc

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Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #5 on: February 08, 2017, 12:03:23 pm »
Granted it's a flying taxi, but the Uber concept will not be roadable, so it's not a 'flying car' or 'roadable aircraft'. We should consider a new thread on VTOL On Demand Mobility.

DONE   ;)
« Last Edit: February 08, 2017, 10:13:56 pm by Jemiba »
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Offline Grey Havoc

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Offline VTOLicious

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Re: VTOL On Demand Mobility
« Reply #8 on: March 13, 2017, 03:24:36 am »
Urban mobility takes shape with Italdesign and Airbus’ Pop.Up




Offline Motocar

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Re: VTOL On Demand Mobility
« Reply #9 on: March 14, 2017, 03:14:46 pm »
The most serious thing that has is its origin "Airbus" remains in the concept of "Drone" and there a Chinese model takes them not much advantage the "EHang" shared since:
 http://www.segurocoche.com/el-coche-volador-puede-ser-una-realidad-a-finales-de-2017/


« Last Edit: March 14, 2017, 03:19:43 pm by Motocar »

Offline Reaper

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Re: VTOL On Demand Mobility
« Reply #10 on: March 16, 2017, 01:36:10 pm »
Agreed AeroFranz! ODM shorter range / slower Multicopter & faster / longer range VTOL aircraft.

Offline Grey Havoc

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Offline Reaper

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Re: VTOL On Demand Mobility
« Reply #12 on: April 25, 2017, 11:25:47 am »
Check the Uber Elevate Summit on live stream: https://www.uber.com/info/elevate/summit/

Highlights so far
Aurora Flight Sciences showed a 1/4 scale Personal Air Vehicle Prototype that they flight tested (incl. transition)


Offline mboeller

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Re: VTOL On Demand Mobility
« Reply #13 on: April 26, 2017, 06:54:58 am »
Lilium Jet from Germany:

https://lilium.com/

VTOL, electric, 300kmh, 300km range ... projected


video of the first flight of a 2seat prototype is available on the website

« Last Edit: April 26, 2017, 07:16:46 am by mboeller »

Online fredymac

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Re: VTOL On Demand Mobility
« Reply #14 on: April 26, 2017, 09:05:22 am »

Offline sferrin

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Re: VTOL On Demand Mobility
« Reply #15 on: April 26, 2017, 09:25:27 am »
Any relation between that Lilium Jet and Aurora's DARPA effort?  Are they close enough in design to cause a ruckus re. patent infringement?   ???
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Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #16 on: April 26, 2017, 10:10:27 am »
The concepts are pretty close, but Lilium carries the fans on the flaps to point them down, Aurora's tilts the entire wing.
One thing that the lilium video on their website does not show is full wingborne transition, which is tricky. I'm also kind of annoyed they call their ducted fans "Jets".
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Offline Sundog

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Re: VTOL On Demand Mobility
« Reply #17 on: April 26, 2017, 04:40:33 pm »
I'm also kind of annoyed they call their ducted fans "Jets".

Yeah, that was the first thing I noticed as well. It sure doesn't look like the Brayton Cycle to me. ;)

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #18 on: April 26, 2017, 07:15:02 pm »
They've also gone through several iterations. They've given up on that retractable canard which characterized the early concepts. I guess they realized that with the cg in the middle, and the wing in the back, they still need lift in the nose to make things work. Their latest iteration looks somewhat closer to the XV-24A.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #19 on: April 27, 2017, 04:59:02 am »
It seems to me that uncowled props/rotors in those positions would be a potential hazard, in ground handling terms.

Offline VTOLicious

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Re: VTOL On Demand Mobility
« Reply #20 on: April 29, 2017, 10:47:39 am »
It seems to me that uncowled props/rotors in those positions would be a potential hazard, in ground handling terms.

From the video it seems as if the entrance and exit is only planned from the front, requiring some kind of gangway.

Offline mboeller

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Re: VTOL On Demand Mobility
« Reply #21 on: April 30, 2017, 04:34:28 am »
Cartercopter teamed up with Mooney for their electric "UBER ELEVATE AIR TAXI CONCEPT" VTOL

Press Release:
http://www.cartercopters.com/system/sdocs/27/original/Carter%20Aviation%20Press%20Release%20-%202017-04-25%20-%20Uber%20Elevate.pdf?1493134124

unfortunately the links in the PDF still don't work. Jeff Lewis has sent me The Summit-Presentation. See attachment.

edit:  attachment deleted
link to the Cartercopter-Presentation:

http://www.cartercopters.com/system/sdocs/28/original/Carter%20Presentation.2017-04-25.Uber%20Elevate%20Summit%202.pdf?1493651657


« Last Edit: May 17, 2017, 11:23:41 am by mboeller »

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #22 on: April 30, 2017, 07:42:18 am »
It seems to me that uncowled props/rotors in those positions would be a potential hazard, in ground handling terms.

From the video it seems as if the entrance and exit is only planned from the front, requiring some kind of gangway.

indeed, the first iteration of Uber vehicles will operate from 'vertiports', which allows you to take advantage of some ground support equipment. Obviously any door-to-door service, which could theoretically land on unprepared surfaces like someone's backyard, would require a different layout. You'd probably want to put the rotors above reach of passengers.

@mboeller: thanks for posting the presentation!
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Offline TomS

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Re: Bell ultra light taxi
« Reply #24 on: January 09, 2018, 12:15:33 pm »
They really went out of their way to conceal any hint of the dynamic systems used in this concept.

Offline hesham

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Re: Bell ultra light taxi
« Reply #25 on: January 09, 2018, 02:09:09 pm »
Nice find RavenOne.

Offline Michel Van

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Re: Bell ultra light taxi
« Reply #26 on: January 09, 2018, 08:16:41 pm »
Video about this



Bells Homepage about "Air Taxi"
http://bellhelicopter.com/company/innovation/ces-2018

This let to wild Internet speculation  about Air Taxi drive system
going over "Blade Runner" and anti-grav units to oversized quadcopter
some sources like the Video above tell that Air Taxi is electrical power Helicopter
and Video on Bell homepage suggest it also automotive,
There is no pilot in that video and passengers not using the controls.
I love Strange Technology

Offline Orionblamblam

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Re: Bell ultra light taxi
« Reply #27 on: January 09, 2018, 09:17:02 pm »
They really went out of their way to conceal any hint of the dynamic systems used in this concept.

There's really only one logical system to consider:

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Offline Foo Fighter

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Re: Bell ultra light taxi
« Reply #28 on: January 09, 2018, 10:09:08 pm »
I can think of more than a few people who many would pay to see moved by this transport system.

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Re: Bell ultra light taxi
« Reply #29 on: January 10, 2018, 03:20:11 am »
I would think an electric helicopter would be more efficient than a giant electric quad/multi-copter.  A distributed lift electric hybrid that transitions to wing borne flight would beat that but for short hops across a city an electric helicopter might be adequate.



Offline galgot

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Re: Bell ultra light taxi
« Reply #30 on: January 10, 2018, 04:09:33 am »
 At Bell PR offices some time ago :
"- Boss, I have this genius idea to make a buzz,
We present a helicopter WITHOUT PROPELLERS" , imagine that !!!"
"- Bill, you just got promoted !"

Online fredymac

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Re: Bell ultra light taxi
« Reply #31 on: February 28, 2018, 03:15:50 pm »
Bell's hybrid electric urban taxi may actually include a tilt rotor configuration (50 second mark) while Airbus is going the quadcopter route.


Offline TomS

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Re: Bell ultra light taxi
« Reply #32 on: March 01, 2018, 07:24:48 am »
Not just tiltrotor.  It looks to be a pretty weird multi-rotor configuration -- the foreground aircraft appear to have stowed rotors on the mid-wing pods and along the tailboom. On the aircraft taking off in the background, those rotors seem to be spinning. 

Offline hesham

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Re: Bell ultra light taxi
« Reply #33 on: March 01, 2018, 07:33:30 am »
Nice beast,I never saw it.

Offline Moose

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Re: Bell ultra light taxi
« Reply #34 on: March 01, 2018, 07:54:13 am »
That Airbus design is basically DARPA's Ares, Son of Transformer, in civilian taxi form.

Offline AeroFranz

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Re: Bell ultra light taxi
« Reply #35 on: March 01, 2018, 10:28:33 am »
Bell's hybrid electric urban taxi may actually include a tilt rotor configuration (50 second mark) while Airbus is going the quadcopter route.



That's actually Uber's design. Bell hasn't unveiled its concept.
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Offline LowObservable

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Re: VTOL On Demand Mobility
« Reply #36 on: March 03, 2018, 05:24:01 am »
Has anyone else noticed that in robo-flying-taxi world, the weather is always perfect?

For the last few weeks, where I live, there hasn't been much decent visibility down at the level where these things are going to fly, except for the day of 50-knot winds. Call me a gutless ***** if you want, but the idea of riding a pilotless vehicle through cloud and heavy rain and ascending/descending through building heights, and knowing there's a bunch of other things whizzing around in the same airspace, sounds less than fun.

Offline Orionblamblam

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Re: VTOL On Demand Mobility
« Reply #37 on: March 03, 2018, 07:34:35 am »
Has anyone else noticed that in robo-flying-taxi world, the weather is always perfect?


Note that a *lot* of these things seem to be funded by/aimed at Abu Dhabi and similar. The likelihood of encountering rain or snow is pretty minimal... but I suspect sand and dust will do entertaining things to the system.
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Offline GTX

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Re: VTOL On Demand Mobility
« Reply #38 on: March 03, 2018, 10:21:26 am »
Note that a *lot* of these things seem to be funded by/aimed at Abu Dhabi and similar. The likelihood of encountering rain or snow is pretty minimal... but I suspect sand and dust will do entertaining things to the system.

Funnily enough though, my first time in Dubai it was raining quite heavily... ;D :o

Offline Orionblamblam

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Re: VTOL On Demand Mobility
« Reply #39 on: March 03, 2018, 10:24:42 am »
Note that a *lot* of these things seem to be funded by/aimed at Abu Dhabi and similar. The likelihood of encountering rain or snow is pretty minimal... but I suspect sand and dust will do entertaining things to the system.

Funnily enough though, my first time in Dubai it was raining quite heavily... ;D :o

Wait till the atomic firesharknados go storming through town.
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Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #40 on: March 03, 2018, 04:42:32 pm »
During Op Granby or as most folk called it Desert shied/storm there was some pretty extreme weather.  Hailstones the size of golf balls and bigger that smashed trailer accommodation used by some of us.

Offline Bgray

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Re: VTOL On Demand Mobility
« Reply #41 on: April 01, 2018, 08:41:25 pm »
The technology looks very pretty--but how much work has been done on regulations for flying? I mean, there are 13,587 yellow cabs, not counting uber and other such services.  In order to make the tiniest dent in traffic, to sell it as it's being sold, as transport for normal peole instead of hte ultra wealthy, you're likely talking several thousand of these flyers over any given major metropolitan area.

So it seems to me that building a flyable model is, while important, not the greatest challenge here.

Offline PaulMM (Overscan)

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Re: VTOL On Demand Mobility
« Reply #42 on: April 01, 2018, 10:50:50 pm »
Has anyone else noticed that in robo-flying-taxi world, the weather is always perfect?

For the last few weeks, where I live, there hasn't been much decent visibility down at the level where these things are going to fly, except for the day of 50-knot winds. Call me a gutless ***** if you want, but the idea of riding a pilotless vehicle through cloud and heavy rain and ascending/descending through building heights, and knowing there's a bunch of other things whizzing around in the same airspace, sounds less than fun.

Ultimately your visibility is meaningless - the premise is total automation, centrally monitored and controlled. You don't have any need to see anything as you don't get control anyway.
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Offline yasotay

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Re: VTOL On Demand Mobility
« Reply #43 on: April 02, 2018, 06:02:12 am »
No doubt the initial efforts will be "day/VFR".  If demand dictates the investment will show up to continue to refine the less optimum flying conditions.  I imagine if it does not become a red herring it will follow the normal investment strategies.

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #44 on: April 02, 2018, 08:20:31 am »
The weather issue is a problem. I imagine hail would wreak havoc with fans and propellers.
However, most of these concepts are short range, with flight times in the order of 15-20 minutes. You can reasonably predict what the weather will be like by the time you're in flight or ready to land. If it is turning really ugly, you simply don't takeoff and find some alternate ground transportation. Not ideal, but not a safety issue either.
With the longer-ranged machines, it's a different story, but i guess no different than what GA aircraft deal with.
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Offline TomS

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Re: VTOL On Demand Mobility
« Reply #45 on: May 09, 2018, 05:22:11 am »
More pictures of Uber's proposed "aerial taxi" aircraft -- different from the glimpses seen before.

Electrically powered, stacked rotors, initially with a human pilot, unmanned later.

They're talking about "skyports" with up to 200 departures per hour -- less than 20 seconds between departures -- which seems absurdly optimistic. 

« Last Edit: May 09, 2018, 05:28:03 am by TomS »

Offline sferrin

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Re: VTOL On Demand Mobility
« Reply #46 on: May 09, 2018, 05:49:31 am »
One wonders why this would be anymore likely to succeed than helicopters on skyscrapers that were all the rage back in the day.
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Offline Jemiba

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Re: VTOL On Demand Mobility
« Reply #47 on: May 09, 2018, 06:21:52 am »
Indeed, this design somehow lacks the look of simplicity, we are used to from other designs,
which are shown just as a passenger cabin with a big quadrocopter.

One wonders why this would be anymore likely to succeed than helicopters on skyscrapers ...

IF those companies, that started into this new business at least partly achieve their goals, the reason
simply will be greatly reduced costs for short range air travel.

My own scepticism about the whole eVTOL hype was somewhat lessened due to a talk with a guy at the
CityAirbus booth on the ILA. He compared this development  with that of the good old car. There were
nearly 30 years, before the car developed into a means of transportation, that not only the rich could afford.
And that means, that VTOL On Demand still has to reach the level of Carl Benz very first car !
It takes a long time, before all mistakes are made ...

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #48 on: May 09, 2018, 07:10:37 am »
cost  ;)

And capital incentive.

Modifying mass transportation involves new infrastructure, investment and capital. There are way much more to expect in term of RoI with the impact of relocating part of our transportation means from low to high ground in the real estate industry and banks than with the system itself.

Today, Uber announced a partnership with the US army to co-develop silent rotors, just to make sure that various interests will collide (and benefits) in that vision.

On the design shown yesterday, I am on the opinion that there are numerous interesting idea but a general lack technical expertise to refine the concept. Obviously a general impression only.

 
« Last Edit: May 09, 2018, 07:28:39 am by TomcatViP »

Offline martinbayer

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Re: VTOL On Demand Mobility
« Reply #49 on: May 09, 2018, 07:16:42 am »
More pictures of Uber's proposed "aerial taxi" aircraft -- different from the glimpses seen before.

Electrically powered, stacked rotors, initially with a human pilot, unmanned later.

They're talking about "skyports" with up to 200 departures per hour -- less than 20 seconds between departures -- which seems absurdly optimistic.

Make that "uber optimistic" ;D...

Martin
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Offline hesham

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Re: VTOL On Demand Mobility
« Reply #50 on: May 09, 2018, 08:06:21 am »
Nice find Tom.

Offline TomS

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Re: VTOL On Demand Mobility
« Reply #51 on: May 09, 2018, 08:17:51 am »
Can't claim too much credit.  The pics are all over the media today.

https://www.theverge.com/2018/5/8/17330524/uber-flying-car-elevate-prototype-la


Offline sienar

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Re: VTOL On Demand Mobility
« Reply #52 on: May 09, 2018, 11:35:59 pm »
More pictures of Uber's proposed "aerial taxi" aircraft -- different from the glimpses seen before.

Electrically powered, stacked rotors, initially with a human pilot, unmanned later.

They're talking about "skyports" with up to 200 departures per hour -- less than 20 seconds between departures -- which seems absurdly optimistic.

I wonder what sort of range they are shooting for. Retracting rotors must mean something longer than city center to suburbs.

Offline wizz33

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Re: VTOL On Demand Mobility
« Reply #53 on: May 10, 2018, 12:30:25 am »
here is a video of a conference on Transformative VTOLs  Workshop

www.youtube.com/user/HeloSociety/videos?disable_polymer=1

Offline TomS

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Re: VTOL On Demand Mobility
« Reply #54 on: May 10, 2018, 03:27:19 am »
Uber white paper on the UberAir concept, including some very high level discussion of vehicle design.

The illustrated design above does not seem to be discussed.  It's described elsewhere as a reference design, with actual air vehicle designs being different.
« Last Edit: May 10, 2018, 05:40:30 am by TomS »

Offline TomS

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Re: VTOL On Demand Mobility
« Reply #55 on: May 10, 2018, 12:53:51 pm »
One of the possible UberAIR partners is Karem Aircraft, with the Butterfly quad tiltrotor.

https://techcrunch.com/2018/05/08/uberair-adds-another-flying-taxi-partner/

Quote
Now, Karem is able to do what people previously thought was impossible, Karem said. The Butterfly (rendered above) is a quad tiltrotor with four large rotors mounted on the wings and tail. The idea is to combine the vertical lift capability of a helicopter with the speed and range of a fixed-wing aircraft. The Butterfly is also designed to be more efficient as a result of its rotors with variable RPM.

“Variable RPM allows us to maintain good efficiency across a wide range of rotor thrust,” Karem Aircraft CEO Ben Tigner told me.

Three parameters that Uber is talking about for its air taxi candidates.

  • Speeds of up to 200 mph
  • Range up to 60 miles on a single charge
  • Cruising altitude 1,000-2,000 feet above ground



Online fredymac

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Re: VTOL On Demand Mobility
« Reply #56 on: July 17, 2018, 02:46:36 am »
Another entry.


Offline mboeller

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Re: VTOL On Demand Mobility
« Reply #57 on: September 17, 2018, 03:18:39 am »
Cartercopter has updated their Air Taxi concept:

http://www.cartercopters.com/ehat_45.html 



They have two new PDF on the website about the new concept:

eVTOL:  http://www.cartercopters.com/pdfs/Carter_Electric_Air_Taxi.pdf

hybridVTOL:  http://www.cartercopters.com/pdfs/Carter_Hybrid_Electric_Air_Taxi.pdf

the eVTOL version seems to be extremly quiet at ~75 EPNdB at take off and ~70 EPNdB during overflight

upps; forgot the press release:
http://www.cartercopters.com/system/sdocs/2018/Carter_Aviation_Press_Release_2018-08-28_Updated_Air_Taxi_Concept.pdf
« Last Edit: September 17, 2018, 03:24:03 am by mboeller »

Offline hesham

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Re: VTOL On Demand Mobility
« Reply #58 on: September 17, 2018, 06:00:50 am »
Amazing find Mboeller.

Offline LowObservable

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Re: VTOL On Demand Mobility
« Reply #59 on: September 18, 2018, 05:11:25 am »
An autogyro is actually the least crazy solution for urban VTOL, with few noisemakers, a reasonably efficient cruise mode and inherent power-off vertical recovery.

But there's one big issue - rotor diameter. You're going to need a lot of take-off-and-landing space to handle the traffic volume that the system needs to function economically, let alone make a dent in urban congestion. (I don't think any conceivable system will actually do the latter.)

Also, note that the optimum cruise speed is in the conventional autogyro range, rather than being much faster as Carter originally planned.
« Last Edit: September 18, 2018, 05:21:38 am by LowObservable »

Offline sferrin

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Re: VTOL On Demand Mobility
« Reply #60 on: September 18, 2018, 05:51:49 am »
An autogyro is actually the least crazy solution for urban VTOL, with few noisemakers, a reasonably efficient cruise mode and inherent power-off vertical recovery.

But there's one big issue - rotor diameter. You're going to need a lot of take-off-and-landing space to handle the traffic volume that the system needs to function economically, let alone make a dent in urban congestion. (I don't think any conceivable system will actually do the latter.)

Also, note that the optimum cruise speed is in the conventional autogyro range, rather than being much faster as Carter originally planned.

And they either need a runway or motor/tip-jets to run up the rotor.
"DARPA Hard"  It ain't what it use to be.

Offline LowObservable

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Re: VTOL On Demand Mobility
« Reply #61 on: September 18, 2018, 04:32:49 pm »
Electric motor for spin-up. Simples!


Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #62 on: September 19, 2018, 06:50:10 am »
Some kitplanes have hydraulic motors. I suspect the high inertia rotors require quite a bit of torque to spin up.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline mboeller

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Re: VTOL On Demand Mobility
« Reply #63 on: November 05, 2018, 06:25:37 am »
another interesting eVTOL Aircraft with fixed wing economics:

https://www.pterodynamics.com/transwing/


Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #64 on: November 05, 2018, 06:34:21 am »
not too bad, not new and quiet hard to make it usable in flight

Offline yasotay

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Re: VTOL On Demand Mobility
« Reply #65 on: November 05, 2018, 07:29:01 am »
Brings new meaning to the term "tilt-wing"

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #66 on: November 05, 2018, 02:51:50 pm »
the wing hinge is going to be quite something.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline Arjen

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Re: VTOL On Demand Mobility
« Reply #67 on: November 06, 2018, 01:13:53 am »
It should be similar to the Grumman hinge:
Quote
Many laborious hours were spent over sketches and with models trying to figure out a way to twist the wings to a vertical position and then fold them back along the fuselage. Finally, Roy Grumman, a fine engineer, found the steps. He saw in all probability that the solution revolved around a pivot. So he took a soap eraser, such as those used in drafting, and used that to represent the fuselage of the plane. Then he took two paper clips for the wings and bent out the short end of each of the clips so that it was normal or perpendicular to the body of the clip. Then he began sticking these short ends into the eraser until he found the proper angle and position at which the clip, when twisted to a vertical position, would also fold back snugly against the eraser. Eureka! It was as simple as that. Once the principle of the “STO-Wing” (as it came to be called) was established, all that remained was some hard engineering work by Grumman’s fine team of engineers to make the mechanism strong and fail-safe.
The STO-Wing was applied to the Wildcat, the Hellcat and the TBF Avenger. The Grumman foldingwing is still in use today, notably on the larger carrier-based aircraft built by Grumman.
https://www.asme.org/wwwasmeorg/media/ResourceFiles/AboutASME/Who%20We%20Are/Engineering%20History/Landmarks/238-Grumman-Wildcat-Sto-Wing-Wing-folding-Mechanism.pdf
Award found here:
http://heroicrelics.org/info/grumman-paperclip/paperclip.html
« Last Edit: November 06, 2018, 01:24:33 am by Arjen »

Offline Jemiba

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Re: VTOL On Demand Mobility
« Reply #68 on: November 06, 2018, 01:48:41 am »
Came to my mind, too, but I think, that relatively few Grumman aircraft ever folded
their wings back in flight ....  B)
It takes a long time, before all mistakes are made ...

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Re: VTOL On Demand Mobility
« Reply #69 on: November 06, 2018, 01:51:13 am »
Not intentionally  ;D

Offline Harrier

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Re: VTOL On Demand Mobility
« Reply #70 on: November 06, 2018, 02:20:58 am »
An autogyro is actually the least crazy solution for urban VTOL, with few noisemakers, a reasonably efficient cruise mode and inherent power-off vertical recovery.


Yes. I once gave a talk at RR Bristol. I asked if train or car was best to get there. They said the speaker last month flew himself in his own autogyro..... :-[
« Last Edit: November 06, 2018, 02:22:31 am by Harrier »
BAe P.1216 Supersonic ASTOVL Aircraft: www.harrier.org.uk/P1216.htm

100 Years  - Camel, Hurricane, Harrier: www.kingstonaviation.org

Offline Zootycoon

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Re: VTOL On Demand Mobility
« Reply #71 on: November 06, 2018, 07:18:18 am »
With all the gyroscopic’s, airloads etc calculating the hinge loads & moments (both static and dynamic) will be fun, not impossible but extremely unforgiving.

Offline galgot

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Re: VTOL On Demand Mobility
« Reply #72 on: November 06, 2018, 10:49:19 am »
Video of the rc model with transitions e all, very cool.
https://www.youtube.com/watch?time_continue=85&v=YcXCCLrB7Ss

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #73 on: November 06, 2018, 12:07:20 pm »
That they scale it up and then I might eat my hat. But...

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #74 on: November 06, 2018, 06:58:44 pm »
Indeed, many things that are "demonstrated" at the RC level do not scale up.
Even full scale vehicles can fly when carrying smaller amounts of batteries, and have very little range.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #75 on: November 07, 2018, 02:37:28 am »
In my humble opinion, pure battery electric vehicles are a blind alley.  Developed on the back of a knee jerk reaction mostly by politicians and dreamers.  Hydrogen and fuel cell tech would reduce the weight of battery components and provide a real solution for car, planes, anything.  Why we continue to faff with pure battery tech I do not know.  Question, how are we going to deal with recycling the number of batteries required for this failure to think in a joined up manner?  Will we have to deal with environmental disasters like we potentially could with nuclear waste?

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #76 on: November 07, 2018, 08:40:36 am »
Rhetoric question - How long have hydrogen fuel cells existed for, and how many successful airplanes are flying them?
 
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline Machdiamond

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Re: VTOL On Demand Mobility
« Reply #77 on: November 07, 2018, 02:40:19 pm »
In my humble opinion, pure battery electric vehicles are a blind alley.  Developed on the back of a knee jerk reaction mostly by politicians and dreamers.  Hydrogen and fuel cell tech would reduce the weight of battery components and provide a real solution for car, planes, anything.  Why we continue to faff with pure battery tech I do not know.  Question, how are we going to deal with recycling the number of batteries required for this failure to think in a joined up manner?  Will we have to deal with environmental disasters like we potentially could with nuclear waste?

(aero engineer working on battery powered airplanes here)

As far as cars are concerned, hydrogen is not a viable alternative to battery powered vehicles from practical, economical and environmental standpoints. I recommend you check this excellent documentary:

Hydrogen cars are already dead (or as Trump would put it, they are a total disaster). You still see a few around because of politics and lobbies. Some groups of people really don't like the idea that you could refuel your car almost (comparatively) for free at home each night.

For airplanes, battery technology is not quite there yet except in some special cases - like VTOL on demand mobility (hey we are staying on topic!) and short range small aircraft such as trainers. While it is only a matter of a few more years before it gets to short haul regionals and freighters - it will be a very long time before it gets to medium to long haul carriers.

As aircraft fuel, Hydrogen has been promising and beaten to death for 30-40+ years and all engine and aircraft manufacturers have given up.

As far as recycling is concerned, you are misinformed. Well designed batteries such as those manufactured by Tesla are 100% recyclable and economically self sustaining due to the high cost of raw materials and due to the original design intent for recycling (unlike many recycling industries). They are also designed to last many years, unlike cellphone batteries.

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #78 on: November 08, 2018, 03:06:48 am »
Thanks for that, always willing to find out what I am missing.  Not an entirely balanced view but much food for thought.  It is interesting to note that the orator suggests hydrogen may make sense for aircraft.

Offline Zootycoon

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Re: VTOL On Demand Mobility
« Reply #79 on: November 08, 2018, 02:23:04 pm »
There’s a widely held belief that the automotive sector will push battery technology to the point that a high energy/power density becomes available.

But this belief is flawed.

The U.K. ATI battery technology road map (as presented at Warwick Uni in May) highlights the flaw. It shows a near term push for a lithium battery technology which will enable a 450-500 mile charge range for a  car (base on the max expected while awake) and a six hour recharge time. Once achieved, the target becomes reduceing cost and the imperative will be moving away from lithium because there’s simply not enough of it. Presently the favourite for a lithium replacement is sodium which is inherently at a lower energy density, but greatly improved availablity and much lower cost.

Of course there maybe be a breakthrough but equally the high energy/power density battery but it could become the next cold fusion.

I too was recently involved in a full size electric twin seat TMG, and it’s very different doing the real thing compared to CGI and model aeroplanes;- just where did all that extra weight come from? the drag is much more than the vsaero predict, even “safe” battery chemistry suddenly have AD’s for random  fires, just how do I protect the occupants from all that lithium in the event of a drama?

As to current batteries being ok for e-vtol? Wingless proposals, not a snowball in ....chance. Winged proposals;-well it’s strange I can only make the claimed performance match the best case weight/optimistic drag is to use a 2d range flight profile;- even a modest assumption for delta altitude during the profile  burns the claimed performance to ash.

E-vtol jet with wings = highly loaded fans =megawatt motors/PE/battery power density in an exceptionally lightweight airframe = fraud.

And finally when I look at Uber’s specified day to day useage profile, with current battery C rating, the  thing will need a brand new 100k$ battery every month...... like that’s going to be practical.

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #80 on: November 09, 2018, 02:41:28 am »
What I miss most is a joined up logic when it comes to clean energy.  Those who promote pure electric do not account properly for the production and shipping of gas for power stations for example.  Add to that the huge pollution from marine diesels in for example, supertankers.  For some time aviation has promoted clean aviation fuel but that has gone on the back burner for all the news there has NOT been.  Apparently Virgin are pushing/investing in clean aviation fuels but also very quiet now.  Apparently a source of pollution more impactful than the vehicles, animal farming.  All that fart gas has to go somewhere.

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #81 on: November 09, 2018, 03:43:40 am »
For some time aviation has promoted clean aviation fuel but that has gone on the back burner for all the news there has NOT been.  Apparently Virgin are pushing/investing in clean aviation fuels but also very quiet now.  Apparently a source of pollution more impactful than the vehicles, animal farming.  All that fart gas has to go somewhere.

Methane and fuel cells are your friends.  Gentlemen... fart your engine.*

And most importantly it take away gases that would damage the bio-sphere before they can be harmful; and that on a cost-efficient way (states with clever ecological policies use to subsidize the removal of methane gas; hence removing it and using the harvested quantities to clean power a vehicle has a double effect on the level of harmful emissions... a double treat also for the taxpayer). 


*the level of discussion was too good - thank you to the above posters - for someone not reasonably attempting to ruin it
« Last Edit: November 09, 2018, 07:35:10 am by TomcatViP »

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #82 on: November 11, 2018, 04:04:00 am »
How about a high flying drone/satellite powered by recycling the atmosphere?  A possible method of cleaning the air AND cheaper communications etc.

Offline VTOLicious

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Re: VTOL On Demand Mobility
« Reply #83 on: November 12, 2018, 12:40:02 am »
...
E-vtol jet with wings = highly loaded fans =megawatt motors/PE/battery power density in an exceptionally lightweight airframe = fraud.
...

Lilium?  ::) https://lilium.com/technology/

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #84 on: November 12, 2018, 04:41:12 am »
A very pretty presentation but, where is the discussion on range and recharge?

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #85 on: November 12, 2018, 06:08:24 am »
Startup for dummies, rule One:
   - Take a problem
   - Simplify it
   - resolve the simplified case
   - Use marketing to claim you solved the problem
....
 
Rule 1bis:
 In case of failure:
   - restart
   - reload
   - repackage

....

Rules 1 (i_th iteration):
    - Insist!
« Last Edit: November 12, 2018, 07:02:21 am by TomcatViP »

Offline elmayerle

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Re: VTOL On Demand Mobility
« Reply #86 on: November 12, 2018, 10:55:16 am »
Indeed, many things that are "demonstrated" at the RC level do not scale up.
Even full scale vehicles can fly when carrying smaller amounts of batteries, and have very little range.
Ejector lift for vtol comes to mind.  Neither the XV-4A nor the XFV-12A ever managed to make the full-scale article work, despite successful sub-scale deomstrations.

Offline Zootycoon

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Re: VTOL On Demand Mobility
« Reply #87 on: November 12, 2018, 11:32:02 am »
Also no discussion on battery power density, C rating, L/D at 300kph cruise, weight of megawatt rated power electronics, weight of 300kph bird strike protection on airframe, weight of ice/rain/hail protection,  weight of crashworthness, crosswind limit, lightening strike protection, wing bending stiffness mismatch between wingborne & vertical flight.....to mention a few.

Fundamentally an e-vtol Jet has only a tiny fraction of the fan area of a helo or quad cop so has to compensate by giving the air much more acceleration, hence it needs very high rotational speed on the fans = megawatt power draw. And they claim this is really quiet;- Try overdriving the biggest electric garden leaf blower by a significant factor and then power up another eleven! yeah it’s going to be real quiet.

Offline Archibald

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Re: VTOL On Demand Mobility
« Reply #88 on: November 12, 2018, 09:38:12 pm »
Lithium sucks, indeed, since the Chinese have most of it and hold the rest of the world at ransom. But sodium, really ? that thing is a bastard, just ask the nuclear industry (hello, Superphoenix, Monju and Clinch River). Corrosive, flammable, reactive, explosive... what's not to like ?  :o
No need for fuel cells, folks. What we need is ammonia IC cars. Ammonia has zero carbon, the fertilizer network already in place, and, most importantly, any plain old IC engine can be modified from gasoline to ammonia pretty easily. All of this also applies to methanol, minus the carbon-free aspect.
Even if it has half the energy of gasoline, an ammonia car range would remain far, far better than any electric car. Or the technology used to make ultra light and ultra efficient electric cars... could be used for an ammonia IC car, beating lithium batteries into a pulp.
Unfortunately, ammonia for cars is like hydrogen peroxide for rockets: its (supposed) safety  issues are completely overblown (toxicity, my ass: isn't gasoline dangerous if you smoke a cigarette, breath the exhaust, or try to drink it ? common...)

Heck in the 60's they made studies of ammonia and methanol fuel aircrafts and helicopters. The US Army had a grandiose project: portable, mobile nuclear reactors to split nitrogen from air and hydrogen from water and recombine that into ammonia to replace gasoline. And then... screw you, Saudi Arabia.
The usual jet or turbine could be converted to ammonia but the aircraft performance would take a big hit. Still far more realistic than any E-VTOL or electric aircraft.

As for hydrogen cars, being a space nerd since the craddle, I can tell you, they are a folly. Handling of liquid hydrogen is a complete and giant PITA, something that really can't be folded into your daily gas station. Unless you turn it into a miniature Cape Kennedy Launch complex, as far as drastic safety rules go. Plus the silly thing has 2.5 times the tank volume of gasoline, methanol or ammonia.
« Last Edit: November 12, 2018, 09:52:42 pm by Archibald »
Conservatoire de l'Air et de l'Espace d'Aquitaine
http://www.caea.info/en/plan.php

Profanity: weaker mind trying to speak forcefully

Political correctness: just bury your head in the sand for the sake of appeasement and "peace for our time"
- https://fr.wikipedia.org/wiki/Serge_Dassault#Affaires_

Offline Archibald

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Re: VTOL On Demand Mobility
« Reply #89 on: November 12, 2018, 10:01:02 pm »
another interesting eVTOL Aircraft with fixed wing economics:

https://www.pterodynamics.com/transwing/



As an aviation nerd, I'm horrified by this thing. Just look at it this way: an electric powered, V-22 Osprey with many more failure modes, all over the design... and mass produced, and flying all over our heads in an urban environnement.
Ah, and asymetric with that !  :(

Repeat that, twice. Then check the V-22 Osprey flaws and abysmal safety records. Can't fly through dust, the washdown big issue, those things. Yeah. What could possibly go wrong ? ah, and Uber want to eliminate the pilot later. WTF ?  ::)
« Last Edit: November 12, 2018, 10:04:31 pm by Archibald »
Conservatoire de l'Air et de l'Espace d'Aquitaine
http://www.caea.info/en/plan.php

Profanity: weaker mind trying to speak forcefully

Political correctness: just bury your head in the sand for the sake of appeasement and "peace for our time"
- https://fr.wikipedia.org/wiki/Serge_Dassault#Affaires_

Offline Machdiamond

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Re: VTOL On Demand Mobility
« Reply #90 on: November 13, 2018, 06:28:01 am »
The biggest problem I see with the Pterodynamics concept is that for proper stability in forward flight, the center of gravity needs to be near the quarter chord of the wing. This means that in a hover the two rear propellers are not allowed to provide any thrust or else the vehicle will flip forward instantaneously. So you end up with twice the thrust capability in horizontal flight than you have in vertical flight, while it should be the other way around.

With a few exceptions, most of the eVTOL projects do not pass the smell test of a sixth grade school science project and yet some manage to attract millions in investment from large corporations.

I wouldn't go as far as calling this fraudulent, I see more a bunch of enthusiasts who should know better but investors should certainly make a bit more due diligence, if at all.

Offline VTOLicious

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Re: VTOL On Demand Mobility
« Reply #91 on: November 13, 2018, 06:58:21 am »
The biggest problem I see with the Pterodynamics concept is that for proper stability in forward flight, the center of gravity needs to be near the quarter chord of the wing. This means that in a hover the two rear propellers are not allowed to provide any thrust or else the vehicle will flip forward instantaneously. So you end up with twice the thrust capability in horizontal flight than you have in vertical flight, while it should be the other way around.

With a few exceptions, most of the eVTOL projects do not pass the smell test of a sixth grade school science project and yet some manage to attract millions in investment from large corporations.

I wouldn't go as far as calling this fraudulent, I see more a bunch of enthusiasts who should know better but investors should certainly make a bit more due diligence, if at all.

I have learned that the Transwing has batteries installed in the outer nacelles. Therefore the CG moves rearwards as soon as the wings fold and the center of thrust matches with the CG in hover.

However, I'm not sure if this concept scales up well... Did you see the video showing the seamless in / outbound transition of the subscale model? Pretty impressive!


« Last Edit: November 13, 2018, 07:08:09 am by VTOLicious »

Offline Orionblamblam

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Re: VTOL On Demand Mobility
« Reply #92 on: November 13, 2018, 09:42:12 am »

With a few exceptions, most of the eVTOL projects do not pass the smell test of a sixth grade school science project and yet some manage to attract millions in investment from large corporations.

I wouldn't go as far as calling this fraudulent, I see more a bunch of enthusiasts who should know better but investors should certainly make a bit more due diligence, if at all.

Replace "eVTOL" with a number of other concepts over the years, and your statement is timeless. Rather more prevalent than eVTOL right now is "system to create drinking water from thin air."
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Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #93 on: November 13, 2018, 09:46:06 am »
Make that single malt whisky and you may have a winner.

Offline Orionblamblam

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Re: VTOL On Demand Mobility
« Reply #94 on: November 13, 2018, 10:43:53 am »
Make that single malt whisky and you may have a winner.

A system to create drinking water from single malt whisky? Or an eVTOL that uses whisky in a chemical fuel cell?
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And so the endless circle of life comes to an end, meaningless and grim. Why did they live, and why did they die? No reason. Two hundred million years of evolution snuffed out, for in the end Nature is horrific and teaches us nothing

Offline TomS

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Re: VTOL On Demand Mobility
« Reply #95 on: November 13, 2018, 10:48:29 am »
Make that single malt whisky and you may have a winner.

A system to create drinking water from single malt whisky?

I can do that, as long as you don't mind processing the water from urine...


Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #96 on: November 13, 2018, 12:20:51 pm »
Single malt whisky from thin air, you can process ur-own.

Offline Zootycoon

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Re: VTOL On Demand Mobility
« Reply #97 on: November 13, 2018, 01:42:06 pm »
I reckon certain e-vtol projects resemble Ponzi schemes. Here’s how it works;-

A group of naive youngsters, maybe a few older nefarious individuals insist that a mixture of start up mentally/nano-technology/quantum/agility/electricifcation/additive manufacturing/an I-phone has solved a problem which has foxed generations before hand, let’s say it’s a scheme to get talented folk from the middle of Paris to the middle of London in 40 mins. They make a CGI, you know the tech that has made donkeys talk and look intelligent. Clueless investors (A) is taken in and flips them a mill. The youths claim they’re on the verge of making a billion, but after a couple of years they’ve missed every target they’ve set themselves. Investor A smells a rat but isn’t prepared to lose, so finds bigger investor/s (b), then flogs his share for a tidy sum, and in so doing ensures a round two investment of a 100 mill. What do you expect the youths to do? Declare that in five years time the customers (the talented folk in Paris) might make it to Calais, spend the night while it recharges, hoop across the channel to Dover where they take another nights rest/recharge?...... no, they just keep saying with a few more million it’ll be cracked. They now appoint some big names to enhance credibility, who keep quiet in exchange for a big salary. The youth directors collude to ensure big cash remuneration while in office and just have to keep it going long enough to cream off a tidy sum. Investor (b) now’s had enough but has too much skin in the game so looks for the next bigger stage investor(C) ........... but like all Ponzi schemes, it’s not sustainable.
« Last Edit: November 13, 2018, 03:29:02 pm by Zootycoon »

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #98 on: November 13, 2018, 03:07:11 pm »
Hahahahaha...brutal...but most likely accurate.

I think the programs most likely to succeed are the ones heavily staffed with traditional aerospace engineers, and bankrolled either by big primes or by tycoons for whom money doesn't even factor in the equation.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #99 on: November 13, 2018, 04:11:02 pm »
The Wright brothers used their own money made out of a bicycle shop. The aerospace experience came to them out of their own curiosity for sciences (and trials and errors). On the other side of the Atlantic, some bankrolled experts achieved only a steam hopping machine that didn't lead anywhere.
Entrepreneurship is not faulty here. It's simply easy to fake toward the legions of credulous folks that just want to participate to something exalting.

The singular problem is that we live in a world where critics are tamed, too often ignored or muted.   
« Last Edit: November 13, 2018, 05:10:26 pm by TomcatViP »

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #100 on: November 13, 2018, 08:20:04 pm »
I'm going to argue that some of the startups don't seem to know as much as the Wright brothers did...
When you put out a fancy rendering, and the hover centroid of thrust does not match the cg, you have to question how likely they are to succeed.
Entrepreneurship is not the problem, but it must go hand in hand with technical knowledge found in the traditional aerospace industry.
Blue origin and SpaceX are great examples of successful companies, but neither are startups, and both recruited heavily from the aerospace OEMs.
I look at the team page on the website of some of these startups, and they're pretty light on gray-bearded engineers and heavy on 'Media directors' (whatever the hell that means)!
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #101 on: November 14, 2018, 09:21:40 am »
Quote
I look at the team page on the website of some of these startups, and they're pretty light on gray-bearded engineers and heavy on 'Media directors' (whatever the hell that means)!
This is absolutely true.

But we have to admit that most of the early work of a startup is to raise money and public interest (both goes in pair in a synchronous way). Hence the focus on media and marketing.
An example is Aerion that had some fancy early project drawings  with no realism. Yet those guys managed to raise enough money and market interest to achieve something that even the best of the Pack like Dassault (the one that should have done this breakthrough) couldn't reach. Now they have attracted some of the biggest Defense contractor that didn't shy to join the fray.

So let's not be over sarcastic over the startup industry that do succeed sometime where the majors tripped over.
   

« Last Edit: November 14, 2018, 09:30:01 am by TomcatViP »

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #102 on: November 14, 2018, 10:20:48 am »
"So let's not be over sarcastic over the startup industry that do succeed sometime where the majors tripped over".

For the simple reason that there have been far too many of these start ups that had no intention of providing a product, they were after a nice little earner and nothing else.  Easy to be sceptical over the latest "Emperors new suit" because we have seen it over and over et bleepin al.
« Last Edit: November 15, 2018, 02:42:14 am by Foo Fighter »

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #103 on: November 14, 2018, 11:24:23 am »
But we have to admit that most of the early work of a startup is to raise money and public interest (both goes in pair in a synchronous way). Hence the focus on media and marketing.

Yeah, it may be naive or unrealistic of me to think that you can maintain your engineering integrity and still get funding. I just get frustrated when i see claims that are demonstrably false. It only takes one of these eVTOLs to start crashing to set back the industry a decade.
So far the startups haven't exactly had a stellar rate of success in the aerospace world, but I do wish Aerion the best.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline Zootycoon

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Re: VTOL On Demand Mobility
« Reply #104 on: November 14, 2018, 12:07:58 pm »
One of the problems in e-vtol is that funding will be tending to flow towards those that promise the most but  don’t have a clue how to deliver. This will be disastrous for those with a more attainable goal and/or development strategy as they’re seen as uncompetitive.

I’m not having a pop at the entrepreneurial spirit which is generally present in aerospace today;- it’s a real breath of fresh air compared to the nineties, when if your name wasn’t Rutan, the best you could expect from an investor was a speech on how stupid you were in even asking. I wholeheartedly agree there are some really impressive and exciting successes, but e-vtol just seems to be heading towards a bubble burst. I hope it doesn’t make a mess for the whole industry.
« Last Edit: November 15, 2018, 02:20:44 am by Zootycoon »

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #105 on: November 15, 2018, 02:46:50 am »
A well funded flying car that went on and on and on, never doing anything near a proper product.  https://newatlas.com/moller-m200g-jetson-flying-vehicle-on-sale-in-2009/9652/

Offline GTX

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Re: VTOL On Demand Mobility
« Reply #106 on: November 15, 2018, 02:02:50 pm »
A well funded flying car that went on and on and on, never doing anything near a proper product.  https://newatlas.com/moller-m200g-jetson-flying-vehicle-on-sale-in-2009/9652/

Yeah.  Anything that small but needing 8 engines (or more if you include their latest hybrid versions) is not a viable option.

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #107 on: November 16, 2018, 06:46:37 am »
typically the multi-engine (or multi-motor) is driven by the need to be failure-tolerant.
Of course with eight piston engines you have a high probability of having a failure....with electric motors, that probability goes down quite a bit.
The amount of oversizing of the motors also goes down. I'm oversimplifying here, but if you have four motors and you lose one, the remaining three have to be sized for 133% of the thrust. If you have twelve motors and you lose one, you only lose something like 8% of the thrust.
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Re: VTOL On Demand Mobility
« Reply #108 on: December 01, 2018, 10:43:55 am »
Roland Berger Study attached - more here too.

Offline Zootycoon

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Re: VTOL On Demand Mobility
« Reply #109 on: December 01, 2018, 04:24:14 pm »

Online fredymac

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Re: VTOL On Demand Mobility
« Reply #110 on: January 07, 2019, 01:06:52 pm »
So Bell's urban air taxi is a hex-copter.


Offline yasotay

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Re: VTOL On Demand Mobility
« Reply #111 on: January 07, 2019, 04:54:58 pm »
X-22A meets carbon and composites.

Online fredymac

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Re: VTOL On Demand Mobility
« Reply #112 on: January 08, 2019, 02:35:26 am »
Even with electric power I would bet this thing will push enough air around to get pretty loud unless fan speed is a lot slower than I think.


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Re: VTOL On Demand Mobility
« Reply #113 on: January 08, 2019, 05:22:56 am »
Assembly and component testing of Bell Nexus.


Offline sferrin

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Re: VTOL On Demand Mobility
« Reply #114 on: January 08, 2019, 05:43:39 am »
Reaches all the way back to the X-22.  :D
"DARPA Hard"  It ain't what it use to be.

Offline Mark Nankivil

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Re: VTOL On Demand Mobility
« Reply #115 on: January 08, 2019, 06:08:28 am »
Thought the same thing too referring to the X-22.  The rotor blade design seems rather plain - would have thought it would have a different shape/layout (broader chord at the root and taper to the blade) which can have some impact on noise levels.

Is that a new Bell logo with the dragonfly styled artwork?  I like that....


Enjoy the Day!  Mark
« Last Edit: January 08, 2019, 06:17:40 am by Mark Nankivil »

Offline Moose

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Re: VTOL On Demand Mobility
« Reply #116 on: January 08, 2019, 10:08:50 am »
Yes the dragonfly logo came with their rebranding to just "Bell" recently.

With the Safran turbine going there will be a decent amount of noise anyway, might have decided going too overboard on quieting wasn't worth it.

The wings and "cruise mode" are pretty interesting. And it's good to see a hyrbid vtol back on the front burner.
« Last Edit: January 09, 2019, 08:36:21 am by Moose »

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Re: VTOL On Demand Mobility
« Reply #117 on: January 08, 2019, 10:10:14 am »
Reaches all the way back to the X-22.  :D

Indeed.  To be honest though it would have been good to see it with only 4 ducts rather than the 6.

Offline Sundog

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Re: VTOL On Demand Mobility
« Reply #118 on: January 08, 2019, 10:18:55 am »
Reaches all the way back to the X-22.  :D

Indeed.  To be honest though it would have been good to see it with only 4 ducts rather than the 6.

It's most likely for safety/redundancy as this doesn't have the weight and complexity of all of the interconnected drive shafting the X-22 was saddled with for drive power and safety.

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Re: VTOL On Demand Mobility
« Reply #119 on: January 08, 2019, 10:20:36 am »
Reaches all the way back to the X-22.  :D

Indeed.  To be honest though it would have been good to see it with only 4 ducts rather than the 6.

It's most likely for safety/redundancy as this doesn't have the weight and complexity of all of the interconnected drive shafting the X-22 was saddled with for drive power and safety.

I realise that - I was just commenting on the aesthetics.

Offline Viper2000

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Re: VTOL On Demand Mobility
« Reply #120 on: January 08, 2019, 12:59:49 pm »
It looks as though the aft fans will swallow the slipstream of the front fans, which doesn't seem very sensible.

I agree with the noise comments; low blade number & activity factor imply fairly high tip MN, which isn't good for noise; not convinced by the selection of 6 stators either, though there isn't really enough duct for cut-off. I am also surprised by the apparent lack of liner in the duct.

I suppose they may just want to build something which flies for PR & will then do a load of trouble-shooting to get acceptable behaviour down the line, but it doesn't strike me as a sensible configuration because it's got such a low wetted aspect ratio, so cruise L/D will be poor (probably significantly less than 6, with my intuition being nearer to 4), whilst the higher disc loading compared with a helicopter will hurt hover performance, as will the transmission losses inherent in all these hybrid-electric schemes.

Indeed, the flight displays in the exhibit imply a cruise speed of (edit) less than 100 KTAS (86 KIAS is 100 KTAS at FL100) (/edit), which is really disappointing, & extra load on the aft rotors (presumably due to the aforementioned slipstream ingestion problem. This requires 100% torque from the GT, which adds to the coefficient of disappointment. The Verge claims that the payload capability is only 600 lbm (272 kg) (https://www.theverge.com/2019/1/7/18168814/bell-air-taxi-nexus-uber-flying-car-hybrid-ces-2019) which means that some of the 5 seats are presumably for show. I note that The Verge also claims 150 mph top speed; this would obviously require assistance from the battery. It's not obvious to me that they can really do this because the average torque in the screenshot is about 70%, so we might reasonably expect the top speed to be 100 KTAS * (1/0.7)^(1/3 = 112 KTAS, or 128 mph, assuming fixed propeller efficiency & drag coefficient (both of which are likely to be optimistic assumptions).

Interestingly 112 KCAS at FL100 is about 150 mph TAS, so it may be that somebody has double-accounted the air density effect, which would be rather embarrassing if true...


At this level of performance, surely you'd be better off in a helicopter? An R66 will do everything that the Bell concept will do (apart from not be a helicopter): https://robinsonheli.com/r66-specifications/
; 50% more payload 10 knots faster in a smaller package without all the electrickery.

From a safety perspective, it doesn't look great either. The lack of any sort of variable area system will force the ducted propellers to be variable pitch, & so the critical failure mode is likely to be blade pitch actuator failure; it's an interesting debate as to what the worst case might be, but I'd want to pay particular attention to failure of either a front or outboard system at maximum dynamic pressure, as I can see that being very exciting & potentially breaking the vehicle or imposing some sort of placard (this may be the driver behind the biplane vertical tail), though I suppose the low cruise speed capability will tend to mitigate this risk to a significant extent, though the fact that departure doesn't break the aircraft doesn't mean that it's recoverable.

Duct misalignment during transition would also probably be extremely exciting, & I note with interest that there doesn't appear to be any way for the pilot to actually see what the ducts are doing (the rear ducts being a particular concern) so that sensor failure could easily lead to an XC-142 type accident.

I hope that great care is taken to make sure that these vehicle are genuinely safe before they start flying over urban areas.


« Last Edit: January 08, 2019, 01:52:00 pm by Viper2000 »

Offline zebedee

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Re: VTOL On Demand Mobility
« Reply #121 on: January 08, 2019, 01:07:41 pm »
Interestingly Bell seem to be touting the lack of any form a parachute as an 'advantage' over its competitors...

"You'll see some of our competitors out there using parachutes and so forth, but Bell will not be doing that in the urban environment that we are talking about being in, We believe in controlled descent to the ground under power which would be provided by the battery system."

Via Flight

https://www.flightglobal.com/news/articles/bell-unveils-design-and-nexus-name-for-urban-air-tax-454735/

Zeb

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Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #122 on: January 08, 2019, 01:50:45 pm »
It looks as though the aft fans will swallow the slipstream of the front fans, which doesn't seem very sensible.

Yes. Vibration and noise can't possibly be good and you cannot tweak that in future versions; it's there as long as the ducts overlap in the front view. My guess is there's no way to handle engine out reasonably without n >6 rotors.

>>I agree with the noise comments; low blade number & activity factor imply fairly high tip MN, which isn't good for noise; not convinced by the selection of 6 stators either, though there isn't really enough duct for cut-off. I am also surprised by the apparent lack of liner in the duct.

I was actually surprised the stators are radial. They could have tried some offset geometry, kind of like Fenestron stators for example. But who knows, noise is black magic as far as i'm concerned...

>>The lack of any sort of variable area system will force the ducted propellers to be variable pitch, & so the critical failure mode is likely to be blade pitch actuator failure

Eh, there's a chance they can design a duct/fan they can live with in both static and cruise conditions. It won't be great in either...but maybe it's a lesser evil than the liability of all the actuators?

All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline sferrin

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Re: VTOL On Demand Mobility
« Reply #123 on: January 08, 2019, 02:26:51 pm »
The more I look at it, 6 looks pretty clunky.  With today's modern FCSs you'd think they'd still be able to get down with a a failure or two, even with only four fans.  The X-22 had a flap in the airstream of each nacelle.  I'd think between those flaps, and nacelle tilt, one could create enough lift to accomplish a rolling landing even with one or two prop motors out.  ???
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Offline Zootycoon

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Re: VTOL On Demand Mobility
« Reply #124 on: January 08, 2019, 02:31:07 pm »
Parachutes are a common feature in e-vtol because the proposers don’t understand how to meet a safety case that won’t need it. It’s a lack of understanding about what they’re doing rather than an impossible task. Furthermore I believe they don’t appreciate that you can’t take credit for a parachute within a safety case;- it’s classified as survival equipment ie only of use after a catastrophic event..... in common with ejection seats, crash helmets, Nomex suits etc.etc

EASA-SC-VTOL-01 will clearly define the the minimum safety requirements for transiting over populated area and if you achieve this with good systems redundancy, the parachute will never be used;- it’s just dead weight which is expensive to maintain.

Bell have a much better understanding of redundancy in safe design, hence no parachute.
« Last Edit: January 09, 2019, 09:46:08 am by Zootycoon »

Offline Viper2000

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Re: VTOL On Demand Mobility
« Reply #125 on: January 08, 2019, 02:37:27 pm »
Quote
Yes. Vibration and noise can't possibly be good and you cannot tweak that in future versions; it's there as long as the ducts overlap in the front view.

Looking at the PFD screenshot in my previous post, things are made worse by the fact that aircraft is at almost -10 degrees AOA in cruise, so the rear set of rotors may be eating a partial wake, which is really horrible (unsteady loading).

Quote
My guess is there's no way to handle engine out reasonably without n >6 rotors.

Yes. The problem is things like bird ingestion mean that simply providing multiple redundancy of motors isn't a panacea.

Quote
I was actually surprised the stators are radial. They could have tried some offset geometry, kind of like Fenestron stators for example. But who knows, noise is black magic as far as i'm concerned...

The big levers are blade count (more is better) & tip MN (less is better; nose is proportional to something like the 6th power of tip MN...). Angling the stators or using weird gap / stagger combinations is probably only worth a few dB (say < 6 dB).

See e.g.

https://vtol.org/files/dmfile/20-TVF5-2018-Brentner-PSU-Jan191.pdf

The above slides are from the 2nd presentation in this video:




Quote
Eh, there's a chance they can design a duct/fan they can live with in both static and cruise conditions. It won't be great in either...but maybe it's a lesser evil than the liability of all the actuators?

According to this article they are using variable RPM for control in the hover,

http://gramsluftfartsblogg.blogspot.com/2019/01/uam-urban-air-mobility-bell-pusser-stv.html


so it's possible that they've got fixed pitch blades. I'm surprised by this decision, because it's hard to get this sort of system to scale up, & probably requires the motors to be quite significantly under-sized in the hover. However, it would go a long way towards explaining the low blade count & activity factor, as they'll be desperate to keep the moment of inertia as low as possible.

This will also contribute to the disappointing cruise speed.

I still think it's a strange decision.

Online fredymac

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Re: VTOL On Demand Mobility
« Reply #126 on: January 09, 2019, 05:05:54 am »
It looks like Bell has placed design priority on safety and liability.  A crash onto a crowded city street would probably generate serious political pressure to restrict air taxi operations as well as boost insurance costs.  I’m guessing safety considerations drove the architecture away from exposed blade helicopters to shrouded rotor designs.  At that point, choosing 6 rotors to enhance safety margins to compensate engine loss is no surprise.

Given these things will probably be flying just above skyscrapers, noise is going to be a big factor in public acceptance.  I have watched bird sized RC quadcopters flying around parking lots and I am surprised how loud they are.  They sound like a gigantic bee buzzing around.  These are exposed rotor quadcopters so I don’t know if a shrouded rotor will significantly cut down the noise.

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #127 on: January 09, 2019, 07:55:49 am »
Without elaborating further on the source, i heard from people with more knowledge of the relevant physics that the duct may not help unless it's long enough in relation to the diameter - something that has to do with the frequencies you're trying to block. Long ducts are a pain, both in terms of structural weight and drag in cruise.
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Offline Viper2000

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Re: VTOL On Demand Mobility
« Reply #128 on: January 11, 2019, 05:09:31 pm »
Quote
Without elaborating further on the source, i heard from people with more knowledge of the relevant physics that the duct may not help unless it's long enough in relation to the diameter - something that has to do with the frequencies you're trying to block.

At a really simple level, the thing which matters is the size of the duct relative to the wavelength of the sound that you're trying to block; if the barrier (i.e. the duct) is small in comparison to the wavelength then the sound will simply diffract around it.

This thesis presents a nice general treatment of low noise design techniques applicable to turbofan airliners.

It's important to understand that civil turbofans are designed quite tightly around certification requirements, & therefore you will find references in the thesis above to "critical polar angles"; these fall out from the interaction between the directivity function, the microphone position, & the flight path of the aeroplane.

The eVTOL concepts in this thread don't have quite such tightly defined paths & microphone positions, & obviously the directivity function is going to be driven by duct vector, so the problem is much more general & therefore difficult.

On the other hand this paper would have you believe that ducted fans operating at subsonic tip Mach number should ideally be silent (see section 6.2 on page 32) because all the tones are cut off. Naturally, this isn't really true, especially if the duct is operated at incidence relative to freestream. However, if the incidence is low & the blades are subsonic, then ducts may reasonably be expected to at least knock a decent hole in the directivity plot close to 90 degrees.

Quote
Long ducts are a pain, both in terms of structural weight and drag in cruise.

Short ducts are also difficult because they're more likely to stall under off-design conditions; drag advantages rely upon the assumption that the drag is due to skin friction; this clearly becomes invalid if the duct is too short & stalls.

I think a lot of these vehicles are quite cynically designed to trade off performance against perceived novelty; as discussed, the published performance seems markedly inferior to an R66 so it might be simpler to take a simple helicopter & go for a more complex rotor system plus NOTAR to hit the noise target.

There may be some DOC advantage to distributed propulsion if propulsors are LRUs (as Bell claim), but this is offset by the capital cost of the spares inventory, & it's fundamentally hard to make this case at vehicle level if the underlying architecture still includes a GT; all these hybrid schemes are one propulsion system for the price of two.

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #129 on: January 11, 2019, 07:06:15 pm »
Thanks, those are interesting points. Yeah, i'm a bit wary of papers presenting theories not substantiated by experimental data. It's hard to capture all the physics involved in acoustics.
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Offline jmspeedfreak

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Re: VTOL On Demand Mobilit
« Reply #130 on: January 12, 2019, 01:40:30 pm »
Sorry, can someone clarify for me the meanings of DOC and LRU.

In case anyone has feel for the answers...

If MN or tip velocity is under 180m/s is it generally accepted that the blade noise will be very low? I’m recalling a NASA project related to Vietnam era tree top flight surveillance called ‘The Quiet One’.

Anyone remember? If most of the time the objective is to keep tip speed very low then 6 props could be part of that justification, likewise an rpm based control strategy would be most of the time operating way down the inertia bucket, hence would only be a real pain if one or two of the props is out. Additionally I though operating two discs in series in the cruise actually gave a modicum of variable area like behaviour as the overall jet velocity is hiked by using two in series obvious counter rotating too. I can imagine the outer pair of ducts being feathered in high speed flight and maybe only these two having variable pitch for roll authority.

Just my take anyway.

Offline Viper2000

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Re: VTOL On Demand Mobility
« Reply #131 on: January 13, 2019, 06:14:31 am »
DOC = Direct Operating Cost;
LRU = Line Replaceable Unit

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #132 on: January 13, 2019, 07:14:47 am »
Some numbers typically floated for quiet operations are Mtip < .45, but that's just one part of the equation unfortunately. Another major contributor is having a non-uniform inflow, so you really try to avoid having a fan behind the stators, for example.
Ideally all of the propulsive units would be simple (no variable pitch) and identical, to keep costs down. These vehicles have to be 'somewhat' affordable for the business case to close.
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Offline yasotay

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Re: VTOL On Demand Mobility
« Reply #133 on: January 13, 2019, 02:00:07 pm »
Just a quick thanks to all recent contributions to this thread.  Very interesting reading indeed.

Online fredymac

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Re: VTOL On Demand Mobility
« Reply #134 on: January 14, 2019, 03:40:47 am »
Some explanations on design trades.  At 1:06 mark, fans and noise are discussed.


Offline VTOLicious

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Re: VTOL On Demand Mobility
« Reply #135 on: January 14, 2019, 06:03:30 am »
It is interesting (and refreshing) to see, that Airbus (CityAirbus) and Bell (Nexus) came up with a completely different solution for the same problem / use case / business case, whatever you wanna call it.

...btw, still waiting for CityA to conduct first flight.

Offline yasotay

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Re: VTOL On Demand Mobility
« Reply #136 on: January 14, 2019, 10:35:39 am »
It appears that the rotors are not "covered" by the... well whatever it is (still a duct?)  SO does this mean that the noise propagation from those rotors will be completely unmasked?

Offline VTOLicious

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Re: VTOL On Demand Mobility
« Reply #137 on: January 14, 2019, 09:23:36 pm »
It appears that the rotors are not "covered" by the... well whatever it is (still a duct?)  SO does this mean that the noise propagation from those rotors will be completely unmasked?

Only the lower rotors are shrouded. A configuration never seen before, I think.
The upper rotors are most likely a bit larger in diameter.
« Last Edit: January 14, 2019, 09:30:36 pm by VTOLicious »

Offline VTOLicious

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Re: VTOL On Demand Mobility
« Reply #138 on: January 17, 2019, 03:53:34 am »
In total 800 kW max continuous power

Offline Viper2000

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Re: VTOL On Demand Mobility
« Reply #139 on: January 17, 2019, 05:00:49 am »
1500 Nm / 49 kg = 30 .6 Nm/kg.

This is even more impressive than the SP260D, which hits 20 Nm/kg.

Clearly we are now heading towards diminishing returns, because the motor mass fractions for practical vehicles will be small, but it's really impressive.

RE the City Airbus rotor shrouds, I think that they are intended to protect against collisions, much like a Fenestron helicopter tail rotor. I don't really understand how they're going to make it quiet, but it's possible that they have a higher noise target than we think, or that they are taking lots of credit for masking by background urban noise.

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #140 on: January 17, 2019, 07:28:39 am »
1500 Nm / 49 kg = 30.6 Nm/kg.

This is even more impressive than the SP260D, which hits 20 Nm/kg.


indeed. One thing to note, though, is that I think Siemens gives their liquid-cooled motor weight exclusive of the cooling system, so it's not "as installed". So when they're claiming 5kW/kg specific power, it's a bit misleading comparison to air-cooled motors. Still, i have no reason to believe they're not among the best motors around, it's just hard to make an apples-to-apples comparison.
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Offline Zootycoon

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Re: VTOL On Demand Mobility
« Reply #141 on: January 17, 2019, 01:39:37 pm »
In my experience, a rule of thumb for highly optimised electric motors means a power density for a constant rated load of 4kw/kg for liquid cooled (cooling system not included) and 2kw/kg for air cooled. At these levels they’re running at high efficiency so it’s difficult to get any better. You can finesse these figures with higher rotor speed and trade with torque density but it’s about as good it gets within the available materials.

The basic motor performance is a function of magnetic flux density, resistivty, and thermal conductivity and these are limited by the best known materials to science.

I’ve seen motor developer fiddle thier figures by quoting from non constant load tests to get investment, headlines etc.

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #142 on: January 17, 2019, 01:51:45 pm »
Last but not least the rotors are fixed... While the supporting beam fully restricts the airflow. Something don't adds up.  We might have here a very early configuration - what in Airbus world would be a "designer" work, something that has yet to be seen by a qualified engineer.
« Last Edit: January 17, 2019, 05:46:46 pm by TomcatViP »

Offline VTOLicious

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Re: VTOL On Demand Mobility
« Reply #143 on: January 17, 2019, 10:12:45 pm »
Last but not least the rotors are fixed... While the supporting beam fully restricts the airflow. Something don't adds up.  We might have here a very early configuration - what in Airbus world would be a "designer" work, something that has yet to be seen by a qualified engineer.

I think you are wrong. Look at the pics. They are building a prototype, not a mock up. Originally first flight was scheduled for late 2018.

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #144 on: January 18, 2019, 05:13:45 am »
The frame suggests an iron bird: something build to test the ctrl laws and motors  Then the propulsion units are not articulated on the mockup meaning that this thing could be called the Vomit-comet.

If you look at the design of the propulsion units, you'll see that it has only blade pitch actuation (just like a propeller on a plane).  The high torque design converge also with this. It means that their intend is to fly like a quad rotor by varying unit power. If they do that with a fixed propulsion units, it means that the cabin will wobble constantly and speed will be a function of attitude. Hence the nick-name: Vomit-comet.

In all probability, Airbus is just bragging showing a concept hastily made out of an R&D project.
« Last Edit: January 18, 2019, 05:32:16 am by TomcatViP »

Offline galgot

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Re: VTOL On Demand Mobility
« Reply #145 on: January 18, 2019, 06:40:58 am »
Yes it does look like the rotors are fixed, so it would work like a quad drone. But That way wouldn't make it "wobble contantly" more than a helo... Some quad drones don't need big change of attitude to change direction . What is interesting is the way there are 2 props per rotors, if that is a motor per prop, it's an interesting way of solving the "engine out" security for available space for the props, better than some other concepts I've seen with six ducted props on each side. Plus you can have bigger props.

Bragging... You mean like building a mockup or something like that ?  ::)  You know... It's funny how whenever a subject mention Airbus, your comments are so much predictable :D
Not that i am a big Airbus fan, We all have our fav, and hated makers, but wow it's so systematic from you.
You've been fired from Airbus or what ? Just curious.
« Last Edit: January 18, 2019, 06:53:46 am by galgot »

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #146 on: January 18, 2019, 07:39:35 am »
OMG   :o


Quote from: galgot
What is interesting is the way there are 2 props per rotors, if that is a motor per prop [...]
Each pod has Two engines (look at the diagonal bracing at the middle and engine description on the cardboard)
« Last Edit: January 18, 2019, 01:33:06 pm by TomcatViP »

Offline galgot

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Re: VTOL On Demand Mobility
« Reply #147 on: January 18, 2019, 08:57:10 pm »
OMG   :o


Quote from: galgot
What is interesting is the way there are 2 props per rotors, if that is a motor per prop [...]
Each pod has Two engines (look at the diagonal bracing at the middle and engine description on the cardboard)

Thanks for the confirmation :)
And ?
« Last Edit: January 18, 2019, 09:07:19 pm by galgot »

Offline VTOLicious

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Re: VTOL On Demand Mobility
« Reply #148 on: January 18, 2019, 10:46:49 pm »
The frame suggests an iron bird: something build to test the ctrl laws and motors  Then the propulsion units are not articulated on the mockup meaning that this thing could be called the Vomit-comet.

If you look at the design of the propulsion units, you'll see that it has only blade pitch actuation (just like a propeller on a plane).  The high torque design converge also with this. It means that their intend is to fly like a quad rotor by varying unit power. If they do that with a fixed propulsion units, it means that the cabin will wobble constantly and speed will be a function of attitude. Hence the nick-name: Vomit-comet.

In all probability, Airbus is just bragging showing a concept hastily made out of an R&D project.

Oh boy 🙄

You should better inform yourself. It's definitely not a iron bird. It was announced long time ago that the CityAirbus demonstrator is scheduled to fly end of 2018.

Offline martinbayer

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Re: VTOL On Demand Mobility
« Reply #149 on: January 18, 2019, 11:14:14 pm »
The frame suggests an iron bird: something build to test the ctrl laws and motors  Then the propulsion units are not articulated on the mockup meaning that this thing could be called the Vomit-comet.

If you look at the design of the propulsion units, you'll see that it has only blade pitch actuation (just like a propeller on a plane).  The high torque design converge also with this. It means that their intend is to fly like a quad rotor by varying unit power. If they do that with a fixed propulsion units, it means that the cabin will wobble constantly and speed will be a function of attitude. Hence the nick-name: Vomit-comet.

In all probability, Airbus is just bragging showing a concept hastily made out of an R&D project.

Oh boy 🙄

You should better inform yourself. It's definitely not a iron bird. It was announced long time ago that the CityAirbus demonstrator is scheduled to fly end of 2018.

So, this being January 18, 2019, how did the maiden flight go?
Would be marching to the beat of his own drum, if he didn't detest marching to any drumbeat at all so much.

Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #150 on: January 19, 2019, 02:54:38 am »
VTOLicious: It's not like something I comment should be a new design. It doesn't change a iota that we have seen this Airbus effort before   I don't understand, neither the tone and the meaning. If then you'd had fall in sympathy with the despicable depiction of what should be me by our fellow Fr poster before (and above), I'd remind you that this is only hysteria.

Oh boy. 

Offline Arjen

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Re: VTOL On Demand Mobility
« Reply #151 on: January 19, 2019, 03:21:03 am »
So, this being January 18, 2019, how did the maiden flight go?
The latest news I have found is a tweet from Airbus Helicopter boss Bruno Even
https://twitter.com/BrunoEven/status/1055749844810321920
Power up of demonstrator on 26 Oct 2018 - not the iron bird, as testing of that started in late 2017. Nothing about a first flight yet.

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #152 on: January 19, 2019, 11:15:42 am »
side note on stacked rotors (two on top of each other, driven by separate motors), be it for open or ducted rotors.
The stacked rotors are undeniably more compact, but unfortunately they don't decrease discloading (thus power required to hover) like individual rotors do. That is, what matters is the projected swept area of the rotors as seen from the top.

Additionally, the propellers have to be optimized to work together (i.e., the lower one is operating in the exhaust of the top one). So when one of the two motors goes out, the remaining propeller is  a) working with some sort of blockage from the stopped prop, regardless of whether it's upstream or downstream, and b) it no longer has the optimum twist since the flow conditions have changed drastically.
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Offline LowObservable

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Re: VTOL On Demand Mobility
« Reply #153 on: January 19, 2019, 07:44:54 pm »
Clearly, I am a Luddite and moreover an oldthinker who unbellyfeels urban VTOL.

Equally clearly, the urban VTOL revolutionaries will be able to:

Invent electrically powered VTOL aircraft that can haul a useful payload ~100 km and return, either doing so several times or recharging in minutes
Make these things quieter than conventional rotorcraft
Make them far less costly than any helicopter or VTOL
Develop an infrastructure that allows thousands of vehicles to operate unmanned over densely populated areas
Make them an order/orders of magnitude safer than any other small aircraft, from Day One.

In short....


Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #154 on: January 19, 2019, 09:23:57 pm »

The stacked rotors are undeniably more compact, but unfortunately they don't decrease discloading (thus power required to hover) like individual rotors do. That is, what matters is the projected swept area of the rotors as seen from the top.

If w is the downward stream speed component of a single rotor disc, 2w will be the one for a stacked rotors (in idealized conditions). Respecting the proper conditions will induce some benefices. In case of a failure, the failed rotor's prop can be feathered. But it is true that the carrying beam structure will induce some losses to say the least. 

Offline Foo Fighter

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Re: VTOL On Demand Mobility
« Reply #155 on: January 20, 2019, 03:44:31 am »
I am not an expert but I never did get the trend for stacked rotors without a separate rotation for each.  After all contra props always (As far as I have seen) have a displacement for each prop.

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #156 on: January 20, 2019, 09:28:50 am »

The stacked rotors are undeniably more compact, but unfortunately they don't decrease discloading (thus power required to hover) like individual rotors do. That is, what matters is the projected swept area of the rotors as seen from the top.

If w is the downward stream speed component of a single rotor disc, 2w will be the one for a stacked rotors (in idealized conditions). Respecting the proper conditions will induce some benefices. In case of a failure, the failed rotor's prop can be feathered. But it is true that the carrying beam structure will induce some losses to say the least.

if you must have a feathering device, you might as well have variable pitch. With eight (or more) rotors, that means eight additional devices that are maintenance and reliability items. One of the advantages of multirotors tout is the small number of moving parts and reliability, which this now goes against. I'm not saying it can't be done, but there's costs associated with it.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline galgot

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Re: VTOL On Demand Mobility
« Reply #157 on: January 20, 2019, 09:58:49 am »
Thanks for these precisions. Maybe one way to avoid such problems in case of a motor out, would be to have a big excess of power diverted to the remaining turning motor for a time, to be at least effective the duration of a fast automatic emergency landing , even in case of disrupting flow due to the upper or bottom non-turning prop… ? Dunno.
Or eject the non-turning prop all together… wait, in town… forget it  ;D
What is the reliability of that kind of motor anyways compare to a helo turbine ?
« Last Edit: January 20, 2019, 10:02:49 am by galgot »

Offline AeroFranz

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Re: VTOL On Demand Mobility
« Reply #158 on: January 21, 2019, 04:51:49 pm »
I don't know about the reliability of the motors, although it should be pretty good with just one moving part.
Typically the vehicles carry a substantial amount of excess power. The early Vahana was, according to the open source code posted on Github, sized for an all-engine operating thrust to weight close to 1.7, although to be fair that seems like a lot.
By oversizing the motors, you can afford to lose one and still have enough thrust generation. The more motors you have, the less you need to oversize them because losing one is a smaller overall loss. One thing to keep in mind is that besides generating enough thrust, the remaining forces must also be balanced. Take the simple case of a quad rotor. If one rotor becomes inoperative and you just increase the thrust on the remaining three equally, the vehicle will flip. More in general, multirotors will speed up the rotors next to the one that failed and maybe throttle down the opposite ones.
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Offline TomcatViP

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Re: VTOL On Demand Mobility
« Reply #159 on: Yesterday at 02:24:36 am »
if you must have a feathering device, you might as well have variable pitch.

To me that's what they have. But I might be overly naive and optimistic.  :D