VTOL On Demand Mobility


Granted, this person is hardly an unbiased observer, but he raises some interesting points about the business case for Evtols. I personally have my doubts about how extensively these things will be used once they enter service. The article mentions rooftop to rooftop inner city flights being the goal, but here in New York, ever since a gruesome accident involving a helicopter tipping over on the roof of the Pan Am building in the late 1970s that resulted in several deaths, there is no chance of rooftop flights ever getting approved in NYC. Southern California on the other hand is the one market where I could see these things become a huge success for short flights.
 
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The problem with rooftop operations, and this has already been mentioned before here, is the complex movement of air masses at the top of a tall building and the low excess power of most VTOL design as being pushed frwd by this industry.

In the case mentioned above, if I do remind well, this was already an issue...
 
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That is indeed a great video. Personally I think those who are working toward hybrid solutions or cargo (Beta, Samad, Vox) are likely to be the ones who win out as they have multiple functions. I think those platforms that can carry a functional number of passengers intra-city have higher probability than a platform attempting to becoming the new city transit bus. Also as pointed out in the video the FAA is not a fast reacting company. The AW-609 mentioned in the video is a perfect example of how quickly the FAA responds to new platform types.

Thus cargo types are likely to be easier to get into the market I think.

UPDATE/EDIT - I failed to mention I also think that the designs with the least moving parts (relative simplicity) might do better as they tend to be less maintenance intensive. This should impact the bottom-line of fiscal viability.

But then, like everyone else, I am guessing.
 
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It is a great video. I have been watching the whole eVTOL and point to point air taxi evolution for a number of years. I do believe without people and companies taking risks and pushing the knowledge boundaries, we wouldn't be here where we are today (good or bad). However as a former ATP rated pilot, flight instructor, and aircraft owner I don't see the practicality of these machines in any large scale movement of people. Paul has touched on multiple good points. I noticed that in the videos and nice graphics, all show nice blue clear(?) LA and California coast lines. But what those days of thunderstorms, fog, and icing. I have flown Twin Otters on skis in the Artic, with whiteout conditions and temperatures of minus 30 to minus 40C. I have also flown multiple aircraft types facing thunderstorms in the NY/NJ area of the east coast in late fall, where radar is really nice to have and ATC will allow your own deviation to scoot around those CB's while the rain beating off the windscreen sounds like nothing you've heard before. Granted I see the certification seems to be toward VFR flight only (so far), but that will even more than limit the number of hours or days service will be available. Factor in the weather in Europe, and similar haze/fog/pollution/typhoon type conditions on the Asian portion of the world, really does not offer the world wide operation Joby (and others) wish to see.

Also not mentioned is the whole support side of the industry. For example, the number of hours of maintenance required to maintain these type of machines. Granted, no reciprocating engine to change oil, plugs and filters on, but will introduce a whole new set of maintenance needs and checks on batteries and electric motors, I'm sure just to keep the FAA types happy. Then there is the pilot (for now) training. Are these going to be the low time guys buidling hours before heading off to the airlines. Certainly won't be the current crop of Uber and taxi drivers plying the roads these days. Do the young people of today even want to do this type of job as envisioned by Joby and others? General Aviation is seemingly an older, white for the most part(?) and higher income activity. Do the public even want to be in the 3D airspace in non-piloted computer controlled vehicles?
I could keep on going on, but hoped I have raised a few more points for readers to consider and comment to.
 
It is a great video. I have been watching the whole eVTOL and point to point air taxi evolution for a number of years. I do believe without people and companies taking risks and pushing the knowledge boundaries, we wouldn't be here where we are today (good or bad). However as a former ATP rated pilot, flight instructor, and aircraft owner I don't see the practicality of these machines in any large scale movement of people. Paul has touched on multiple good points. I noticed that in the videos and nice graphics, all show nice blue clear(?) LA and California coast lines. But what those days of thunderstorms, fog, and icing. I have flown Twin Otters on skis in the Artic, with whiteout conditions and temperatures of minus 30 to minus 40C. I have also flown multiple aircraft types facing thunderstorms in the NY/NJ area of the east coast in late fall, where radar is really nice to have and ATC will allow your own deviation to scoot around those CB's while the rain beating off the windscreen sounds like nothing you've heard before. Granted I see the certification seems to be toward VFR flight only (so far), but that will even more than limit the number of hours or days service will be available. Factor in the weather in Europe, and similar haze/fog/pollution/typhoon type conditions on the Asian portion of the world, really does not offer the world wide operation Joby (and others) wish to see.

Also not mentioned is the whole support side of the industry. For example, the number of hours of maintenance required to maintain these type of machines. Granted, no reciprocating engine to change oil, plugs and filters on, but will introduce a whole new set of maintenance needs and checks on batteries and electric motors, I'm sure just to keep the FAA types happy. Then there is the pilot (for now) training. Are these going to be the low time guys buidling hours before heading off to the airlines. Certainly won't be the current crop of Uber and taxi drivers plying the roads these days. Do the young people of today even want to do this type of job as envisioned by Joby and others? General Aviation is seemingly an older, white for the most part(?) and higher income activity. Do the public even want to be in the 3D airspace in non-piloted computer controlled vehicles?
I could keep on going on, but hoped I have raised a few more points for readers to consider and comment to.
Welcome! Wonderful insights. Thank you. Please feel free to go on and on at your leisure as this is a place of aero-geeks who actually enjoy that sort of thing. With your background you certainly add tremendously to the bona fids of the conversation.

Look forward to reading more of your insights.
 
Great assessment. One point not mentioned is many of these schemes offer a 5 minute energy reserve. I’m still puzzling at what this means in the real world. It really doesn’t allow for diversion range, maybe 5km max, and is a major problem for the operator if it lands off the recharging grid. So practical operations will require a high density of landing pads each equipped with tens of Mega Watts, ( Giga Watts if a hub) capacity charging;- just look at electrical grid emerging from a power station to get a feel for the size of such electrical sub stations …. Remember this is in addition to the power demand that’s already installed to power the area.

This is mind bogglingly massive and Uber expensive infrastructure, especially if introduced into existing urban areas. and paid for by who ? It’s in that ridiculously low ticket price, right?
 

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@twinotterpilot for what it's worth you can make the case that if you're flying urban trips under ten minutes in duration, then it's unlikely that you will ever be caught off guard by bad weather. It also means you don't fly if it's raining/snowing, which doesn't help the business case...so yeah, not great

@Zoo Tycoon five minutes reserves seems ridiculously low...i thought the industry consensus was closer to twenty (which may still be marginal). I will note that there's also a big difference in what amount of energy this constitutes, depending on flight profile.
For example, in a diversion case, are you descending/transitioning/coming to a hover one inch off the landing pad, and then climbing, transitioning, and flying to an alternate location, or can you claim to divert to the alternate pad while still on the wing? In the first case, those extra steps are easily the equivalent of five minutes of wingborne flight.
 
@Zoo Tycoon five minutes reserves seems ridiculously low...i thought the industry consensus was closer to twenty (which may still be marginal). I will note that there's also a big difference in what amount of energy this constitutes, depending on flight profile.
For example, in a diversion case, are you descending/transitioning/coming to a hover one inch off the landing pad, and then climbing, transitioning, and flying to an alternate location, or can you claim to divert to the alternate pad while still on the wing? In the first case, those extra steps are easily the equivalent of five minutes of wingborne flight.

I’m seeing most suggest that the average flight duration is 20-30minutes with a 5 minute diversion reserve …. I had to look twice when I first saw this too. They’re really desperate on installed energy at anything close to a real payload.
 
If someone crash on the pad, 5 min will be very short to plan for new contingencies while waiting for the landing zone to be secured (and no, you are not going to park your beheading prone VTOL in the street). I doubt that the FAA or any other will valid such idea.
For example, commercial aircraft under 5t have to fly in constant gliding distance of a crash compatible zone.
If that is translated to VTOL, every operator would have to setup multiple landing pads in his area of operation. When I see the money wasted in design and luxury proposition, I can only see that as dubious or delusional.
 
There's no gliding involved with these designs. Expect ballistic 'chutes to become mandatory.

pull the 'chute'.

EASA and FAA have already said Chutes cannot be credited in the operational safety case. Also a parachute capable of rapid operation for a 5ton craft is heavy, about 5% of load it’s supporting is a good rule of thumb.
 
@Zoo Tycoon five minutes reserves seems ridiculously low...i thought the industry consensus was closer to twenty (which may still be marginal). I will note that there's also a big difference in what amount of energy this constitutes, depending on flight profile.
For example, in a diversion case, are you descending/transitioning/coming to a hover one inch off the landing pad, and then climbing, transitioning, and flying to an alternate location, or can you claim to divert to the alternate pad while still on the wing? In the first case, those extra steps are easily the equivalent of five minutes of wingborne flight.

I’m seeing most suggest that the average flight duration is 20-30minutes with a 5 minute diversion reserve …. I had to look twice when I first saw this too. They’re really desperate on installed energy at anything close to a real payload.
I'd imagine, as with ETOPS, that it depends how many landing pads there are, within that 5 minutes of range, in theory it should be possible to keep one clear at any time....certainly going to be an exciting 5 minutes....
 
The solution is often simple: add an ICE engine and a gas tank to fly longer (and do some trimming in the mission profile).
The fanatical vision they have sold to the media is only akin to digging your own grave, something very peculiar when it comes to flying...
 
The solution is often simple: add an ICE engine and a gas tank to fly longer (and do some trimming in the mission profile).
The fanatical vision they have sold to the media is only akin to digging your own grave, something very peculiar when it comes to flying...
Very true, a lot of transport modes, need a lot of power for a short period, then a much lower level, very large improments in fuel efficiency can be found, especially with fairly static throttle settings,like ships, trains etc. running these things with a little wankel or similar would more realistic, at least for the first/next 10 years or so.
 
re: ballistic chutes, as @Zoo Tycoon mentioned, they're fairly heavy, and so far there is still a dead man's curve associated with their use. I would also consider the experience traumatic, if it were to be on an eVTOL that had to use it. The impact velocities of these things also mean you're likely throwing away the airframe.

These eVTOLs are incredibly sensitive to reserves - however you want to define them - so i'm not surprised low numbers are being thrown around. In reality, meeting corner cases means your effective range is pretty short.

re: hybrid solutions. You can play with pure series or different levels of parallel hybridiazation (how much power comes from the battery vs the ICE engine plus fuel) . But quite often once you add up the masses of the generators, ICE, fuel tank and systems, the perceived advantages tend to disappear. that being said it's highly dependent on the mission profile. For short trips it makes zero sense. For longer trips the goodness of the specific energy of hydrocarbons begins to outweigh having to carry the added powertain components.
 
I'd imagine, as with ETOPS, that it depends how many landing pads there are, within that 5 minutes of range, in theory it should be possible to keep one clear at any time....certainly going to be an exciting 5 minutes....

Yes that’s right;- The problem if an emergency pad gets occupied, an in transit now cannot declare it as a diversion. So what do they do to maintain their flight certified operation? The reserve pad factor could be as high as two pads in close proximity to destination for every one in flight. Aircraft are very cheap compared to a recharge equipped pads. 10 aircraft coming into a hub could need say 15 pads at the hub and another 5 empty pads close by. Imagine a thunderstorm sweeping through stopping a bunch of out goings while at the same time a bunch of incoming are committed to destination.
 
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EASA and FAA have already said Chutes cannot be credited in the operational safety case. Also a parachute capable of rapid operation for a 5ton craft is heavy, about 5% of load it’s supporting is a good rule of thumb.

Do you have a source for both claims?

EASA and eVTOL parachutes;-


“Therefore this objective cannot be met by the use of non-steerable parachutes.”

Parachute mass;-

Note an 8 Kg emergency parachute for a 115Kg standard seat mass.

Google is your friend.
 
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Coanda - My claim is “ cannot be credited in the operational safety case” which is very different to your interpretation of my claim ie“ EASA/FAA have 'ruled out' parachute recovery ”. The operational safety case is the basic loss model, ie how many times a catastrophic/Hazardous/Major/Minor event occurs compared to the requirement of the Cert Stan (CS). In essence EASA has said the DOA must demonstrate the necessary reliability in the event of a single catastrophe failure only with a controlled descent and specifically not an unsteered parachute. No compliance to CS, then no airworthiness certification. Thus a parachute becomes a post event survivable enhancement in the same context as crashworthiness, a fire axe, a life jacket (or an ejection seat if military). My guess is eVTOL are so energy marginal we won’t see any DOA trading chargeable payload for such post crash safety but it’s really up to the individual DOA. So no, EASA has not ruled parachutes out nor did I claim that. But remember if the operational safety case compliance is demonstrated then there’s no need for parachute QED.

Parachutes have fundamental certification issues anyway;- they mustn’t have single point failures both when intensionally used and when inadvertent used;- very difficult conflicting requirements …. And what’s in the landing zone? 5 or so tons, roaring in at 10-15 ft/sec can do a lot of damage to those underneath. You could quite possibly squash more people underneath one of these than it has inside it. I know that’s what the steerable chute is all about but again if the loss model is satisfied you don’t need it.

As for the parachute mass fraction, your 3% doesn’t include a the single point load attachment on the the airframe stressed to the vehicle mass times a dynamic factor appropriate to a parachute opening, maybe even a parachute that’s been ballistically spread….essential for low altitude and highly stressing for the parachute. These eVTOL airframes are not comparable to C150’s or C172’s. All told, I stand behind the 5% figure.
 
Coanda - No worries..agree to disagree, Not trying to catch out or weasel out, I guess I should have explained the original terminology a bit better. I use this stuff all the time 9-5 and it’s sometimes difficult to reboot.

You’re correct in that we’ll see what happens;- we’re not the architects scheming these things out.

Standing back with some hard won experience and a bucket of popcorn is kinda fun.
 
For what it's worth, about five years ago one of the leading ballistic parachute companies gave me some quotes for a subscale eVTOL prototype. Please understand that this is highly dependent on a number of factors, such as vehicle mass and desired rate of descent (obviously) but also things like vehicle deployment speed (does the system need a 'slider' to delay canopy opening and decrease shock?) and density altitude.

All the approximate system weights quoted and volumes did NOT contain rocket, activation or harness subsystems. The complete parachute system would have a 20-30% of increase in weight and 10-20% of increase in volume. Also, as noted before, this does not include the weight applied to the airframe for attachment points, potential extra drag, etc.

Anyway, for a vehicle MTOW ranging between 900 and 1300 kg (most 5-seater UAMs will end up weighing 7,000 lbs/3,180 kg), for a range of descent rate values, at sea level, we were quoted a parachute weight between 12 and 20 kg. At higher altitudes this would obviously go up (I'm thinking it would make sense to use a worst case scenario of 4K95; there are plenty of world capitals at high altitude that experience high temperatures). It also leaves a dead man's curve below 100 ft/~25m, which realistically no fast deploying chute is ever going to be able to take care of. I think companies working the problem are considering downward pointing rockets, which makes sense but now you are carrying pyrotechnics on your vehicle all the time.
 
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A retro-rocket system would have to control attitude and so would need something throttleable (at least rudimentarily) and distributed - I'm guessing anywhere between six and a dozen rockets with enough moment arm to produce the required moments. If someone asked me to integrate such a system on the vehicle, i would venture that you would end up affecting structures and load paths, and drag due to fairing what are essentially tubes oriented mostly vertically.
Anyway, compared to the mortar there are maybe ten times as many and they may be more complicated devices. on the other hand i will note that the mortar solution was relatively maintenance-free. We were told that typically maintenance was every ten years for a custom sealed system, less if you were in a harsh UV environment. Visual inspection of the system once a year, otherwise.
 
For what it's worth, whilst doing some research for a project some years back, a parachute manufacturer told me to budget 10% of T/O mass for a recovery parachute.

Oh, and a healthy and happy New Year to everyone.
 
A retro-rocket system would have to control attitude and so would need something throttleable (at least rudimentarily) and distributed - I'm guessing anywhere between six and a dozen rockets …..essentially tubes oriented mostly vertically.

Holy smoke;- I pity anyone unlucky enough to be stood underneath as the efflux’s will be lethal at quite a distance. I once saw the furrow cut by a Sea Dart rocket motor efflux though a reinforced concrete pad which was a startlingly deep/long. It surprised us but not the guys who played with these things to pay their mortgage. Granted much larger but there’s plenty of scary clips of people who stood in the backblast of things like RPG’s which show the potential for small motors. Surely the whole industry won’t survive an accident where a bunch of well heeled executives get to live at the expense of a group of school Moms/kids?
 

"Today, the 'fake it until you make it' culture is still alive and well - as is the repressive culture of secrecy and the aggressive use of NDAs for employees. It's a model that has its advantages - and helps churn out extremely valuable and sometimes innovative companies. But it also means the ingredients are still in place for another Theranos scandal. "

I think that sooner or later there will be a similar reckoning for the Evtol industry. There are too many inexperienced startups trying to build quite advanced aircraft designs, coupled with overly optimistic timelines, along with business plans that don't make much sense when closely scrutinized. I'm shocked that publications like the Wall Street Journal or the Economist have not done an in depth expose of this industry. I think in the next few years there will be a bloodbath that will see many of these companies fail with only the strongest like Joby or Archer surviving.

This reminds me of VLJ bubble 15 years ago that was fueled by a promising aircraft that was going to revolutionize aviation called the Eclipse 500. If you have never heard of it this excellent article explains why it failed.


"A disaster of this size has many causes, but the most fundamental was a fantasy about the economics of designing, building and supporting airplanes. The company also predicted impossibly low empty weights, which then led to unattainable performance and range predictions, and it expected to accomplish all of this in record setting time."
 
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"Today, the 'fake it until you make it' culture is still alive and well - as is the repressive culture of secrecy and the aggressive use of NDAs for employees. It's a model that has its advantages - and helps churn out extremely valuable and sometimes innovative companies. But it also means the ingredients are still in place for another Theranos scandal. "

I think that sooner or later there will be a similar reckoning for the Evtol industry. There are too many inexperienced startups trying to build quite advanced aircraft designs, coupled with overly optimistic timelines, along with business plans that don't make much sense when closely scrutinized. I'm shocked that publications like the Wall Street Journal or the Economist have not done an in depth expose of this industry. I think in the next few years there will be a bloodbath that will see many of these companies fail with only the strongest like Joby or Archer surviving.

This reminds me of VLJ bubble 15 years ago that was fueled by a promising aircraft that was going to revolutionize aviation called the Eclipse 500. If you have never heard of it this excellent article explains why it failed.


"A disaster of this size has many causes, but the most fundamental was a fantasy about the economics of designing, building and supporting airplanes. The company also predicted impossibly low empty weights, which then led to unattainable performance and range predictions, and it expected to accomplish all of this in record setting time."
Another close aerospace parallel was the commercial RLV craze of the nineteen nineties, with companies like Kistler, Kelly Space & Technology, et al threatening to blacken the skies with satellite constellations, Elon style.
 
"A disaster of this size has many causes, but the most fundamental was a fantasy about the economics of designing, building and supporting airplanes. The company also predicted impossibly low empty weights, which then led to unattainable performance and range predictions, and it expected to accomplish all of this in record setting time."
This is not only about the aviation industry. Anyone still remembers the bubbles about Second Life? or MySpace? Companies like Mercedes investing Megabucks in virtual showrooms that would replace blahblahblah?

Basically, there are many people with more money than smarts. Anytime people start to invest into technologies they don't understand, then they do deserve what's coming to them. Con men will never be in short supply.
 

Evtol industry…….'fake it until you make it' culture is still alive and well ……. sooner or later ….too many inexperienced startups trying to build quite advanced aircraft designs……. next few years there will be a bloodbath……..A disaster ….. the most fundamental was a fantasy about the economics ……..predicted impossibly low empty weights…….unattainable performance and range predictions,…………accomplish all of this in record setting time.

In the near future prison’s (State Pen’s) will no longer have their inmates stitching mail bags, or breaking rocks, instead they’ll be hosting innovation hubs, delivering TED talks and running techno creativity centres. Ah for these modern times.
 
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In the near future prison’s (State Pen’s) will no longer have their inmates stitching mail bags, or breaking rocks, instead they’ll be hosting innovation hubs, delivering TED talks and running techno creativity centres. Ah for these modern times.

Who will be the audiences? If they're inmates, wouldn't that be 'cruel and unusual' punishment?
 

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It's not quite a evtol but still a fascinating concept. But there already is an ongoing effort to convert Cessna Caravans for unmanned cargo flights that would be a much more practical solution. Also a large unmanned aircraft is going to have a hard time being approved to fly over populated areas.

 
The USAF awarded Jetoptera, Inc. a Direct to Phase II Small Business Innovation Research (SBIR) contract. Jetoptera will design, build out and test an Upper Surface Blown Wing (USB) equipped, powered high-lift test article integrating Jetoptera’s Fluidic Propulsive System (FPS™), to characterize and further demonstrate the potential of FPSTM to create a signature managed propulsion for VTOL aircraft. The experimental data will be used to deliver a conceptual design of a High Speed Vertical Take Off and Landing (HSVTOL) aircraft.


 
C'mon. Have you flown an LSA? Teenagers think they are as good as any normal airplane. 40 something years old... Don't.
 

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