VTOL On Demand Mobility

Zoo Tycoon

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And yet another short haul electric project materializes. I'm not an aircraft engineer but those engines seem ridiculously small for an aircraft of that size.



I reckon this as one of the more reasonable proposals although with the usual caveats;- it’s wing aspect ratio gives good cruise performance, while its wing area, combined with flap (Cl max) yields the very low landing speeds (55kts) which is essential for getting into the small strips. Yes the wing mass and turbulence response are both undesirable.The claimed mass fractions don’t look too unrealistic but the performance claims again seem to lack a climb fraction, battery aging fraction, battery operating low temperature fraction, real world considerations such as anti icing etc and again it maybe over reliant on maintaining natural laminar flow.

Yes the motors do look small but assuming they’re axial flux they might not get that much bigger. The prop idea is really novel and technically interesting, but I don’t like the concept of having the pax walking through the prop arc to board the aircraft. Props are real dangerous and Pax can be real dumb….. a combination made safe by a few switches?

One aspect never mentioned by these wannabe companies is the public liability aspect and potential litigation. I once worked with the former chief engineer of BAE Systems Jetstream business and he informed that this market sector was particularly bad compared to others. The basic problem was the operating organisations (airlines and airports) were typically too small/marginal to adequately manage the full range of business and technical risk. Incidents and business failures would routinely spill over to the aircraft provider, who was sued as they represented a very lucrative, indeed the most, cash rich target. The main reason BAESYSTEMS pulled out of the sector was a continuous trading loss coming from legal defence costs. Very few claims against them were successful but they had to pay money out of the business to fight every single one, and there were a lot.
 
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AeroFranz

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“In a normal aircraft, it makes sense to have this quite complex and heavy mechanism on your propeller in order to operate optimally over the whole range,” said Norcia. “Electric propulsion provides some opportunities to just massively simplify the aircraft. So all four of the propellers are fixed-pitch: the ones in front are pitched for takeoff and climb out, and the rear ones are for cruising.”

With a heavy, complex, expensive traditional engine, it would be silly to double the number just so you don’t have to use variable pitch propellers for takeoff. But with light, simple, inexpensive electric engines, it makes perfect sense to do so, even if it looks unusual.

The front and rear propellers are only both active during take-off and climbing, with the front ones folding away afterwards as then the rear ones take over completely for cruise. It mechanically simplifies things — no heavy duty hinges and hydraulics — and in fact putting the prop back there seems to improve efficiency by about 10%, said Norcia. “It’s pretty cool,” he added. (And they’ve applied for a patent.)
In the renderings the rear props are folded while on the ground - makes sense since you don't want to let passengers wander into the sharp bits. However those are referred to as 'cruise props' and the front ones as 'takeoff/climb out', so BOTH sets of props are folding, is my interpretation.
I'm glad they have picked a sensible configuration, it is less likely they will go back to the drawing board once they realize all the hidden problems of unconventional layouts (i'm looking at you, Eviation).
I would have thought their vertical tail would be smaller, given how with four electric engines (and with the proper powertrain architecture) they can essentially guarantee there will never be a strong 'motor-out' yawing moment. The big verticals are the bane of conventional twins, it's curious theirs seem similarly sized even though at first sight they have a solution that doesn't need it.
Other things to note: the presence of pusher props means there's no good place for a flap, which is typically inboard. Maybe they don't need one because the wingloading is low enough. But then, as mentioned previously, they have a combination of high aspect ratio and low wingloading, which is precisely what you don't want for flying in rough air.
I wonder where the batteries go...under the floor?
 

alberchico

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And yet another short haul electric project materializes. I'm not an aircraft engineer but those engines seem ridiculously small for an aircraft of that size.



I reckon this as one of the more reasonable proposals although with the usual caveats;- it’s wing aspect ratio gives good cruise performance, while its wing area, combined with flap (Cl max) yields the very low landing speeds (55kts) which is essential for getting into the small strips. Yes the wing mass and turbulence response are both undesirable.The claimed mass fractions don’t look too unrealistic but the performance claims again seem to lack a climb fraction, battery aging fraction, battery operating low temperature fraction, real world considerations such as anti icing etc and again it maybe over reliant on maintaining natural laminar flow.

Yes the motors do look small but assuming they’re axial flux they might not get that much bigger. The prop idea is really novel and technically interesting, but I don’t like the concept of having the pax walking through the prop arc to board the aircraft. Props are real dangerous and Pax can be real dumb….. a combination made safe by a few switches?

One aspect never mentioned by these wannabe companies is the public liability aspect and potential litigation. I once worked with the former chief engineer of BAE Systems Jetstream business and he informed that this market sector was particularly bad compared to others. The basic problem was the operating organisations (airlines and airports) were typically too small/marginal to adequately manage the full range of business and technical risk. Incidents and business failures would routinely spill over to the aircraft provider, who was sued as they represented a very lucrative, indeed the most, cash rich target. The main reason BAESYSTEMS pulled out of the sector was a continuous trading loss coming from legal defence costs. Very few claims against them were successful but they had to pay money out of the business to fight every single one, and there were a lot.
You raise a good point about liability. In the U.S. there was an important piece of legislation enacted called GARA that shielded manufacturers like Cessna and Piper from frivolous liability claims and allowed the general aviation sector to roar back to life. I assume somethimg similar could be put in place to help the Evtol sector thrive. Just out of curiosity, does Europe have anythong similar to help protect its smaller GA manufacturers from liability abuse ?

 
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TomcatViP

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I wonder where the batteries go...under the floor?

It would sound good for the stability. But given the large span wing, maybe in the center wing section. There is also the fact that cabin section is rather minimal when you think that passengers would have to crawl their way forward ro reach their seats.

passenger-hero-tablet-1200.jpg


Probably a little extra work needed.
 

Zoo Tycoon

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It would sound good for the stability. But given the large span wing, maybe in the center wing section. There is also the fact that cabin section is rather minimal when you think that passengers would have to crawl their way forward ro reach their seats.

I would put the battery in the wing and quite outboard too, as it offsets spar bending I.e. span loading. Sure, the fuselage frame extending down to landing gear needs to be a bit chunky but this is minor compared to the mass saving in the wing spar. Whilst the cg will be a bit higher, adding some more main wheel track maybe required to keep a sensible turn over angle.
 

alberchico

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I wonder if the solution favored by the Tecnam P-Volt that involves mounting the bulk of the batteries in a streamlined belly pod is the best one. I believe that would be the safest location in case of a thermal runaway event. Considering that Tecnam and Rolls Royce have more experience with the certification process than these start ups, maybe that configuration has the best chance of getting approved by regulators. But there would be quite a bit of drag with a belly pod though, so it's a tradeoff between performance and safety.
 

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TomcatViP

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Well, you can do a recess belly pod and have the battery pack flushed with the outer skin.
In any way, the risks with a thermal runaway and fire would require a new kind of fire wall that can sustain that kind of fire. So, the extra mass of the firewall should be combined with a structural element (imagine that the firewall is made of extra thick aluminum sheet or thinner stainless steel).
That's why, IMOHO, the overhead central wing position could be a good candidate as are the center wing sections (you can over dimension your wing spar there to surround a battery pack). .
 
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Zoo Tycoon

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I wonder if the solution favored by the Tecnam P-Volt that involves mounting the bulk of the batteries in a streamlined belly pod is the best one. I believe that would be the safest location in case of a thermal runaway event. Considering that Tecnam and Rolls Royce have more experience with the certification process than these start ups, maybe that configuration has the best chance of getting approved by regulators. But there would be quite a bit of drag with a belly pod though, so it's a tradeoff between performance and safety.

Ah….with an underfloor battery pod then CS23.563 c 1-3 becomes seriously challenging. This is the regulations concerning landing gear collapse and landing on the belly. Having seen the intense fire that emerges from a punctured battery,this’ll never be tolerated in a certification compliance. Making a pack that you can impact into the runway at 12+fps, with asymmetric loading, with several tons of aeroplane on top, sliding at maybe 100fps on asphalt and guaranteed not to disrupt…. seriously challenging…..and if realised extremely heavy.

Also such a pod increases both the wing spar bending and wetted area (drag).

Best development approach;- delete the problems by locating the battery in the wing, within a vented fire box.
 

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I think the idea of the pod is to be capable of being released in flight in case of an emergency. If there is a battery fire, the best way to put it down could be to drop it away. Then, either a safety battery take over or a dead stick landing has to be done anyways.
 

Zoo Tycoon

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I think the idea of the pod is to be capable of being released in flight in case of an emergency. If there is a battery fire, the best way to put it down could be to drop it away. Then, either a safety battery take over or a dead stick landing has to be done anyways.

Ah no, not certifiable under CS23.1300 where maximum mass that can detach is 0.5kg. Good requirement too as a ton or so, of burning
battery pack coming in at 9.81m/s2 is an unwelcome gift to anyone on the receiving end.
 
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TomcatViP

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The idea into that is not to be at the end point of the whole 10000lb of an a/c crashing. ;)
Single engine a/c operating under cs23 have anyway to route plan for crash landing.

See it has a radical adaptation of fuel jettison...
 
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Zoo Tycoon

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Single engine a/c operating under cs23 have anyway to route plan for crash landing.

So prior to 2017, commercial operation of Single engined turboprops in Europe were limited to VFR, so inherently good weather only operations. This made commercial operations close to impossible. Then came along “EASA Commission Regulaton (EU) 2017/363 of 1 March 2017 IFR operations of single engine turbines on commercial flights” which allows IFR flights if the type being used, is of established reliability and CS23 compliant. From what I can tell this puts them on an equal operational status as twins and it doesn’t specifically mention any engine failure route planning or restrictions.

It would be really appreciated if you could point me in the direction of SET specific engine failure route planning or restrictions.
 

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@Zoo Tycoon : The confusion comes from the category of a/c:
Turbine and Jet are class A
Propeller single and multi engine reciprocated with less than 9pax and 5700kg or less are class B

Commercial flights of those two categories have different limitations.

Then this is on top of my head only (I should know better).
 
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GTX

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The landing gear with its total absence of wheels is interesting. You have to wonder what's the logic behind such a choice.
 

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I think the idea of the pod is to be capable of being released in flight in case of an emergency. If there is a battery fire, the best way to put it down could be to drop it away. Then, either a safety battery take over or a dead stick landing has to be done anyways.

Ah no, not certifiable under CS23.1300 where maximum mass that can detach is 0.5kg. Good requirement too as a ton or so, of burning
battery pack coming in at 9.81m/s2 is an unwelcome gift to anyone on the receiving end.

ISTR there's a basic aviation ops reg that outlaws dropping anything from an aircraft (well, civil ones, anyway), so it's not just a certification issue, it's an ops one.

CAA really aren't likely to be enamoured of the potential of flaming battery packs dropping on, for instance, hospitals, schools, or chemical plants.

And that's before the Security Services start considering the unpleasant security complications of an aircraft designed to drop a 1 tonne kinetic energy weapon....
 
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DWG

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The landing gear with its total absence of wheels is interesting. You have to wonder what's the logic behind such a choice.

I can't help suspecting: "Oh god we need to save another 500lbs or we'll never be able to lift off"

And definitely not: "So what happens if we land the aircraft on three 10cm2 pads on a wet pasture?"

On top of which it's going to complicate their ground handling, though I suppose they manage with skid-equipped helicopters.

In their favour, packing a ballistic recovery chute does mean they won't need to consider run-on landings in their failure conditions.
 

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www.Vy400.com :
"Early position holders will receive a custom completion with exclusive interior and exterior design, colors, and paint scheme. This lighter, faster, racing-inspired edition, will be designed and completed to your unique taste and specifications as an early position holder."
"With custom completion, the total purchase price is estimated at USD $6,000,000."

"The Vy 400 VTOL aircraft is expected to be launched at a price of approximately $3.5m."

"15 VTOL prototypes have been built and tested by the company prior to the production of Vy 400.

Of the 15 prototypes, 14 were installed with electric engine propulsion for flight testing, while one was installed with a gasoline engine."

"The Vy 400 VTOL aircraft is powered by a Pratt and Whitney Canada PT6A-67F turboprop"

So they're charging $2.5m for racing stripes and seats, and planning to certify not one, but two variants ('lighter, faster') in the next 30 months, despite not having built a production standard aircraft to date ('electric engine', 'gasoline engine', PT6A).

And with a new build-to-print contractor - I hope Kaman have demanded money up front!

"The geo-fencing and pulse sensor technologies further ensure smooth, safe and targeted flying, while avoiding obstacles in the flight path. The systems allow the aircraft to fly back to the designated area."

What does this even mean?

(Considering geo-fencing is mostly used in relation to UAVs, I really hope they're not implying it has autonomous capability)
 

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Fly by the Playstation, I guess.
(you can also see the raised seat headrest for the pilot on the port seating position in the cockpit)

But if that thing has a sense and avoid system, by itself, it's revolutionary (Kaman?)
 

AeroFranz

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The landing gear with its total absence of wheels is interesting. You have to wonder what's the logic behind such a choice.
REALLY odd. Especially since a tilt-wing configuration gets a very nice payload/range boost if used in STOL mode. This may not be the most frequent use case, but when possible, you could really improve the performance of the vehicle.
 

alberchico

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View: https://www.youtube.com/watch?v=6uktNthAPKE&ab_channel=EHang


Finally we get to see factory that EHang has built to produce these things in large numbers. They even have a fire fighting version, which you can see in action below. I have no idea how practical this would be in a real world situation, but it's nice to see they are racing at full speed to certify this technology and put it into service.

View: https://www.youtube.com/watch?v=3oVlwOHszhg&ab_channel=EHang



This video provides an overview of the company's evtol operations. At 44 seconds in you will see the spacious control room that is required to operate all these vehicles autonomously. Considering the massive investments in infrastructure that are required for these types of operations, as well as all the trained personnel required, I wonder how long it might take this company to make a profit on these evtols.

View: https://www.youtube.com/watch?v=YsUTGjX3YDk&ab_channel=EHang
 

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Fly by the Playstation, I guess.
(you can also see the raised seat headrest for the pilot on the port seating position in the cockpit)

But if that thing has a sense and avoid system, by itself, it's revolutionary (Kaman?)
X Plane 11 I would expect.
 

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Curious if there is a BRS (Ballistic Recovery System) installed in the EHang design in the event of a power loss, guidance system hack, or uncommanded roll into a building. I have not seen any tests with these type vehicles of a BRS system. The VY400 is supposed to be designed with a BRS system, but I'm curious how this would work in VTOL mode.
 
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Dynoman

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The problem with recovery of a VTOL aircraft via BRS is that BRS systems similar to a Cirrus require forward speed or a drop in altitude of 900-1000 ft to inflate the parachute canopy. Aviation Safety Resources has designed a ballistic chute system that inflates multiple small chutes that require less time to inflate.
 

Zoo Tycoon

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The problem with recovery of a VTOL aircraft via BRS is that BRS systems similar to a Cirrus require forward speed or a drop in altitude of 900-1000 ft to inflate the parachute canopy. Aviation Safety Resources has designed a ballistic chute system that inflates multiple small chutes that require less time to inflate.

According to EASA, a BRS cannot be credited within the certification safety case. They’re classified as survival equipment. If the certification is satisfied, the loss model achieved, it means the BRS is obsolete, and becomes a very costly burden for the operator to carry around (it’s mass displaces a fare paying pax) and maintain. Likewise if the BRS is essential for the safety case, the thing is not certifiable. Indeed with the risk of inadvertent deployment it may degrade the certification.
 

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According to EASA, a BRS cannot be credited within the certification safety case. They’re classified as survival equipment. If the certification is satisfied, the loss model achieved, it means the BRS is obsolete, and becomes a very costly burden for the operator to carry around (it’s mass displaces a fare paying pax) and maintain.
This is true according to the article below. In fact EASA penalizes manufacturers for the inclusion of a BRS system in their designs. EASA's goal is to push manufacturers to devise a means of a "controlled" and "steerable" descent, or essentially a controlled crash in the event of a catastrophic failure. Unfortunately, many of the designs provide no other means of vertical lift to control the rate of decent other than the designs primary powered lift system.

 

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Interestingly they're only contracting for c3 hours operation a day (1000 hrs/year), that seems on the low end for profitable operation.
 

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AFWERX program update:


Some news regarding Barracuda:
 

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results are rightly described as "remarkable." The lithium-metal battery with this architecture had an energy density of 560 Wh/kg. For context, there are research consortiums dedicated to breaking through the 500-Wh/kg density threshold in order to power next-generation electric vehicles, while today's best-in-class lithium-ion batteries have energy densities of 250 to 300 Wh/kg.

 

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And a competing technology: Fuel cell with Hypoint design promising high output power for a lower mass (devoid of the H2 storage system mass)


You can download their white paper on their website that is rather complete but still intuitive, even if IMOHO their claim to have invented air cooled Fuell Cell is rather dubious.
They also have what seems to be an error on their price scale (up to 500$/KW) in the GA, VTOL range of power (I can't believe they would seriously charge 250 000$ for a 500KW engine with only a 15000h life span uninstalled).
 

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Bristow signs MoU to assist in development and take 50 aircraft, but the design is eSTOL rather than eVTOL, which seems a little odd given Bristow is a helicopter operator.

On the plus side, they have a realistic assessment that Part 23 certification will take them until 2026, unlike the various eVTOL manufacturers claiming they'll have it done within 18 months.
 

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The Transwing configuration is elegantly simple compared to many other VTOL approaches. On the question of the high loads on the wing pivot hinges and mechanism, that is certainly a challenge but not one I think is that is technically challenging to overcome in my opinion.

It might not be "technically challenging" (you can always add more material) but it probably won't be light.
 

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results are rightly described as "remarkable." The lithium-metal battery with this architecture had an energy density of 560 Wh/kg. For context, there are research consortiums dedicated to breaking through the 500-Wh/kg density threshold in order to power next-generation electric vehicles, while today's best-in-class lithium-ion batteries have energy densities of 250 to 300 Wh/kg.

This makes me wonder if sodium batteries could be amenable to a similar chemistry and enable cheaper high power density than lithium.
 

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This makes me wonder if sodium batteries could be amenable to a similar chemistry and enable cheaper high power density than lithium.

Given how much more reactive lithium is than sodium, I suspect it would be cheaper, but less capable - given the length of time we've had lithium batteries and how ubiquitous they are, we'd already have seen sodium challengers for the existing lithium battery technologies if they were viable, and we haven't.

And then there's the weight factor, lithium's atomic weight is 7, while sodium's is 23, so a lithium battery would always have an energy density advantage even over a sodium battery with otherwise identical chemistry and performance.
 

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Good counterpoints. I was hoping sodium could be a cheap low-rent alternative for lithium in contingencies.
 
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CATL is marketing a Sodium battery, one can probably look at the spec sheet for a rough idea on how this chemistry would work out.:
Seem usable but inferior, probably make sense in fixed storage and less mass critical applications like trains or ferries and some low end cars.

If we are talking about metal air batteries overall though, it is still far from mature with unsolved cycle life/safety/etc problems and would likely come only after both solid state and silicon anode technology which is decade(s) down the line.
 

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