The future of the helicopter is electric.

[Reely340]

We know weight / stability of current helicopters works, with a certain margin.
E.g. lightening the helicopter's structure (mast, blades, frame) won't work or it'd been done already.

Swapping in an electirc motor (and possibly gearbox) for the current combustion type might give an weight advantage in case of piston-engines but definitely will incur a hefty penalty when looking at recent turbines power/weight ratio.

For the sake of this argument we'd kindly and assume NO weight penantly when switching to electirc drive train.
Considering that takeoff in an S300C at 3000ft and ISA+30 with two wellfed occupants and full tanks is not possible,
we can assume that the power source must not be heavier than AVGS.
Looking at available space the volume of the powersource might be al little more voluminous per MJ (energy measure).

Looking at the graphics we may pick anything to right of "Gasoline" (weight issue) and upward of LNG if we want similar endurance and tank volume as with AVGAS.

If one looks at where Li-Ion Battery oder Zinc-Air Battery is positioned it becomes quite evident that current production technology work work:
We'd need twice the physical tank volume for a Li-Ion battery (zinc-air would be same volume as avgas tank)
but would get far less then one tenth endurance due to lacking energy/weight density.

That would insinuate the S300C would be out of "fuel" after 20 Minutes hovering.

BUT if the tech guys manage to get Lithium Borohydride "to fly" (pun intended) the world (of piston helos) would change:
A LiBH4 battery packs the energy both tighter (volume) AND lighter (weigth) than any of our beloved liquid gasolines.


Energy sources grouped according to volume density and weight density

[Reely340]

Originally Posted by Arnie Madsen

The smaller the aircraft , the better electric works (drones etc) .... much larger and results diminish .... something to do with molecules of air on a small propeller at high rpm .... compared to larger blades at lower rpm. (small works better).

Bad example. Electric drones only work because customer is happy with 20 mins endurance.
Load them up to carry juice for the 3h helo pilots are used to and they'd not be able to takeoff.
Beef up engines, rotors and electronics so that they be ableto fly, you#d be back to square one,
having to add more battrey to achive 3h ... ad infinitium.

=> Li-Ion won't cut it, ever. If you want a combustion helo's endurance, that is.
As a 20 min toy they do extremely great.

[Reely340]

Originally Posted by Reely340

BUT if the tech guys manage to get Lithium Borohydride "to fly" (pun intended) the world (of piston helos) would change:
A LiBH4 battery packs the energy both tighter (volume) AND lighter (weigth) than any of our beloved liquid gasolines.

let me add that above is true IF and only if that new Lithium Borohydride Battery will provide its massive energy in a fast fashion.
If fully darining it take 3 years, it might be great in sattelites but not in high yield applications like helos.

[cattletruck]

I must admit I remain very impressed with Oskar's ingenuity, besides the battery limitations I'm sure his rig lets him explore other ideas such as his quad electric tail rotors. If I were ever crazy enough to undertake a similar venture I would relocate the tail rotors to both sides like elephant ears but on shorter booms. This will then allow both sides to provide anti-torque in the hover and when moving forward one side can be reversed so that both sides can provide a propelling force.

Thanks for the graph Reely340, it really does put batteries in perspective (and also wastage of energy by liquid fuels).

[MeddlMoe]

This Technology is also very promising for hydrogen powered electric aircraft:
https://www.fraunhofer.de/en/press/r...-scooters.html

[MeddlMoe]

Originally Posted by cattletruck

If I were ever crazy enough to undertake a similar venture I would relocate the tail rotors to both sides like elephant ears but on shorter booms. This will then allow both sides to provide anti-torque in the hover and when moving forward one side can be reversed so that both sides can provide a propelling force..

The Airbus Racer configuration?

[MLH]

Originally Posted by MeddlMoe

The Airbus Racer configuration?

Or a coaxial design.

[WillyPete]

Originally Posted by cattletruck

I must admit I remain very impressed with Oskar's ingenuity, besides the battery limitations I'm sure his rig lets him explore other ideas such as his quad electric tail rotors. If I were ever crazy enough to undertake a similar venture I would relocate the tail rotors to both sides like elephant ears but on shorter booms. This will then allow both sides to provide anti-torque in the hover and when moving forward one side can be reversed so that both sides can provide a propelling force.

Thanks for the graph Reely340, it really does put batteries in perspective (and also wastage of energy by liquid fuels).

Yeah this is what I proposed above.
Don't see why it couldn't work.

[Fark'n'ell]

A three phase electric motor weighs close to 3000 lbs and draws about 300 amps.I would think a battery to supply that amount of energy for a small amount of time would weigh about the same..Have'nt started on the airframe yet

[Arnie Madsen]

Originally Posted by cattletruck

I must admit I remain very impressed with Oskar's ingenuity, besides the battery limitations I'm sure his rig lets him explore other ideas such as his quad electric tail rotors. If I were ever crazy enough to undertake a similar venture I would relocate the tail rotors to both sides like elephant ears but on shorter booms. This will then allow both sides to provide anti-torque in the hover and when moving forward one side can be reversed so that both sides can provide a propelling force.

Thanks for the graph Reely340, it really does put batteries in perspective (and also wastage of energy by liquid fuels).

As far as the tail rotor , Oskar said he tested many different methods ... and was somewhat surprised that multiple independent small rotors were the best .

It is agreed that the current test model looks like a thorn bush on the end of the boom but I expect he will tidy it up some day ..... on that note it appears that Bell Helicopters came to the same conclusion with their multiple electric tail rotor prototype.

Another thing to keep in mind is that Tesla cars took a giant leap forward with their motors .... something like permanent magnets on the armature itself which makes tremendous torque ... I am not an expert on electrics but have the proper info on a different computer and will post it later.

Oskar is not using a Tesla motor but found something unique for his main power ... later I will post it also.

======================
EDIT to add pictures

.

[CTR]

Looks like Bell covered the open rotor “thorn bush” configuration also in their patent for the electric tail rotor.

Great minds think alike.

[skridlov]

https://www.theverge.com/2022/5/26/2...part-135-evtol

[Lonewolf_50]

Originally Posted by skridlov

https://www.theverge.com/2022/5/26/2...part-135-evtol

From the above link

The company says it aims to have a full-scale air taxi service in operation by 2024.

Who is their customer based believed to be? That might be a very pricy cab ride.

[Winemaker]

One question is where these machines, if certified, will be allowed to land. It's not as though one can sort of randomly pop down and pick up passengers....... Duration might also be an issue..... My brother lives on Pine Lake in Sammamish, Washington; one of the residents wanted to use his helicopter to commute to work; he was allowed a single landing per day with time limitations over vociferous opposition of other residents.

[Less Hair]

If the market would require all those electric VTOLs wouldn't we see way more helicopters used today for short passenger flights on all those expected drone routes?

[ShyTorque]

A disadvantage of battery powered aircraft is that they don’t burn off fuel in flight. The aircraft weighs the same at destination as on departure and the performance remains the same throughout.

Not really a problem for a small helicopter remaining at low altitudes, but definitely so for something larger, a utility aircraft or an aeromedical/ SAR one.

[601]

nasa have actualy just developed new wire cable to convert the flat electrons into round ones, by narrowing the cable down (like a funnel) it squashes them into a ball which greatly increases the rate at which work can be done

Gee it is amazing how technology solves everything.

It has been discovered that making electrons into small cubes and converting them into magnets solves the problem having wasted space around spherical electrons in a cable and flat electrons (no power left at the end of the cable)
It also dispenses the need of the permanent magnets in the motors. Replacement magnets are fed in as cubical electrons

However, research is still required into the square sectioned cable and the difficulty of moving cubes of electrons, that are magnetically attracted, around a bend in the cable and how to convert the cubical electrons into large permanent magnets.

Word has it that they may solve this problem in 20 or 30 years.
http://www.dumbscience.com

[Winemaker]

Originally Posted by 601

Gee it is amazing how technology solves everything.

It has been discovered that making electrons into small cubes and converting them into magnets solves the problem having wasted space around spherical electrons in a cable and flat electrons (no power left at the end of the cable)
It also dispenses the need of the permanent magnets in the motors. Replacement magnets are fed in as cubical electrons

However, research is still required into the square sectioned cable and the difficulty of moving cubes of electrons, that are magnetically attracted, around a bend in the cable and how to convert the cubical electrons into large permanent magnets.

Word has it that they may solve this problem in 20 or 30 years.
http://www.dumbscience.com

Well I'm holding out for the toroidal electrons, as getting zapped would be a delicious experience. Plus they could just slide down the outside of (round) wires greatly reducing friction.

[fdr]

electric efficiency

Originally Posted by ShyTorque

A disadvantage of battery powered aircraft is that they don’t burn off fuel in flight. The aircraft weighs the same at destination as on departure and the performance remains the same throughout.

Not really a problem for a small helicopter remaining at low altitudes, but definitely so for something larger, a utility aircraft or an aeromedical/ SAR one.

Originally Posted by ShyTorque

A disadvantage of battery powered aircraft is that they don’t burn off fuel in flight. The aircraft weighs the same at destination as on departure and the performance remains the same throughout.

Not really a problem for a small helicopter remaining at low altitudes, but definitely so for something larger, a utility aircraft or an aeromedical/ SAR one.

unless they can be jettisoned...

Good point on efficiency, though. Fuel fractions are a major driver of excess power available.

Nick P had commented on the mass of electric motors vs engines, and his figures are correct for most motors, but there are some stunning motors available. A long time back, a certain French inventor came up with a nice little design that was plonked into the back end of a B206 for testing, and it was lighter than the RGB that it replaced. The power cables were about a wash. The motor design was pretty neat, but the tech owner was particularly sensitive to IP issues and barely gave information to the engineers to do the test. The size form was neat, and the output was scalable. The rotor efficiency can be improved by an incremental margin, but not enough to make up for the battery power density. What would be intriguing would be to have a hybrid design using the same novel motor as a generator to reduce mass, and using same for drives. staying with a lightweight generator with a reduced fuel load and using high density batteries... maybe there is a future. The novel motors were light, really really light. Haven't spoken to the guy for many years, his paranoia may have had justification, but Lordy it made it hard to get anything done.

As to what can be done on the rotor, about 25 years ago (? 97? could have been around 2003...) there was a neat little engineering note in the AIAA JoA that covered some interesting CFD done with Wayne Johnsons CAMRAD II on autorotation of a disk (+ dangly bits) applying lift enhancing tabs, LET's to a rotor. There was no methodology of the structure which has been a pain for implementation. I had been doing tabs on propellers for about 10 years by then, and had transferred that to flight testing on a 12":1' scale helicopter. The CFD gave an improvement of 20% in autorotation, but used a design that was known to be far from optimal from the prop and rotor testing, but was at least interesting, as LETs alter the L/D in such a way that it is conceivable that they preclude autorotation in a fixed geometry. In the end, auto worked OK, but it was a very uncomfortable flight getting out there to try it the first time. Parachutes from a helo have some obvious technical drawbacks. Glad to never have to see if the technique would work to remove the blades without removing the top of the cabin.

The curious outcome suggested that the variation of the coefficients of CL and CD were effective as follows...

• Baseline 63105 blade, NACA smooth, rotor stall at 82% Nr, measured fuel flow, 62 units( fuel flow and engine power were quite linear)
• MOD 1, (leading edge of blade, certified later) rotor stall at 77% Nr, 58 unit fuel flow... pitch link loads reduced
• MOD 1 & 2 (adding an LET...) rotor stall at 68%, 39 unit fuel flow. loads per MOD 1. Acoustic spectrum attenuated, but added a 1600hz line
• collective loads measured and no significant change from baseline, other than SR was reduced, as was vibration.

The MOD 2 change appeared to be considerable, and raised questions about the accuracy of the measurements, but the Nr was strobed and was valid, and the stunning control effect was that the baseline chopper gets to LTE about the same time it runs out of rotor, Mod 1 recovers some pedal at the stall, indicating the torque demand has definitely improved, and then with the tab, approaching the stall, the pedal demand was 50% of the left pedal of the baseline case. The last check before going into translational flight and autos was to go to idle, set full up collective and see if the rotor could accelerate, and it did, was able to accelerate and lift off and hover with a full up collective, Unmodified, the rotor would not accelerate to flight speed. This little project languished as it became secondary to modification to jet aircraft, and my helicopter had one bit of design that made high speed testing of a tab uncomfortable from a risk aspect, it had a TRB that was not confidence building for dropping bits off. I did some failure tests, and videoed the tabs departing from the rotor, and at low speed they had departed merrily away from. the TR disk, but in forward flight that may not have been the case. Was working up to testing NOTAR or fenestron before going back to a light structure TRB, but a UH-60 TR would have worked... The tabbing model CFD'd in JoA I also flew, and it was not effective at improving CL/CD, it did definitely increase CL, but that is never in doubt, only whether the rotor AOA puts the CL/CD into the position where stunning changes occur. Tabs shift CL by around 0.4 - 0.6 CL for the same AoA, dependent on multiple parameters but that is indicative. How it is done on a rotor is somewhat more interesting than the CFD model, in the real world that config made almost no improvement.. hardly a surprise. The CD however is altered stunningly at mid AOA levels, like those associated with props and rotors and fans, sections that are constrained from approximations of ideal blades. We did the tabs as well on the CART 2 test rig of NREL, and that was effective, but then the CART 2 section is a pretty awful analogue of optimised wind turbine blades. Torsion loads were no factor which was similar to the rotor. The tabs do mitigate a bit the hysteresis of the coefficients from pitching effects, the stuff that Boeing Vertol was trying to sort out on the CH47s VR7 blade section by using VGs. John C Lin and co of NASA showed how wild the CD shift could be, however the implementation on a propeller, rotor or fan blade has some constraints that make the hover value that I got closer to the practical limit than Lin, Storms, Carranto and co's theoretical limits. If anyone has a test vehicle that is NOTAR or has a fenestron, (or a UH-60...) the LET is worth the candle IMHO.

[jimjim1]

There are a few companies spending huge sums on drone style Air Taxis.

Also Bell and Airbus have something in this area too.

Most info from https://craft.co/lilium/competitors.

The three below apparently total about 2400 employees. These are engineers who are all in great demand and will not be cheap. Total investment so far is over $1B.

I have found:-
## Joby Aviation ##
Santa Cruz, US

845 employed

Funding raised $691M

## Lilium ##
Munich, Germany

In 2020 employed 400 people, now 908

Maybe raised something like $500M

NasdaqGS

Sept 2021 $10
May 2022 $ 2.82
Market Cap $814M

## Velocopter ##
Bruchsal, Germany

530 employed
$372M raised