PPRuNe Forums

PPRuNe Forums (https://www.pprune.org/)
-   Rotorheads (https://www.pprune.org/rotorheads-23/)
-   -   Electric tail rotor; an alternative? (https://www.pprune.org/rotorheads/615965-electric-tail-rotor-alternative.html)

abgd 3rd Dec 2018 23:05

The other reason you don't need a lot of power to the tail during autorotation is that you don't have to overcome the torque of the main rotor. A smallish battery would be enough.

I completely understand PilotDAR's point about thinking about certification throughout the design process, but there's still a big difference between discussing innovations that obey the laws of physics and those that don't.

Pilot DAR 4th Dec 2018 00:52


I'm not sure how you'd train to cope with anything that causes a stuck main rotor actuator.
I trained for stuck collective and it was manageable. Helicopters have a few more vulnerable lift, thrust and control elements than airplanes do. A lot of design consideration has gone into maximizing reliability, and creating compensating systems or flying techniques. Generally, they work, and if indeed, helicopters were flown like airplanes (avoiding hovering), more failures would be more manageable, but then it would kind of defeat the basis for choosing a helicopter for the role. Helicopter operations by their nature require accepting some additional operating risk, and vulnerability. For my experience, a main transmission driven tail rotor/fan provides the greatest opportunity to design out failure points and increase reliability.

Washeduprotorgypsy 4th Dec 2018 02:12

Seeing as this thread is a slapstick offshoot of the Leicester aw169 thread. And using 10-15 % Q as TR power consumption on an aw169 , AEO xmsn rating of 1500 hp. The electric motor off the Cessna 172 will substitute nicely for a electric driven tr on the aw169 , though coming up short by 70 hp if you take 15% Q to be closer to what the mechanically driven version can muster.

So you add the weight of a an Lyco 0-320(+10%) ..~300 lbs on to the tail end, ~350 lbs for the generator, ~600 lbs nose ballast , 400 lbs structural reinforcement. Voila....a perfect locomotive. A little sluggish in pitch when the electronic motor control gets buggy and the need for speed in the necessary autorotation occurs. There is no reason this can't work.

You would expect an electric motor employed in human carriage at altitude to be quite reliable , say close to what the failure rates on an elevator motor might be. Speak to your millwright or elevator buddies as to what a cutting edge gearless motor in the 150 hp department might weigh......~2000 lbs. Making it aviation grade, you build the frame out of aluminium and use titanium bolts.~1700 lbs. I don't want wreck it for Star Wars fans around Christmas time but this I is fantastic ground bound technology.



[email protected] 4th Dec 2018 06:23


I trained for stuck collective and it was manageable.
only if the collective is stuck in mid-power position or close to it - did you try it at very high power or very low power? Presumably it was on a single with a hand-throttle rather than a FADEC twin.

Washeduprotorgypsy - finally, the voice of reason:ok:

gevans35 4th Dec 2018 06:36

https://cimg0.ibsrv.net/gimg/pprune....61d59fb20e.png

GrayHorizonsHeli 4th Dec 2018 11:10

Thanks Gypsy for the morning laugh lol

dClbydalpha 4th Dec 2018 11:51


Originally Posted by Washeduprotorgypsy (Post 10327325)
Seeing as this thread is a slapstick offshoot of the Leicester aw169 thread. And using 10-15 % Q as TR power consumption on an aw169 , AEO xmsn rating of 1500 hp. The electric motor off the Cessna 172 will substitute nicely for a electric driven tr on the aw169 , though coming up short by 70 hp if you take 15% Q to be closer to what the mechanically driven version can muster.

So you add the weight of a an Lyco 0-320(+10%) ..~300 lbs on to the tail end, ~350 lbs for the generator, ~600 lbs nose ballast , 400 lbs structural reinforcement. Voila....a perfect locomotive. A little sluggish in pitch when the electronic motor control gets buggy and the need for speed in the necessary autorotation occurs. There is no reason this can't work.

You would expect an electric motor employed in human carriage at altitude to be quite reliable , say close to what the failure rates on an elevator motor might be. Speak to your millwright or elevator buddies as to what a cutting edge gearless motor in the 150 hp department might weigh......~2000 lbs. Making it aviation grade, you build the frame out of aluminium and use titanium bolts.~1700 lbs. I don't want wreck it for Star Wars fans around Christmas time but this I is fantastic ground bound technology.

Not sure where you are plucking your numbers from. 1 hp / lb electric motors have been available for over a decade. 3 hp / lb electric motors have been flying for a couple of years. Changes your numbers somewhat, particularly when you consider you are taking out two gearboxes a driveshaft and its supports.


Originally Posted by [email protected] (Post 10327390)

Washeduprotorgypsy - finally, the voice of reason:ok:

Cognitive bias at its best.

"A steamship can never cross the Atlantic for it would consume more coal than it can carry."

[email protected] 4th Dec 2018 11:57

Where is the battery going to go and how much will it weigh?

The answer to most problems lies in battery technology and therefore size/weight vs power. In the future maybe but now????

Much the same is the improvements in steamship technology and efficiency did but it's not an overnight solution.

SASless 4th Dec 2018 12:08


"A steamship can never cross the Atlantic for it would consume more coal than it can carry."

For sure some steamships took on more sea water than they could carry!

dClbydalpha 4th Dec 2018 12:23


Originally Posted by [email protected] (Post 10327595)
Where is the battery going to go and how much will it weigh?

The answer to most problems lies in battery technology and therefore size/weight vs power. In the future maybe but now????

Much the same is the improvements in steamship technology and efficiency did but it's not an overnight solution.

It's not an overnight solution, we started many years ago, it just seems that very few people recognise it.

This thread isn't about the All Electric Rotorcraft it is about an Electric Tail Rotor so for the moment generator driven I would suggest. Battery technology is advancing, but I expect FW to take the lead on all electric flight. Don't dismiss the ETR because of battery technology.

[email protected] 4th Dec 2018 12:50


but I expect FW to take the lead on all electric flight. Don't dismiss the ETR because of battery technology
perhaps because you can cover the wings and the top of the fuselage with solar panels - you haven't got that surface area on a RW.

If you are going for a generator you will need to drive it mechanically (MRGB most likely) = more weight/more complexity and the single point of failure ceases to be in the TR drive chain (as with conventional TR) but at the drive for the generator - how is that so much better?

You could take a NOTAR and bolt the generator on in place of the fan but you still have a mechanical TR/Fenestron at the other end - again what progress/advantage?

Perhaps just improve design/maintenance so people can't leave the nut off the end of the TR servo arm..........

dClbydalpha 4th Dec 2018 14:10

Crab, I think the FW will see commercial benefits sooner, as the efficiency improvement is possibly greater.

The MGB already drives the TRDS and so no real added complexity... in fact layout could be made simpler.

There would still be multiple generators, in fact I envisage load balancing. For example I can't see the need for full RIPS concurrent with long periods of high TR demand

petit plateau 4th Dec 2018 14:31


Originally Posted by Washeduprotorgypsy (Post 10327325)
Seeing as this thread is a slapstick offshoot of the Leicester aw169 thread. And using 10-15 % Q as TR power consumption on an aw169 , AEO xmsn rating of 1500 hp. The electric motor off the Cessna 172 will substitute nicely for a electric driven tr on the aw169 , though coming up short by 70 hp if you take 15% Q to be closer to what the mechanically driven version can muster.

So you add the weight of a an Lyco 0-320(+10%) ..~300 lbs on to the tail end, ~350 lbs for the generator, ~600 lbs nose ballast , 400 lbs structural reinforcement. Voila....a perfect locomotive. A little sluggish in pitch when the electronic motor control gets buggy and the need for speed in the necessary autorotation occurs. There is no reason this can't work.

You would expect an electric motor employed in human carriage at altitude to be quite reliable , say close to what the failure rates on an elevator motor might be. Speak to your millwright or elevator buddies as to what a cutting edge gearless motor in the 150 hp department might weigh......~2000 lbs. Making it aviation grade, you build the frame out of aluminium and use titanium bolts.~1700 lbs. I don't want wreck it for Star Wars fans around Christmas time but this I is fantastic ground bound technology.



Tesla Model S motor weight is 70 lbs for 362 hp (see https://chargedevs.com/newswire/elon...uction-motors/). Compare that with your stated 2000 lbs for 150 hp.

[email protected] 4th Dec 2018 17:16

dClbydalpha -

The MGB already drives the TRDS and so no real added complexity.
that is my point, you have replaced a well functioning mechanical system (TR drive failures are rare) with an electric one which is just as likely to fail, so what is the advantage?

Petit plateau - but how much do the TESLA batteries weigh?

dClbydalpha 4th Dec 2018 17:35


Originally Posted by [email protected] (Post 10327843)
dClbydalpha so what is the advantage?

Better control of noise footprint.
Less moving parts.
Less maintenance.
Less unfriendly lubricant.
No need for TRDS alignment.
More freedom in tail rotor design compromise.
More options in MGB layout.

I'm sure there are more.

Why keep asking about battery weight? A claim was made earlier about motor weight ... I think people are answering that and that alone.

chopjock 4th Dec 2018 18:29


Originally Posted by [email protected] (Post 10327843)
dClbydalpha - so what is the advantage?


Better control of noise footprint.
Less moving parts.
Less maintenance.
Less unfriendly lubricant.
No need for TRDS alignment.
More freedom in tail rotor design compromise.
More options in MGB layout.

I'm sure there are more.

Able to switch it off in event of un commanded full pedal...

GrayHorizonsHeli 4th Dec 2018 18:32


Originally Posted by petit plateau (Post 10327712)
Tesla Model S motor weight is 70 lbs for 362 hp (see https://chargedevs.com/newswire/elon...uction-motors/). Compare that with your stated 2000 lbs for 150 hp.


and how big will your generator need to be to power that beast? seeing pics of the tesla motor, it's the size of a large beer cooler, or to be more accurate the size of many americans beer bellies.
there's the battery with mood killing weight option to charge up and store that huge thirsty electrical appetite, or an equally sized (if not bigger) generator needed to power the motor live. And the bigger the generator, the bigger the power robbed, and the bigger turbine engine required to drive it all...its all relative isnt it? And relatively speaking, it all just keeps getting bigger and heavier.

I'm no electrical wizard by any means, but to get that published HP, knowing they use a 100KWh battery, thats alot of juice to be squeezed from a small bolt on generator.

dClbydalpha 4th Dec 2018 18:54


Originally Posted by GrayHorizonsHeli (Post 10327883)
I'm no electrical wizard by any means, but to get that published HP, knowing they use a 100KWh battery, thats alot of juice to be squeezed from a small bolt on generator.

90 kVA is about 40 kg already in use. Full RIPS takes some juice too.

[email protected] 4th Dec 2018 21:22


Better control of noise footprint.
Less moving parts.
Less maintenance.
Less unfriendly lubricant.
No need for TRDS alignment.
More freedom in tail rotor design compromise.
More options in MGB layout.
but will you match the power and controllability of a conventional TR? No one is going to give up performance just to replace a system that is both reliable and mature technology.


I'm sure there are plenty of problems with maintaining electric motors in the aviation environment and Elon Musk already acknowledges the issues with cooling high performance motors.

As to noise footprint - the TR still has to move the air whether it is driven my a driveshaft or an electric motor and the unequally spaced blades that already exist in modern TR, especially Fenestrons, have already significantly reduce noise footprint,

It seems an odd solution to a problem that hardly exists, especially since the crash that sparked this discussion doesn't look likely to be a TR drive failure anyway.

BTW I wouldn't hold up RIPS as a great success - it is very power hungry and heavy.

dClbydalpha 4th Dec 2018 21:47


Originally Posted by [email protected] (Post 10327998)
but will you match the power and controllability of a conventional TR?

... Elon Musk already acknowledges the issues with cooling high performance motors.

... It seems an odd solution to a problem that hardly exists ...

BTW I wouldn't hold up RIPS as a great success - it is very power hungry and heavy.

Yes, why wouldn't it? Simply changing the means of providing the rotation won't reduce performance. If anything it gives the potential for greater control.

Cooling high performance motors is where the major advancements in design and production have occurred. HEVs are major driver for this.

A problem that industry have been asked to provide solutions to. So somebody thinks it exists.

BTW RIPS is an example where industry has moved to make helicopters more viable. It being power hungry is exactly my point.

The technology is here, the engineering is possible. The question is whether the economics will move us in this direction or elsewhere.


All times are GMT. The time now is 00:05.


Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.