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Electric tail rotor; an alternative?

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Electric tail rotor; an alternative?

Old 1st Dec 2018, 17:32
  #21 (permalink)  
 
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Originally Posted by gevans35 View Post
I think so too, powered by a generator run off the main engine(s).

Actually, why not the main rotor too? They do it in ships so why not aircraft?

Would take a lot of development though...... Elon Musk?
I thought this was just a joke/trolling, but since it seems that some of you are serious:

I can see only one thing that speaks for an electric TR and that is that you wouldn't need pitch controlled blades. I'll mention a few things that come to mind that speaks against it, although I'm sure there are many more:
  • I'm sure there's a lot of computer control in most modern helicopters already, but this would have to be entirely computer controlled to be at all flyable. That would open up a new can of worms when it comes to safety. I know that "fly-by-wire" is popular these days, but personally I only consider it "safe" as long as everybody is equipped with ejection seats.
  • The reason they use electric motors on ships is first and foremost because it's difficult to get the mechanical energy to where you want it. Imagine the arrangement of driveshafts and gears that would be needed to transfer the power from the engine(s) to multiple azimuth thrusters placed on different locations, some probably near the bow. On trains they often do the same, but from what I understand that's for similar reasons (you want drive on as many wheels as possible because trains generally have bad traction) and because making gearboxes that can take the punishment over time is difficult. However you twist it, converting mechanical energy into electrical energy and then back again means that you'll both have a lot of extra potential points of failure and waste a significant part of the energy. Driveshafts and gearboxes waste energy too (through friction in bearings etc.), but considering how simple (geometrically) this is on a helicopter I'm convinced that using driveshafts and gearboxes is much more efficient.
  • There's nothing inherently "environmental friendly" about electrical motors. It all depends on what form the energy is available in to start with. If you use a combustion engine to turn fuel into energy, you have mechanical energy as the source. What is considered "environmental unfriendly" is the combustion engine itself, converting the energy to electricity after the engine makes no sense (although some cars do this to ride the hype). If you have electricity as the power source using for example a battery or fuel cells, things are very different.
  • As mentioned above, the only "gain" by using an electrical TR that I can see it that you wouldn't need pitch controlled blades. That said, changing the pitch is very quick and doesn't take a lot of power. The RPM is already there, ready to be used. A fixed pitch blade rotor would have to vary the RPM instead, and I believe this would be much too slow to be practical due to the inertia in the rotor. I guess that if you could make it by some revolutionary new hyped nano-materials that's stronger than steel but weighs nothing, the inertia problem could be overcome. I don't know of any such materials outside the world of hype though.
In addition I'd just like to mention that I believe Elon Musk's strongest asset is his ability to create hype and "impress people" enough to invest in him. I think time will reveal a different picture of him, and I certainly wouldn't like to fly anything designed or built by him or anyone like him.
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Old 1st Dec 2018, 17:45
  #22 (permalink)  
 
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Sorry as this seems to have drifted from the main thread.

The advantages of an electric tail rotor is that it can run at speeds independent of the main rotor. This allows the design to not be limited to one compromise. It, importantly, gives greater control over noise.

The assumption that a motor would be as heavy as a TGB, IGB, MGB tail pickoff and driveshaft is not one that I would make.
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Old 1st Dec 2018, 18:06
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Great discussion chaps, but don't put your patent applications in just yet, think you've been beaten to it... If I'm not mistaken the team at Leonardo won an award for their work from the RAeS the other evening as well!
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Old 1st Dec 2018, 18:16
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Originally Posted by pba_target View Post
YouTube linky: electric tail rotor

Great discussion chaps, but don't put your patent applications in just yet, think you've been beaten to it... If I'm not mistaken the team at Leonardo won an award for their work from the RAeS the other evening as well!
My point exactly ... the technology is already available. The concept of an electric tail rotor is not a reason to dismiss someone's statements.
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Old 1st Dec 2018, 18:22
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Originally Posted by pba_target View Post
YouTube linky: electric tail rotor

Great discussion chaps, but don't put your patent applications in just yet, think you've been beaten to it... If I'm not mistaken the team at Leonardo won an award for their work from the RAeS the other evening as well!
I would have been surprised if someone wasn't working on it..... Boeing too? Airbus? Robinson?
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Old 1st Dec 2018, 19:24
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Most things have already been tried as already mentioned in this thread. What would surprise me is if an electric tail rotor would be competitive when it comes to reliability and efficiency as long as the power plant is a combustion engine.

Here is a paper on the model shown in the youtube clip, although I didn't see much of interest in there: http://www.cleansky.eu/sites/default...3_-_eletad.pdf

It's obvious that an electrical TR could be made, it would probably be much cheaper to produce than the current mechanical solutions as well. What I seriously question is whether it would be "competitive" with regards to the criteria that matter, especially when it comes to safety. How would you do a autorotation with an electrical tail rotor?
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Old 1st Dec 2018, 19:34
  #27 (permalink)  
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Nadar
How would you do a autorotation with an electrical tail rotor?
You do know you can autorotate with or without a working tail rotor right?
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Old 1st Dec 2018, 19:47
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Nadar, there are efficiencies to be gained by the ability to vary tail rotor speed. It allows a designer to move the compromise points. Plus as I stated before the ability to tailor the noise footprint.

As to autorotation, how much torque is the tail rotor dealing?
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Old 1st Dec 2018, 20:02
  #29 (permalink)  

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As to autorotation, how much torque is the tail rotor dealing?
That depends on if you want to turn (left or right) and keep the aircraft in balance.

Irrespective of how the turning rotor is actually powered, it still needs a blade pitch control system. Varying the speed of rotation isn't the full answer.
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Old 1st Dec 2018, 20:05
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Originally Posted by ShyTorque View Post
That depends on if you want to turn (left or right) and keep the aircraft in balance.
Accepted, but say as a ROM % of that in powered hover?

I also wonder why the assumption that an electric tail rotor wouldn't work in autorotation?
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Old 1st Dec 2018, 20:07
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Originally Posted by ShyTorque View Post
Irrespective of how the turning rotor is actually powered, it still needs a blade pitch control system. Varying the speed of rotation isn't the full answer.
Fully agree with that! But having control of both is not a bad thing.
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Old 1st Dec 2018, 20:31
  #32 (permalink)  

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Originally Posted by dClbydalpha View Post
Accepted, but say as a ROM % of that in powered hover?

I also wonder why the assumption that an electric tail rotor wouldn't work in autorotation?
a) I'm not familiar with the term ROM%

b) Did anyone assume it wouldn't work in autorotation? I certainly didn't. However, the tail rotor would still absorb a lot of energy even in autorotation so presumably its electrical power generator would need to be driven by the main rotor transmission, or a very large capacity battery would be required if engine driven generators no longer provided electrical power.
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Old 1st Dec 2018, 20:38
  #33 (permalink)  
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Originally Posted by ShyTorque View Post
a) I'm not familiar with the term ROM%

b) Did anyone assume it wouldn't work in autorotation? I certainly didn't. However, the tail rotor would still absorb a lot of energy even in autorotation so presumably its electrical power generator would need to be driven by the main rotor transmission, or a very large capacity battery would be required if engine driven generators no longer provided electrical power.
Presumably you could get away from powering an electric tail rotor all the way down in autorotation until just before the flare when it's time to spool it back up again to assist a little later with the run on...
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Old 1st Dec 2018, 20:39
  #34 (permalink)  

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Surely you cannot be serious?
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Old 1st Dec 2018, 20:40
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I would think battery. Battery technology is going forward in leaps and bounds so maybe not so big
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Old 1st Dec 2018, 20:44
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ShyTorque, my apologies, ROM is Rough Order of Magnitude. I ask because this determines the power demand at a critical phase.
Nadar seems to have implied that auto with an ETR would be different to "conventional". I'm not sure why this would be the case, in auto I would presume a design where the MGB is still driving the generators. Question for my own interest, how many helicopters out there revert to battery when in autorotation and how many retain electrical generation?

note: during "conventional" autorotation, the tail rotor is powered by the MGB.

Last edited by dClbydalpha; 1st Dec 2018 at 20:46. Reason: Subsequent posts
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Old 1st Dec 2018, 20:49
  #37 (permalink)  
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Originally Posted by ShyTorque View Post
Surely you cannot be serious?
That's what you would do with the gear isn't it? OK just kidding..

Last edited by chopjock; 1st Dec 2018 at 21:15.
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Old 1st Dec 2018, 22:03
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OMG there are dozens of chop jocks now, invading this thread!
What happened to the original thread FFS?
Electric TR's. Where do these people come from?
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Old 1st Dec 2018, 23:01
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I had a small RC helicopter with an electric tail rotor once. Worked fine until it sparked a few times and stop dead.
I dont think this helps any. Just thought I would share
playing it safe since the mods deleted my last post
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Old 1st Dec 2018, 23:42
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Originally Posted by GrayHorizonsHeli View Post
I had a small RC helicopter with an electric tail rotor once. Worked fine until it sparked a few times and stop dead.
How much did you pay for it? What kind of certification did you get with it?
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