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Electric tail rotor; an alternative?

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Electric tail rotor; an alternative?

Old 5th Dec 2018, 19:17
  #121 (permalink)  
 
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Originally Posted by [email protected] View Post
The advantages seem purely theoretical and you have yet to establish the need for an ETR.

Millions of hours flown with the conventional tail rotor in all aspects of the helicopters versatile roles and the number of TR failures and malfunctions is very small.

One crash with an as yet undetermined cause but some form of TR issue and you are proposing ETR as the saviour to that scenario and ignoring the realities of system failure/loss of power in the ETR, not to mention that many of the solutions, such as jelly's, ignore the amount of time many helicopters spend in the hover as opposed to the high speed cruise.

Keep on with your blue-sky thinking but I will be surprised if we see ETR in the next 10 years at least.
At what point have I ever proposed an ETR as a solution to tail rotor failure?

Why do you say I don't consider system failure or loss of power? The motor will meet the required failure rate as will the generation system. They are already multiple redundant systems.

All things start as theoretical. However analysis and testing so far have backed up the theory. Do you believe there are no practical advantages to a variable speed rotor?

I will continue, thanks, as long as there is a commercial incentive. I don't establish the need, that's done by either regulation or operational requirement. Whether that will happen with an ETR is out of my hands, but so far it has been worthy of attention up to an iron bird.
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Old 6th Dec 2018, 14:15
  #122 (permalink)  
 
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Grey horizons, glad you enjoyed. I always feel equally reassured when making consumer purchases with the Inspector #45 tag.

Pilots en mass around the world are finally getting their biggest wishes met with the advent of the ETR. They can live with the chronic lower back problems from the cruddy seating, if only the archaic driveshafts and gearboxes would disappear.

So...back to this locomotive.

We have got power to weight figures for electric motors being flung around the conversation with nary a mention of duty cycle, never mind record in service. Kinda of like sailors arguing where mean sea level sits in 100 foot seas....amusing but pointless.

Seeing as we are improving the type , I think it fair to ask the new ETR model to have the ability to hover at max continuous for prolonged periods. So using the aw169 as our testbed once again, this occurs at 1350 hp. So using 15% of Max continuous Q as being TR consumption again........ 200 hp.

Sure electronic motor controls have made leaps and bounds in the past couple decades. Complete control of the waveforms operating within the stators of a synchronous motor allowing near perfect efficiency of the principles of electromagnetic induction. Have the ground bound and efficiency obsessed , industrial process industries not innovated and taken advantage of this? Of course they have, sparing no amount of complexity in order to achieve efficiency of power. Lighting fast microprocessors paired with power transistors and resistors, all guided by millions of lines of possibly conflicted computer code.....what kind off fault or failure mode could possibly present itself? So much better than a clunky old driveshaft and gearbox, and there are no bearings to fail in an electric motor. Even If there were , you just use mag/lev tech.(Always use a [email protected] to do the same job a builders string has been doing for the past 10,000 yrs...so much cooler and its called "progress".)

After perfect efficiency has been obtained in controlling the repulsive electro magnetic forces between the rotor and stator where do you find your power density gains? Higher voltages through better cooling(.....like all the practical geometries haven't been tried yet) Insulation that doesn't melt or crack, and conductors that don't melt or heat up too much. I know that if we just stretch a little harder cold fusion , super conductors, super steel the weight of feathers are just around the bend....but in the meantime we are stuck with good old copper. Yes even consumer grade products like Tesla and Dyson. Though I feel we are on the cusp of a wave of stc's replacing the 1930's vintage, starter genies still on most helicopters with beer can size , LED backlit , hollow plastic ones accomplishing the same thing.

So we need an electric motor based on the best of industrially vetted technology to operate consistently at 200 hp to mirror our max continuous hover missions for SAR or aerial work. Doing a little window shopping I came up with this https://www.ziehl-abegg.com/us/en/pr...maxvent-owlet/. (Pg.44 of 66)

A drop in fenestron. Good looking, scimitar-scalloped blades , meets all the euro engineering approvals. 1.4 m diam. Bout right for the back end of a aw169. Power to weight for continuous duty? 50 hp at the svelte weight of 637 kg. Ahh but all that steel fat to be trimmed. Shes's gonna need some beefing up in the motor (4x 50) I think it's a fair trade off to add all that extra copper and substitute steel for aerospace material and call it even ~650 kg....she 'll taxi like a freight train because thats all She'll ever do.

I guess until the next invention comes along we are stuck with the practical limit of the electric motor being a quadcopter the size of most windscreens. Send me enough money and I'll build you one to ride in. You can't beat em join em.
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Old 6th Dec 2018, 15:18
  #123 (permalink)  
 
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Where is that Like button again..........
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Old 6th Dec 2018, 15:22
  #124 (permalink)  
 
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Originally Posted by Washeduprotorgypsy View Post

So we need an electric motor based on the best of industrially vetted technology to operate consistently at 200 hp to mirror our max continuous hover missions for SAR or aerial work. Doing a little window shopping I came up with this https://www.ziehl-abegg.com/us/en/pr...maxvent-owlet/. (Pg.44 of 66)

A drop in fenestron. Good looking, scimitar-scalloped blades , meets all the euro engineering approvals. 1.4 m diam. Bout right for the back end of a aw169. Power to weight for continuous duty? 50 hp at the svelte weight of 637 kg. Ahh but all that steel fat to be trimmed. Shes's gonna need some beefing up in the motor (4x 50) I think it's a fair trade off to add all that extra copper and substitute steel for aerospace material and call it even ~650 kg....she 'll taxi like a freight train because thats all She'll ever do.
If the Tesla motor I referenced was built like that industrial fan you pulled up, then the Tesla S car would be about the size and shape of the freight train you are imagining. Instead that Tesla motor, scaled to your stated needs of 150hp was "(say) 70lbs for (a 150hp generator + a 150hp motor)" based on "Tesla Model S motor weight is 70 lbs for 362 hp". You appear to now be moving the goalposts out to 200hp. Fair enough, I can do that sum.

But so that the design goal does not move around, what is the weight of the power takeoff & shafting & control & gearboxes for the tail rotor on the AW169 ? And how long do you expect to sit in the hover for at that power ?
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Old 6th Dec 2018, 15:34
  #125 (permalink)  
 
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Originally Posted by Washeduprotorgypsy View Post

I guess until the next invention comes along we are stuck with the practical limit of the electric motor being a quadcopter the size of most windscreens. Send me enough money and I'll build you one to ride in. You can't beat em join em.
Maybe you're correct, but organisations such as NASA, Rolls Royce, Bell and others would appear to disagree with you.
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Old 6th Dec 2018, 17:07
  #126 (permalink)  
 
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The Siemens motor in the Extra 330 LE is rated at 260 kW continuous and is 50kg. But don't let facts get in the way of plucking random numbers out of thin air.
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Old 6th Dec 2018, 17:44
  #127 (permalink)  
 
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The 330LE is constructed with light-weight materials and is suitable for 20-minute flights, including take-off, climbing and five minutes of full throttle flight.
that's very useful.......

The electric 20-minuters..........
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Old 6th Dec 2018, 17:53
  #128 (permalink)  
 
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Battery capacity?
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Old 6th Dec 2018, 18:27
  #129 (permalink)  
 
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Originally Posted by gevans35 View Post
Battery capacity?
"Extra 330LE aircraft are powered by an electric SP260D motor with a power output of 260kW (348hp). The electric motor was developed by Siemens with support from Germany’s Aeronautics Research Program (LuFo). The motor can drive propellers directly without the use of a transmission, and can deliver 2,500 revolutions per minute at rational speeds. It has a continuous torque of 1,000nm and link voltage of 580v. The motor has a maximum coolant inlet temperature of 90°C and efficiency of 95%. The aircraft features two battery packs, each with 14 high-power Li-Ion battery modules with a capacity of 18.6kWh. The aircraft’s motor weighs 50kg including airscrew bearings, and has a low power-to-weight ratio of five kilowatts per kilogram, which was achieved with the use of new simulation techniques and sophisticated lightweight construction." from https://www.aerospace-technology.com...tric-aircraft/

What is the weight of conventional tail rotor transmission, power offtake, controls, etc ?
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Old 6th Dec 2018, 18:30
  #130 (permalink)  
 
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Originally Posted by [email protected] View Post
that's very useful.......

The electric 20-minuters..........
So at least you now acknowledge the existence of a suitable motor with an appropriate continuous rating.

Now where's that like button

Last edited by dClbydalpha; 6th Dec 2018 at 18:51.
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Old 6th Dec 2018, 19:06
  #131 (permalink)  
 
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So at least you now acknowledge the existence of a suitable motor with an appropriate continuous rating.
hmmm, not quite - 5 mins at max continuous isn't going to cut the mustard in pretty much any helicopter role and a 20 minute max life????

Why haven't Extra elected to use a generator with a prop in the slipstream on it? Cooling issue perhaps with going longer than 20 minutes?

It is a small step in the right direction but a very long way from challenging a conventional TR.
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Old 6th Dec 2018, 19:14
  #132 (permalink)  
 
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Does one need more than 5 minutes continuous, would 30 minutes at 90% suffice?

I read 20 minutes as battery life, the ETR application would be generator driven.

Surely a prop in the slipstream makes no sense... drag?
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Old 6th Dec 2018, 19:24
  #133 (permalink)  
 
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Does one need more than 5 minutes continuous, would 30 minutes at 90% suffice?
I've spent over an hour in the hover at max continuous, so no, it isn't enough.

The 20 minute limitation clearly is battery life on the Extra which is why I asked about a generator as you suggest for ETR - if the answer to that is cooling then you would have to keep 'resting' your ETR to stop it overheating.
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Old 6th Dec 2018, 19:36
  #134 (permalink)  
 
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Originally Posted by [email protected] View Post
I've spent over an hour in the hover at max continuous, so no, it isn't enough.

The 20 minute limitation clearly is battery life on the Extra which is why I asked about a generator as you suggest for ETR - if the answer to that is cooling then you would have to keep 'resting' your ETR to stop it overheating.
I wouldn't get too hung up on the "Extra" motor, that was designed for an aerobatic aeroplane. An ETR would need a motor optimised for that application and rated/de-rated to provide 100% continuous output for OGE hover if that is what is necessary. The "Extra" application is just an indication that a suitable motor could be sourced.

I doubt that Leonardo would have developed a prototype ETR and ground tested it if they didn't see any advantage, or think it had a chance of working in flight.

Last edited by gevans35; 6th Dec 2018 at 19:56.
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Old 6th Dec 2018, 22:43
  #135 (permalink)  
 
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Originally Posted by [email protected] View Post
hmmm, not quite - 5 mins at max continuous isn't going to cut the mustard in pretty much any helicopter role and a 20 minute max life????

Why haven't Extra elected to use a generator with a prop in the slipstream on it? Cooling issue perhaps with going longer than 20 minutes?

It is a small step in the right direction but a very long way from challenging a conventional TR.
I'm struggling to understand your interpretation of "continuous". The motors I have encountered have a continuous rating, a five minute max rating (~125%) and a five second emergency rating (~160%).

I'll say again the technology is available. In my personal opinion the research into flux, isolation and thermal flow modelling over the past few years is exceptional.

So Crab, there is an ETR that can do everything your mechanical TR can do ( let's face it it would have to otherwise it wouldn't be flyable)

Disadvantages
Not yet certified.
Needs electrical source, changing the safety case for the EPGDS.

Advantages
Less installation constraints.
Simpler installation and maintenance.
Power sharing with other systems.
Easily varied rotor speed.

For a number of years I looked at a variable speed tail rotor, but mechanically the penalty was just too much. The ETR changes the equation. ... I admit that I don't know whether it changes it enough, time will tell.
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Old 6th Dec 2018, 23:01
  #136 (permalink)  
 
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Originally Posted by dClbydalpha View Post
Advantages
Easy change to dual (or more) redundant tail rotors as suggested here -
https://publicapps.caa.co.uk/docs/33/CAPAP2003_01.PDF
CAA PAPER 2003/1
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Old 6th Dec 2018, 23:39
  #137 (permalink)  

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JimJim1,

The twin tail rotor concept was thought of very many years ago. From a purely academic/theoretical point of view, a tail rotor at each end of the helicopter would be a better design. But it wouldn't be convenient. Early designers realised that the single tail rotor at the rear end was a necessary compromise.
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Old 7th Dec 2018, 07:18
  #138 (permalink)  
 
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DcL - I'll take your word for the advancement of the technology - I'm just a guy who flys helicopters for a living not a boffin. but given these constraints
Disadvantages
Not yet certified.
Needs electrical source, changing the safety case for the EPGDS.
how close are we really to seeing ETR in production?
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Old 7th Dec 2018, 10:34
  #139 (permalink)  
 
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I have always liked this method of implementing twin tailrotors. They're not mounted on the tail, admittedly.

I don't know whether they provide redundancy in this case, but as a concept I don't see why it couldn't.

Last edited by abgd; 7th Dec 2018 at 13:19.
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Old 7th Dec 2018, 13:24
  #140 (permalink)  

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That machine isn't very practical, for a number of reasons discussed here a long time ago.
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