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Electric tail rotor; an alternative?

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Electric tail rotor; an alternative?

Old 5th Dec 2018, 09:11
  #101 (permalink)  

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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.
Indeed. Fitting RIPS adds so much weight to some aircraft that some operators have decided against buying it as an option, because they prefer more usable payload.
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Old 5th Dec 2018, 10:10
  #102 (permalink)  
 
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Originally Posted by ShyTorque View Post
Indeed. Fitting RIPS adds so much weight to some aircraft that some operators have decided against buying it as an option, because they prefer more usable payload.
And for others it allows them to operate in conditions not previously possible and therefore increasing usability of their asset. As a Customer, you take your choice.
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Old 5th Dec 2018, 10:19
  #103 (permalink)  
 
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Except that it is not reliable so you can end up committed to an IFR transit in icing conditions and then find yourself without ice protection - have you seen how many pages of malfunctions there are in the 139 QRH just for IPS?

And you lose a valuable vibration absorber which can cause AP/AFCS problems.

Just the sort of issues you want with an electric TR..............

The idea that something is better just because it is electric and new is just fanciful. However, if the advances in electric motor and battery technology were as fast as computer growth and processing power, we might see some viable alternatives but we still struggle with generation and storage for electric power.

How well are electric cars going to do in UK with a National Grid generating system that creaks at the seams on a still winter morning when consumer demand is high and generation output maximums are reached?
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Old 5th Dec 2018, 10:49
  #104 (permalink)  
 
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Originally Posted by [email protected] View Post
The idea that something is better just because it is electric and new is just fanciful. However, if the advances in electric motor and battery technology were as fast as computer growth and processing power, we might see some viable alternatives but we still struggle with generation and storage for electric power.
The idea that because something is new it is somehow less capable or even a "fantasy" is also false. Massive advancements have been made in electric technology. Serious research began a decade ago, full scale ground testing of an ETR last year. An ETR first and foremost must meet the requirements of being a tail rotor, hence the careful development. If regulations or operations give an advantage to an ETR equipped aircraft, then it will happen. However I think that we are gradually moving towards all electric aircraft, the VTOL version is unlikely to look like a conventional helicopter, development may therefore diverge.

Out of personal interest what rate of RIPS failures are people experiencing?
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Old 5th Dec 2018, 10:52
  #105 (permalink)  

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Originally Posted by dClbydalpha View Post
And for others it allows them to operate in conditions not previously possible and therefore increasing usability of their asset. As a Customer, you take your choice.
Of course, that's why it was designed in the first place, but it has proved to be at a possibly unexpectedly high cost, both financially and as an aircraft payload penalty.
But surely the question here is: why add complication to replace a well proven, simple mechanical tail rotor system that has proved very reliable for decades? It's worth bearing in mind that many tail rotor failures have been caused by external damage - these failures will still occur on an electrically driven system. In my experience (having been flying helicopters for a living for just coming up to forty years and fixed wing for some years prior to that), the items that have proven most unreliable on all the aircraft I've flown have mainly been electrical or electronic. Same with the road vehicles I've been driving since the 1960s. Water ingress is a perpetual issue as well as mechanical ones. Well designed gearboxes are very reliable indeed because they are so simple. Electric motors and generators are not so reliable and need more maintenance.

As far as "saving the environment" goes, noise reduction has been mentioned more than once. From what I've seen very recently, relatively straightforward innovations in rotor blade design seem to be a very good way forward.
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Old 5th Dec 2018, 11:08
  #106 (permalink)  
 
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Originally Posted by ShyTorque View Post
As far as "saving the environment" goes, noise reduction has been mentioned more than once. From what I've seen very recently, relatively straightforward innovations in rotor blade design seem to be a very good way forward.
Nothing is straightforward. The fact that these innovations are even happening shows the will to move forward. ETR is one of a number of initiatives as you say.

Real advantages may be gained in new designs where the geometric constraint of a TRDS doesn't apply. However see my previous response on all electric, that step may never come.
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Old 5th Dec 2018, 11:39
  #107 (permalink)  
 
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Originally Posted by [email protected] View Post
dClbydalpha - 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?
My understanding is that the original poster is proposing an electrical transmission for the tail rotor rather than the existing conventional transmission, i.e. no batteries involved. To do this one would need to have the corresponding increase in generation, which crudely will be approximately equal in weight to the motor (assuming that the existing generator is operating near its design limit and so does not have the requisite spare capacity). So that would be (say) 70lbs for (a 150hp generator + a 150hp motor). Still a long way different than the objection raised of 2000 lbs for 150 hp system.

You can go further and propose to relocate the prime mover to wherever is convenient in the aircraft (i.e. low rather than high, or whatever) and put an electric drive on the main rotor(s) with an electrical transmission. Sort of the helicopter equivalent of a diesel-electric ship main propulsion, for much the same reasons. As a further refinement you then only need to put a few small/light batteries in the system and you can run the prime mover over a much narrower rpm band and still handle transient peak power loads; such a system typically has a better fuel economy. Taking an approach like this might be interesting if folk are having problems designing gearboxes, which I understand they are. Tilt wing transmissions are also complex and heavy and have awkward failure modes.

This is an interesting time to be a designer.
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Old 5th Dec 2018, 11:49
  #108 (permalink)  
 
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My thoughts exactly.
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Old 5th Dec 2018, 12:38
  #109 (permalink)  
 
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Originally Posted by petit plateau View Post
This is an interesting time to be a designer.
As in " may you live In interesting times" 😁.

The ETR generation is not exclusive with the rest of the generation system. For a lot of the time the ETR will not be at peak load, when it is, other systems may not. A thorough ELA will show this and it may be that the weight penalty for RIPS can be shared with ETR, just a thought?

In my opinion I wouldn't go anywhere near electric main rotor for a conventional setup.
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Old 5th Dec 2018, 13:01
  #110 (permalink)  
 
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Originally Posted by dClbydalpha View Post

In my opinion I wouldn't go anywhere near electric main rotor for a conventional setup.
An opinion shared by NASA and Rolls Royce who are suggesting electric tilt rotor designs.

Last edited by gevans35; 5th Dec 2018 at 13:23.
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Old 5th Dec 2018, 14:32
  #111 (permalink)  
 
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Real advantages may be gained in new designs where the geometric constraint of a TRDS doesn't apply. However see my previous response on all electric, that step may never come.
Those already exist in the form of NOTAR, Twin rotor (Chinook) and contra-rotating MRs so it's not exactly ground breaking.

If it's not a good idea for the MR, why is it such a great one for thew TR?

Everyone would like to see a helicopter replacement that looks like a scaled up drone or quadcopter but to give it a useful payload is a long way from fruition.
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Old 5th Dec 2018, 15:18
  #112 (permalink)  
 
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Crab, my initial post at #12 explains why it may be good idea.

A fenestron type ETR could be stopped in forward flight and yaw control achieved by a simple rudder. Massive increase in component life and reliability.
​​​​​​
in the event of engine failure, any yaw in the descent could be controlled by rudder. The ETR would automatically spool up quickly under battery power for the vinegar strokes at the end.

Under normal ops, a conventional variable pitch mechanism would be used.

If made as a 'smart' system, the AW169-type failure could be mitigated by computer controlled reversal of direction of rotation with variable RPM to effect emergency yaw control. All of this is technically feasible today. If the pedals were driven to full deflection and held there, an ETR could be computer controlled to lock the heading. Heading could be managed by autopilot-type hdg bug on the HSI for example. Any excess rate of rotation could trigger a heading lock function.

Food for thought, or just fantasy?

JJ
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Old 5th Dec 2018, 15:23
  #113 (permalink)  
 
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Originally Posted by [email protected] View Post
Those already exist in the form of NOTAR, Twin rotor (Chinook) and contra-rotating MRs so it's not exactly ground breaking.

If it's not a good idea for the MR, why is it such a great one for thew TR?

Everyone would like to see a helicopter replacement that looks like a scaled up drone or quadcopter but to give it a useful payload is a long way from fruition.
Who said it was groundbreaking? NOTAR has its issues and advantages. As does Tandem, and coaxial, and contra... It doesn't have to be groundbreaking to be useful. This thread started because one poster was accused of trolling for suggesting an ETR... numerous others have weighed in that it isn't practical. In fact we now seem to have reached a point where it is, it's just a case of whether it offers sufficient advantage to move from the status quo. Are you unable to see the advantages of an ETR or is it having assessed it judge it isn't worth it?

I thought the reason to avoid the MR was covered in my earlier posts. That would be close enough to the all-electric aircraft, which I don't believe will look like a helicopter, so no point going down that branch - even if a continuously variable rotor has its attractions.

Quad, Quad tilt ... who knows what will emerge over the next 10 years?
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Old 5th Dec 2018, 15:46
  #114 (permalink)  
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Originally Posted by dClbydalpha View Post

I thought the reason to avoid the MR was covered in my earlier posts.
One advantage of a MR setup could be only one engine required (Turbine generator) to give twin engine confidence (Battery back up for 10 minutes)...
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Old 5th Dec 2018, 15:51
  #115 (permalink)  
 
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Are the proposed electric tilt-rotor designs cross-shafted?
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Old 5th Dec 2018, 16:27
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Originally Posted by JohnDixson View Post
Are the proposed electric tilt-rotor designs cross-shafted?
I don't know for sure but I doubt it. I assumed they rely on the multiple motors for redundancy, but I could be wrong.

Here's a bit more info on the RR one which they say could be flying in the early to mid 2020s.

https://robbreport.com/motors/aviati...rough-2806843/

And NASA.

https://data.nasa.gov/dataset/Hybrid...enge/6x4v-g98n

Last edited by gevans35; 5th Dec 2018 at 16:50.
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Old 5th Dec 2018, 17:02
  #117 (permalink)  
 
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Originally Posted by chopjock View Post
One advantage of a MR setup could be only one engine required (Turbine generator) to give twin engine confidence (Battery back up for 10 minutes)...
Once you've redesigned that much I suspect there are much better configurations than the conventional layout.

Originally Posted by JohnDixson View Post
Are the proposed electric tilt-rotor designs cross-shafted?
I'm not sure there would be a need. I can't recall whether Project Zero was.

Last edited by dClbydalpha; 5th Dec 2018 at 18:27.
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Old 5th Dec 2018, 18:18
  #118 (permalink)  
 
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Welcome to Erector by Meccano The original inventor brand!

I'll let you know how my trial runs go when I electrify this thing.

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Old 5th Dec 2018, 18:24
  #119 (permalink)  

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If the pedals were driven to full deflection and held there,
I don't think this is necessarily what occurred in the 169 accident. Depending on the actual failure, the tail rotor servo control valve going to full deflection doesn't necessarily mean that the pedals are driven at all. The pilot may have held full opposite pedal but the servo could have run away in the opposite direction to his input.
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Old 5th Dec 2018, 18:37
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Are you unable to see the advantages of an ETR or is it having assessed it judge it isn't worth it?
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.
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