Firstly, why wouldn't it work for an ETR?
Secondly, why do you want the tail rotor driven in "perfect synchronisation" with the main rotor?

I think that the obvious question to ask is:
If an electrically driven tail rotor could be made as reliable as a shaft driven one and it was around about the same price, same weight and had benefits such as lower maintenance costs, why isn't such a system in use already?

That's exactly what is being asked by the authorities. As well as a strive for efficiency, the push to an ETR is environmental. It can make an impact on the noise footprint, critical in approving modern air operations.

There are already electric motors and actuators on the critical parts list, you can't choose to ignore all the FBW advancements and the lessons learned. We know how to design, build and certify using redundant feeds and multiple wingdings isolated electrically and thermally. It is not a big step in to the unknown ... not saying it is cheap, but if the regulations allow for a competitive advantage to be gained then the business case will follow. I am most definitely not advocating using RPM alone or stopping the TR in flight. But changing RPM allows optimisation to particular phases of flight.

Thanks for sharing the weight estimate. I came up with a similar %delta for the ETR. The motor about 25kg, the feeds another 10kg and the generator 40kg. So 75kg replacing about 65kg. So a weight gain, but I am convinced that the MGB could be further simplified and you have greater choice over where the generator is placed.

Not quite.
When you are dealing with servos and hydraulic fluids some odd things can happen.
For example, on the UH-60 Black Hawk there is a cable/pulley/spring tensioning lash up in the Tail Rotor Servo Assembly that, if it fails, leads the TR Blades to neutral pitch. (I read up on a rare case of this occurring a few years ago. The commentary from the Blackhawk experts did note that it was very rare, and an internal bit failed ...). I am trying to recall if there was a tail servo hardover in a Seahawk back in the distant past that led to a "stuck pedals" approach ... but memory is fading there.

There were some mechanical conditions I vaguely recall that would lead to flat pitch or stuck pitch in the Huey ages ago when I went through flight training (TH-1E and TH-1L models, I don't have the manuals for them anymore).
It may be that your instructor was being "model specific" in his observations.

The simple answer is the advances in technology driven by the hybrid and electric vehicle markets over the past decade now make production of such a system feasible. The operational environment is changing which may make it attractive to the market place. Hence the new interest and why a system has been ground tested.

I'm not sure how you'd train to cope with anything that causes a stuck main rotor actuator.

Control rod failure is one that immediately comes to mind.

Lonewolf, I suspect that there is some misinformation out there, as the tail rotor control quadrant basic design purpose in life not as you described. Rather, that quadrant and associated large spring is designed to address the loss of a cable side to ballistic damage od maintenance error. As long as one cable remains intact, the pilot flies the remaining cable against the spring and almost 100% authority is retained. What you referred to was that the basic tail rotor assembly is two, crosswise mounted paddles with four blades, and the built-in blade angles are set up to generally match the tail rotor requirements between 40 and 120 or 130 ( can't remember now ) KIAS with reasonable sideslip, as in where one might be if all the tail hydraulics were lost. That situation was flown ( both stages of the TR servo depressurized ) and we were almost able ( in this failure mode one would still have the yaw boost servo which is up forward ) to get back to a hover but could not stop the right yaw drift below 10-15 kts.

More like bad memory.
Yes, your point on the neutral position is part of what I was trying to get at.
I was trying to describe the TR servo assembly. Failure there, not just a cable failure, would render any inputs moot I think. The tail quadrant caution light would illuminate if one of the two failed. (there are 1st stage and 2d stage) Not, as noted, a common problem.
As you describe it, yes, 40 and 120 ring a bell. (I seem to recall that as the number in the NATOPS).
The recent failure I tried to describe was a failure inside the servo assembly itself, actually, the quadrant, on the ground, so they never got into a hover. Physical failure. There's a point around which it all pivots, on which the cable guards are mounted. I need to go back and see if I can find notes on that. Will post if I can find them. I think it was that sleeve/post that failed.
As I remember that system, John, without hydraulics you can't move the paddles. Your point on the servos triggers some old memory.
If you lose hydraulics in that channel, I don't recall that you can move the paddles without boost.
But now I need to go and look at the old NATOPS systems diagrams. I am pretty sure that in that flight control, the Blackhawk and Seahawk are alike enough. No CILA, though, in the Black Hawk.
As to the training, you guys were test pilots.
What they didn't want people doing, operationally, was coming into a hover with inability to control the nose, and not having the tail authority to control the aircraft down close to the ground. The run on / stuck pedals approach was considered lower risk, as well as the benefit of letting the cross wind assist in holding the nose position as one got close to the ground so you could get slower before touchdown.

I guess my point, badly made, was that you need to know the specific failures that will leave you with loss of controlability even if you don't have loss of drive/thrust. Each model will have its own quirks. The blythe "we only do it because it's fun training" I don't think is a responsible position to take.

A design function that the Hawks have is a backup ( #3 ) hydraulic pump that is electrically driven, and is the same as the two primary pumps in flow/pressure capability, and this pump backs up the first stage pump pressure to the TR servo 1st stage, hence there is triple redundancy, source-wise for hydraulic pressure back at the TR servo.

As to your remark about doing it because its fun training is well taken here, as it was possible ( or at least used to be ) to depressurize both tail rotor servo stages by pulling the backup pump c/b, deselecting the #1 Primary servo and selecting the tail rotor LDI switch. . At least I think that was the sequence. It did succeed in depressurizing both stages as we intended. Anyhow, after that flight there was some reconsideration by the senior mechanical controls engineers, who were concerned that a switch back to a pressurized system with a bunch of pedal force being applied, would create a cable whiplash that might result in the cable coming off the intermediate cable attachment devices. Hence your point is very good advice.

First: With engine out what's generating sufficient energy to drive the TR?

Second: To keep the TR in the correct RPM range.

How long does an autorotation take? A couple of minutes perhaps? So not a very large capacity required then.

Or drive the generator from the transmission...

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.

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.

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:

Thanks Gypsy for the morning laugh lol

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.

Cognitive bias at its best.

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

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.

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

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.

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..........