Helicopter electric tail rotors

Oskar

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Regarding lag time, have you noticed any control input-to-control response lag time compared to the old mechanical version?
What is the role of the microprocessor; it would seem that the potentiometer's signal could go straight to the tail rotor motor controllers?
Brian,

The micro reads the analogue input from the potentiometer, calculates what thrust command should be sent to the tail, and then converts it into a signal which the tail motor controllers can read. I'm using PWM which nearly all motor controllers will read.

Since the micro knows what the main motor torque is, it automatically compensates for main rotor torque variations. It's really nice to fly as it requires a lot less foot work than a conventional tail rotor. During startup the tail motors automatically speed up as power is applied to the main rotor.

When testing engine outs in the hover I found that the response of the tail was not as fast as a variable pitch tail rotor. This is mainly because the motor controller response parameters are still set at very low levels, I'll have to program them to be more responsive.
 

C. Beaty

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A mechanical tail rotor runs at constant speed whatever the thrust requirement. At zero thrust, it’s still eating a fair amount of power.
Oskar's fixed pitch, variable speed electric drive eats zero power at zero thrust. That’s the difference. A constant speed, variable pitch electric drive would be less efficient than a mechanical drive.
 

Oskar

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A mechanical tail rotor runs at constant speed whatever the thrust requirement. At zero thrust, it’s still eating a fair amount of power.

That's exactly where the big gains come from. At 100% rotor rpm the mechanical Mosquito tail rotor eats 1.4kW of power while providing zero thrust, which means that once the rotors are spinning the power requirement will never be less than 1.4kW.

The electric tail rotor on the other hand eats 1.1kW in the hover, which means that the power requirement will never be more than 1.1kW.
 

Smack

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Since the micro knows what the main motor torque is, it automatically compensates for main rotor torque variations.

Wow, I had not heard you mention THAT before. Yes, that would be a huge advantage for a helicopter; fatigue-reducing for sure.
There doesn't look to me much in the way of aerodynamic stability aids (vert stabilizer, strakes, things like that) on the Mosquito, but do you anticipate that higher forward speeds would require less (automatically compensated) tail rotor thrust (I don't know if the main rotor torque would be constant regardless of airspeed?)?
Another advantage for the electrical route. :)
I'm interested in how reducing controller response time affects the lag time perception.

Brian
 

Martin W.

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Wow, I had not heard you mention THAT before. Yes, that would be a huge advantage for a helicopter; fatigue-reducing for sure.
There doesn't look to me much in the way of aerodynamic stability aids (vert stabilizer, strakes, things like that) on the Mosquito, but do you anticipate that higher forward speeds would require less (automatically compensated) tail rotor thrust (I don't know if the main rotor torque would be constant regardless of airspeed?)?
Another advantage for the electrical route. :)
I'm interested in how reducing controller response time affects the lag time perception.

Brian
Brian - Agreed , it would be a great advantage .... beleive it or not Arthur Young inventor of the Bell Helicopter had such a system in his electric powered test model back in the 1940's ... a small spinning gyroscope mounted in a gimbal and hooked to a rehostat , when the torque tried to turn the fuselege it would send more or less electricity to the tail rotor to compensate.

Oskar .... love your experiments , thanks for sharing
 

hillberg

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Wow, I had not heard you mention THAT before. Yes, that would be a huge advantage for a helicopter; fatigue-reducing for sure.
There doesn't look to me much in the way of aerodynamic stability aids (vert stabilizer, strakes, things like that) on the Mosquito, but do you anticipate that higher forward speeds would require less (automatically compensated) tail rotor thrust (I don't know if the main rotor torque would be constant regardless of airspeed?)?
Another advantage for the electrical route. :)
I'm interested in how reducing controller response time affects the lag time perception.

Brian
What you get is a less qualified helicopter pilot, Seen it go to hell in a hand basket -A H 60 pilot goes to a smaller helicopter and because of the "automatic" features that pilot will have issues with other helicopters - Power management, heading etc, A guaranteed accident you can see from a mile away.
 

Oskar

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What you get is a less qualified helicopter pilot, Seen it go to hell in a hand basket -A H 60 pilot goes to a smaller helicopter and because of the "automatic" features that pilot will have issues with other helicopters - Power management, heading etc, A guaranteed accident you can see from a mile away.

Isn't that like saying you have to turn off the governor when flying a Robbie?
 

DennisFetters

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A mechanical tail rotor runs at constant speed whatever the thrust requirement. At zero thrust, it’s still eating a fair amount of power.
Oskar's fixed pitch, variable speed electric drive eats zero power at zero thrust. That’s the difference. A constant speed, variable pitch electric drive would be less efficient than a mechanical drive.


Group,

There is a big difference between someone that just works in helicopter theory some of the time and someone that actually is a Commercial helicopter pilot with over 5000 hours of flight time and designed, built, tested, and manufactured a respectable number of helicopters as well as has experienced about every emergency and nonemergency situation in a multitude of different types of helicopters.

Theories have their place, but actual real-world practicality will win the day, every time. Don't get me wrong. I encourage people to experiment, but there are norms that in the end, must be met.

1. The fact is, I can comfortably hold a properly designed tail rotor and gearbox in one hand, as well as the aluminum tail rotor shaft and bearings. It is only a few pounds. It is simple and reliable and is not affected by electronic interference or shorts.

2. The power loss from bearings and gears in a properly designed shaft-driven tail rotor system is 3% or less, not significant.

3. The batteries or power generation system, as well as the props, motors, controllers, and control input modules that would be necessary to fly 3.5 to 4 hours would be far heavier than a tail rotor system driven by a shaft.

4. For the helicopter to maintain flight stability, it will still need the proper size of horizontal and vertical stabilizers, so there is no saving of weight by being able to discard them in lue of an electrical system. With the proper size horizontal stabilizer, you only require 5% or less of the total power being generated for cruise flight speeds using a shaft-driven antitorque system. Without the horizontal stabilizer, you will still require 10% or more of total power being generated for antitorque.

5. With a battery-powered tail rotor system, you may indeed use 100% of the total power generated for lift in the main rotor system. However, to carry around enough batteries to last 3.5 to 4 hours of flight time, every time you fly and to meet every condition would require that 15% power you thought you would save just to left the extra battery weight. Sure, flying more in forward-flight would save battery power so you need less battery weight, but now you have limited the very thing that was unique to helicopters in the first place... Indefinite hover time.

5. With an electric-powered tail rotor system, now you take a standard refueling time of fewer than 5 minutes and turn it into perhaps hours. That alone is not practical, plus now you have to have an extension cord and charger with you on the helicopter, which also adds to the overall weight, or you can't freely fly from airport to airport, again not practical.

6. More importantly than any other characteristic of helicopter performance is how well it handles in an emergency, like a loss of power situation. In the event of power loss, you need to enter autorotation. With a shaft-driven tail rotor system, the main rotor blades are powering the tail rotor, and you have an instant reversal of thrust available to yaw the aircraft in the directions required without any hesitations, while the blades continue turning the same direction in rotation. With the electric tail rotor driven system, you would have to rely on the motors and propellers being able to overcome inertia, stop immediately, build back RPM (making more inertia to overcome) and turn the other direction every time yaw needs to be corrected, which may need to be done several times a second during the emergency. Your propellers are designed to thrust efficiently in one direction, but not the other, therefore yaw control when you need it the "fastest and mostest" will not be fully available.

Therefore, after taking a logical approach after looking over the effects, drawbacks, and characteristics of each mode of operation, it becomes clear that an electrically powered tail rotor system has no real advantages over the traditional time-proven shaft driven tail rotor, and in fact has disadvantages.
 

hillberg

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Isn't that like saying you have to turn off the governor when flying a Robbie?
I flew Robbies before any governors and those pilots who just rely on those toys will have issues getting in Enstroms, Brantleys, Hughe 300s,
Hillers , Bell 47s, Sikorsky S-58 with the wright 1820s. Mini 500s - Angel ch 7 -Mc-1 RotorWays and Turbine Execs etc.
R -44 have many accidents because of power topping and over pitching -pilots who rely on governors lose the "Power management" side of helicopters,
I know pilots who teach in R-22s who train with the governors off as "Emergency procedure" the whole flight until the student understand the issue

And turbine torque meters and ToT limits are easily anticipated to hit limits before the Ng - 🤗 Like the Bell 205, 206, 212, H 500
 
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grevis

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I am surprised that on a forum where someone takes the time to share information about their unique project other members are instantly writing things to slam what they are doing. Especially surprised by Fetters, who has endeavored to design small single seat helicopter for the market in the past and no doubt had his own share of critics (was that fun having people critique what you were putting your efforts into).

I dont agree with Fetters comments above about the horizontal stab having such an effect on tail rotor requirement in forward flight. Anyone who has flown a Mosquito finds they function really well without a horizontal stab, and a vertical stab is the only one really beneficial at all. The mosquito air was never fitted with stabs, and I think its obvious to anyone with common sense that Oscar is in the early stages of trialing ideas, probably not too worried about the final layout yet.

Aside from the goal of his project, from the info Oscar has given in this thread and the other thread on the subject it has given lots of really useful data. He has been able to produce the exact power requirements of his machine to fly with and without the tail power requirement, and how well theoretical numbers line up with real world readings. I own a Mosquito and know if you ask the designers/factory they will not know the exact power required by their machines. Id bet the same is true of the Mini500, no truly accurate data like that. Anyone designing different engine setups/ideas for these types of machines would find that data incredibly useful.

As far as the idea of the electronic compensation for torque, why not try it for a test. The governor isnt an essential item but was added to make a pilots life a bit easier, why cant the same be true of this. Even without a governor machines use mechanical throttle correlators, isnt that doing the same thing, trying to make the pilots job easier! (Hillberg, do you disconnect your correlator on every machine you fly so you can say its just a toy and your a real helicopter pilot!)

There also seems to be comments that assume Oscar has only flown a Mosquito air and doesnt know how helicopters work. Has anyone asked if hes flown other machines. Maybe he knows a bit more about them than has been put in this forum thread.

Gary
 

Martin W.

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A mechanical tail rotor runs at constant speed whatever the thrust requirement. At zero thrust, it’s still eating a fair amount of power.
Oskar's fixed pitch, variable speed electric drive eats zero power at zero thrust. That’s the difference. A constant speed, variable pitch electric drive would be less efficient than a mechanical drive.

Other advantages ... may be quieter (Bell claims it is) .... safety on the ground (turned off) ...... redundancy (Bell claims 3 of the 4 rotors can fail and the remaining one can provide enough anti-torque)

I wonder if they also installed a conventional rudder it may handle yaw in forward flight and electrical could be shut down ..... I expect increased drag could be an issue and nullify any gains ...... I am not an expert in such things.

As far as reliability I think it is fair to say that industrial generators and motors rarely fail ...... and maintenance is practically nothing .... could also provide some huge savings compared to life-limited components of conventional driveshafts , bearings , 45* gearbox , and tail rotor itself .... I bet a pair of blades on the Bell 429 are north of $30,000 ....... I am normally not a fan of electric cars or aircraft but in this case I am.
 

hillberg

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I am surprised that on a forum where someone takes the time to share information about their unique project other members are instantly writing things to slam what they are doing. Especially surprised by Fetters, who has endeavored to design small single seat helicopter for the market in the past and no doubt had his own share of critics (was that fun having people critique what you were putting your efforts into).

I dont agree with Fetters comments above about the horizontal stab having such an effect on tail rotor requirement in forward flight. Anyone who has flown a Mosquito finds they function really well without a horizontal stab, and a vertical stab is the only one really beneficial at all. The mosquito air was never fitted with stabs, and I think its obvious to anyone with common sense that Oscar is in the early stages of trialing ideas, probably not too worried about the final layout yet.

Aside from the goal of his project, from the info Oscar has given in this thread and the other thread on the subject it has given lots of really useful data. He has been able to produce the exact power requirements of his machine to fly with and without the tail power requirement, and how well theoretical numbers line up with real world readings. I own a Mosquito and know if you ask the designers/factory they will not know the exact power required by their machines. Id bet the same is true of the Mini500, no truly accurate data like that. Anyone designing different engine setups/ideas for these types of machines would find that data incredibly useful.

As far as the idea of the electronic compensation for torque, why not try it for a test. The governor isnt an essential item but was added to make a pilots life a bit easier, why cant the same be true of this. Even without a governor machines use mechanical throttle correlators, isnt that doing the same thing, trying to make the pilots job easier! (Hillberg, do you disconnect your correlator on every machine you fly so you can say its just a toy and your a real helicopter pilot!)

There also seems to be comments that assume Oscar has only flown a Mosquito air and doesnt know how helicopters work. Has anyone asked if hes flown other machines. Maybe he knows a bit more about them than has been put in this forum thread.

Gary
I have seen pilots go from auto stabilized/governed machines to other helicopters without with deadly results, Pilot who had little training with power management and coming to the fact that hours is not enough.

I have designed and built helicopters and if you think we don't know the power requirements you are sadly mistaken, Even with type certified aircraft you can readily find performance charts for any environment .

His bio has R-22 on it. So it's safe to say he has "minimum" training. It's nice to experiment. But it's foolish to think a problem exists when none is there. One thing a real experimenter does is research his "theory" - see the pros and cons.

Here is what I see. A multi powered / fixed pitch prop "thrusters" that only work against main rotor torque.
1. more complex = more failure modes
2. only thrusts against main rotor touque = no torque / no thrust = reduced yaw control to no yaw control in adverse conditions.
3. entry of more human factors ie: did I charhe the battries or unplug that pesky charger?
4. what mission statement other than just to do it? Are you actually learning something ? Has it any impact on the industry / hobby ?

It's his toy - His experiment - Hate to see him wad up his stuff without a warning of caution.
 

hillberg

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Other advantages ... may be quieter (Bell claims it is) .... safety on the ground (turned off) ...... redundancy (Bell claims 3 of the 4 rotors can fail and the remaining one can provide enough anti-torque)

I wonder if they also installed a conventional rudder it may handle yaw in forward flight and electrical could be shut down ..... I expect increased drag could be an issue and nullify any gains ...... I am not an expert in such things.

As far as reliability I think it is fair to say that industrial generators and motors rarely fail ...... and maintenance is practically nothing .... could also provide some huge savings compared to life-limited components of conventional driveshafts , bearings , 45* gearbox , and tail rotor itself .... I bet a pair of blades on the Bell 429 are north of $30,000 ....... I am normally not a fan of electric cars or aircraft but in this case I am.
No rudder and that 429 will be returned to normal category after the tests are done. It was to capture a patent (future revenue stream)
Had a friend in generator & electric motors - they do fail and the stinky smoke smells awful -
 

Martin W.

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Oskar ..... your project is both innovating and intriguing thus creates a large interest ...... including guys like me who sometimes go off topic but dont let that distract you .... most of us are on your side. thanks
 

Oskar

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Thanks to those supporting the experiment, much appreciated. When wandering into the unknown there are times when you doubt your sanity, but at the end of the day it’s always better to be able to say “I gave it a go” than “I wonder what would have happened if…”

You need the critics as well though, because every now and they will say something that you hadn’t thought of, and in the process save you lots of wasted time and effort. So keep on trying to shoot down!
 

DennisFetters

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I am surprised that on a forum where someone takes the time to share information about their unique project other members are instantly writing things to slam what they are doing. Especially surprised by Fetters, who has endeavored to design small single seat helicopter for the market in the past and no doubt had his own share of critics (was that fun having people critique what you were putting your efforts into).

I dont agree with Fetters comments above about the horizontal stab having such an effect on tail rotor requirement in forward flight. Anyone who has flown a Mosquito finds they function really well without a horizontal stab, and a vertical stab is the only one really beneficial at all. The mosquito air was never fitted with stabs, and I think its obvious to anyone with common sense that Oscar is in the early stages of trialing ideas, probably not too worried about the final layout yet.

Aside from the goal of his project, from the info Oscar has given in this thread and the other thread on the subject it has given lots of really useful data. He has been able to produce the exact power requirements of his machine to fly with and without the tail power requirement, and how well theoretical numbers line up with real world readings. I own a Mosquito and know if you ask the designers/factory they will not know the exact power required by their machines. Id bet the same is true of the Mini500, no truly accurate data like that. Anyone designing different engine setups/ideas for these types of machines would find that data incredibly useful.

As far as the idea of the electronic compensation for torque, why not try it for a test. The governor isnt an essential item but was added to make a pilots life a bit easier, why cant the same be true of this. Even without a governor machines use mechanical throttle correlators, isnt that doing the same thing, trying to make the pilots job easier! (Hillberg, do you disconnect your correlator on every machine you fly so you can say its just a toy and your a real helicopter pilot!)

There also seems to be comments that assume Oscar has only flown a Mosquito air and doesnt know how helicopters work. Has anyone asked if hes flown other machines. Maybe he knows a bit more about them than has been put in this forum thread.

Gary


I didn't mean to hurt your feelings, and I am not trying to slam you. But if slamming you is trying to open your eyes to reality, then I guess that is a slam, and I'm sorry for that.

I do hope you will go back and read to understand what I said in my post, which is completely different than what you have said I said. I don't have to repeat it, it is there for all to read. I didn't discourage anyone from experimenting, quite the contrary, I said in doing so "there are norms that in the end, must be met". I explained those norms, and why your system will not meet them.

If you do not agree with me on the effect a stabilizer has on forward flight, then you should read back in past years on this forum the in-depth writings about that topic. Sure, on your slow-moving little mosquito-type helicopters it will have less effect, but still has an effect, and they would fly better with stabilizers. The Mini-500 was capable of up to 120mph flight speed, so I have to put a great deal of effort into its stability and power usage.

Anyway, time is the greatest judge. I have seen ideas come and ideas go for many years, some my own. I say that I have over a million-dollar education in just making mistakes alone, but I learned from every one of them and applied the knowledge gained over the years, thus worth it. I honestly wish I would have had a forum available when I was first designing my helicopter, where I could have had some old-timers that had real hands-on experience give me advice. I sure would have treated them with better respect and gratitude.
 

hillberg

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Thanks to those supporting the experiment, much appreciated. When wandering into the unknown there are times when you doubt your sanity, but at the end of the day it’s always better to be able to say “I gave it a go” than “I wonder what would have happened if…”

You need the critics as well though, because every now and they will say something that you hadn’t thought of, and in the process save you lots of wasted time and effort. So keep on trying to shoot down!
It's not "shoot down"
It's "What if?"
🤗
and preparing for the bumps.
 

Smack

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Oskar, just to address #6 above, maybe designate some of your multiple tail rotors to more efficiently thrust port and the other to more efficiently thrust starboard? Maybe only use the port thrusters to yaw CCW and the starboard to yaw CW?
I agree that a vert/horiz stabilizer might be useful.
Keep up the good work and updates.
Brian
 

Oskar

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Oskar, just to address #6 above, maybe designate some of your multiple tail rotors to more efficiently thrust port and the other to more efficiently thrust starboard? Maybe only use the port thrusters to yaw CCW and the starboard to yaw CW?
I agree that a vert/horiz stabilizer might be useful.
Keep up the good work and updates.
Brian

Brian,

There are various options, first prize would of course be something in the line of this (you can see the props reversing at 2:45):


At the moment I've got reversing active on most of the motors which already generates more than enough reverse thrust, even with asymmetric props. Will need to go untethered to test the dynamics further, the main batteries arrived today so the next step is to get them all tested ready for mounting.
 
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