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Trip,

 

That isn't a bad suggestion. Ice bear, if this is what you meant, I apologize. I just didin't want a centering force applied to the stick when trim is released/off.

 

Yogi, I had no idea the Arduino could do that Sounds pretty interesting.

 

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Hi

Yogi, I had no idea the Arduino could do that Sounds pretty interesting.

I simply could program a codesnippet, that run to a previous learned position, if I press an assigned button.

 

But at moment it would be much simpler.

Thus the FTR system is independent from the simulator logic, I can activate it before using the VR googles. Thereby I can give the stick the position I want and set the center.

 

To the defense of icebear: he used the system only some minutes without VR, in front of my 3m screen with beamer from behind.

regards / gruesse yogi

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Today I talked with a friend of mine who is a professional helicopter pilot. I told him our discussion and asked for clarification.

 

He told me, as you said Heloguy, that if you press the stick in eg the upper right corner and turn hydraulics of it will stay there.

BUT he explained me, that in the moment you touch the ground you have to look with one eye to the mast moment indicator and bring it to neutral to not destroy the mast. So in almost every heli (at least every Heli with rigid rotor) the stick always stands neutral when it is turned off. The EC-135 for example is very sensitive for that (he told me), you have to repair the mast every time you do not mind. In the case of mountain terrain, they even have to switch off the autopilot when landing, because this would otherwise damage the mast.

 

So the stick is always in the same position in the cockpit when you start a flight. And we need that in my opinion as well. That´s all I wanted to say all the time! I have never spoken of a centering force.

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Very interesting IceBear, I would love to hear other helicopter pilots discuss this to have it confirmed if possible.

 

Let's remember to stay mostly on topic though, so keep it related to upcoming microhelis.de FTR module.

 

I still have one question pending; if a pilot prefers not to use trim (in real helicopter), does he turn all related switches off and there is no "spring force" at all as long as hydraulics remain operational?

 

I ask this for two reasons. Assuming my statement is correct I would want the option to turn off the FTR module for simulating this behavior in real aircraft. Also it would more or less mean that if we fly in DCS with trim deactivated and have little to no spring centering on our cyclic (just damping) that we are having a realistic experience no?

 

Trip

 

PS- Also I would like to hear about similar things with pedals and collective. Collective is just pure damping/friction so it stays where you put it, is that correct? Pedals I read in the Gazelle test done by US Government, had no centering force. This I think means just damping/friction would be realistic on pedals? The way it was written seemed to indicate this might not be the same across all helicopters so details on what different helis are like would be appreciated as well. Are there helis with spring centered pedals, and if so which ones? Are there helis with trim force on pedals, and if so which ones?


Edited by TripRodriguez

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Hi,

 

after talking to icebear via FB, I think he is mostly right, and I have to implement this behavior.

Most rotorhead constructions use some kind of a "bendix" element to intercept axial forces.

CIMG3509.thumb.JPG.8a1a6c9227637be675ad8bc6bb07dfea.JPG

(the yellow part in this picture from an BO-105 head)

This part takes all centrifugal forces, so these heads do not need thrust-bearing like the RC-helicopters.

But this part makes even more: it also generates a restore force. And this force will align the mainblade when hydraulic is shut off.

So the stick will get a nearly centered position.

(I found it even in the UH-1 head, engineered before the BO-105 head.)

Link to one patent I found: tie-bar

@trip: helicopter pedals (as far as I know) have no centered position, and I should finally remove my spring from my damper. :huh: The damper will remain, because they simulate the behavior of the linkage rod.

The collective normally has adjustable friction, so the pilot can adjust it until he feels well with it.


Edited by yogi149

regards / gruesse yogi

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Ice bear, glad you were able to confirm. I'm familiar with mast bending in rigid rotor head helicopters, as I have worked on them as a mechanic, but I have not yet flown them as a pilot.

 

I've flown helicopters with rigid underslung rotorheads, as well as fully articulated rotor systems. In all of them, you neutralize the cyclic during startup and shutdown in order to prevent damage to the rotor system components.

 

In an underslung rotor, such as the Huey, or B206, it is because the rotor could swing on its hinge and contact that mast (mast bumping). On a fully articulated rotor system, such as the H-60, or H-53, you could damage the flap restrainers or droop stops. In some cases, with extreme control inputs, and depending on the helicopter, you could contact the aircraft itself with the blades.

 

Trip, you are correct in assuming that there are no spring forces (known as force gradient) in the controls when trim is turned off. Hydraulic damping would be the only thing felt, due to how the system works (again depending on the helicopter; as an aside, an OH-6 has no hydraulic assistance in the controls, everything is a direct linkage, so there would be no damping). In some cases, when trim is turned off, automatic flight control systems turn off automatically, as they need trim to function.

 

As for your last question, it depends upon the helicopter. A B206 only has trim for the cyclic. The pedals have no trim, and the collective uses a friction knob to maintain position. In a CH-53 and some models of the UH-60, there is trim for all controls. The collectiive has a trigger that releases the force gradient when depressed, allowing you to set a collective setting for the trim to hold. Same with pedals (switches are usually on the front of the pedals for you to press with the balls of your feet). Other models of H-60 only have trim on the cyclic and pedals, with a friction knob for the collective.

 

It really just depends on the helicopter, and how much money the end user is willing to spend.

 

Even with trim turned off, for most helicopters, I would believe the hydraulic damping would be realistic, even the Gazelle in your aforementioned example.

 

As for your last question, I have never heard of any helicopter with centering forces in any controls, only trim that provides force gradient as set by the user.

 

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What exactly are you wanting us to notice?

 

You definitely cannot do that with a cold H-1, H-60, H-53, H-47, etc. Like I said, you CAN do this with an OH-6, or an R22, or R44.

 

I never said all helicopters the controls can't be moved with the power off. I just said most of the ones I have flown.

 

I also don't notice any tendancy for the controls to return to neutral power off. He moves them there.


Edited by heloguy
 

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Hi,

I also don't notice any tendancy for the controls to return to neutral power off. He moves them there.

I have seen several such startup videos, where the pilot moves the stick before powering up the hydraulic.

And I know at least one video where the pilot make this move with spinning rotor.

sec. 35>

 

We will program the virtual centering at the push of a button.

(after crash :music_whistling:)

regards / gruesse yogi

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Hi,

 

after talking to icebear via FB, I think he is mostly right, and I have to implement this behavior.

Most rotorhead constructions use some kind of a "bendix" element to intercept axial forces.

[ATTACH]157045[/ATTACH]

(the yellow part in this picture from an BO-105 head)

This part takes all centrifugal forces, so these heads do not need thrust-bearing like the RC-helicopters.

But this part makes even more: it also generates a restore force. And this force will align the mainblade when hydraulic is shut off.

So the stick will get a nearly centered position.

(I found it even in the UH-1 head, engineered before the BO-105 head.)

Link to one patent I found: tie-bar

@trip: helicopter pedals (as far as I know) have no centered position, and I should finally remove my spring from my damper. :huh: The damper will remain, because they simulate the behavior of the linkage rod.

The collective normally has adjustable friction, so the pilot can adjust it until he feels well with it.

 

 

Yogi,

I missed this post before. The yellow part you are showing looks like what I've seen called a 'TT' (torque/tension) strap. It replaces the bearings in a fully articulated rotor system. It allows the blades to flap, hunt, and twist. Yes, it has a resting position, but I do not believe it would have enough force to neutralize the entire control system, unless they are not hydraulically driven.

 

If a helicopter's primary control servos are hydraulically driven, it is impossible to move them when the hydraulic pumps are not operating. Therefore, if you for whatever reason held the controls away from neutral, and removed hydraulic power, it would be impossible for them to return to center.

 

Normally, as stated before, this is not the case, because on shutdown, the pilot neutralizes the controls to prevent damage to the rotor system.

 

The Huey rotor system is semi-rigid and underslung. It teeters on top of the mast for flapping, and does not allow for the blades to hunt. There is no such thing like that BO-105 part on the UH-1 head.


Edited by heloguy
 

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I have seen several such startup videos, where the pilot moves the stick before powering up the hydraulic.

 

The rotor was spinning at 35sec, so the hydraulic pressure should have been on already, if this helicopter has hydraulic servos (not familiar with this model).

 

Certain helicopters do not use hydraulic primary servos. These, it would be possible to move the controls with the power off. These are usually small helicopters.

 

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Hi heloguy

There is no such thing like that BO-105 part on the UH-1 head.

but I think part 81 in this picture:

UH-1BandD.jpg.0ed60cb5325fb49a8b5b37ef1e85f992.jpg

must be a torsion tie bar.

I found this drawing when designing our small RC-helicopter rotor-head:

681466115_Bell-205-Huey-500-Kpfe-k.thumb.jpg.a33bc3bb68a0071582eba044e30f8871.jpg

:music_whistling:

 

I wrote that the rotor spins in this video, but I have seen many videos where the pilot move the stick for checking the movement.

regards / gruesse yogi

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Hi heloguy

 

but I think part 81 in this picture:

[ATTACH]157055[/ATTACH]

must be a torsion tie bar.

I found this drawing when designing our small RC-helicopter rotor-head:

[ATTACH]157056[/ATTACH]

:music_whistling:

 

I wrote that the rotor spins in this video, but I have seen many videos where the pilot move the stick for checking the movement.

 

I can confirm (I have just spoke with a former Huey maintainer) that a Huey does not use TT straps. That part is to reinforce the centrifugal motion of the blade's weight on the rotor system. Basically it is there to help hold it on, not to bring it back to center. That part does not work the same way as TT straps in a rigid rotor system, such as the BO-105.

 

I can also confirm that the controls do not return to center with the power off.

 

Again, on the moving of controls without power, it is because the controls are most likely mechanically driven, and most likely on a smaller helicopter. Nothing as big as an H-60, or larger.

 

Perhaps I should simplify, the smaller the helicopter, the more likely you can move the controls power off, the larger the helicopter, you must have hydraulic power to move the controls.


Edited by heloguy
 

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Hi,

I can confirm (I have just spoke with a former Huey maintainer) that a Huey does not use TT straps. That part is to reinforce the centrifugal motion of the blade's weight on the rotor system. Basically it is there to help hold it on, not to bring it back to center.

 

I can also confirm that the controls do not return to center with the power off.

 

Again, on the moving of controls without power, it is because the controls are most likely mechanically driven, and most likely on a smaller helicopter. Nothing as big as a Huey, or larger.

but the manufacturer and the airworthiness directives call it "tension torsion straps" :music_whistling:

http://www.airwolfaerospace.com/awa/products/products-bell-uh-1-204-205-210-212-214

 

and

 

https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&cad=rja&uact=8&ved=0ahUKEwiR-ZeuyYjSAhWBGywKHYTmDnMQFghfMAk&url=https%3A%2F%2Fwww.caa.govt.nz%2FAirworthiness_Directives%2FUH1.pdf&usg=AFQjCNEUeA5eX2Ugca8lIx1seJLRKshl2Q&sig2=bx_SzZ-Jd6aVFw4EUCUfDQ

 

but I agree that the reposition force should not be high.

 

My opinion agrees with yours, that the stick center must be made manually.

But for those customers who want a centering function, independently it is real, we can add this in the program.

regards / gruesse yogi

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Hi,

 

but the manufacturer and the airworthiness directives call it "tension torsion straps" :music_whistling:

http://www.airwolfaerospace.com/awa/products/products-bell-uh-1-204-205-210-212-214

 

and

 

https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&cad=rja&uact=8&ved=0ahUKEwiR-ZeuyYjSAhWBGywKHYTmDnMQFghfMAk&url=https%3A%2F%2Fwww.caa.govt.nz%2FAirworthiness_Directives%2FUH1.pdf&usg=AFQjCNEUeA5eX2Ugca8lIx1seJLRKshl2Q&sig2=bx_SzZ-Jd6aVFw4EUCUfDQ

 

but I agree that the reposition force should not be high.

 

My opinion agrees with yours, that the stick center must be made manually.

But for those customers who want a centering function, independently it is real, we can add this in the program.

 

 

I was not aware that they were called the same thing, though I can assure you, the TT straps in a Huey rotor system, and the TT straps in a rigid rotor system do not perform the same function.

 

I am wondering, though, Yogi, will the EC-135 control set I recently ordered have spring force on the cyclic stick? Or just dampers?

 

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Windows 11 x64

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Hi

I was not aware that they were called the same thing, though I can assure you, the TT straps in a Huey rotor system, and the TT straps in a rigid rotor system do not perform the same function.

technical they do the same job: keep the bladeholder and blade to the center hub against the centrifugal force.:pilotfly:

The rotorhead for the EC-135 is working different, there is only a hole in the 70mm thick carbonfiber beam inside of the blade. This head do not use a TT strap against the centrifugal force.

I am wondering, though, Yogi, will the EC-135 control set I recently ordered have spring force on the cyclic stick? Or just dampers?

The control set you ordered has oil filled dampers with removable springs.:music_whistling: If removed there are only the dampers active.

regards / gruesse yogi

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The Tension-Torsion, or TT, strap on a UH-1H has the primary function of bearing the blade's centrifugal load, but also has a secondary function of providing a rough blade-pitch centering force during hydraulics-off flight.

 

The TT strap was set so that the neutral torsion (twist) point of the strap, and therefore the minimum collective tension or resistance, was felt at around 22-24 PSI TQ.

 

During a maintenance test flight the pilot had to achieve a range of collective input between 10-35 PSI TQ, as well as maintaining a relatively stable hover.

 

This was to reduce the effort required to maintain level flight (22-24) for extended periods, conduct a landing (10) or execute a go-around (35) in the event of a hydraulics failure.

 

The TT strap had no noticeable effect, aside from retaining the blade, during normal hydraulic-assisted flight.

 

- Horsey

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What exactly are you wanting us to notice?

 

You definitely cannot do that with a cold H-1, H-60, H-53, H-47, etc. Like I said, you CAN do this with an OH-6, or an R22, or R44.

 

I never said all helicopters the controls can't be moved with the power off. I just said most of the ones I have flown.

 

I also don't notice any tendancy for the controls to return to neutral power off. He moves them there.

 

@Heloguy I'm sure Yogi linked that video, and specifically mentioned my name because he knows that the real life behavior specifically of the Gazelle controls is what I'm most interested in.

 

That said, I am also interested in the behavior of other helicopters, especially the Huey. I could open another whole can of worms and get us talking about that cyclic in the KA-50!

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Guys we have two active helo pilots in our sim group, one flew uh1s and HH-65s andbo108s (Iirc) and now flies s-76s, the other HH-65. Many many thousands of hours. If you want I can drag him on here for questions. Just let me know.

 

Los

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Today I had the opportunity to fly yogi´s FTR for the second time, now in a slightly improved version. The main differences I felt were mainly the better aligned axes, a weaker resistance when FTR is active but you do not press Trim Release and much weaker rattling with Trim Release pressed.

 

The "rattling" is still noticeable, but now just as strong as with a Microsoft Sidewinder FF, yogi gave to me as a comparison. Perfect it would be without this little resistance, but now you can live with it very well. Yogi said, it is technically justified and is attached to the magnets in the stepper motors. Without pushing trim release, it is immediately away.

 

The weaker springs with active FTR I liked very much. It allows you to have small to medium corrections without having to press Trim Release.

 

Overall, the system now felt very ready. I´m now waiting for what it would cost me to upgrade my existing stick to the new FTR. :huh:


Edited by Icebear
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Today I had the opportunity to fly yogi´s FTR for the second time, now in a slightly improved version. The main differences I felt were mainly the better aligned axes, a weaker resistance when FTR is active but you do not press Trim Release and much weaker rattling with Trim Release pressed.

 

The "rattling" is still noticeable, but now just as strong as with a Microsoft Sidewinder FF, yogi gave to me as a comparison. Perfect it would be without this little resistance, but now you can live with it very well. Yogi said, it is technically justified and is attached to the magnets in the stepper motors. Without pushing trim release, it is immediately away.

 

The weaker springs with active FTR I liked very much. It allows you to have small to medium corrections without having to press Trim Release.

 

Overall, the system now felt very ready. I´m now waiting for what it would cost me to upgrade my existing stick to the new FTR. :huh:

 

Great feedback! I'm gonna hold off picking up a cyclic until these are available!

[sIGPIC][/sIGPIC]

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Review coming soon guys, my Cyclic is shipping today! Super, super excited! :pilotfly: I imagine it will take a while to make it's way across the big pond and through customs but I had to share my excitement. =D


Edited by TripRodriguez

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