Spirit System

I put my Spirit2 on an old Trex 450 XL (Flybar) heli and am doing test hovering flights to tune the settings. All seems fine at Idle1 (2800) head speed rpm but at Idle2 (3000) the cyclic oscillates as if the cyclic gain is too high. At Idle3 (3200) it's worse, so I have been reducing the cyclic gain by 10% increments from 60% originally. Now at 40% it seems better but not solved.

The question is, should I keep lowering the cyclic gain to, say 20%? What are the disadvantages? The info box (when you hover the mouse over in Spirit Settings), indicates a range of 60% - 70% for optimal results. I have checked the 'flybar mechanic' box in Advanced/Expert Settings. Everything else is set-up carefully as-per the wizard and manual. It's my 6th heli with Spirit, so I think I'm familiar with initial setup but only now am exploring 'fine-tuning' as the standard settings have until now, been fine for me.

Other considerations:
1. Are there any other settings which will have the same effect as 'cyclic gain' which I can try?

2. This is an old heli with a fair amount of use. The head mechanics are 'ok', as-in all screws are tight, nothing bent, etc. but as you'd expect there's much more 'slop' in the mechanism from servos to blades as it's a flybar setup. I'm wondering if this wear/slop is contributing to the problem, and that the Spirit2, which is of course much more sensitive than the GY401 gyro it replaced, is trying to over-correct.

There's a limit to how much 'tweaking' I want to do with this heli and I have the feeling that I could be chasing this issue for a while. Yes, I could try to buy all new bearings for the head, but with its age etc. it will be difficult. and Yes, I could have put a flybarless head on it, new servos, etc. but decided to leave it as-is except for the Spirit2 to control it. Ultimately, the easy-fix is to reduce the headspeed to where the problem goes away, and just fly it, but I thought I'd ask here to see what your views are.

Cheers, Andy
UK

Normal gain levels one would expect for a flybarless model will not work because the flybar is trying to stabilize the helicopter; it's like two gyros trying to work simultaneously fighting each other.

Lower the gain until the oscillation goes away and don't worry about how low the value is. Your flybar is providing the stabilization on this model, and in this configuration you're essentially using the spirit as a head holding gyro for the tail only. The flybar mechanic setting is supposed to make it possible to use rescue and stabilization modes but I am fairly certain that is separate from trying to use cyclic gain.


From the manual:

1 STANDALONE GYRO AND FLYBAR
Owners of flybarred helicopters can take advantage of the heading hold gyro, which keeps the tail in the direction given by the transmitter regardless of effects from wind or any outside forces.

Connect the rudder servo to the CH4 port of the Spirit unit. If you also use a standard receiver, you will need to connect GEAR (or AUX) from your receiver to the AUX port on the Spirit unit. Also, you will need to connect your receiver RUD port to the RUD port on the Spirit unit.

Even if you do have a flybarred model, you can also connect the unit in the same way as a you would a flybarless one. This allows you to use the full potential of the unit including Stabilization and Rescue mode. In order for this to work correctly, it is necessary to enable the Flybar mechanic parameter in the Advanced/Expert window during setup. All other parameters can be configured just the same as with a flybarless head."

thestructured wrote:Normal gain levels one would expect for a flybarless model will not work because the flybar is trying to stabilize the helicopter; it's like two gyros trying to work simultaneously fighting each other.

Lower the gain until the oscillation goes away and don't worry about how low the value is. Your flybar is providing the stabilization on this model, and in this configuration you're essentially using the spirit as a head holding gyro for the tail only. The flybar mechanic setting is supposed to make it possible to use rescue and stabilization modes but I am fairly certain that is separate from trying to use cyclic gain.


From the manual:

1 STANDALONE GYRO AND FLYBAR
Owners of flybarred helicopters can take advantage of the heading hold gyro, which keeps the tail in the direction given by the transmitter regardless of effects from wind or any outside forces.

Connect the rudder servo to the CH4 port of the Spirit unit. If you also use a standard receiver, you will need to connect GEAR (or AUX) from your receiver to the AUX port on the Spirit unit. Also, you will need to connect your receiver RUD port to the RUD port on the Spirit unit.

Even if you do have a flybarred model, you can also connect the unit in the same way as a you would a flybarless one. This allows you to use the full potential of the unit including Stabilization and Rescue mode. In order for this to work correctly, it is necessary to enable the Flybar mechanic parameter in the Advanced/Expert window during setup. All other parameters can be configured just the same as with a flybarless head."

Many thanks for this. I flew the heli today and lowered the cyclic gain as far as possible to 20% - much better at the lower 2 headspeeds but at 3000 rpm the problem persists, so the gain is still too high. I guess with lighter flybar paddles (if now available) it would improve further but perhaps I'm at the limit of achievement with this old heli, and should just continue at the lower HS, or indeed abandon the Spirit2 and return to the tail gyro, but the 'stabilisation and rescue modes' are valuable to me though I didn't experiment with that today.

My setup is a Jeti REX3 receiver connected in 'single wire' mode using the Jeti Integration Cable (signal at AIL pin, power at RUD port) as per the manual. Looking at the manual text copied above (thanks), does it mean that I should check the Flybar mechanic parameter ONLY if connected with a standard receiver, i.e. this parameter is selected when only tail gyro is needed? If so, this would mean with my setup I shouldn't select this parameter but just reduce cyclic gain as much as possible? Now I'm confused as to whether checking the 'flybar mechanic' parameter should disable all except tail gyro, but that's not what I'm seeing.

If I were able to reduce the cyclic gain to zero instead of 20% min, it should give me what I need but I'm unsure as to why there's SOME gain needed in a flybar setup. Tomas - can you explain for me, please?

Many thanks again, Andy