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In my first toe-dipping experiences into flybarless systems over the last few weeks with a Futaba system on my 90, I've been mirrored by a club mate in exactly the same time frame also trying a fbl setup for the first time with a 3GX on a TRex 600.
I've found it interesting to compare the differences between the setup procedures.
With the Align system, he has his Tx set to 120 deg CCPM and the setup instructions make a lot of noise about ensuring the swash plate is dead level and all push rods are accurate etc. He also doesn't appear to have (or hasn't found it yet?) the ability to fly the main two (i.e. not the tail) axes in rate mode, so is confined to heading hold only on roll and pitch axes. So, he sets everything to dead level on the swash, picks it up into the hover and it just sits there, and the assumption is that the dead accurate setup is making the heli hover bang on. Or is it? Is the accurate setup just a good and easily measurable starting point and the gyros are actually tilting the swash away from level to maintain the attitude of the machine.
I think it is.
The reason why I think this is that the Futaba system is quite different - my Tx is set to mechanical mixing (i.e. not CCPM) so all the swash plate control is managed by the fbl unit, and I also have the ability to run all 3 axes in rate mode. In fact the instructions tell you to do this, and use the trims and/or adjust the push rod lengths to get it to hover steady in rate mode before putting into heading hold mode. Like we used to do in the old days with tail gyros to find the neutral hovering centre of the tail system.
Having done this with my Futaba and made sure all the rods were accurately made, swash dead level and c/g bang on before I started, my swash is now noticeably tilted in the heli neutral position, and the fbl unit has subsequently been switched into heading hold mode for a perfectly trimmed setup.
I'm kind of not surprised to be fair. The heli has all sorts of forces acting on it when the blades are spinning because it's basically a giant gyroscope, so the combination of the side affect from the tail rotor and the gyroscopic procession effects mean that in order to hold a stationary hover, the swash is going to have to be tilted to overcome these. It goes without saying really.
These are just my observations, and I find the different design approaches quite interesting. I kinda understand the Futaba approach better than the Align approach as the theory of roll and pitch axes centering is actually identical to tail gyro centering.
I'm not saying the Align approach is wrong, just different, but the whole idea of getting everything perfectly centered and level and then assuming that your setup is making the heli hover spot on is kinda flawed. It's a shame Align users can't measure the levelness of the swash plate when it's hovering, but hey ho.
I agree that accurate setup helps because at the end of the day it's the only thing you've got measure stuff against with a fbl setup of any kind. You need a bench mark to work from. Both systems seem to work well for sure, and have their pros and cons. The Futaba seems to need more setup time and tweaking and the Align system was very aggressive out of the box.
Enough waffle, just thinking out loud.
I've found it interesting to compare the differences between the setup procedures.
With the Align system, he has his Tx set to 120 deg CCPM and the setup instructions make a lot of noise about ensuring the swash plate is dead level and all push rods are accurate etc. He also doesn't appear to have (or hasn't found it yet?) the ability to fly the main two (i.e. not the tail) axes in rate mode, so is confined to heading hold only on roll and pitch axes. So, he sets everything to dead level on the swash, picks it up into the hover and it just sits there, and the assumption is that the dead accurate setup is making the heli hover bang on. Or is it? Is the accurate setup just a good and easily measurable starting point and the gyros are actually tilting the swash away from level to maintain the attitude of the machine.
I think it is.
The reason why I think this is that the Futaba system is quite different - my Tx is set to mechanical mixing (i.e. not CCPM) so all the swash plate control is managed by the fbl unit, and I also have the ability to run all 3 axes in rate mode. In fact the instructions tell you to do this, and use the trims and/or adjust the push rod lengths to get it to hover steady in rate mode before putting into heading hold mode. Like we used to do in the old days with tail gyros to find the neutral hovering centre of the tail system.
Having done this with my Futaba and made sure all the rods were accurately made, swash dead level and c/g bang on before I started, my swash is now noticeably tilted in the heli neutral position, and the fbl unit has subsequently been switched into heading hold mode for a perfectly trimmed setup.
I'm kind of not surprised to be fair. The heli has all sorts of forces acting on it when the blades are spinning because it's basically a giant gyroscope, so the combination of the side affect from the tail rotor and the gyroscopic procession effects mean that in order to hold a stationary hover, the swash is going to have to be tilted to overcome these. It goes without saying really.
These are just my observations, and I find the different design approaches quite interesting. I kinda understand the Futaba approach better than the Align approach as the theory of roll and pitch axes centering is actually identical to tail gyro centering.
I'm not saying the Align approach is wrong, just different, but the whole idea of getting everything perfectly centered and level and then assuming that your setup is making the heli hover spot on is kinda flawed. It's a shame Align users can't measure the levelness of the swash plate when it's hovering, but hey ho.
I agree that accurate setup helps because at the end of the day it's the only thing you've got measure stuff against with a fbl setup of any kind. You need a bench mark to work from. Both systems seem to work well for sure, and have their pros and cons. The Futaba seems to need more setup time and tweaking and the Align system was very aggressive out of the box.
Enough waffle, just thinking out loud.
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