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 Post subject: pitching forward in FFF
PostPosted: Sat 12. Jan 2019 18:06:15 
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The CG is slightly tail heavy, if anything, but during high speed passes, I definitely have to ride the elevator to keep it from nosing down.

Not sure how to solve this. I don't usually fly speed passes so it hasn't bothered me much but I know I need to optimize a few things on the heli (Oxy 4) for this season and figured I'd start by eliminating this pitching behaviour first.

Anything in the Spirit settings that might be causing this?


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PostPosted: Sat 12. Jan 2019 20:30:45 
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Hello,

I recommend to check if the swashplate is really levelled when you tick Servos/Subtrim (tuning). At this moment all servo arms should be centered.
At the same time swashplate must be level as well and at the same time collective pitch angle should be exactly 0°.

When fixing the CG it can be also improved.

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PostPosted: Sun 13. Jan 2019 3:18:25 
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ZeXx86 wrote:
Hello,

I recommend to check if the swashplate is really levelled when you tick Servos/Subtrim (tuning). At this moment all servo arms should be centered.
At the same time swashplate must be level as well and at the same time collective pitch angle should be exactly 0°.

When fixing the CG it can be also improved.


Hi Tomáš,

I set this heli up with Soko initially but went back in just now and confirmed the swash position and collective pitch with subtrim tuning enabled. I just eyeballed the swash and folded the blades back for a quick 0 degree test and both appeared perfect. No indication that the geometry is causing this.

Could a rear set CG cause nosing forward in FFF if Spirit is fighting the CG?




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PostPosted: Sun 13. Jan 2019 20:24:20 
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Hi,

it is very likely that improper CG is causing this.

You can move battery just temporarily to see how the behavior will change.

Sometimes when moving with collective pitch up and down one of the servos are moving unequally. This then could cause the behavior as well.
Or one servo is slower than other due to a friction or other mechanical issue.

You could verify (ideally with a Cyclic Leveler) that the the swashplate is really level also at the low and high pitch position. In case it is unequal you can fix it with the Servo Travel Correction. You can find it in the Servos tab.

Hopefully this will help you.

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PostPosted: Mon 14. Jan 2019 1:09:03 
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Joined: Wed 01. Mar 2017 23:39:31
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ZeXx86 wrote:
Hi,

it is very likely that improper CG is causing this.

You can move battery just temporarily to see how the behavior will change.

Sometimes when moving with collective pitch up and down one of the servos are moving unequally. This then could cause the behavior as well.
Or one servo is slower than other due to a friction or other mechanical issue.

You could verify (ideally with a Cyclic Leveler) that the the swashplate is really level also at the low and high pitch position. In case it is unequal you can fix it with the Servo Travel Correction. You can find it in the Servos tab.

Hopefully this will help you.


Thanks Tomáš. I moved the pack as far forward as the canopy allows and while it’s still not perfect, the pitching issue was pretty much non existent. I think that solved it.

I think I kept moving rearward trying to solve the pitch issue and kept making it worse despite it being counterintuitive.

Thanks!


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