Zero pitch at mid-stick problematic - 550L #2

[EjectEjectEject]

Sounds like you're good to go.

Have you checked the blade pitch of each blade from the same side of the heli to ensure tracking is going to be OK?

Upper and lower pitch range symmetrical?

[PaoloFCantoni]

Originally Posted by EjectEjectEject

Sounds like you're good to go.

Have you checked the blade pitch of each blade from the same side of the heli to ensure tracking is going to be OK?

Upper and lower pitch range symmetrical?

I reset the Collective and Cyclic pitch on Wednesday night - the evening prior to the test flight - to +-12° Collective and +-6° Cyclic on my AR7200BX - so that should be OK.

On the test flight, tracking seemed to be good. The same side pitch check - Do you mean folding both blades back so they're on the same side of the heli and you can compare the pitch of both blades against each other? If so, then yes! That's how I check zero pitch, since if they are at the same level at mid stick (and therefore will track correctly), the geometry requires that the pitch is zero.

I'll let you know how it goes.

Paolo

[EjectEjectEject]

(oops - system error)

[EjectEjectEject]

The fold-back checks for 0 pitch, but not tracking.

Tracking is just a difference in pitch between the two blades - but the "trick" is in measuring them. If you measure one blade then put the gauge on the other blade without moving the blades then you can get erroneous readings due to the heli not being level.

Leveling it is a PITA so the easiest way is to put the blades at 3 o'clock and 9 o'clock - measure one blade at mid stick - take the gauge off - spin the blades 180 degrees - and measure the other blade from the same side of the heli.

That way you get a comparison between the two and it doesn't matter if the heli isn't level by a few degrees as it affects each blade by the same amount. Normally you won't be able to get it much better than within about 1/2 degree without using turnbuckles, but that should be fine.

[PaoloFCantoni]

Thanks for that Eject,

I now get the difference, conceptually...

But I only have that great NZ invention: the Soko Heli Tool - so measuring tracking deltas could be problematic. I don't have the other kind of pitch gauge. I guess I could jury-rig one with the Soko.

Incidentally, if I have adjusted the zero pitch (exactly) using fold-back and then I look "down" the folded back blades and I get a "straight line" for the blade cross section (rather then a very shallow "V") won't I have tracking pretty much right? Any other change in tracking should be caused by dynamic effects/differences in flight? No?

Paolo


BTW: could you delete the erroneous :32 min post? It might confuse someone.

[EjectEjectEject]

Originally Posted by PaoloFCantoni

Thanks for that Eject,

I now get the difference, conceptually...

But I only have that great NZ invention: the Soko Heli Tool - so measuring tracking deltas could be problematic. I don't have the other kind of pitch gauge. I guess I could jury-rig one with the Soko.

Incidentally, if I have adjusted the zero pitch (exactly) using fold-back and then I look "down" the folded back blades and I get a "straight line" for the blade cross section (rather then a very shallow "V") won't I have tracking pretty much right? Any other change in tracking should be caused by dynamic effects/differences in flight? No?

Paolo


BTW: could you delete the erroneous :32 min post? It might confuse someone.

Not sure to be honest - I've never used the soko tool (sounds too complicated for me).

I guess if it does what it's supposed to though it should sort the tracking out as part of the setup.

[PaoloFCantoni]

So I'm happy with the maiden flight after the rebuild.

As I mentioned there was a tiny bit of tail wag (during the 1min test flight) caused by Gyro gain a bit too high, which I adjusted before the flgiht and appear to have "nailed" first time.

Visually, tracking appeared pretty "spot on".

The wind was a bit on the high side, so nothing too adventurous - just testing with piros and pitch pumps, as well flying in all upright orientations.

So, once again, thanks to all who helped me get the bird in the air, especially Eject.

Paolo

[EjectEjectEject]

You're very welcome - glad it's all going well!