Cyclic Pitch

[mike_drz]

My HK-500 with all align head flybared is drifting backwards.

The swash is perfectly level, but I notice I have more positive cyclic pitch at 8 degrees and -7. I measured it at mid stick using the elevator and then from the back using aileron.

Is 1 degree off either way within acceptable limits? Not sure if the backward drift is because of CG balance issues. Its causing some trouble when Im trying stationary rolls.

[Gladius]

Originally Posted by mike_drz

Is 1 degree off either way within acceptable limits? Not sure if the backward drift is because of CG balance issues. Its causing some trouble when Im trying stationary rolls.

Your CG is the first thing I would check. Was it windy when you flew? Wind will push a FB'ed heli around more than a FBL. Did the heli drift backward regardless of its orientation to the wind?

Ideally, you want equal positive and negative pitch, but it's not critical.

[mike_drz]

Hey Gladius

Thanks for the reply. Yeah it drifts back regardless of orientation. Wasn't too windy. Some days it does it less than others; but one thing is constant, it drifts aft.

What's the best way to check CG? Do I just extend the blades and try balance it from the blade holders? Ive got the battery tray drop mod and the battery is pretty far forward already. I guess in the worst case I'll just have to use more forward trim tab than I'd like.

[Gladius]

Set everything up like you're going to fly. Turn the rotors so the blades stick out to the sides with zero pitch. Put a fingertip under each bolt that holds each blade. Slowly lift the heli off the ground with your fingertips, paying close attention to whether it pitches forward or backward as it comes off the ground. If it does either, your CG is off.

What size batteries are you using?

[mike_drz]

Thanks for the tip I checked the CG. With the battery where I usually mount it, it does lean back a bit. I moved the batt. Forward and then it actually moved the CG forward bias. I also noticed it balances to the left because th esc and wires are mostly on that side. It only slightly drifts to the left. I'll play around with the positioning, may even try a bigger battery.

I'm using a turnigy 3000 mAh 6S 20C.

[Gladius]

That's a pretty small battery. I have a Turnigy nanotechnology 25C (also 3000mah) that comes down pretty spent after each flight. I have some 40C sky lipos that work much better, and balance the heli perfectly.

I forgot to mention in my last post, but you should really avoid using trim to counter an unbalanced heli. It will work if you are only flying upright, but if you invert the heli, the trim and the unbalance won't counter each other anymore - they actually work together!

[mike_drz]

Your sky lipo is also 3000 mAh? Now that I spend more time in IU my flights are getting pretty short. 4 minutes or so, in normal mode I get 6 min. Would a 4000 mAh fit? Or is it just that the higher C batt is bigger?

I want to avoid using the trim like you said. I'm spending more time on inverted flight and it drifting makes it harder to learn.

[Gladius]

Yes, the Sky Lipo is also 3000mah, and yes, a higher C rating tends to be a little heavier. I can get 4 minutes out of my nanotech, and 4:30 out of my Sky Lipos. I could get more if I switched to a smaller pinion, but I like my headspeed!