ideas HK500GT tail authority problem

[helijohn]

I am nearly tearing out my hair.

My HK500GT is really bugging me.

I bet the fix is simple.

As I lift of it turns to the left in a slow piro sort of way.

It is a bit like the gyro is reversed but in a slo mo way!

The gyro, CSM560, is set up correctly with throws and directions all as they should be. I am using rate mode until I can find the solution.

In rate mode with the servo arm at centre I have a few degrees or right rudder but I have tried it with zero degrees too.

There is not a lot of movement left on the tail shaft for much more pitch!!

I have tried altering the gains until I am sick of it but TBH this is not really showing gain symptoms.

Even with full right stick the heli turns left. This makes me think the tail thrust is just inadequate.

I have tried different tail blades.

I have tried higher and lower headspeeds and different pitch setting too.

Help me before I go bonkers.

Binning this is not an option.

[trillian]

What tail servo is on there?

What doesn't make sense is that even with right stick it still wants to turn left.

[helijohn]

What tail servo is on there?

What doesn't make sense is that even with right stick it still wants to turn left.

Tell me about it. I even set it with some big angle of right turn and it didn't help. I have flown without gyro back in the day so I expected to be able to beat this in rate mode. I had a HK401B on it previously and it was just the same.

Turning left smacks of torque turn and that points to a weedy tail thrust.

It has a Goteck coreless motor digital servo BB on the tail and it seems to be responding OK to inputs.

[Tripler]

Trim in centre on tx when start up? If its a DX tx bin that have you tried another rx?

[helijohn]

have you tried another rx?

No I haven't but it all seems fine on the bench and as much as I can see when spooled up.

[p4ddy]

Belt drive? I assume both the tail drive & pully are metal? If either are plastic they can slip.

[carpwally]

Hi had a tail holding problem on the HK600 dont matter what we did it would not hold this was the standard belt drive and HK tail borrowed the tail of one of our members 600 tail with an align tail unit popped into the hover and the tail was rock steady so binned the HK tail unit and replaced it with the align unit retaining the tail boom and belt

[helijohn]

Hi had a tail holding problem on the HK600 dont matter what we did it would not hold this was the standard belt drive and HK tail borrowed the tail of one of our members 600 tail with an align tail unit popped into the hover and the tail was rock steady so binned the HK tail unit and replaced it with the align unit retaining the tail boom and belt

Interesting!

How was it different apart from the make??

[carpwally]

only thing we put it down to was the engineering of HK tail leaves a little bit to desire but changing to the genuine Align tail unit and blade holders cured it and I have not given it anymore thought

[Raptormad2]

Yep as above I had the tail keep blowing out on my hk 500 even though it had the metal tail just couldn't sort it so fitted an align tail and no problem since then have converted it to torque tube because the belts kept shredding no problems since.

[helijohn]

It feels like there isn't enough throw to give the thrust. I've checked for slippage and think I can rule that out.

[trillian]

only thing we put it down to was the engineering of HK tail leaves a little bit to desire but changing to the genuine Align tail unit and blade holders cured it and I have not given it anymore thought

I wonder if it's a thrust bearing / race problem in the grips?

[dillwhacker]

Is the pitch arm definitely moving all the way when it's spooled up - could it be binding at high RPM? (seems unlikely)
Is the servo too weedy to apply full pitch when its spinning and loading the servo?

[trillian]

It feels like there isn't enough throw to give the thrust. I've checked for slippage and think I can rule that out.

You don't need too much just in a hover, something like 6 or 7 degrees I think. Most tails easily go to 20 degrees, give or take a bit. It sounds more like the gyro is not able to do its job for some reason. If it was slipping belt / pulley I would think you'd see the inconsistent tailrotor speed and the gyro would be trying to go to full pitch to correct.

[helijohn]

You don't need too much just in a hover, something like 6 or 7 degrees I think. Most tails easily go to 20 degrees, give or take a bit. It sounds more like the gyro is not able to do its job for some reason. If it was slipping belt / pulley I would think you'd see the inconsistent tailrotor speed and the gyro would be trying to go to full pitch to correct.

Yes, I set the tail pitch to a fairly big angle so that on rate with centre stick I knew there was a good bit of pitch. And it is a slow piro creep rather than an erratic struggling effect.

Is the servo too weedy to apply full pitch when its spinning and loading the servo?

I can see the tail disc moving a fair bit on command input. It seems to have plenty of pitch. But I admit I can't really see it while watching the heli slowly but inevitably turn.

I wonder if it's a thrust bearing / race problem in the grips?

That's one I can't answer. I have another complete tail assembly I can substitute but I want to establish why this one (if it is a fault) is not working.