Ar7200BX - Tail drops during piro

[Skeezix]

I have 4x 550 class helis that all have an AR7200BX with DSMX sat on them. All 4 helis have the same problem where the tail will drop during a piro. It is disconcerting, and I have yet to be able to tune the 7200BX to eliminate this.

Can anyone suggest an fix?


Cheers.

[Ah Clem]

Is the Piro compensation set in the correct direction?

I have about eight BeastX's in service (including some AR7200BX's) and the tail stays nice and flat on all of then while pirouetting.

[Skeezix]

Originally Posted by Ah Clem

Is the Piro compensation set in the correct direction?

I have about eight BeastX's in service (including some AR7200BX's) and the tail stays nice and flat on all of then while pirouetting.

Yes - piro comp is set correctly. I should have mentioned that in the first post. I'm trying to manouver the heli all around the field while piro-ing. After the second piro or so, the tail drops and I have to fight that in addition to trying to 'drive' the heli around the field while piro-ing.

[theasp]

Hi I had the same problem on a 250 was advised to check swash level
although the heli was set up correctly or so I thought

After initialisation the swash was low to the rear corrected this in parameters A and tail dip went away

I found that the swash level tool I used was faulty

Hope this observation helps

ASP

[Skeezix]

Piro optimization is correct, and so is the swash level.
Any other recommendations would be appreciated.

Thanks.

Originally Posted by theasp

Hi I had the same problem on a 250 was advised to check swash level
although the heli was set up correctly or so I thought

After initialisation the swash was low to the rear corrected this in parameters A and tail dip went away

I found that the swash level tool I used was faulty

Hope this observation helps

ASP

[Coco66]

When you say that the tail drops, you mean you have an "elevator down" effect?

[Skeezix]

That is correct - the tail drops like a small down elevator input has been given, rather than piroing on the main shaft axis.

Originally Posted by Coco66

When you say that the tail drops, you mean you have an "elevator down" effect?

[HeliAxe]

Have you tried turning up dial 1, head gain?

[Ah Clem]

I am very curious to see what this, eventually, turns out to be.

[Smoggie]

Is the CG correct?

If not the CG then I'd double check the swash, sounds to me like it's out of level (yes i know you said it was level, but it's gotta be something that's causing it)

[HeliAxe]

If I understand correctly and all 4 of your helis are experiencing the same problem, it's obviously a common issue, possibly stemming from your radio

Put your radio in monitor view and see if the elevator output isn't outputting back elevator during rudder inputs.

When you setup helis number 2, 3 and 4 in your radio, did you copy them from model number 1 or start from new default models?

Try defaulting one of your models in your radio and start again in case you have something funny going on there like some sort of undesired trim or funky mix.

Try another radio if you have one, or borrow a buddies if you can.

just some ideas.

[Coco66]

HeliAxe, I'd bet you are right, sir. Let's see.

[Skeezix]

Ah yes - I believe I did copy the model over when I added a new heli to the transmitter, and tune it from there. That may very well be the issue. Next time I am at the field I will try to adjust pot #1 on the AR7200 to see if that changes anything, as well as checking the monitor on the transmitter to see if I'm getting any down elevator when applying rudder.
Thanks for all the feedback. I'll be sure to post my results once I have them.

Originally Posted by HeliAxe

If I understand correctly and all 4 of your helis are experiencing the same problem, it's obviously a common issue, possibly stemming from your radio

Put your radio in monitor view and see if the elevator output isn't outputting back elevator during rudder inputs.

When you setup helis number 2, 3 and 4 in your radio, did you copy them from model number 1 or start from new default models?

Try defaulting one of your models in your radio and start again in case you have something funny going on there like some sort of undesired trim or funky mix.

Try another radio if you have one, or borrow a buddies if you can.

just some ideas.

[HeliAxe]

[sutty]

If I were to guess, I would say centre of gravity or unlevel swash. Why that would be rearward on all four helicopters I couldn't say, but those two seem to fit.

There is only so long that an FBL controller can hang onto the correction for constant errors, or there is in the way they choose to configure them. I think they can do a better job, but then other unwanted tendencies occur like feeling very robotic, and difficulties in controlling them on the ground, tip overs etc, so I think they have to have some decay on the control loops.

You can clearly see the decay on cyclic on the bench, since if it were to behave like a heading hold tail, it would stay hard over after a cyclic input, but the MB does not, as do many others. Also, I think you can see something of this in step N, piro comp, where the longer you are in there the harder it is to observe the piro comp effect, as the automatically entered swash deflection, or wobble, seems to get less and less with time. This could be a red herring, since I'm not sure why that should happen in set-up, but it certainly does do this.

This leads me to think that if it were a Tx trim issue, or some manual inadvertant elevator, for whatever reason, it would be seeing that as an input right from the outset, and it would be backing out of the piro right at the start, not after a several turns, which is the described behaviour.

If mechanically off level, a little backwards physical trim on the swash, as a result of a faulty swash levelling tool, or levelling methodology, then this could easily explain how this issue applies to all four helis simultaneously, and why it takes several turns to become evident.

Trying to put the battery all the way in, and not ever having checked the CoG could also account for it applying to all four.

Higher gain would help I think, if it's possible to run with it. We don't know if this has been optimised, but even then I think it would be like masking over an issue, and it would probably still be evident, but to a lesser extent.

Consistent radio error, not so convinced, I think it resets the received radio values to zero during each initialisation, and even if it didn't it would do it from the outset, just as it would with an incorrect piro comp setting, and probably with pilot input. Who knows though, it's certainly a toughy and not been described before, or at least not across four helis at once.

Cheers

Sutty

[crashcopterman]

I've read all of this and a few things seem possible, like radio setup possibilities, but rather unlikely. I like Sutty's last post, but I think we could help the OP more if we could see a clip of this behavior on the effected machines.

Steve