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FrSky/Taranis throttle trim

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WayneB23/02/2020 08:31:33
19 forum posts

Morning all,

Ive had my Taranis a while and flown some electric helicopters with it ok. Thought I would dig out an old MA XCell I/C model and cannot get the throttle trim to work at all. I believe others may have mentioned this before, maybe it was Pete Christy I’m not sure.(apologise if it wasn’t), any way if anybody has any light to shed that would be great.
Thanks Wayne.

Peter Christy23/02/2020 08:57:57
1716 forum posts

Hi Wayne,

I did have an issue with the throttle trim on an i/c helicopter, but it wasn't that the trim wasn't working! It was the fact that because of the way I'd applied the throttle curve, any adjustment to that curve had a dramatic effect on the idle - resulting in a "hot" start.

The whole saga can be found here: **LINK**

The mistake I made was following advice about general computer programming that I was taught as a college student! This was to apply any maths (ie: mixing!) late in the process to reduce any "rounding" errors. In this case, this was the wrong thing to do! Applying the curves at the input stage solved the problem, though I still had to separate the throttle and pitch functions.

I posted my setups as part of that thread, and the final version has worked well. Of course, that was all written a few years ago now (OpenTx-2.1.9) so you may have to play "catch-up" to copy it into a current version.

I've recently updated to the latest OpenTx, but haven't had chance to fly the model again due to the weather. However, if you have a problem, I will happily email you a copy of my current setup. Just bear in mind that it is currently untested on the latest version of OpenTx, and will need checking! PM me your email address if you need this.




Bob Cotsford23/02/2020 10:50:42
8230 forum posts
454 photos

Could it be some combination of trim at idle only and reverse throttle on the model Settings tab possibly combined with throttle being reversed in Outputs? I know I once had some odd trim behaviour using trim at idle but can't remember the details now.

PatMc23/02/2020 11:48:08
4318 forum posts
524 photos

Could it be a faulty trim switch ? Have you tried the trim on another model memory ?
I can't remember how long I've had my Taranis but it is an original from the first batch in UK. Last year I changed a couple trim switches that had failed.

Mark H7523/02/2020 14:13:13
5 forum posts

Have you tried the switch tests from Tx itself?

WayneB23/02/2020 14:46:05
19 forum posts

Have put onto another model memory and trim all works fine. Put it onto ccpm and the trim function for the throttle channel has stopped. Being a helicopter function it could now all be linked to flight modes and throttle curves or just the way I have programmed it. On electric helicopters I never used the throttle trim, so all was good. Anyway thanks all for your input, all gratefully accepted, put a module in the back of my old JR PCM9x and good to go. Maybe will look into this further when I have more time.

cheers again.

Peter Christy23/02/2020 17:37:47
1716 forum posts


Just a thought: When you select ccpm it will certainly inhibit the throttle trim for the pitch function, and you may have to re-enable it on the throttle.

The helicopter I was setting up was an old HeliBoy - mechanical mixing, not ccpm.

Nonetheless, I had to be very careful to select the correct inputs to the throttle and pitch channels to ensure no cross-over between the trims. I forget exactly what I did now - I'll try and get Companion up and have a look later - but its possible that you (or ccpm!) has implemented the throttle function in such a way as to by-pass the trim.

I don't think any of the OpenTx devs fly i/c helis, so its possible they've missed this!



WayneB23/02/2020 19:00:29
19 forum posts

Thanks for the info Pete.
I shall have another look at it when I get time. It’s a bit of a blow for me really as was hoping to stay with OpenTx for the near future. But does seem a bit of a constant battle for anything that does not go to a flight controller in some way or electric.

Thanks for your help everyone, much appreciated.


Peter Christy24/02/2020 11:04:41
1716 forum posts

Wayne: PM sent!



WayneB24/02/2020 11:39:30
19 forum posts

PM sent, cheers Wayne.

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