Trim Idle Only doesn't work correctly with Crossed Trims

[davemcddd]

As a gas/glow flyer, this OpenTx problem is the only remaining sore spot in the Taranis programming.

OpenTx 2.0, 2.1, and 2.2 for the Taranis all have a bug in it when using the Trim Idle Only function with crossed trims. (The Trim Idle Only functions perfectly without crossed trims, and crossed trims function perfectly without the Trim Idle Only selected.) The bug is that the Trim Idle Only function sticks with the THR trim button instead of following the assigned throttle trim. So with crossed trims this results in the assigned elevator trim operating with the Throttle Idle Only algorithm, and the assigned throttle trim not using the Throttle Idle Only algorithm. There are several different ways of getting around this bug, but the best solution is to allow the Trim Idle Only function to work correctly with crossed trims.

To view the open issue on Github about fixing the Trim Idle Only and crossed trims problem, go to this link:
https://github.com/opentx/opentx/issues/5635

I'm really hoping Aloft can use some of their influence to convince the OpenTx development team to finally resolve this issue.

 

[Wayne]

Thanks, I added a quick note there for some support. They usually get to these smaller issues pretty quickly. Not like it is a new feature that will require tons of work, hopefully just a simple bug fix.

 

[sande005]

Actually, this has been an issue since before 2.0. I a few years ago opened an issue about it, that got closed with no action, due to perceived lack of need. So if you would like this resolved, please go to the link above and add your comment.

For those wondering about cross-trims: The normal throttle trim lever now controls elevator trim, normal rudder lever controls aileron, etc. For those of us flying mode 2, this allows you to keep your hand on the most important stick, while using the other hand to adjust ele and ail trim without reaching across. Especially on first flights, makes it so much easier to dial in a model. The "bug" described above is only important if you also want your throttle trim (what was the normal ele trim lever) to only be effective at low idle. Which almost all fuel flyers do want.... Works fine in standard trim configuration, but not when you set up cross trims.

 

[Wayne]

Sorry, it is annoying for sure when something like this goes unfixed for more than a very short time. I'll see if I can get any traction for you, I try to stay out of the developers hair whenever possible, but sometimes a little nudge helps. Also, don't be shy about keeping your thread over there updated from time to time. Squeaky wheel gets the oil..

 

[davemcddd]

Wayne, we would all really appreciate it if you could spur some action on finally fixing this problem. It's been an open issue since November 29, 2013. (you read that right......for more than 4 years) I'm not sure why the OpenTx developers have been so dead set against fixing the trim idle only problem when crossed trims are used.

https://github.com/opentx/opentx/issues/170

For me this is the only true embarrassment about the lack of programming capabilities of the Taranis.

 

[Wayne]

Added a comment. Lets see if they say anything in that thread.

 

[davemcddd]

Thank you Wayne!

 

[RCdiy]

See pull request
https://github.com/opentx/opentx/pull/5664

 

[davemcddd]

Can you please explain the difference between a Pull Request and an Issue?

 

[RCdiy]

A pull request is a request to change code.
Some one changes code to address an issue. They then do a pull request. The other OpenTX developers look at the code and decide to accept or reject the changes.

A pull request address an issue. When a pull request is accepted the associated issue is closed presumably being satisfactorily solved.

 

[IRW2411]

This could be just a silly guess but I'm wondering if you have the radio set for mode 2 - from the description it sounds as though it could be mode 1 - Companion 'Radio Profiles' - Bottom of page 1 - Set Up -

 

[IRW2411]

Just checked the Taranis - Bottom menu page 1

 

[davemcddd]

Not a mode selection problem. The OpenTx developers acknowledge that the Trim Idle Only function does not work correctly if the trims are crossed in the software.

 

[IRW2411]

mmmm' interesting - I'm a mode 2 flier (about 4 years on Taranis and only recently Horus X12s) and have never experienced this difficulty

 

[davemcddd]

What version of OpenTx are you using?
Are you using crossed trims AND the Trim Idle Only function at the same time?

 

[IRW2411]

Dave - I'm not quite sure what you mean by Trim Idle Only - I use the conventional trim only (if there are 2 possibilities ). To shut down I use Special functions switch SF override set at -110. Once I'm happy with the idle speed I rarely touch the trim. Currently using 2.2.1 (which is giving me a couple of issues) Refer my post on model saving/selection.

Cheers

 

[davemcddd]

I'm still running 2.1, but 2.2 still has the problem.

Go to the MODEL SETUP screen (page 2). About half way down you will see the Trim Idle Only selection box. Checking it will activate the function.

Trim Idle Only is very useful for glow/gas engines since the throttle trim only affects the servo position at idle and has no affect on the full throttle servo position. So adjusting the throttle trim to get the engine to idle at the desired RPM won't cause the servo to over or under drive the carb at the full throttle position. Without the Trim Idle Only function activated changing the trim to get the desired idle RPMs will also shift the servo position at full throttle. This will either result in the carb not quite fully opening, or possibly stalling the throttle servo once the carb has reached the fully open position.

Setting up a throttle kill activated by a switch is something I also do, and it works perfectly. But the Trim Idle Only problem isn't related to setting up a throttle kill switch.

 

[Wayne]

Hmm, I'll ask a silly question now that you have explained that. Why not simply use normal trims, and set the output for the throttle channel to limit the MAX throttle position. This will not be changed regardless of trim value unless you have some MASSIVE trim value. If your max limit is something like 80%, then I doubt trim will ever come into play.

 

[davemcddd]

Limiting the MAX throttle position can prevent the throttle servo from over-traveling, but will not keep the throttle servo from under-traveling at the full throttle position if the throttle trim is lowered.

The Trim Idle Only function eliminates the need to fiddle with the radio travel adjustments or the carb linkage adjustments if the throttle trim ends up needing to be adjusted. It's been a standard feature on nearly every radio for at least the past 30 years, except for the lowest level entry radios.

 

[IRW2411]

OK now understand what you're talking about - ability to set max/minimum end points. Yes I do use them on my other radios and being 'old school' (>40 years) set up primarily mechanically and fine tune electronically.