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JR 28X twin engines trim

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Old 12-09-2016, 07:46 AM
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jkjunior
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Default JR 28X twin engines trim

Hi everyone,

I have an A-10 jet and I would like to know how I can have two throttles trim, one to right engine and one to left engine

Thanks

Joćo Karmo
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Old 12-10-2016, 07:08 PM
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I cannot help you directly as I have no experience with that radio. However perhaps I can give you an idea of how to proceed since a friend and I just did this using a Futaba 18MZ radio.

Futaba calls what I'm referring to as "Conditions". I believe that JR has the same sort of thing, at least they did when I was using JR, but they call it a "Flight Mode". We setup the twin turbines on my Skymaster F-14 Tomcat with two conditions, one for each engine. They are selected by a three position switch. In one position the left engine responds to the tx like any single; throttle and trim so you can start it by itself, shut it down or adjust the throttle trim which I do not recommend on a Turbine, that's only for start and shut down. Then we created a second Condition for the other engine setting it up the same way and accessed by flipping the three position switch to the second engine. There are no throttle inputs directed toward the running engine while you start the second. Once it's running, you flip the three position switch to the third spot and that combines the two engine conditions. This allows both engines to respond to the throttle simultaneously and both will respond to retarding the trim to shut them down.

Now here is the tricky part and I cannot explain it very well as it's been too long and my friend figured it out. There has to be an offset mix added to the third switch position to get the engine response you want and I do not remember more than that. You can check the servo/channel operation in the monitor screen and work from there. Sorry I don't remember exactly what was done there, but my friend did it and just sent me the file.

Good luck, it's a bit of a challenge but not outside the capabilities of that radio.
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Old 12-10-2016, 11:57 PM
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AWorrest
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jkjunior should post his question on the JR 28x information thread in the RC Jets forum,
 
It would be very strange if it weren’t simple to do on the 28X as the setup for twin throttle trims is straight forward on lesser JR transmitters.
 
Allan
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Old 12-12-2016, 06:06 PM
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Originally Posted by AWorrest View Post
jkjunior should post his question on the JR 28x information thread in the RC Jets forum,
 
It would be very strange if it weren’t simple to do on the 28X as the setup for twin throttle trims is straight forward on lesser JR transmitters.
 
Allan

I can set it for twin engines but there are not a option to separate the trim. I posted it now at thd JR28X INFORMATION.

Thanks
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Old 12-12-2016, 09:39 PM
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I hope they have the answer for you. Ever since the XP9303/PCM9XII through the XG11, JR transmitters supported twin engines with the option of having separate trims. Surprisingly the XG14 doesn’t. I was able to program the XG14 for twin engines with separate trims by using two program mixes. I can’t say if this programming would work on the 28X as I don’t own one. The 28X manual is pretty but not very helpful.
 
Allan

Last edited by AWorrest; 12-12-2016 at 10:00 PM.
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Old 12-13-2016, 11:48 AM
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I don't think program mixes will get him what he wants. I don't know if you programmed your XG14 for twin turbines or IC engines, but the turbines have some different trim requirements having to do with startup and shut down with nothing in what you might call a "typical" trim usage.
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Old 12-13-2016, 04:37 PM
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I can set it for twin engines at the wing type menu but there are not a option to separate the trim. The radio sugest #1 and #14 channel for twin engines but does not offer different trim
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Old 12-13-2016, 06:03 PM
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Zeeb and I are having a good time finding solutions for a radio that neither of us own! The 28X does state that separate trims are available for multi engines. While JR manuals sometimes are wrong, to my chagrin, there are times that the manual is correct when I think it is wrong.
 
On the 12X any auxiliary channel can be used for the left motor channel but only two channels allow separate trim. I would suggest you try each channel, starting with GEAR, as the second motor channel and see if it allows a separate auxiliary trim. I don’t know what the 28X wing type menu looks like for selecting the second motor channel. The 28X manual doesn’t go into that depth.
 
On the JR 12X, there is a spot in the wing type menu where you can pick the channel for the left motor. Under that you activate the throttle trim for that channel. On the 12X, activating it will allow for a common throttle trim. But if you pick either FLAP or AUX3 as the left motor channel and while having the TRIM below it activated, you can drop down another line and activate AUX TRIM for the left motor. This gives a separate trim for the left motor.
 
Good luck,
Allan
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Old 12-13-2016, 06:46 PM
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I got success now. I had to disable the throttle trim at the trim system and create 2 new aux trim and attach to each engine
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Old 12-14-2016, 06:06 PM
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Originally Posted by jkjunior View Post
I got success now. I had to disable the throttle trim at the trim system and create 2 new aux trim and attach to each engine
While Allan and I have been trying to help, we've been a bit at odds about how to proceed. For Allen, considering the setup of my Skymaster TomCat, I'd NEVER have tried it with my 12X.... lol

In order to start a turbine, you have to be able to isolate both the trim and throttle functions from each engine as it requires several actions of the trim and throttle to initiate a start. While that's not a big deal when neither engine is running, starting the second one without isolating both the trims and the throttle from the running engine has to be done since part of the start process is to move the throttle to wide open with the trim fully up.

If the running engine responds to that full throttle up, it's going to create an issue.... lol

Besides that issue, after they are running, you need to combine them for throttle response.

So for the OP; why are you wanting separate trims and what type of thrust power source are you using?
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Old 12-14-2016, 07:42 PM
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Hi Zeeb,
I use 2 jet central cheetah 140 in my skymaster A-10. You have to separate trim to start on engine at a time and in case of some fire in flight you have to cut only one turbine to land
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Old 12-14-2016, 09:50 PM
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Originally Posted by jkjunior View Post
Hi Zeeb,
I use 2 jet central cheetah 140 in my skymaster A-10. You have to separate trim to start on engine at a time and in case of some fire in flight you have to cut only one turbine to land
Okay, PLEASE reconsider my posts about separating the engines in both throttle response AND tririm function. What you want to achieve cannot be done by just separating the trims.....
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Old 12-15-2016, 04:30 AM
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It works perfect now. I can start one engine at time and cut them separately. Sorry if i was expressing me wrong.
Thanks for your time and help!
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Old 12-15-2016, 07:16 PM
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Originally Posted by jkjunior View Post
It works perfect now. I can start one engine at time and cut them separately. Sorry if i was expressing me wrong.
Thanks for your time and help!

Glad you got it working. Sorry that neither Allan or I had the correct answer for you but as he said, neither of us have had or used this particular model JR radio.
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