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Jan 05, 2020, 04:47 PM
Registered User
Thread OP
Help!

Extremely Erratic Behavior first time flying with new transmitter


I just purchased a Spektrum DX8G2 and binded it to my Carbon Cub S+, which I originally purchased as the RTF version with its own controller. I've flown it dozens of times fine with the DXe that came with it.

After getting it all set up and functioning perfectly on the ground, I took it out to fly for the first time.

About 10 seconds after takeoff, I started experiencing severe random movements from all of the control surfaces and the throttle. It would still accept my inputs from the controller, but I had to basically fight it down and lightly crash it into the ground to be able to land. No damage, thankfully.

I would like to get to the bottom of why this happened because the plane is unflyable until it's fixed. There are a few variables to consider:

New Transmitter.

I downloaded the setup from Spektrum's website for the Carbon Cub S+, and the only changes that I made were to add the optional flaps, which I did according to the instructions. Plugged the recommended servo into Aux2, channel assigned to Aux2, set to Switch D on the transmitter. You can't use the normal flaps system for a few reasons having to do with the GPS channel, but I won't get into that here.

I also created a mix for Aux2 to elevator to account for pitch change when the flaps are deployed.

Suspicions

This is my first computer transmitter, so perhaps I have done something in the wrong order. What's the correct way to select a model in the DX8 and then connect before a flight? I do it in this order:

1: Power on the transmitter and select the Carbon Cub S+, if applicable
2: Plug the battery into the aircraft
3: Push the bind button twice on my DX8, after which the plane begins to search for the GPS signal (not sure why I need to do it twice, but that's what it makes me do).

Thanks so much for your help. To reiterate, the plane behaves completely normally on the ground, even when I pick it up and jostle it around. Leads me to believe that it may have something to do with altitude or distance.

This kind of sucks because I can't really test it without taking it out and attempting to fly it, which at this point is unsafe and runs the risk of destroying my model.
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Jan 05, 2020, 07:44 PM
Perpetual Noob
BoxCar31's Avatar
Once the aircraft is bound it should stay paired with your DX8. I would go through the transmitter's menu and check the settings from the manual against what is actually stored in the plane's setup. The other thing I would do is be certain you have updated the software in the trannie. If you haven't, it is possible the Cub is using some functions that had programming errors and that is part of the problem.

The other thing is, of course, any changes you did between the two transmitters such as dual rate and expo differences.
Jan 05, 2020, 08:46 PM
Registered User
Thread OP
Quote:
Originally Posted by BoxCar31
Once the aircraft is bound it should stay paired with your DX8. I would go through the transmitter's menu and check the settings from the manual against what is actually stored in the plane's setup. The other thing I would do is be certain you have updated the software in the trannie. If you haven't, it is possible the Cub is using some functions that had programming errors and that is part of the problem.

The other thing is, of course, any changes you did between the two transmitters such as dual rate and expo differences.
Hey, thanks so much for your reply.

I may have figured this out. The AUX1 channel on my transmitter was reversed. AUX1 is the return to home function, which is assigned to the I button with 100% and -100% values, depending on whether it's pressed or not. So my transmitter was constantly telling the plane RETURN TO HOME RETURN TO HOME RETURN TO HOME and it was fighting with me for control. Usually, my control inputs would cancel the return to home, but because of how it was set up, the command was being issued over and over and over again.

As it happens, return to home is disabled below 30 or 50 feet or something like that, so that explains why I was able to take off and ascend a little bit before it started acting out.

I'll have to wait until next weekend to test it, but it seems promising.
Jan 12, 2020, 10:08 PM
Maggie is in charge
ncsky's Avatar
I had this same experience today trying to help a new flyer with this plane. It worked with the rtf transmitter that comes with it, but when we bound it to my DX9 and flew it same bad results you experienced.

Please let me know if the reversed aux I fixes the issue for you. O just checked my radio and AUX I is reversed. I used the Spektrum setup file.
Jan 12, 2020, 10:21 PM
Registered User
Thread OP
Quote:
Originally Posted by ncsky
I had this same experience today trying to help a new flyer with this plane. It worked with the rtf transmitter that comes with it, but when we bound it to my DX9 and flew it same bad results you experienced.

Please let me know if the reversed aux I fixes the issue for you. O just checked my radio and AUX I is reversed. I used the Spektrum setup file.
Hey there. Yep, I tested it and AUX1 reversal was the issue. It flew flawlessly after I un-reversed the channel. It says in the manual "Make sure AUX1 isn't reversed," so I'm surprised that the Spektrum setup file still has this problem if it's a known issue. Especially to protect against people like me who assume that there are no issues in the Spektrum-provided setup and I don't need to check things like that.

You'll know if it's fixed for sure without needing to take off by seeing if the home location is automatically set after the plane acquires GPS, indicated by a wag of the ailerons and rudder (automatically set = bad). With AUX1 reversed, the transmitter will send the "set home location" to the plane without you pushing the I button. But if everything is set up correctly, you'll need to hold the I button (or whatever you have hooked up to AUX1) to set the home location.
Jan 13, 2020, 11:34 AM
Registered User
12dylan34
I think what you have discovered is that the sophisticated electronic control system of the RTF Carbon Cub S+ is not as easy to understand as just flying plane.
Nice to get it sorted though.
Treat it as all part of the learning experience
Jan 13, 2020, 06:20 PM
Maggie is in charge
ncsky's Avatar
Quote:
Originally Posted by 12dylan34
Hey there. Yep, I tested it and AUX1 reversal was the issue. It flew flawlessly after I un-reversed the channel. It says in the manual "Make sure AUX1 isn't reversed," so I'm surprised that the Spektrum setup file still has this problem if it's a known issue. Especially to protect against people like me who assume that there are no issues in the Spektrum-provided setup and I don't need to check things like that.

You'll know if it's fixed for sure without needing to take off by seeing if the home location is automatically set after the plane acquires GPS, indicated by a wag of the ailerons and rudder (automatically set = bad). With AUX1 reversed, the transmitter will send the "set home location" to the plane without you pushing the I button. But if everything is set up correctly, you'll need to hold the I button (or whatever you have hooked up to AUX1) to set the home location.
Thank you for getting this solved. I called Horizon to see if they had any ideas and if there was a problem with the setup file. They responded "no". Glad you figured it out. Moving forward I will not use the setup files anymore.
Jan 13, 2020, 06:40 PM
Maggie is in charge
ncsky's Avatar
Quote:
Originally Posted by 12dylan34
Hey there. Yep, I tested it and AUX1 reversal was the issue. It flew flawlessly after I un-reversed the channel. It says in the manual "Make sure AUX1 isn't reversed," so I'm surprised that the Spektrum setup file still has this problem if it's a known issue. Especially to protect against people like me who assume that there are no issues in the Spektrum-provided setup and I don't need to check things like that.

You'll know if it's fixed for sure without needing to take off by seeing if the home location is automatically set after the plane acquires GPS, indicated by a wag of the ailerons and rudder (automatically set = bad). With AUX1 reversed, the transmitter will send the "set home location" to the plane without you pushing the I button. But if everything is set up correctly, you'll need to hold the I button (or whatever you have hooked up to AUX1) to set the home location.
Thank you for getting this solved. I called Horizon to see if they had any ideas and if there was a problem with the setup file. They responded "no". Glad you figured it out. Moving forward I will not use the setup files anymore.


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