I have started this dedicated thread at the suggestion of another contributor.

This issue has was raised on the main 'Arducopter 2.8 / 2.8.1 released' thread and can be viewed here.


I'm still puzzled by this twitching, however look at the latest log from today and in a little more detail I can see a very small change in the THR IN trace which appears to be directly connected at the time all the motors twitch (see below).

Is the THR IN trace taken straight from the Rx ?

Not only have I done the things as detailed in the main thread, but I have also:

Grounded the aircraft (in case of interference)
Repositioned Rx to top stack
Reprogrammed all ESC

I have attached the latest log.

Would dropping the ESC Update Speed in MP from 490 - 400hz help ?

Any suggestions would be appriciated, in the mean time i am trying to get hold of a duplicate Rx.  Any chance it could be the APM ?

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You do not set any "framerate".

In the LNK-Frequency menu you choose FASST betweeen MLT/MLT2/7ch.

It is also noted on the main-screen under the timer ST2 where you read MLT/MLT2 or 7ch.

MLT2 I think is for the R6014FS/HS and the MLT is for your R6208SB.

However when I had that twitching on my R6014HS there was no difference changing betweeen MLT/MLT2.

You either has yours on MLT or MLT2 as 7ch is for 617 or fewer channels. 7ch will not bind to your receiver.

Hope you sort it out, but I would have tested/borrowed another brand. At the moment It is so cold outside in Norway so unfortunately I can not go outside and test my T8FG/R6008HS combo or retest my R6014HS to see if the twitching still persist.

While I had the Futaba gear on my ArduCopter I also tested if the receiver was set in High-Speed mode, but it was not... but you might check yours... I think think Normal-Speed is a good choice when connecting to the APM.

Best Regards,


Thank you for the reply Arild, its appriciated.

I had visited that as a possibility and can confirm I have the radio set to MLT mode, although have also tried MLT2 with no success.

Can you confirm you have experienced the same issues with this radio combo ?

Today I visited the UK service centre for Futaba and met up with 2 very helpful people.  I had to rule out it was not the Tx.  One of the engineers came with me to the field and we first tested my Tx and the twitches were of course present.  Then having copied over all the settings to their new and test Tx, same problem was experienced.

To recap, so far I have swapped out and tested the following.

  • APM 2.5 (with a brand new one)
  • Transmitter
  • Receiver (same make, slightly different model)
  • Different way of powering APM with its own LiPo and uBec.

I have tried so many things with no luck as described previously.

The Futaba T8FG is certainly not a cheap Tx / Rx combo, so I'd like to think that it can't be incompatible with the APM, whilst bearing in mind I have no doubt others use this radio with their APMs.

I have uploaded the latest log here and again you can see the spikes in THROTTLE IN, ROLL IN, particulalry PITCH IN and YAW IN.


I can't see it being a motor or ESC as these spikes are still present, even when conducting a simulated flight on the desk with the motors and ESCs not powered !

I am desperate to resolve this issue, any suggestions ?

I'd appriciate anyone making comment who use the Futaba T8FG with APM 2.5 and if you have had issues.

All the best,


Hi again,

I am sorry I have no logs, but so I wish I had.....

It is to cold for me to go outside right now, but I just had to try a small lift inside...

The quad I had problems with is the old APM1.4 1280 chip, so no logs on that one. So I put my Futaba R6014HS in my JDrones-Hexa running APM 1.4 2580 chip.

I did a lots of testing while activating the "Tuning" option in the maps on the flight page in mission-planner.

No spikes showed up, so I got a little braver and cleaned the living room for a little hoover test.

It lifted nice, but less than 15 seconds into the flight I got a really scary twitch and I had to put it down. Fortunately no harm done to either floor or hexa :-)

I am so sorry I did not read more about logging the rc_in channels before the tests and have this twitch in a log to show you.... but for my self I do not need any log to see that it was what happened before I switched to FrSky system... good thing is that I have the CC Bec Pro delivering good power to the APM so I did not got any brownouts inside.

Some days ago I had a very nice flight with the Hexa outside in my garden. My "FrSky" radio is also the T8FG which the FASST-tx-module is removed and replaced with a FrSky DIY Telemetry module and an FrSky D8RII telemetry receiver. (The previous owner got his antenna in a propeller and he bought another T8FG. I bought both using the malfunction one as a learning radio for my son - but after some time I converted to FrSky because the repaircost from Futaba was to high)

I wish I could test more outside to help you now, but I have to wait for warmer weather :(

If the weather warms up a bit in the near future, I will activate rc_in in the logs, and do a test with the R6014HS and R6008HS receivers.

Just to clear up a little thing: both my TX'es I use for my APM is the Futaba T8FG. One stock with FASST, and one as said switched the radiomodule for FrSky.

Best Regards,


Thanks again for your efforts Arild, its appriciated.

I have sent a message to Marco Robustini to see if there could be a developer input or some other level of debug which will help get to the bottom of this issue.

As i said previously, the T8FG is a good Tx / Rx and used widely, so i can't believe it hasn't been seen before.

I'm hoping it could be a timing issue that could be resolved in software or similar.

Having invested a lot of money into the Tx / Rx, I can't now bin that and try something else unfortunately.

I will keep this thread updated to how I get on. I'm just so desperate now to resolve it having spent the past 3 months trying to get to the bottom of the issue.

I have a new set of skids and gimbal sitting here which is waiting to go on, but i can't put it on until this fault is resolved.

Thanks again,


Hi Steven, I'd like to see a video (recorder from the ground without wind) with the problems you mention, only to assess the level of these twitching in flight, thanks!

Steven, i see one of your videos, this one:


Do you mean the "twitching" at: "0:42 <-> 0:44", "0:14<->1:22""??? :-)
Welcome to the "twitching club" (LOL, damn)!
I have already reported to the dev list this kind of problem from months, still unresolved because the logs do not see anything abnormal, but it does to me.

Marco :-(

We could have an encoding problem with this Futaba setup. It's hard to diagnose without a radio system at hand, watching for signals on a scope to understand why we would have a problem encoding it.

I have no Futaba here to check, but i'm sending a link of this thread to another developper working on the ArduPPM side who could perhaps have that to test.

In the mean time, you could update your PPM encoder to version 2.3.10 and see if the problem has gone.

A couple performance enhancements in this version could solve your problem.


And instructions here :


In the meantime you could try as well to connect only 4 channels. It could solve the problem.


Hi Marco,

Thank you for the reply.

Its difficult for me to pick a day without wind, thats the beauty of the great british weather.

However on these videos the wind was very light despite the wind noise you can hear being picked up on the microphone.

This is from ground view - http://youtu.be/q_ECxFx8hsY

From on board - http://youtu.be/JE_-3gtYzH0 and  http://youtu.be/Hvs6Udx_bT0

The second onboard video you can see large spike upon take off which created for an interesting lift.

The log for that second flight is uploaded here - http://www.networkedsolutions.co.uk/temp/2012-12-05%2020-09%2030.zip

Many thanks Marco,


Hi Olivier, i've the latest ArduPPM and i don't remember this twiching during my latest tests, but i'm not sure.
This kind of problem has also been reported in the dev list months a go by me.

Yes you are correct Marco and the large one on throttle up prior to take off.

If there is anything I can do my end to assist in the solving of this problem I'd be happy to.

Is there an explanation to why the "spikes" can be seen on the IN channels in the logs.  Are the signals logged prior to or after the PPM encoding ?

All the best,


Yes, is just a guess but for me Oliver is right, is "guilty" of ArduPPM, the PWM signal that comes out of our Futaba anything like it.
I use Futaba T12FG (you can see my tx in a lot of my videos) with Orange FASST compatible rx.

I tried both "PWM" in "Fast PWM", same problems (some receiver has the ability to set these modes, the Futaba HS do, same as Orange FASST).
I use same rx with Mikrokopter and DJI and i've no twitching... :P
Obviously the logs are collected after decoding pwm.
If you can (I have already) update ArduPPM on your APM and let us know if it still does.

Stay tuned...

Thank you Olivier.  I presume the procedure is the same for APM 2.5 ?

Is there a way to determine what version of the PPM encoder I am currently using prior to reflashing (just for documenting sake).

I'm trusting you on this one and hoping I don't brick my APM ;-)

Kind regards.


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