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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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,


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 :-(

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...

OK, flashed the PPM without issue :-)

I taken the Hex for a short simulated desk flight by arming the APM, moving the sticks subtly as if i was in flight and then disarming. During this process no motors or ESCs received power.

The initial logs look promising with no apparent spikes on the IN channels.  I was always seeing spikes on the PITCH IN channel and this is the latest trace after the PPM upgrade.

I did see a single spike on motors 3, 4, 5 and 6 though, but not sure if this is just coincidental.

Latest log has been uploaded here - http://www.networkedsolutions.co.uk/temp/2012-12-06%2017-36%2034.zip

Thank you for your assistance so far.


Steven, you can see the same twiching in my video of the release 2.8.0 at "1:07" (pump up the volume), two little twiching:


I remember that once these "twiching" I got shot the drone in the air during take-off, as you, saved because it is anchored on a network of protection.

Yep, you can hear them exactly the same as mine.

I am so glad I am not alone, this has been driving me mental !

I have the same issue and posted it in this Thread.

Futaba T8FG and 6208SSB Receiver. The Spikes are on 15% Throttle and 50% Throttel




Nice, always Futaba... well, now look to feedback from the "ArduPPM team", i think this thing will be resolved only by "debug/mod" them.
It could also be that the pwm encoder does not detect for some strange reason one of pwm input signal from the receiver and sends a signal to APM for "switch flight mode on 4" (failsafe), but that you would see in the log.
Uwe, in your log where is the issue? Do you remember the exact time?
Chat soon...

Hi Uwe,

Having looked at your logs (2012-10-23 17-32 1.log), although you seem to have an issue on your throttle in trace, the other PITCH IN, ROLL IN and YAW IN seem fine where as I'm seeing the spikes across all channels.

Its also good you have the same Tx / Rx combo as me.

I noticed in one of the other threads you changed your PPM firmware back to APM 2.x PPM Firmware v2.2.65, is that still the case ?

Many thanks,


Steven, we are discussing this in the dev team. Please could you try the same APM and frame with another radio brand, if possible, so that we can be sure that the problem does not come from the power supply or other occulte reason.

If it is confirmed, then we'll have to find a similar radio hardware and analyze what's going one at the signal level so that you can stop to become mad.

I suspect something uncommon in the Futaba PWM channels sequence, frame rate or timings that could produce momentary glitches in the ppm encoder.


Unfortunatly Olivier I don't think I will have access to another brand.  A friend of mine who flies model helicopters uses exactly the same Futaba T8FG as me.

Are you talking about the power supply on the APM or external.  Even when the APM was powered by USB on my desk I was still experiencing spikes.  I also run the APM from the main motor and ESC LiPo but then changed to a seperate uBec and LiPo as I thought that may have been causing the issue, of course it wasn't.

Having upgraded the PPM encoder, I will report back tomorrow if the problem is resolved or improved.

In the mean time you are welcome to have access to all my recent logs if that assists.

Alternatively, is there another level of debug / logging you could add to the ArduCopter code which could assist in isolating the issue.  I happy to run any beta firmware if it helps.

Thank you for your help and I'm now starting to regain my sanity ;-)


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