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 ?

Views: 8947


Reply to This

Replies to This Discussion

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.

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.


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...

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 ;-)


You don't need to fly to see the problem if there are glitches, it should exhibit without even arming.

So just use mission planner, open the configuration / radio channels view (green bargraphs) and check here if you can see channel glitches on ch3 from time to time when playing with TX channels sticks and switches.

I can't help more until a have such a radio in my hands, but we'll try to find a solution as fast as possible.

If you know some hardware guys at Futaba, you can eventualy ask them if they want to enter in touch with our dev team to speedup this problem resolution. But i feel that as soon as we'll have a radio to test with we'll find the reason.


As previoulsy posted from my test after upgrading the PPM, its looking better.  I will test again a little longer in a minute though to be sure.

I just wanted to take it for a flight tomorrow as its more obvious then when you hear it beep and twitch.

I had tried the bar graph route on the Mission Planner, but I think as the spikes are only very brief and no doubt only a ms or 2, I don't think the refresh rate on the bars is quick enough to catch them.

If you were close by I'd happily loan you my Tx / Rx to assist in your development :-)

I also have the same radio, which I had the same fault with exept it was with a Heli a couple of years ago and upgrading the TX firmware sorted it out (though I also had to rebuild the Heli as the glitches happened while trying to do a low "pyro flip") but apart from that is has been fine with the APM 1, 2 and 2.5 and various other Futaba RX's.

Good luck !

I have to also add that I am currently chasing this problem.

APM2.5 new running 2.8.1 FW
Futaba T9CHP with TM-8 FASST module
R6208SB Rx

Pronounced glitches in flight, especially with a fresh battery.
Reviewed the logs and the spikes appear on the -IN channels.
Have purchased a brand new Tx (the same model) and the same spikes happen.

Bugger, spoke to soon.  Having upgraded the PPM, went for a longer test "flight" on the bench.

Spikes still seen on IN channels as below.

The THROTTLE IN one seems particulalry bad as in numerous spikes in such a short time :-(

The motor trace is horrendous and possibly worse than prior to the PPM upgrade :-(


Reply to Discussion



Season Two of the Trust Time Trial (T3) Contest 
A list of all T3 contests is here. The current round, the Vertical Horizontal one, is here

© 2019   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service