Unexpected motor glitches (speed up) with Tri Hex and Octo APM 2 & APM 2.5 using 2.73

It seems since going to 2.7 and up to 2.73 I am having uncontrollable glitches with the motors. I think I have isolated everything, no bullet connectors, checked the amperage draw of the 880 motors to see if bearings could be the problem.
I have 2 units, TriHex & Octo with 1 inch carbon fiber tubing for the arms, exhibiting the same glitches, I don't know what's causing it. This morning I flew the TriHex for about 10 seconds and about 5 feet high and suddenly it rolled completely over upside down all within less than a second and broke 5 props, anybody else having this problem or a solution. I'm not flying anymore until I have a fix.....I see 2.74 is in the works but don't see anything that would fix this....Don

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My Futaba 12FGH has 12 channels, this is the way I have it setup:
Channels 1-4 standard
Channel 5 to 5 on APM (mode switch)
Channel 6 to camera roll pin 10 on APM 2
Channel 7 to camera pitch to pin 11 on APM 2
Channel 8 is not used
Thinking way back when I first started getting glitches was with 2.7 and have had them come and go ever since, sometimes pretty bad, sometimes none at all.
Also around the same time I started using 2.7 was about the time I also started
using channels 6 & 7 for camera stabilization, although not 100% sure on that.
It appears the glitches don't appear that much in calm air, I sometimes think they happen more with pitch and roll inputs.
Am also trying to get the voltage readout correct with the autto system, but that's for another time.
Jan, to try and help what would you suggest I try, thanks for your help....Don

Hi Jan,

After a few minutes of ground tests, my results seem to confirm your findings that the APM2-ch6 is involved in the ESC speed glitches. So I'm very glad that you shared this discovery with us.

  • There are glitches when APM2-ch6 is given a constant value of about 1922.
  • There are NO glitches when APM2-ch6 is given a constant value of about 1121.

Here's my set up, for the sake of completeness:

I use Spektrum DX7 transmitter with OrangeRx R910 receiver, with the first 4 channels connected to the APM2 in the usual way.

The RX's ch5 is connected to APM2's ch6. (I don't actually use this feature, but it is connected, this channel is controlled with the GEAR 2-pos switch of my DX7, according to the config page of APM Planner, it toggles between values 1922 and 1120 ms)

The RX's ch6 is connected to the APM2's ch5. (I use this for flightmodes, 6 flight modes following the instructions posted on these forums, using a 3-pos switch and a 2-pos switch.)

The RX's ch7 is not used.

TLOG & RLOG are attached. I use small cyclic-stick movements to induce the glitches. And I switch between APM2-CH6 high and low every 5~10 seconds or so, showing that the glitches occur only when APM2-CH6 is given a high signal.

Redpalm, Jan,
I think you have figured the glitches out. I just flew for a little over 10 minutes with my hex. Prior to the flight I looked at where my values were for channel 6 which is what I use for my camera tilt. As I said earlier I didn't think I had the glitches before using the camera tilt, although I started using 2.7 around that same time. On this last flight I know where 1922 is about on my tilt control knob. Anytime I am near that area, I get glitches, and it seems more pronounced with cyclic input, but not 100% sure about that. When I move the tilt near 1100, no glitches at all. So until someone figures the fix for this, I will just change my tilt settings.....I am 100% convinced that is the problem.......Don

For me, the random ESC blips (very brief duration pulses) clearly do stop occurring when I give CH6 a low value, and they are easily reproducible when I flip a 2-pos switch on my TX to give APM2-CH6 a high value.

However, I now have a new problem. It is a random, less frequent, more sustained uncommanded pitch/roll, which caused two crashes so far.

The very quick glitches that I previously had never caused me to crash because the quad always quickly returns to level. But the new misbehaviour is more dangerous. It is like a loss of control. I will need more tests to trace the cause... I can't be sure if the APM2 is to be blamed for this.


After getting similar symptoms when I replaced the APM2 with KK2 and also during a bench-test without any FC (just a 1-to-4 servo wiring), I am convinced that my problem isn't the APM2.
I suspect it is ESC/motor-overheating.
Bench-test also revealed resonance vibrations with my sloppily assembled US$40 quad frame from OMGFLY.

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