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S900 doing "J Hook" while flying straight
1459 17 2015-4-17
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TravisSRT
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Hello, I have tried to find a thread about this and didn't see one.  I am in a bit of a panic as I need to get this sorted before a job tomorrow.  My S900 with A2, GH4 and Futaba 14SG is flying perfectly except for one thing.  After a few minutes of flight when i give her full forward or full reverse she will go straight and then rotate to the right causing her to stop dead in her tracks from spinning completely around.  This only seems to happen after flying for a few minutes and I calibrated compass immediately before flight.  Otherwise she flies great.  This happens in both GPS and ATTI mode.  I do not have manual enabled as I do not know how to fly in manual and can't afford to crash this aircraft.  Any help is greatly appreciated!  I am in Raleigh, NC USA if that helps.

I took an iPhone video of this and also had the GH4 running and will post both as soon as I can get them uploaded.
2015-4-17
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TravisSRT
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Here is video from the GH4 while it happens.  I am giving full forward stick and nothing else.  Left hand is completely off the RC.
2015-4-17
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smee56
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Sounds like a similar issue that the phantoms used to have. What happens if you fly backwards? same problem?
2015-4-18
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TravisSRT
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smee56@gmail.co Posted at 2015-4-18 21:12
Sounds like a similar issue that the phantoms used to have. What happens if you fly backwards? same  ...

Exactly,, same thing forward or reverse
2015-4-18
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smee56
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Sounds like your GPS Compass could be out of alignment. Rough landing, transport etc? Even a small turn can have a big effect on it.
have you gone through IMU calibration?



2015-4-18
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TravisSRT
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smee56@gmail.co Posted at 2015-4-18 23:23
Sounds like your GPS Compass could be out of alignment. Rough landing, transport etc? Even a small t ...

No hard landing.  I tried turning the puck 10 degrees left for declination but that didn't have any effect on this and actually made it fly off at an angle instead of straight.  I haven't done IMU yet, do you think that could be it?
2015-4-18
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TravisSRT
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Haven't calibrated IMU to see if it fixes but here is video of it doing it today...
2015-4-18
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smee56
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I would defiantly calibrate the IMU, that should hopefully fix any navigation errors. If turning the compass has not made any difference i would put it back to the correct position.
2015-4-18
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TravisSRT
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Ok, i'll try that today if the weather improves enough to fly and let you know.  Thank you for taking the time to reply
2015-4-19
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TravisSRT
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smee56@gmail.co Posted at 2015-4-18 23:23
Sounds like your GPS Compass could be out of alignment. Rough landing, transport etc? Even a small t ...

I did IMU, RC Stick, and Compass Calibration with no improvement.  Called DJI and they told me that since I was using a 3rd party RC (Futaba 14SG) that they couldn't help me.   I asked if DJI made a controller that would work and he said "no" but that he still couldn't help me.  Suggested I pull the A2 and send it in for evaluation 4-6 week expected turnaround..
2015-4-20
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smee56
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This has to be the best case of limited support ever. Hope that sending it back fixes it for you, it is strange. This is the first time i have heard of an A2 doing it
2015-4-20
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dennismurry08
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It looks like you have "Banking" enabled in the assistant. Have you tried it without the banking enabled? Just wondering...
2015-4-20
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TravisSRT
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I don't think I have banking enabled, i'll double check.  It's under IOC right?  Someone suggested that one motor might be cutting out/ or ESC overheating?  Does that seem logical to you?
2015-4-21
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joe
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How does it hover in GPS mode.  If it stays in place without any toilet bowl effect then your compass should be OK.
If it happens in ATT mode then that would also say it is not a compass issue.
Is there any Geofencing or flight limits set?  
As a sanity check look at your channel monitor in the Futaba,  Move your controls to the limit and make sure there is not unexpected action.
A accidental mix etc even between the  switch channels can cause some strange reactions.

The unusual thing is you seem to be saying this does not happen until you have been flying a few minutes.
One other possibility is voltage sag on hard forward acceleration.  Have you tired a vertical climb.  Maybe a RTH failsafe is being initiated.

Are there any LED status indication when the J turn happens?

If you hold the elevator stick forward does the craft continue to fly but in the opposite direction or just stop?

Motor ESC is a possibility but it doesn't seem to fit the effect you are describing.  Doing some low altitude tests where you can see and here the props might help you determine if a motor ESC is cutting out.  I would do some bench tests to test out any motor ESC issues.  Run a full output for a period of time similar to when you observe the issue.

Best of Luck
2015-4-22
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dylan
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I have an s1000 with A2 - but it kind of looks like it's changing modes mid-stream  - do you have any fence or limits set? IOC and POI mode are off?
2015-4-28
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TravisSRT
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So I finally got a chance to fly it and look at the flight logs on the IOSD and it appears that for some reason motors 4 and 6 are maxing out and that is the same time that the rotation is happening.  It only happens on full speed forward or reverse at high RPM.  It hovers fine and does this in GPS or ATTI modes.  
2015-4-28
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TravisSRT
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Any ideas what might cause this?  I'm using Pulse 16,000 MAH batteries.. Overloaded?
2015-4-29
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TravisSRT
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Sending to DJI for inspection/repair under warranty... Will post updates when I hear from them or get her back.
2015-5-10
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