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C8 HL agressive right bank on take off

Discussion in 'Cinestar 8' started by Scott Strimple, Sep 17, 2014.

  1. Scott Strimple

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    Cinestar 8 HL (Quadrocopter style)
    MK 2.5
    BL V3
    10amp 6s LiPo
    MX20 tx GR16 rx
    Movi M5 w/ Spektrum DX8 tx
    GH4 camera

    This aircraft had made 4 uneventful flights about 10 days prior to the events I'm describing. It had been stored in our shop. We transported it to the job site, set up, calibrated the compass, ran our pre-flight checks and proceeded to launch. During takeoff I noticed a very aggressive right bank tendency which required an inordinate amount of left aileron to counter this. I flew the C8 for about 4 minutes this way while we tried the different features to see if there was any effect. Alt hold, GPS pos hold both worked. Absent any GPS hold however the C8 wanted to bank right quite a lot. I landed, we decided to re calibrate the compass and try again. This time when I added power, I did so ever so slowly and we noticed the a/c listing to the right as power was increased. I countered with full left aileron trim and the C8 lifted off normal and appeared to fly normal ... albeit with full left aileron trim. When we landed, the motor shut off stick commands would not shut off the motors until I had reduced the amount of aileron trim to a point where the parameters were within limits for this command. We did not attempt any more flights.

    Once back in the shop I connected MK tools to review the settings... everything was as it should have been and as it has been for previous flights. I then mounted the C8 to my test stand and measured the prop rpm to confirm what we were seeing. The motors on booms 5-8 were in fact spinning at a much higher rpm than 1-4. Interestingly, even with the aileron trim set to full left ... at idle, booms 5-8 still spin higher. Once I start to add power however, the rpm on all motors seem to stabilize and the aircraft then would lift straight up as one would expect. Once the power is reduced to idle the rpm all reduce in unison and then a split second after that you hear and see the motors on boom 5-8 increase idle rpm again.

    Watch the video at the following link: password "uwp"



    Thanks for any help y'all can provide!
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Scott:

    The aileron trim will certain prevent a motor shut down command because the FC never "sees" the required stick positions.

    I cannot explain why things should have changed (did you do a firmware upgrade, by chance), but the flight characteristics you describe suggest that you need to re-calibrate the ACC on the FC board with the FC board absolutely level.

    That ACC calibration is done using the Tx sticks (left stick to top right hand corner and hold until it beeps), so it's *just* possible that you did an inadvertent ACC "recalibrate" with the FC not level.

    Andy
     
  3. Steve Maller

    Steve Maller UAV Grief Counselor

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    I echo Andy's comments. I found several months ago that I had fallen into a habit (unknowingly) of initializing my ACC instead of the gyros every time I flew (ahh, aging... :( ). While fine if the copter was level, if it wasn't, this could induce the kind of behavior you see. You also may want to swap out your FC board for another one and try that. These things can get fried, and a failing or failed gyro could do this.

    Good luck.
     
  4. Scott Strimple

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    Hmmmm... very interesting.. Now that you point this ACC recalibrate out, I do recall when calibrating the compass that I could not remember (checklist was in the car.. of course I was too smart to go get it... o_O) if the left stick was up left or up right .. so I probably did in fact do that. I'll recal the ACC and let you guys know if it fixes things. Thanks so much fellas!
     
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  5. Scott Strimple

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    Update! Andy and Steve.. you were (as I'm sure you knew) correct! A quick leveling of the C8 and movement of the left stick to the upper right corner has fixed the problem!

    Thanks again!
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Glad to hear it fixed things.
    Now you can ponder how I knew that the "inadvertent ACC re-cal" was a possibility..... :rolleyes:

    Andy
     
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  7. Adam Paugh

    Adam Paugh Distributor

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    Dang! Skookum support work, Steve and Andy!

    Greetings,
    Adam
     
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  8. Gary McCready

    Gary McCready Active Member

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    I've always thought that ACC calibration (and compass) should be a more complicated stick or switch movement, so you didn't do it accidentally. I used to do this very tedious Cinestar on a big box dance, with shims, to get things perfectly level, and do the ACC calibration. Now I have a small piece of plastic I put on top the FC screws, put a bulls eye level on it, done. With the DJI you have to move the ATTI/ GPS switch 5-6 times to get it to to into calibrate compass mode, very difficult to do accidentally.

    "I found several months ago that I had fallen into a habit (unknowingly) of initializing my ACC instead of the gyros every time I flew"
    Steve, I feel your pain. Went out yesterday to fly my CS and got "calibration error", and didn't have my level. Did a guess and go! No clue how I got "uncalibrated".
     
  9. Steve Maller

    Steve Maller UAV Grief Counselor

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    This forum should be officially subtitled "Ask Me How I Know". :rolleyes:
    So glad this all worked out.
     
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  10. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    As far as any alleged advice I might volunteer, I think the forum should be called: "Please do not ask me I how I know." :rolleyes:
    Not that I've ever accidentally recal'd the ACC, put a prop on upside down, put a clockwise prop on a motor that spins CCW, or anything like that, of course....

    Andy
     
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  11. Gary McCready

    Gary McCready Active Member

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    And just when, after 2 years, you think you have made every mistake possible....While plugged into the NC, the side of your USB card hits the top of your Power distribution board. Fried FC and NC!
     
  12. Steve Maller

    Steve Maller UAV Grief Counselor

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    Ugh.
     
  13. mathewfarrell

    mathewfarrell Member

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    As an interesting bit of kookery, I had these same symptoms when I first got my 2nd-hand CS8 rig.
    It turns out my problem was that the GPS switch also gave full right or full left aileron
     
  14. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Bonus points for recognizing the problem before it turned into small pieces of carbon fiber....

    Andy.
     
  15. mathewfarrell

    mathewfarrell Member

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    Uh, yeah. Right
     
  16. Derek Cooper

    Derek Cooper Active Member

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    With firmware 2.1, MK changed the ACC calibration - you have to hold the stick for 5 seconds. That should get around the problem of mistakenly calibrating ACC when you meant to spin up the gyros.

    And I can't stress enough how performing an in-flight ACC calibration improves flights. We reported our success with the process last week - post here:

    http://forum.freeflysystems.com/ind...ation-during-flight-tried-it.6471/#post-63972
     
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  17. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    That's absolutely correct Derek. Amongst other things calibrating the ACC tells the flight controller what is meant by "level" -- so it's pretty critical!

    Andy
     

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