Can't get off the ground.

I just built a 3DR Hex Frame using an APM 2.5 with the uBlox GPS.  I'm using 40A ESC's and 880 Kv motors.  I have a Walkera Devo 7 transmitter, so I added a Walkera 7 channel receiver.  I also added the 3DR 915 Mhz telemetry option. Everything seems to work as it should.  The only problem is that it doesn't fly.  It just flips over on its back when the throttle is increased.

I've read just about all there is to read in the wiki.  I'm using the latest Mission Planner. (As of Feb 09/13).  I've loaded the APM with the latest Hex firmware and it currently has all the default parameters.  

I've gone through the ESC calibration process. (All the motors seem to work properly).  I've calibrated the receiver output. (As per the WiKi, the transmitter is set to Airplane mode and not Helicopter mode). I've done the level calibration (placing the frame on its side, front, back etc).  The APM is mounted on soft foam.

I checked the rotation using the 'motors' command.  The motors are all turning in the right directions.  I installed my 10X4.5 props using the 1045-R props on the CW motors and the 1045 props on the CCW motors.   All the props blow down when activated.  

I'm an experienced quad flyer. But, my maiden flight wasn't successful. After connecting the battery, I waited until I had a good 10 satellite GPS fix.  I put it in Stabilize mode, then ran up the throttle very slowly expecting to see the Hex lift off the ground into a wobbly hover.  Instead it revved up and abruptly flipped over on its back.

It was just below freezing outside, (-3C or 26F) so went through through the ESC calibration procedure again in the colder temps.  I also checked the receiver calibration and the level calibration.  Another flight test yielded the same results, but this time with a broken prop.

What is consistent  is the way it flips over.  Despite a light throttle input, it seems to  rev up faster that it should.  The response doesn't seem  linear.  It then flips backwards and to the right. This happened both times I tried to fly it.  So it appears that the front left motors are putting out more power than the rest.

I made a youTube video of the maiden flight and captured the errant behavior.  (It's 18 seconds long).  The front of the Hex is pointing away from the camera.  After arming it, I blipped the motors to make sure it was armed.  Then, as I slowly increased the throttle, the thing just jumped over on its back:  https://www.youtube.com/watch?v=g7b6FgANr0g

I've gone over everything again and again.  I spent last evening going over the Wiki and can't seem to find anything wrong.  Any ideas of what I need to tweak to keep this from happening ???

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Replies

  • Have you double and triple checked that you have the wiring correct on the PDB, the 6 wire multi cable is connected the APM the correct way round and not reversed, that is S1 on the PDB is connected to output pin1 on the APM etc and that the esc three pin signal cable for motor 1 is connected to the three pin header at S1 on the PDB.

    worth checking.

  • I have had similar occurrences where I had forgotten to set the frame orientation.

    The default is x but I have mine setup as +

    Have you checked the orientation?

  • Admin

    @Jim,

    I have a friend who had the same problem. It turned out that his APM2.5 was oriented 180 degrees out of alignment with the multicopter frame. Have you verified that the APM2.5 is mounted with the correct orientation in relation to the frame?

    Just a thougth.

    Regards,

    TCIII

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