Takeoff Stability

Posted by Lee Stone on November 17, 2011 at 12:47pm

Hello,

I have finally completed my arducopter.  All the bits telemetry,sonar and motors seem to work ok, but the one thing I can't seem to do is takeoff.  The front of the arducopter (in x configuration) seems to rise up before the back.  I can compensate using the controller and managed to get it up to about head height but I'm sure something is wrong. I've tried:

1) Recalibrating the ESC's

2) Recalibrating the RC controller channels

3) Checked the centre of gravity

4) Disassembled the arducopter and checked all my wires on the power distribution board

5) Checked prop setup

The artificial horizon seems to respond correctly.  I am now stumped.   Can anyone suggest anything else I can try?

 

Thanks in advance,

 

Lee.

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Replies

  • Lee Stone November 19, 2011 at 1:41pm

    Thanks  for all your replies.  I've been working through your suggestions and it does turn out to be caused by a defective propeller in position #4 (in my X setup).  I replaced #2 and #4 with new propellers and it cured the tendency to want to flip backwards.  I still have some work to do as it does seem to veer a bit, but I have identified a motor shaft slipping in position #1 (grub screw loose) and also have lost an E clip at the bottom of the other (#3).

    Thanks,

    Lee.

  • Developer
    Jason Short November 17, 2011 at 3:47pm

    Did you balance your props? Are the filter pads on the APM IMU soldered? Did you run the level command to set the level of the copter? How much do you have to compensate? 20%, more?

    Jason

  • Björn Geir Leifsson November 17, 2011 at 3:21pm

    Also if not solved by the above advice, check that the props are properly fastened, even a very subtle "slip" on the axle will affect the power of that prop.

  • Moderator
    Michael Pursifull November 17, 2011 at 2:19pm

    The most common issue with getting of the ground the first time is some combination of:

    Thinking of the arms with different numbers. In +, #3 is the forearm, #4 is the rear, etc

    Swapped cables in the ESC to APM connections, often swapping #1 and #2

    Motors spinning in the "wrong" direction. #3 and #4 should be clockwise, #1,#2 should be CCW.

    Fixing the wrong prop for the motor direction. #3 and #4 (front and rear in a + config) should have the "R" label, and any labels should be facing up.

    Setting an X frame for + configuration or vice versa, or not having the APM mounted in the correct orientation for the intended frame flight configuration.

     

    Even detail oriented builders will often have one or more of the mistakes listed above, even when they think they have checked each one. Have a buddy go over it with you, like a checklist, or hold the frame in your hand and throttle it up, and "feel" how it responds as you rotate it. Either of these two approaches usually helps find the problem. 

     

     

  • steve November 17, 2011 at 2:15pm

    I spent hours one day thinking this was anything other than a prop issue because they visually looked ok but then I switched the side that was having trouble lifting with the opposite corner and the problem went with the prop. Changed the prop and all was ok again. Switch your props that way and see if things change.

  • Gareth Rens November 17, 2011 at 12:56pm

    Have you tried running the auto-trim calibration? Turn the copter on. Hold the throttle stick in the bottom right corner (like arming) for 20-30s. If you watch the three leds, they will blink in a pattern. Quickly fly the copter as steady as you can in one position for 45s. Do this a few times and see if it helps. Also, dont fly in the wind, it will work against the auto trim settings... Oh and fly it out of ground effect.

     

    Let us know what happens :)

     

    G

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