Quad Fell from the sky

Well I just got my new APM 2.5 and set up my new camera Quad. On the first real flight with the system at the RC field to start the tuning process the motors just stopped and down she came from ~10 ft in the air.

Here is what I have:

HK.com X-550 frame

HK.com X-550 Camera gimbal

4 = 30amp Tunigy Plush ESC

4 = 28-36 1100kv motors

11x4.7 props

3600mah 11.1v turnigy nano tech

Canon Digital Elf 10mp

My thoughts is that the ESC that is powering the avionics overheated and shut the throttle off. now my question is:

If 1 ESC overheated will it shut off power to all the motors or will it only kill the one ESC that is overheated?

here is the video of from the quad during the crash..

It suffered minor damage and if fully functional again. The landing gear/gimbal took the brunt of the damage and a little CA and Carbon fiber reinforcement and good as new. 

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  • Hi Joseph,

    I figured out EXACTLY what happened.  You can see it clearly using your log file 2012-07-15 22-03 2.log and APMLogVisualizer version 1.34.

    Don't feel bad, I made a similar mistake and crashed my copter, but it was almost for sure, "operator" error, like my crash.  The copter simply did what you told it to.  However, there is an extremely small possibility it was a radio transmitter/receiver problem.

    Ok, here goes.  First, when your GPS clock reads 15:45:11.248, you started increasing the throttle, while in the Altitude_Hold mode.

    On my computer time zone it reads 15:45, you're in New Mexico, so yours would be 16:45 or 17:45, not sure which.  I'll just say what mine says....

    So, at 15:45:11.248, you're in Alt_Hold mode, and all is well.  You start increasing your throttle at this time.  The way Alt_Hold works, is it maintains the same altitude until you increase the throttle a certain point, then it increases the altitude SETPOINT, so the copter starts rising.  You may have hit the throttle by mistake, at any rate, something made the throttle go up.

    At time 15:45:15.504, the Nav throttle (and RC3ServoOut) starts going up, to go to the new altitude.

    At time 15:45:16.752, the copter starts to rise, and the Nav Throttle and RC3ServoOut start to drop.

    Everything is still going fine, the copter is level....

    Here's the problem.

    At 15:45:18.0, the throttle stick on the transmitter goes to zero (must have been the operator :-) ).  This is what made the copter crash a bit later.

    At the same time, RC3ServoOut goes down again, and it's simply going to drop down to a lower altitude setpoint because that's how alt_hold works.

    At 15:45:18.496, you switch from the alt_hold mode to the Loiter mode.

    The RC3ServoOut is still too low for the copter to keep rising, which it still is rising, however, at

    at 15:45:18.752, the copter starts falling in altitude, as it should, since the throttle is zero. 

    at 15:45:19.248, you raise the throttle, but at 15:45:19.504, the throttle is already back to zero, so you went Up and Down on the throttle real fast.

    Keep in mind, at this point, the copter is still fairly level, but it is dropping, but you're not totally in trouble yet.

    Here's the trouble.  At 15:45:19.752, you switch from Loiter mode to Stabilize mode. 

    Keep in mind that the throttle is zero. 

    This is when the motors stopped, and the copter fell.

    I've attached two screen shots of the APMLogVisualizer graph.  The first one is zoomed in on the crash.

    The second one has a bit more of the previous, so you can see the throttle rising.

    Keep in mind that the barometric altitude goes up at the very end, while crashing.  This is because it's flipped and the barometer is being fed straight on air, so it's no doubt a false reading.  Your sonar is not working either when the copter is flipped.

    So, the problem is most likely operator error, but also could be radio problems.

    Glad it didn't hurt the copter, and now you can begin to look at the "operator" or the radio transmitter/receiver.

    Dan Gray



  • Check your power distribution.  Not all ESCs are going to fail at the same time.  I believe I have the same motors as you, the only difference is I have the Blueseries 40a ESCs.  These ESCs are overkill for the motors.  My ESCs never overheat. I thnk you are cutting it too close with 30A, last time I tested the motors drew 22amps at full throttle. I tested with a 10.45" prop and the motor squeezed into my vice.   Add the fact that the Chinese made the ESC (mine too) and 22amps makes a 30amp ESC heat up.  That's why I went with the 40amp ESC.  Also the NTM motors don't have the best bearings in the world.  You may want to see if the motors are getting tight or if a ball bearing is failing.  The added friction would cause you to draw more power from the ESC.  There's posts on the net on how to replace motor bearings, once the bearings are replaced with American Ball Bearings or similar the motors are very good.   A tell tale sign that it's the bearings is if the motor is hard to turn, or if it's easy to turn and when the motor is running it sounds like a intermittent "pop corn" sound.


  • If power is lost to the main computer, then signals stop to the esc's, and being safety conscious, they stop, and the craft falls. Use a good switching supply and put a big cap on the +/- leads.

    I doubt it's software related, because if the program locked, the PWM hardware registers would have stayed as would the ppm and the motors would have just froze at the power they were at.

  • It happened again.

    Here is the latest log. First flight was good. no issues. Second flight it flew for a bit then boom motors stopped and down it came. 

    2012-08-21 16-42-16.rlog

  • Can you download and post the log file from the flash rom?  Were you using Telemetry? If so, the TLog files would be helpful.

    Dan Gray

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