APM copter flipped on takeoff, after many successful flights.

When trying to takeoff in Alt-Hold, sometimes my motors surge, and the heli jumps about a foot in the air very fast. This has not been a problem, as I usually just handle it by continuing to gain altitude and the heli settles out and flies normal. I'm guessing this has to do with some kind of pressure change in the atmosphere before takeoff? 

Well This time, my heli just flipped over on takeoff. There was really nothing I could do, and no time to react. I've had many flights with this heli flying fine... and I replaced propellers and the heli flew fine after. So it was not a propeller or motor mistake. I'm stumped as to why this happened...

I've also had this same thing happen on a little quad I have APM copter on. One time during takeoff, it just flipped right away. This happens after many successful flights, and the quad flew fine after the incident with no changes to configuration.

Can anyone tell my why this happens? Why does sometimes APM copter just decide to flip on takeoff?

I've attached the data-flash log for review. Any help with this issue would be greatly appreciated.

Thanks,

Nick

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I suggest you start by connecting to Mission Planner, click on the terminal button, connect to your copter. Then run tests => motors. Check that all the motors are working, all spinning the correct direction and pay special attention to what motor starts first. Check your frame type. I have a X frame and I accidentally started the wizard and backed out immediately. It changed my frame type from "X" to "+" and I cart wheeled on take-off

To me it seems like you maybe rotated tha pixhawk or swapped motors ?  It seems to try to fly normally, but the output only inreases the error.

Thanks for your time to look at my log.

I know how it seems like that, this crash was really weird. I did not change ANYTHING! And it flew completely fine after changing only 2 damaged propellers. It had literally 20+ flawless flights and then this happened.

My props are bolt-on and did not come loose. 

Motor configuratuon was un-changed

Pixhawk was not moved

I know it seems like simple user-error, but I did everything exactly the same that I can think of like I always do. I'm pretty experienced at building quad's and hex's and I know how to set up and test for proper motor direction. I did not change my frame shape or any settings in mission planner. ALL I did was replace 2 damaged propellers and it flies fine after this. It also flew fine with no changes just the day before this flight.

This same exact thing also happened on a quad I have, after many successful flights, one day it just flipped on takeoff. Change propellers and it works fine now and has had many more successful flights.

It seems very rare.. maybe some kind of mechanical error like one motor spools up slower then the rest, idk. Still hoping I can get some help to pinpoint this issue.

Thanks,

Nick

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