quick analysis related first accident

It was hard to say for me at beginning what have happened during this test. Lucky me drone didn't crash too much. The only one destroyed part is propeller of 4th motor. But hope can yes it for next initial testing because only small part is chipped.

What did happen then:

After take off drone somersaulted and hit ground in 4th engine direction. What can be a root cause of that:

1. Unbalanced frame
2. Problems with any motor ( probably 4th one)
3. fixed ESC problem ( as you remember at beginning i cut wires too much and maybe soldering was not so good

4. badly created connections
4. Naza configuration issues,

I did one another test later to double check and observe what will happen. Results are there: second take off test. You can see there same issue it look like 4th engine not work correctly.

I quickly dropped first items from causes list. Unbalanced frame - no, frame is balanced , I do not have any additional elements attached to frame, is should works.

Than I did start to thinking about ESC. That was something that scared me , if there is something wrong with ESC need to disassembly drone and did solder ESC once again and maybe go to any service point to fix it.

When I was watching on ESC and connections I found that something wrong was with 3 wires that connect motors with ESC. They were crossed. I did run engines again and did watch with directions propellers are turning: CW or CCW. It was turning in wrong direction. I did fix it and then propeller started to rotate in right direction. You can check it on my previous videos how that was connected before. 

Yes, with previous configuration 4th properer was rotating in wrong direction and this was issue why drone has failed down.