After a week spent working on my Arducopter 2, I have still failed to get it airborne and I've broken two props already. In the interests of other people avoiding the misery I've had to go through, I'll post my lessons/experience here in a summarised form. The brevity of what I've written doesn't reflect the amount of effort put in, or combinations of solutions attempted. I'll conclude with that I think the problem is and I invite suggestions from more experienced users.
My first mistake was to not check that the GPS cable was plugged into the correct port. I believe my AC was shipped with it plugged into the incorrect port, and this prevented it from arming. I spent a long time trying to get the motors to arm, setting up again & again, trying different TX/RX combinations and even switching between two APM1.4s that I have. Eventually I pulled out the GPS and got it to arm, and that prompted Chris to suggest that I may have it plugged into the wrong port. Given that the ports on the IMU and the APM board are identical, some sort of warning about this in the 'Troubleshooting' page may be helpful.
However my problems were not over. I then could not get the AC off the ground - it flipped first time out and broke a prop. I went through the appropriate troubleshooting menu for flipping and wobbling and got no further.I decided to change radios from DX7 to DX8, because the latter has a throttle curve and permits very slow throttle advance - allowing one to catch a flip before it goes over and analyze it. I couldn't get an AR7000 or AR8000 to send signal to the APM, eventually an OrangeRX 9 channel worked. I did some slow 'flips' and noticed that it was pitch instability - in both directions, implying that the stabilizing compensation was reinforcing rather than offsetting a change. Roll and yaw stability seemed to be working.
I ran the latest firmware, reset everything and saw that various sensor feedbacks in the APM Planner were now garbage (fluctuating all over the place). I switched IMUs again, set everything up again, and my second IMU showed stable feedback although the compass on this one seems to be broken. Nevertheless, encouraged by the stable gyro feedback I decided to try to fly again. I set up and slowly raised the throttle, but although I tried to catch it, this also ended in a flip and another broken propeller.
This is about as much as I can stand at the moment. Given that there are two different issues on two different IMU boards & that I have ruled out all other options, I have to assume that they are both faulty. My question then is - has anyone else been sent out-of-box faulty goods by uDrones? Is quality control an issue? I don't know if sending the boards back to them will help, but maybe someone else has done this and had success?
I also fly a GAUI 330x with a HoverFly Pro board, and I also fly two MK hexas, so I'm not a total newbie when it comes to quads. I've just never had this many problems on any one project.