I have dug further into learning the log graphing capabilities since a recent crash during auto mission that was discussed here: http://ardupilot.com/forum/viewtopic.php?f=80&t=13041. I now believe I had an IMU failure based on some other forum posts that describe a divergence between IMU and IMU2 values as a hardware failure, but would like confirmation from someone more experienced. The first two graphs show a divergence between IMU and IMU2 for the AccX and AccY values followed by a steady loss in altitude till it ended up in a tree. I only see a slight divergence in AccZ but it goes back immediately. The second graph is just a zoom-in at the end of the first graph.
I have ruled out a mechanical failure as all the escs/motors perform fine on the bench and desRoll/Roll and desPitch/Pitch track together fine (last image). Everything appears to checkout on the bench but I don’t want another failure in flight. I have attached the log and would be much appreciative to anyone who looks further at this for me. I am almost done with repairs but don’t want to put a failing Pixhawk FC back in the air.
After receiving no feedback here I decided to submit a support request to 3DR, particularly because I noticed people with reports of IMU failure on Pixhawk purchased between June 2014 and February 2015 appear to be receiving replacements. I purchased my board on September 22, 2014.
Support from 3DR was super quick and they confirmed that IMU1 had indeed failed. I have been asked to test the board again in an auto-mission flight but after a nearly $1k repair job I surely don’t trust this thing. I have an old quad I can put it on but I hate to risk a crash just for the sake of testing.
In my case the support staff have offered a 15% discount on a new pixhawk. I am tempted to just buy a new Pixhack to take advantage of some of the features in the system. But after not finding much evidence of usage for larger work copters with Pixhack I might just take them up on the discounted board. A little disappointed but you have to go into all this knowing they might fall out of the sky at any moment and it may not be your fault.
Just wanted to update that 3DR has agreed to replace the Pixhawk after all. Extremely happy with their level of service on this.