Admins, Thanks for the new area!! I'll be the first to add a new thread here. Let's talk about ArduPilot/Copter code snippits and parameters that may have changed during the 1.3.1 --> 1.5.2 evolution. Here are the commits that occurred between 1.3.1 and 1.5.2 where the commit message contains the word motor. I got this by using the following command. (there are lots of ways to get this, I made a new branch at remotes/origin/master but I didn't have too. ) git log SOLO1.3.1..1.5.2 --oneline |grep -i motor 696a95c AP_Motors: fix bug found during review e79654d AP_Motors: Allow adjustment of thrust priority parameters 3348d49 AP_Motors: Increase min esc pwm when thrust priority is set 2282a8b AP_Motors: Add support for two stage landing detection 7f97102 Revert "SITL: Apply thrust loss to all motors" 1f3d257 AP_Motors: publish the headroom scaler a77a5a2 SITL: Apply thrust loss to all motors 75d0202 AP_Motors: Add yaw headroom control to mixer That's not to say that these are the ONLY commits that may effect the ESC operation, but it is a good place to start. Since all non sitescan Solo's (well almost all) are flying with 1.3.1. As this is a fairly short list it should be easy to analyse each commit in the light of ESC/pwm/parameter changes. Once we are done with these we can move on to the others.