I finished building my hexacopter and on my test flight it wouldn’t take off. It was right at the cusp of flight, but wouldn’t get completely off the ground. I’ve searched around the web and everyone mentions checking THR_MAX parameter in MP. So, I’ve checked there and no THR_MAX parameter is listed in any of the sections.
Here’s a screenshot of the full parameter tree drilled down into the THR section and you can see there is no THR_MAX setting.
Since I’m still fairly new and this is my first DIY, I assume I did something wrong in the setup to cause this setting to be missing, but I used the wizard with Hexacopter in X configuration and did all the calibrations (minus the ESC calibration because I’m using DJI ESC/motors). Is the setting possibly missing because I didn’t do the ESC calibration, or is it something else I messed up/overlooked?
Since posting this, I did figure out that my DJI ESC bullets needed to have two bullets switched (documentation says if the motor doesn’t spin in the right direction, flip two of the bullets) on all the CCW motors. The copter now takes off, so that issue is fixed. However, I still am curious what happened to the THR_MAX setting in 3.3? I confirmed I do see it when loading firmware 3.2.1, so it mysteriously disappeared from 3.2.1 to 3.3?
A search of the ArduCopter Parameters http://copter.ardupilot.com/wiki/arducopter-parameters/ for THR_MAX came up empty. Try yourself.
What happened to it from 3.2.1 to 3.3? I know there was a reason for the THR_MAX parameter before and I can’t find anything in the release notes about it being removed/replaced/modified. I know I’m new to this, but it would seem a big deal to remove a maximum thrust setting with nothing in the release notes, so I’d like to educate myself on what’s happening here and maybe learn something from it.
Yes, THR_MAX was removed in Copter-3.3 but as far as I know, nobody was using that parameter. We certainly never documented how it could be used.
In any case, the maximum thrust output can be adjusted using the MOT_THST_MAX parameter which is documented here: copter.ardupilot.com/wiki/motor-thrust-scaling/