i running apm2.6 with latest "stable" 3.0.1 firmware. I use latest MP 1.2.83 to make my settings. In moment my copter fly very stable in stabilised mode. Today i decide to test other flight modes. At first i tried AltHold. Switching into this mode nearly cut off my motors. See graph on top. Of course i have corrected the THR_MID parameter as shown on the ardurcopter homepage. My value here currently is at 428 for 6kg take-off weight.
Some words about the copter. It is a hexa for heavy playload. Today the take-off weight was 6kg. max take-off weigh is 8kg and min is 4,5kg. Currently I have mounted 6 t-motor 4012-400 with 15x5 carbon props at 6s(22.6v).
I have less vibrations on apm and gps/compas module because motors and props are very balanced. The Apm is mounted with all other electronics on a separate rubber isolated layer. Also this layer hold the separate battery for powering the apm and other electronics. this mean this layer brings a lot of mass against the mainframe with their heavy main batteries, motor mounts and esc s. This is generally god against vibrations.
My accel log:
simple hovering is between 70 and 90 seconds in log file. all other is starting landing and some throttle tests.
So i try to find the problem in main settings. And here especially for THR_ALT_I / P.
MP defaults and currently unchanged settings for THR_ALT_P and THR_ALT_I are
THR_ALT_P = 1.0
THR_ALT_I = 0.0 .
Did i have to change this setting? Is this the problem? Currently i am unsure because the wiki only talk about 2.x firmwares. http://code.google.com/p/arducopter/wiki/AC2_AltHoldMode