today i fly first time a pixhawk autopilot. after flying two years apm2.6 i spend my hexa a new pixhawk. everything is fine but i have a strange problem with altitude hold in mode alt-hold and position-hold. in this both modes i can increase vertical speed more than in loiter or auto mode.
and if i do this. increasing speed in position-hold or in alt-hold my copter suddenly shoot in the sky. mostly at ~11ms vertical speed.
first i was thinking this is a problem from barometer pressure. maybe caused by airflow. also i noticed that my altitude showing on taranis suddenly dropped from 25 meters to -17 meters in this moment. and of course this will spinn up motors to full throttle. but after review my log file i am unsure what caused the problem.
i noticed that CTUN BaroAlt do not droping altitude. i noticed that Gps RealAlt Drop to -17m while GPS Alt is corresponding with baro altitude. as you can see in yellow that Throttle OUT jump to 1000 while GPS Real Alt drop to -17. only switching to stabilised bring my copter back to controlled flying.
my pixhawk runs under arducopter rev. 3.2.1 hexa x.