I'm working with an APM2 after months of experience with an APM1 in an EasyStar. The new APM2 has an airspeed sensor and typically shows 8-10 mph when sitting on the bench. On its last flights, we tested Manual and got the plane trimmed and flying well. We tested Stabilize and it flew even better (!) in that mode. The last test was with RTL.
When switched into RTL, the plane turned back to Home. It was at just about the Default Altitude of 250 feet, but it started to descend. It was at about 200 feet when crossing Home and starting the RTL turn. It continued to descend through the turn to the point we had to go back to Manual and recover to safe altitude.
On the bench, whenever the APM2 goes into Auto or RTL, nav_pitch goes to -5 and the elevator servo is send into a corresponding nose-down position. The -5 degrees just happens to be the Min Pitch configuration setting. So, I know what's causing the dive, but why?
Can anyone say why the APM would command a descent when at target altitude in an Auto mode? I need to find the reason before attempting flight again. It's using version 2.28 firmware. The params file is attached. Thanks.