Noticed last night testing a new flight controller (F405 Wing running Plane Chibios version) an issue which only appears in APM Planner (not in Mission Planner or Q Ground control which both work perfectly in this regard). If you hold the plane in its normal (belly down) orientation, then the horizon displays and respons to roll/pitch perfectly. If however you invert the plane and point nose down (to the ground), the AH points skywards (not groundwards).
@pauljatherton Interesting - could you please send me the tlog which is recorded by the APM planner? I will try to reproduce it with my pixhawk FC and compare the data with yours.
Sorry Arne, Haven’t managed to do this yet. Its very easy to produce though - simply point the FC front at the ground and rotate around the roll axis by 180deg and you will see it!