first of all, many thanks to all contributors to this nice project. I'm really enjoying it!
The problem is the following: When switching to modes which include automated control of speed (FBW-B, Loiter, RTL), the plane dives down heavily and motor speeds up to full speed (also when i set throttle to < 50% on sender). Other modes like Stabilize and FBW-A are working very well. I'm using an airspeed sensor which seems to show reasonable measurements. Cruise speed is set to 16 m/s, which is the speed the plane reaches when flying with about 60% throttle. I'm using APM1 (2560) with GPS in a Graupner Kadett 2400 airplane.
Right now I'm clueless on how to fix this, so any help is highly appreciated.