Fixed-wing aircraft in SITL with Real Flight 8 constantly trying to hover

Hello,
I am trying to run SITL using Mission Planner and Real Flight 8. I can connect to RF 8. I tried to control a simple airplane (Cessna 182). If I fly it with the Joystick I can see the correct attitude of the airplane in MP, but if I try to set the autopilot in any of the autonomous or semi-autonomous modes (even the FBWA) the airplane just tries to seat on its tail. I thought was a tuning problem, but even using the auto-tune feature the airplane goes crazy and tries to climb with 90° pitch. I hope someone has some suggestion.
Thanks.