Lack of Throttle in SITL

Hi,

I’m new to ArduPilot, and I am trying to set up SITL simulation using RealFlight 9.5. I’m using ArduPilot’s Multiplex Acro Master found here:

I can get control of the aircraft using ArduPlane and perform a basic loiter flying in circles. However, I can only achieve this by setting the Minimum Throttle setting in the Parameter file to 100%. ArduPlane does not seem to provide any sort of throttle control and wants to stay only at the minimum defined value. If I set it to 20-30% the throttle will rest at 20-30%. Is there any other setting I may have missed for this fault to occur?