Fixed shaft turboprops do not act as though they have a fixed shaft

Version: SU13

Frequency: Consistently

Severity: High

Context: During aircraft simulation

Bug description: On an aircraft which has free_turbine set to false, the simulator will continue to treat the engine as though it is a free turbine turboprop rather than a fixed shaft turboprop. This leads to the engine N1 rpm and the prop rpm percentages potentially being massively different. In my case an N1 rpm of 80% is leading to a prop RPM of ~50%, however as the engine has a fixed shaft, the N1 and prop rpm should be of an equal percentage as they are both physically linked and dependent on one another.

Hello @meqolo

I have logged this issue in our backlog.