We’re looking into incorporating the new propeller physics into our simulation
of the RAT (ram air turbine) in the A320neo. The RAT isn’t a typical prop, as
it doesn’t spin by itself, but possesses resistant torque which outside
airflow overcomes to spin the turbine and generate electrical power. Would the
new propeller physics be able to handle this? Would any additional work or
modifications be necessary on our end?
The ‘new propeller physics’ seem to be entirely aerodynamic but the ‘engines’
model needs a fix to get the combination to work. The particular issue is the
(piston) engine friction isn’t implemented as a friction, instead it seems
to be a very odd ‘reverse torque’ dynamic force with no stable equilibrium
(which is the opposite of friction, which is inherently stable, i.e. motion
will stop across a wide range of initial states). That is with a piston engine
though and you might be ok with the RAT being a turboprop - I don’t know what
happens if that ever goes negative in MSFS. Engine off, piston props
uncontrollably accelerate negative if the RPM goes negative more than a small
amount - nothing to do with the real world, this is just a quirk of the
FSX/MSFS engine/prop simulation. This issue has been reported before but it is
confused with people posting that propellers do stop when the aircraft is on
the ground (nothing to do with the issue described here) and also can stop
when the prop is feathered (again nothing to do with this engine-related
issue). The point is there is no stable zero-RPM point that works across
multiple airspeeds and accidentally having the model move the RPM negative
causes the engine model to accelerate out of control. To be fair, hardly
anyone has ever tested any MSFS prop aircraft in the air with the engine off
(I recommend anyone try it in the Cessna 152)
Hello @IcemanFBW This is not possible at the moment as you can’t have a
combination of jet engine and propeller engine. On a turboprop, you could try
creating a fake engine that only produces negative torque and use the RPM to
compute the power but we haven’t tested so we can’t give any guarantee it
would work. We would need to develop a dedicated feature for this. In the
meantime, you’ll need to develop your own system I’m afraid. Regards, Sylvain