We are trying to develop a proper FCS flight model for our F-35, but using the
default FCS features the response at high speed seem very sluggish. Is it
possible to have an explaination of the FCS logic in MSFS and what are the
parameters we need to tinker with to affect its behavior?
Hello @Indiafoxtecho Apart from stall protection, only these parameters are
exposed:
hitting the load limit defined with these parameters when flying in these high
speed conditions? Regards, Sylvain
Hello @FlyingRaccoon Thanks for your reply, but I think my question was not
clear enough - so I will elaborate it a little. First thing, however, I
believe there is a mistake in the entries you mentioned from the SDK
documentation you mentioned - as the description says ft per second^2 while
these entries typically are in "g"s and they seem to be so in MSFS (e.g. from
Asob F/A-18 E) positive_g_limit_flaps_up = 9.9 positive_g_limit_flaps_down =
9.9 negative_g_limit_flaps_up = -3 negative_g_limit_flaps_down = -3
load_safety_factor = 2 load_g_limiter_g = 7.5 Back to the question, I was
looking for more details like: - Autotrim logic (if any) or target AoA or
G-load (some military FBW-FCS system aim to a specific AoA with the stick at
rest, or will bring the aircraft to 1G -although the latter seems to have been
abandoned by modern aircrafts). - PID entries (are they the same as the A/P?
or are they separate but not exposed) - Surfaces actually controlled by the
AP Reason for asking is that we have been trying to implement it in our F-35,
but the planes becomes practically not controllable above M0.8 - it is not a
g-limiter problem as the plane does not seem to react even to minimal
controls… things seem to get a little better by increasing the trim
authority, but that should not be a factor… or should it?
Hello @Indiafoxtecho The unit error in the documentation will be fixed with
SU10. As for the control at high speed, some other parameters you can check
are FBWPitchTrimScalar and FBWHighSpeedRollSpeedScalar in
systems.cfg AUTOPILOT section. They will be documented with SU10 but
are already available in SU9. Check the F/A-18 for reference. AP is
controlling aileron for roll and elevator for pitch unless you use the
aileron_to_elevator_gain parameter in the flight_model.cfg
AIRPLANE_GEOMETRY section (will also be documented for SU10). You can also
check your elasticity tables and use the Debug Aircraft Tracking window to
check how your control surfaces are moving. Regards, Sylvain
Hi! Could you please extend what this means? AP is controlling aileron for
roll and elevator for pitch unless you use the aileron_to_elevator_gain
parameter in the flight_model.cfg AIRPLANE_GEOMETRY section (will also
be documented for SU10). I thought this was used for Elevons… Hence my
surprise.
Yes, that’s for elevons. We use this parameter on the F/A-18. I’m just saying
that the surfaces controlled by the AP depends on the geometry configuration
basically.
Understood, Thanks!