The description of the elevator lift coefficient parameter says that it
“defines the lift coefficient slope of the elevator control surface.” Why,
during level flight with the elevator at essentially zero deflection, does it
affect the pitch angle at which the airplane flies? (And to be clear, it’s not
just the airplane pitch angle. It appears to result in a different
contribution of lift from the tail, which affects the lift contribution needed
from the wing, which affects the drag, etc.) Shouldn’t the lift coefficient
from the elevator be the same at zero deflection, regardless of the elevator
lift curve slope? That is, shouldn’t the elevator lift curve pass through the
same CL at zero elevator deflection regardless of slope? Changing the elevator
effectiveness scalar, which I had hoped might be an alternative way to change
the effectiveness of the elevator control without affecting the aerodynamics
(that is, no change in lift with zero elevator deflection, and a change in
elevator deflection needed to obtain the desired flight path change (from
elevator aerodynamics), has exactly the same effect.
Hello @donstim It also depends on horizontal stabilizer incidence and you
probably want to adjust it to keep the same incidence when changing lift
coefficients. Also if you’re still testing using the A320, the FBW will try to
maintain 1G in level flight using trims so that can influence what you see in
game. Regards, Sylvain
Thank you for the answer. I don’t have any expertise/experience with
stabilizer/elevator aerodynamics, but I expected the angle of attack for the
elevator to be pretty much unaffected by small changes in the stabilizer
angle. Does MSFS use the same change in angle of attack for both? From a
flight simulator airplane flight model designer perspective, I expected (was
hoping for?) an elevator effectiveness parameter that was only dependent on
the input to that control. This would be similar to what I would expect from a
change to the legacy parameter for a pitching moment due to delta elevator and
the SDK description for how that is handled by MSFS. But maybe that parameter
is also not so “pure” (i.e., maybe it is also affected by the stabilizer
angle)?