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Alec246 avatar image
Alec246 asked Alec246 commented

Is Angle-of-Attack Rate Derivative "Cmα" implemented in the Flight Model Code?

While reading some material on Aerodynamics, I found this parte on Angle-of-attack Rate Derivatives, and the following Text seemed very interesting regarding what I can currently experience in MSFS2020.

"The derivatives with respect to rate of change of angle of attack ˙ α arise primarily from the time
lag associated with wing downwash affecting the horizontal tail. This affects the lift force on the
horizontal tail and the corresponding pitching moment; the effect on vehicle drag usually is neglected."

"The wing downwash is associated with the vorticity trailing behind the wing and, since vorticity is
convected with the local fluid velocity, the time lag for vorticity to convect from the wing to the tail
is approximately:


cma.jpg


I wonder if this Time Lag is taken into account, of if the Flight Model System is instantaneously changing Tail Angle of Attack, without taking into account the Delay there is for the Downwash from the Wing to reach the Tail, this depending on the Arm Distance between the Wing and the Tail. This seems like a very important characteristic to model, that can have profound impact on the Pitch Axis Handling of all Airplanes in the Sim.

And if I remember correctly, on the Legacy Tab, the Cmα Deriv is shown with 0s

Thanks!



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FlyingRaccoon avatar image
FlyingRaccoon answered Alec246 commented

Hello Alec,

Yes, the downwash lag to tail is taken into account in our flight model. :)

Regards,
Sylvain

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Makes me really happy that the FlightModel goes this deep into the simulation :)


It's just a matter of some polishing and we can get some pretty good results


Thanks!


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