On Monday 16 August 2010 18:57:35 Hal V. Engel wrote:
> Stuart,
>
> I've got some other things "in the oven" for the P51D JSBSim model. Among
> other things I found a significant error in one of the drag functions,
> CDde, and this cascaded changes to other areas to get things working the
> way they should. I will be pushing these changes into my fgdata clone on
> gitorious in the next week or so and then will be requesting that those
> changes be merged into fgdata. So it would probably be better to just
> wait for that code to be merged in the main fgdata repository since this
> does not seg fault for most users for some reason.
Hi Hal,
Would you elaborate on the error in CDde? It looks like the same CDde used in
most aeromatic aircraft so if there is an error in the P51d we (still) have
an error in many jsbsim aircraft.
Thanks,
Ron
<function name="aero/coefficient/CDde">
<description>Drag_due_to_Elevator_Deflection</description>
<product>
<property>aero/qbar-psf</property>
<!-- I prefer aero/qbarUW-psf to eliminate crosswind velocity component -->
<property>metrics/Sw-sqft</property>
<!-- this is the wing area, tail area is available in metrics/Sh-sqft but Dave
Culp argues for the use of Sw-sqft -->
<abs>
<property>fcs/elevator-pos-norm</property>
</abs>
<!-- this is an absolute value so that the drag function can not go negative.
my experiments with x-foil show that drag always increases with a
control surface deflection. I prefer to use fcs/elevator-pos-rad
instead of the normalized value. -->
<value>0.035</value>
<!-- Constant can be tuned to taste. -->
</product>
</function>
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