Elevator stiffness:
The "Pitch moment due to alpha" factor is currently unusually high, I think this is the cause why we need such an efficient elevator factor.
Decreasing "Pitch moment due to alpha" enables decreasing the "Pitch moment due to elevator", which becomes softer.
J3Cub.xml, lines about 1406 - 1443:
- Code: Select all
<function name="aero/moment/Pitch_alpha">
<description>Pitch moment due to alpha</description>
<product>
<property>aero/qbar-psf</property>
<property>metrics/Sw-sqft</property>
<property>metrics/cbarw-ft</property>
<property>aero/alpha-rad</property>
<table>
<independentVar lookup="row">aero/Re</independentVar>
<tableData> <!-- Du Y -->
1668183 -2.0327
3707224 -1.3432
</tableData>
</table>
<value>0.3</value> <!-- 0.3 dany, tests, stiffness issue -->
</product>
</function>
<function name="aero/moment/Pitch_elevator">
<description>Pitch moment due to elevator</description>
<product>
<property>aero/function/qbar-induced-psf</property>
<property>metrics/Sw-sqft</property>
<property>metrics/cbarw-ft</property>
<property>fcs/elevator-pos-rad</property>
<!--value> -1.2004 </value--> <!-- Du Y -->
<!--value> -1.8 </value--> <!-- from dany93 -->
<!-- + -0.10584 (5.88%) = -1.90584 -->
<table>
<independentVar>/sim/model/j3cub/pa-18</independentVar>
<tableData>
0 -1.8
1 -1.9058
</tableData>
</table>
<value>0.67</value> <!-- 0.67 dany, tests, stiffness issue -->
</product>
</function>
See the factors
<value>0.3</value>
<value>0.67</value>
at the bottom of the products.
These values are temporarily used for easier tuning in tests. They enable stall, reaching 18 - 20 deg AoA and 3 points touchdown. J3Cub 65 hp to PA18 160 hp tested.
Can you confirm and tell if you see no drawback?
If you find them acceptable, we can later merge them in their respective tables and delete the <value> lines.