Howto:Implement pushback
Currently, pushback is only used on JSBSim planes. It should be possible with YASim aswell, but it has never be done yet.
Systems/pushback.xml
Create the following directory, if not present $FG_ROOT/Aircraft/.../Systems and create a file named pushback.xml with the following content:
<system name="pushback"> <channel name="Pushback"> <switch name="systems/pushback/linked"> <default value="0"/> <test logic="AND" value="1"> /sim/model/pushback/position-norm == 1 /gear/gear/wow == 1 </test> </switch> <switch name="systems/pushback/force"> <default value="0"/> <test logic="AND" value="/sim/model/pushback/magnitude"> systems/pushback/linked == 1 gear/unit[0]/wheel-speed-fps lt 500 </test> <output>external_reactions/pushback/magnitude</output> </switch> </channel> </system>
.xml
After the </propulsion> tag we add a reference to the pushback system:
<system file="pushback"/>
And at the end of the FDM, the following is needed to attach the forces of the pushback to the aircraft. The location should be somewhere near the nose wheel of the aircraft (where the pushback truck is connected).
<external_reactions> <force name="pushback" frame="BODY"> <location unit="IN"> <x> -139 </x> <y> 0.0 </y> <z> -71.0 </z> </location> <direction> <x>1</x> <y>0</y> <z>0</z> </direction> </force> </external_reactions>
-set.xml
Below the </sim> tag in the aircraft -set.xml file, we add our menu dialog. A generic one is available at $FG_ROOT/gui/Dialogs/pushback.xml. Add the following lines to include it in the Equipment menu of the aircraft. Note: if the menubar and default tags are already there, you do no need to add them again. Just place the stuff between them.
<menubar> <default> <menu n="5"> <item n="10"> <label>Pushback</label> <name>pushback</name> <binding> <command>dialog-show</command> <dialog-name>pushback</dialog-name> </binding> </item> </menu> </default> </menubar>
Models/ .xml
In your planes model file, we add a reference to one of the generic pushback models, or a custom made truck, shipped with your plane. Edit the offsets to fit your plane; the z offset should be at ground level, while the x offset is at the nosewheel(center).
<model> <name>Pushback</name> <path>Models\Airport\Pushback\Goldhofert.xml</path> <offsets> <x-m>-25.0</x-m> <y-m>0</y-m> <z-m>-4.0</z-m> </offsets> </model>