Howto:Implement aerial refueling capability

This howto teaches you how to implement aerial refueling capability to both tanker and/or receiver aircraft.

Receiver aircraft

Add the following blocks of code to your aircraft's -set.xml file (all after the </sim> tag). Make sure to check for pre-existing blocks/structures and insert the new blocks within them as applicable.

• Radar is needed to check if you are close enough from the tanker.
  • It also seems to check that the receiving aircraft's heading is within +/-90deg of the direction of the tanker,
• The <refuel> properties defines
  • what type of refueling you are capable of (probe and drogue, or boom)
  • if your refuel system is ok to receive (use the serviceable property if you have a switch to open the refuel trap for example).
  • the maximum rate of fuel (in lbs per minute) that can be transferred (defaults to 6000)
  • the offset of the probe/trap from the aircraft model origin. (+x is towards the rear of the aircraft, +y is to the right facing forwards, +z is up)
• aar.nas is the actual system that checks the two above mentioned criteria and if both are true, refuels your tanks.

 <instrumentation>
  <radar>
   <range type="int" archive="y">20</range>
   <minimized type="bool" archive="y">false</minimized>
  </radar>
 </instrumentation>

 <systems>
  <refuel>
   <type>probe</type>
   <serviceable type="bool">true</serviceable>
   <max-fuel-transfer-lbs-min>6000</max-fuel-transfer-lbs-min>
   <offset-x-m>0</offset-x-m>
   <offset-y-m>0</offset-y-m>
   <offset-z-m>0</offset-z-m>
  </refuel>
 </systems>

 <nasal>
  <aar>
   <file>Aircraft/Generic/aar.nas</file>
  </aar>
 </nasal>

The aircraft can receive fuel from the KA6 with the above code. To receive fuel from the KC-135, replace 'probe' with 'boom'.

Tanker aircraft

To allow your plane to be used as a tanker by others players, you only need to add the following blocks of code to your aircraft's model .xml file (usually located in Aircraft/.../Models/):

 <multiplay>
  <refuel>
   <type>probe</type>
  </refuel>
 </multiplay>

Replace 'probe' with 'boom' in the files for a boom-equipped tanker. This influences what aircraft can receive fuel! Or give the two lines if the tanker get both a boom and probes (like recent kc135) in this case you will be able to refuel both type of aircraft.

For the moment, flyable tankers are: KC135, victor and KC130 (in Aircraft/c130) if you need an example.

To add an AI refuelling aircraft, add it to AI/tankers.xml.

Serviceable option

Releases of FlightGear after 2.0.0 allow any callsign to be a tanker. The tanker property is transmitted over multiplayer, permitting for example to prevent refueling if the refueling probe is not operational. With FlightGear 2.0.0 and older, refueling is possible only if the tanker uses a "MOBIL" callsign (e.g., MOBIL3).

For this to work, add the following code in your aircraft's -set file (be sure not to be in another block):

<tanker type="bool">false</tanker>

Switch this property true or false to allow following aircraft to refuel or not.