The airspeed indicator can be initialized in an instrumentation.xml file.
If not specified, the generic indicator will be loaded 
from the Aircraft/Generic/generic-instrumentation.xml.

The normal setup is :

  <airspeed-indicator>
    <name>airspeed-indicator</name>
    <number>0</number>
    <total-pressure>/systems/pitot/total-pressure-inhg</total-pressure>
    <static-pressure>/systems/static/pressure-inhg</static-pressure>
    <has-overspeed-indicator>1</has-overspeed-indicator>
  </airspeed-indicator>

<total-pressure> is optional --- defaults to "/systems/pitot/total-pressure-inhg"
<static-pressure> is optional --- defaults to "/systems/static/pressure-inhg"
<has-overspeed-indicator> is optional --- defaults to 0 / off

The <has-overspeed-indicator> provides a property for "barber-pole" animation,
 and is set to 0 / false by default ,

If enabled , these properties should be added in the set file ,
with that aircraft's correct figures.

    <airspeed-indicator>
        <ias-limit>248.0</ias-limit>
        <mach-limit>0.48</mach-limit>
        <alt-threshold>13200.0</alt-threshold>
    </airspeed-indicator>


The default values are for a Beechcraft B1900D .

<ias-limit> is the aircraft's VNE (never exceed speed) in KIAS

<mach-limit> Mach speed limit.

<alt-threshold> altitude at which these figures were calculated.

Note : <mach-limit> is the mach limit at <alt-threshold>
This was designed for indicated airspeed limits , but could probably be extended 
for mach limits.