<?xml version="1.0"?>
 
<!-- Douglas A-4F Skyhawk Autopilot Configuration -->

<!--

  Autopilot Modes:
  
  - APC (Autopilot Power Compensator).  Applies throttle
    based on AoA.  If below target AoA, reduces power (min 70%),
    if above target AoA, increases power (max 100%).
    
  - Attitude Hold
  
  - Heading Hold
  
  - Control Stick Steering
  
-->

<PropertyList>

<!-- Spoiler control logic -->
<logic>
  <input>
    <and>      
      <equals>
        <property>controls/flight/spoilers-armed</property>
        <value>true</value>
      </equals>
      <equals>
        <property>/controls/gear/gear-down</property>
        <value>true</value>
      </equals>
      <equals>
        <property>gear/gear[1]/wow</property>
        <value>true</value>
      </equals>
      <less-than>
        <property>controls/engines/engine[0]/throttle</property>
        <value>0.7</value>
      </less-than>
    </and>
  </input>
  <output>controls/flight/spoilers</output>
</logic>

<!-- Alarm ladder logic -->
<logic>
  <input>
    <greater-than>
      <property>surface-positions/spoiler-pos-norm</property>
      <value>0.1</value>
    </greater-than>
  </input>
  <output>sim/alarms/spoiler</output>
</logic>

<logic>
  <input>
    <greater-than>
      <property>surface-positions/speedbrake-pos-norm</property>
      <value>0.1</value>
    </greater-than>
  </input>
  <output>sim/alarms/speedbrake</output>
</logic>

<logic>
  <input>
    <and>
      <greater-than>
        <property>gear/gear[0]/position-norm</property>
        <value>0.01</value>
      </greater-than>
      <less-than>
        <property>gear/gear[0]/position-norm</property>
        <value>0.99</value>
      </less-than>
    </and>
  </input>
  <output>sim/alarms/gear</output>
</logic>


<!-- min/max acceleration -->
<filter>
  <type>gain</type>
  <enable>
    <condition>
      <greater-than>
        <property>/accelerations/pilot-g</property>
        <property>/instrumentation/g-meter/g-max</property>
      </greater-than>
    </condition>
  </enable>
  <input>/accelerations/pilot-g</input>
  <output>/instrumentation/g-meter/g-max</output>
  <min>-5</min>
  <max>10</max>
</filter>

<filter>
  <type>gain</type>
  <enable>
    <condition>
      <less-than>
        <property>/accelerations/pilot-g</property>
        <property>/instrumentation/g-meter/g-min</property>
      </less-than>
    </condition>
  </enable>
  <input>/accelerations/pilot-g</input>
  <output>/instrumentation/g-meter/g-min</output>
  <min>-5</min>
  <max>10</max>
</filter>

<logic>
  <!-- Engage/disengage logic for APC -->
  <input>
    <and>      
      <equals>
        <property>controls/engines/engine[0]/apc</property>
        <value>true</value>
      </equals>
      <equals>
        <property>/controls/gear/gear-down</property>
        <value>true</value>
      </equals>
      <greater-than>
        <property>engines/engine/n2</property>
        <value>0.6</value>
      </greater-than>
      <less-than>
        <property>controls/engines/engine[0]/throttle</property>
        <value>0.9</value>
      </less-than>
      <not-equals>
        <property>gear/gear[1]/wow</property>
        <value>true</value>
      </not-equals>        
    </and>
  </input>
  <output>controls/engines/engine[0]/apc</output>
</logic>

<!-- Throttle servo -->
<filter>
  <name>SERVO-DRIVER:throttle</name>
  <debug>false</debug>
  <feedback-if-disabled>true</feedback-if-disabled>
  <enable>
    <condition>
      <equals>
        <property>controls/engines/engine[0]/apc</property>
        <value>true</value>
      </equals>
    </condition>
  </enable>
  <input>/autopilot/internal/throttle-cmd</input>
  <output>
    <prop>/controls/engines/engine[0]/throttle</prop>
  </output>
  <type>noise-spike</type>
  <max-rate-of-change>0.3</max-rate-of-change>
  <!-- Ensure that the APC doesn't drop itself out -->
  <max>0.9</max>
</filter>

<!-- AoA with throttle (Approach Power Compensator - APC) -->
<pid-controller>
  <name>AoA-with-throttle</name>
  <debug>false</debug>
  <enable>
    <condition>
      <equals>
        <property>controls/engines/engine[0]/apc</property>
        <value>true</value>
      </equals>
    </condition>
  </enable>
  <input>
    <prop>orientation/alpha-deg</prop>
  </input>
  <reference>
    <prop>sim/aoa-indexer/target-deg</prop>
  </reference>
  <output>
    <prop>/autopilot/internal/throttle-cmd</prop>
  </output>
  <config>
    <Ts>0.02</Ts> 
    <Kp>-0.03</Kp>
    <beta>1.0</beta>
    <alpha>0.1</alpha>
    <gamma>0.0</gamma>
    <Ti>20.0</Ti>
    <Td>0.0</Td>
    <u_min>0.01</u_min>
    <u_max>0.9</u_max>
  </config>
</pid-controller>

  <!-- =============================================================== -->
  <!-- Roll Axis Modes                                                 -->
  <!-- =============================================================== -->

  <!-- Wing leveler --> 
  <pid-controller>
    <name>Wing Leveler (Turn Coordinator based)</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/heading</prop>
      <value>wing-leveler</value>
    </enable>
    <input>
      <prop>/instrumentation/turn-indicator/indicated-turn-rate</prop>
    </input>
    <reference>
      <value>0.0</value>
    </reference>
    <output>
      <prop>/controls/flight/aileron</prop>
    </output>
    <config>
      <Kp>0.5</Kp>        <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>       <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

  <!-- Heading Bug Hold.  2 stage cascade controller. -->

  <!-- Stage #1 sets target roll based on diff between current heading -->
  <!-- and heading bug. -->
  <pid-controller>
    <name>Heading Bug Hold (DG based) Stage 1</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/heading</prop>
      <value>dg-heading-hold</value>
    </enable>
    <input>
      <prop>/autopilot/internal/heading-bug-error-deg</prop>
    </input>
    <reference>
      <value>0.0</value>
    </reference>
    <output>
      <prop>/autopilot/internal/target-roll-deg</prop>
    </output>
    <config>
      <Kp>-1.0</Kp>        <!-- proportional gain -->
      <beta>1.0</beta>     <!-- input value weighing factor -->
      <alpha>0.1</alpha>   <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>   <!-- input value weighing factor for -->
                           <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>        <!-- integrator time -->
      <Td>0.00001</Td>     <!-- derivator time -->
      <u_min>-20.0</u_min> <!-- minimum output clamp -->
      <u_max>20.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

  <!-- Stage #2 drives the ailerons to achieve the desired roll deg. -->
  <pid-controller>
    <name>Heading Bug Hold (DG based) Stage 2</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/heading</prop>
      <value>dg-heading-hold</value>
    </enable>
    <input>
      <prop>/orientation/roll-deg</prop>
    </input>
    <reference>
      <prop>/autopilot/internal/target-roll-deg</prop>
    </reference>
    <output>
      <prop>/controls/flight/aileron</prop>
    </output>
    <config>
      <Kp>0.1</Kp>        <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>       <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

  <!-- True Heading hold.  2 stage cascade controller. -->

  <!-- Stage #1 sets target roll based on diff between current heading -->
  <!-- and target heading. -->
  <pid-controller>
    <name>True Heading Hold (DG based) Stage 1</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/heading</prop>
      <value>true-heading-hold</value>
    </enable>
    <input>
      <prop>/autopilot/internal/true-heading-error-deg</prop>
    </input>
    <reference>
      <value>0.0</value>
    </reference>
    <output>
      <prop>/autopilot/internal/target-roll-deg</prop>
    </output>
    <config>
      <Kp>-1.0</Kp>        <!-- proportional gain -->
      <beta>1.0</beta>     <!-- input value weighing factor -->
      <alpha>0.1</alpha>   <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>   <!-- input value weighing factor for -->
                           <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>        <!-- integrator time -->
      <Td>0.00001</Td>     <!-- derivator time -->
      <u_min>-20.0</u_min> <!-- minimum output clamp -->
      <u_max>20.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

  <!-- Stage #2 drives the ailerons to achieve the desired roll deg. -->
  <pid-controller>
    <name>True Heading Hold (DG based) Stage 2</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/heading</prop>
      <value>true-heading-hold</value>
    </enable>
    <input>
      <prop>/orientation/roll-deg</prop>
    </input>
    <reference>
      <prop>/autopilot/internal/target-roll-deg</prop>
    </reference>
    <output>
      <prop>/controls/flight/aileron</prop>
    </output>
    <config>
      <Kp>0.1</Kp>        <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>       <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

  <!-- Nav1 hold.  2 stage cascade controller. -->

  <!-- Stage #1 sets target roll based on diff between current heading -->
  <!-- and target heading. -->
  <pid-controller>
    <name>Nav1 Hold Stage 1</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/heading</prop>
      <value>nav1-hold</value>
    </enable>
    <input>
      <prop>/autopilot/internal/nav1-heading-error-deg</prop>
    </input>
    <reference>
      <value>0.0</value>
    </reference>
    <output>
      <prop>/autopilot/internal/target-roll-deg</prop>
    </output>
    <config>
      <Kp>-1.0</Kp>        <!-- proportional gain -->
      <beta>1.0</beta>     <!-- input value weighing factor -->
      <alpha>0.1</alpha>   <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>   <!-- input value weighing factor for -->
                           <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>        <!-- integrator time -->
      <Td>0.00001</Td>     <!-- derivator time -->
      <u_min>-20.0</u_min> <!-- minimum output clamp -->
      <u_max>20.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

  <!-- Stage #2 drives the ailerons to achieve the desired roll deg. -->
  <pid-controller>
    <name>Nav1 Hold Stage 2</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/heading</prop>
      <value>nav1-hold</value>
    </enable>
    <input>
      <prop>/orientation/roll-deg</prop>
    </input>
    <reference>
      <prop>/autopilot/internal/target-roll-deg</prop>
    </reference>
    <output>
      <prop>/controls/flight/aileron</prop>
    </output>
    <config>
      <Kp>0.1</Kp>        <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>       <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>


 <!-- =============================================================== -->
 <!-- Pitch Axis Modes                                                -->
 <!-- =============================================================== -->

 <!-- Simple pitch hold --> 
 <pid-controller>
    <name>Pitch hold</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/altitude</prop>
      <value>pitch-hold</value>
    </enable>
    <input>
      <prop>/orientation/pitch-deg</prop>
    </input>
    <reference>
      <prop>/autopilot/settings/target-pitch-deg</prop>
    </reference>
    <output>
      <prop>/controls/flight/elevator-trim</prop>
    </output>
    <config>
      <Kp>-0.05</Kp>      <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>1.0</Ti>        <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
   </pid-controller>

 <!-- Simple angle of attack hold --> 
 <pid-controller>
    <name>AOA hold</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/altitude</prop>
      <value>aoa-hold</value>
    </enable>
    <input>
      <prop>/orientation/alpha-deg</prop>
    </input>
    <reference>
      <prop>/autopilot/settings/target-aoa-deg</prop>
    </reference>
    <output>
      <prop>/controls/flight/elevator-trim</prop>
    </output>
    <config>
      <Kp>-0.05</Kp>      <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>0.5</Ti>        <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

  <!-- Altitude hold.  2 stage cascade controller. -->

  <!-- Stage #1 sets target rate of climb based on diff between current alt -->
  <!-- and target altitude. -->
  <pi-simple-controller>
    <name>Altitude Hold (Altimeter based) Stage 1</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/altitude</prop>
      <value>altitude-hold</value>
    </enable>
    <input>
      <prop>/position/altitude-ft</prop>
    </input>
    <reference>
      <prop>/autopilot/settings/target-altitude-ft</prop>
    </reference>
    <output>
      <prop>/autopilot/internal/target-climb-rate-fps</prop>
    </output>
    <config>
      <Kp>0.3</Kp>          <!-- proportional gain -->
      <Ki>0.0</Ki>          <!-- integral gain -->
      <u_min>-16.67</u_min> <!-- minimum output clamp -->
      <u_max>8.33</u_max>   <!-- maximum output clamp -->
    </config>
  </pi-simple-controller>

  <!-- Stage #2 drives the elevator-trim to achieve the desired climb rate. -->
  <pid-controller>
    <name>Altitude Hold (Altimeter based) Stage 2</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/altitude</prop>
      <value>altitude-hold</value>
    </enable>
    <input>
      <prop>/velocities/vertical-speed-fps</prop>
    </input>
    <reference>
      <prop>/autopilot/internal/target-climb-rate-fps</prop>
    </reference>
    <output>
      <prop>/controls/flight/elevator-trim</prop>
    </output>
    <config>
      <Kp>-0.01</Kp>      <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>       <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

  <!-- AGL hold.  2 stage cascade controller. -->

  <!-- Stage #1 sets target rate of climb based on diff between current agl -->
  <!-- and target agl. -->
  <pi-simple-controller>
    <name>AGL Hold (Altimeter based) Stage 1</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/altitude</prop>
      <value>agl-hold</value>
    </enable>
    <input>
      <prop>/position/altitude-agl-ft</prop>
    </input>
    <reference>
      <prop>/autopilot/settings/target-agl-ft</prop>
    </reference>
    <output>
      <prop>/autopilot/internal/target-climb-rate-fps</prop>
    </output>
    <config>
      <Kp>0.3</Kp>          <!-- proportional gain -->
      <Ki>0.0</Ki>          <!-- integral gain -->
      <u_min>-16.67</u_min> <!-- minimum output clamp -->
      <u_max>8.33</u_max>   <!-- maximum output clamp -->
    </config>
  </pi-simple-controller>

  <!-- Stage #2 drives the elevator-trim to achieve the desired climb rate. -->
  <pid-controller>
    <name>AGL Hold (Altimeter based) Stage 2</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/altitude</prop>
      <value>agl-hold</value>
    </enable>
    <input>
      <prop>/velocities/vertical-speed-fps</prop>
    </input>
    <reference>
      <prop>/autopilot/internal/target-climb-rate-fps</prop>
    </reference>
    <output>
      <prop>/controls/flight/elevator-trim</prop>
    </output>
    <config>
      <Kp>-0.01</Kp>      <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>       <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

  <!-- Glideslope hold. -->

  <!-- Stage #2 drives the elevator-trim to achieve the desired climb rate. -->
  <pid-controller>
    <name>Glideslop Hold</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/altitude</prop>
      <value>gs1-hold</value>
    </enable>
    <input>
      <prop>/velocities/vertical-speed-fps</prop>
    </input>
    <reference>
      <prop>/instrumentation/nav[0]/gs-rate-of-climb</prop>
    </reference>
     <output>
      <prop>/controls/flight/elevator-trim</prop>
    </output>
    <config>
      <Kp>-0.01</Kp>      <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>       <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

  <!-- vertical speed hold -->
  <pid-controller>
    <name>Vertical Speed Hold</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/altitude</prop>
      <value>vertical-speed-hold</value>
    </enable>
    <input>
      <prop>/velocities/vertical-speed-fps</prop>
    </input>
    <reference>
      <prop>/autopilot/settings/vertical-speed-fpm</prop>
      <scale>0.01667</scale>
    </reference>
    <output>
      <prop>/controls/flight/elevator-trim</prop>
    </output>
    <config>
      <Kp>-0.01</Kp>      <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>       <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>


 <!-- =============================================================== -->
 <!-- Velocity Modes                                                  -->
 <!-- =============================================================== -->

 <!-- Auto throttle --> 
 <pid-controller>
    <name>Auto Throttle (5 sec lookahead)</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/speed</prop>
      <value>speed-with-throttle</value>
    </enable>
    <input>
      <!-- <prop>/autopilot/internal/lookahead-5-sec-airspeed-kt</prop> -->
      <prop>/velocities/airspeed-kt</prop>
    </input>
    <reference>
      <prop>/autopilot/settings/target-speed-kt</prop>
    </reference>
    <output>
      <prop>/controls/engines/engine[0]/throttle</prop>
      <prop>/controls/engines/engine[1]/throttle</prop>
      <prop>/controls/engines/engine[2]/throttle</prop>
      <prop>/controls/engines/engine[3]/throttle</prop>
      <prop>/controls/engines/engine[4]/throttle</prop>
      <prop>/controls/engines/engine[5]/throttle</prop>
      <prop>/controls/engines/engine[6]/throttle</prop>
      <prop>/controls/engines/engine[7]/throttle</prop>
    </output>
    <config>
      <Kp>0.1</Kp>        <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>10.0</Ti>       <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>0.0</u_min>  <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

 <!-- Hold speed by varying pitch trim (Two stage cascading controller) --> 
 <pid-controller>
    <name>Speed hold (vary pitch trim) Stage #1</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/speed</prop>
      <value>speed-with-pitch-trim</value>
    </enable>
    <input>
      <prop>/autopilot/internal/lookahead-5-sec-airspeed-kt</prop>
    </input>
    <reference>
      <prop>/autopilot/settings/target-speed-kt</prop>
    </reference>
    <output>
      <prop>/autopilot/settings/target-pitch-deg</prop>
    </output>
    <config>
      <Kp>-1.0</Kp>       <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>1.0</Ti>        <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-15.0</u_min><!-- minimum output clamp -->
      <u_max>15.0</u_max> <!-- maximum output clamp -->
    </config>
  </pid-controller>

 <pid-controller>
    <name>Speed hold (vary pitch trim) Stage #2</name>
    <debug>false</debug>
    <enable>
      <prop>/autopilot/locks/speed</prop>
      <value>speed-with-pitch-trim</value>
    </enable>
    <input>
      <prop>/orientation/pitch-deg</prop>
    </input>
    <reference>
      <prop>/autopilot/settings/target-pitch-deg</prop>
    </reference>
    <output>
      <prop>/controls/flight/elevator-trim</prop>
    </output>
    <config>
      <Kp>-0.05</Kp>      <!-- proportional gain -->
      <beta>1.0</beta>    <!-- input value weighing factor -->
      <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
      <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                          <!-- unfiltered derivative error -->
      <Ti>1.0</Ti>        <!-- integrator time -->
      <Td>0.00001</Td>    <!-- derivator time -->
      <u_min>-1.0</u_min> <!-- minimum output clamp -->
      <u_max>1.0</u_max>  <!-- maximum output clamp -->
    </config>
  </pid-controller>

</PropertyList>
