Roy Vegard Ovesen:

Here are some updates to the KAP140 autopilot in the default c172. It now uses
ailerons and elevator instead of aileron-trim and elevator-trim. I've started
to "upgrade" it to the "two axis altitude preselect" version. Vertical speed
select rounds to nearest 100 fpm.

I've also modified the c172 electrical configuration to turn on the gps
instrument.

Perhaps the most important change is that the nasal script for the KAP140 has
moved from data/Nasal to the c172p aircraft subdir. So it is important that
you delete data/Nasal/kap140.nas. Having the kap140.nas script as a global
script was not a good solution. Now it is aircraft specific, and thus
included in the c172p-set.xml file. Ideally I would like it to be instrument
specific, so that it would be included whenever the KAP140*.xml instruments
where included on the panel.

Aircraft/c172p/Models/c172p-2d-panel.xml

@@ -267,7 +267,7 @@ Legacy 2D instruments and actions for the 3D C172P cockpit.
    <y>-20</y>
   </instrument>
 -->
-  <instrument include="../../Instruments/KAP140TwoAxis.xml">
+  <instrument include="../../Instruments/KAP140TwoAxisAlt.xml">
    <name>KAP140 Autopilot</name>
    <x>880</x>
    <y>20</y>

Aircraft/c172p/Systems/KAP140.xml

@@ -132,8 +132,8 @@
                           <!-- unfiltered derivative error -->
       <Ti>15.0</Ti>       <!-- integrator time -->
       <Td>0.0</Td>    <!-- derivator time -->
-      <u_min>-0.9</u_min> <!-- minimum output clamp -->
+      <u_min>-1.0</u_min> <!-- minimum output clamp -->
-      <u_max>0.9</u_max>  <!-- maximum output clamp -->
+      <u_max>1.0</u_max>  <!-- maximum output clamp -->
     </config>
   </pid-controller>
 
@@ -153,7 +153,7 @@
       <prop>/autopilot/KAP140/settings/target-turn-rate</prop>
     </reference>
     <output>
-      <prop>/controls/flight/aileron-trim</prop>
+      <prop>/controls/flight/aileron</prop>
     </output>
     <config>
       <Kp>0.15</Kp>        <!-- proportional gain -->
@@ -232,6 +232,15 @@
     </config>
    </pid-controller>
 
+   <filter>
+    <name>pressure-rate-filter</name>
+    <debug>false</debug>
+    <type>double-exponential</type>
+    <input>/autopilot/internal/pressure-rate</input>
+    <output>/autopilot/internal/filtered-pressure-rate</output>
+    <filter-time>0.1</filter-time>
+   </filter>
+
   <!-- Vertical Speed (VS) Mode --> 
   <pid-controller>
     <name>Vertical Speed (VS) Mode</name>
@@ -241,13 +250,13 @@
       <value>vs</value>
     </enable>
     <input>
-      <prop>/autopilot/internal/pressure-rate</prop>
+      <prop>/autopilot/internal/filtered-pressure-rate</prop>
     </input>
     <reference>
       <prop>/autopilot/KAP140/settings/target-pressure-rate</prop>
     </reference>
     <output>
-      <prop>/controls/flight/elevator-trim</prop>
+      <prop>/controls/flight/elevator</prop>
     </output>
     <config>
       <Kp>5.0</Kp>      <!-- proportional gain -->

Aircraft/c172p/c172p-set.xml

@@ -104,5 +104,11 @@ Started October 23 2001 by John Check, fgpanels@rockfish.net
    <rpm type="double">700</rpm>
   </engine>
  </engines>
+ 
+ <nasal>
+  <kap140>
+   <file>Aircraft/c172p/kap140.nas</file>
+  </kap140>
+ </nasal>
   
 </PropertyList>