From b2806f714ddf677dd2994a50ee205c8b9f0f3aa5 Mon Sep 17 00:00:00 2001
From: ehofman <ehofman>
Date: Fri, 26 Sep 2003 16:58:15 +0000
Subject: [PATCH] Jim Wilson: This has been on my local copy for a while (well
 tested :-)) It fixes a problem with the auto throttle jumping around
 needlessly.  Adjustments are calculated based on the last calculated
 autothrottle setting rather than reading the throttle setting from the
 property tree.

---
 src/Autopilot/newauto.cxx | 16 +++++++++-------
 src/Autopilot/newauto.hxx |  1 +
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/Autopilot/newauto.cxx b/src/Autopilot/newauto.cxx
index 5c2109ecd..81708ff2a 100644
--- a/src/Autopilot/newauto.cxx
+++ b/src/Autopilot/newauto.cxx
@@ -903,17 +903,17 @@ FGAutopilot::update (double dt)
 	total_adj = (1.0 - throttle_integral->getFloatValue()) * prop_adj + 
                                      throttle_integral->getFloatValue() * int_adj;
 
-                      total_adj = current_throttle->getFloatValue() + total_adj;
+                      current_ap_throttle = current_ap_throttle + total_adj;
 
-	if ( total_adj > 1.0 ) {
-	    total_adj = 1.0;
+	if ( current_ap_throttle > 1.0 ) {
+	    current_ap_throttle = 1.0;
 	}
-	else if ( total_adj < 0.0 ) {
-	    total_adj = 0.0;
+	else if ( current_ap_throttle < 0.0 ) {
+	    current_ap_throttle = 0.0;
 	}
 
 	globals->get_controls()->set_throttle( FGControls::ALL_ENGINES,
-					       total_adj );
+					       current_ap_throttle );
     }
 
 #ifdef THIS_CODE_IS_NOT_USED
@@ -1186,7 +1186,9 @@ void FGAutopilot::set_AutoThrottleEnabled( bool value ) {
         if (TargetSpeed < 0.0001) {
           TargetSpeed = fgGetDouble("/velocities/airspeed-kt");
         }
-	speed_error_accum = 0.0;
+        speed_error_accum = 0.0;
+        // initialize autothrottle at current control setting;
+        current_ap_throttle = current_throttle->getFloatValue();
     }
 
     update_old_control_values();
diff --git a/src/Autopilot/newauto.hxx b/src/Autopilot/newauto.hxx
index 49e88c451..467847f18 100644
--- a/src/Autopilot/newauto.hxx
+++ b/src/Autopilot/newauto.hxx
@@ -85,6 +85,7 @@ private:
     double climb_error_accum;   // climb error accumulator (for GS)
     double speed_error_accum;   // speed error accumulator
 
+    double current_ap_throttle;  // current ap stored throttle setting used to set all engines
     double previous_speed;  // used to detect acceleration rate
 
     double TargetSlope;         // the glide slope hold value
-- 
2.39.5