From 330024e0b7d0bdf67134a2af4b471ef644062bfe Mon Sep 17 00:00:00 2001
From: curt <curt>
Date: Sat, 15 Oct 2005 20:03:17 +0000
Subject: [PATCH] Allow a single vacuum system to be driven by multiple pumps. 
 This allows modeling of a simple single vacuum system with a pump source on
 each engine in a multiengine aircraft.  The highest rpm engine takes priority
 for driving the vacuum system.

---
 src/Systems/vacuum.cxx | 22 +++++++++++++++++-----
 src/Systems/vacuum.hxx | 11 +++++++----
 2 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/src/Systems/vacuum.cxx b/src/Systems/vacuum.cxx
index 256e6efaf..3e75aa323 100644
--- a/src/Systems/vacuum.cxx
+++ b/src/Systems/vacuum.cxx
@@ -11,10 +11,10 @@ VacuumSystem::VacuumSystem ( SGPropertyNode *node )
     :
     name("vacuum"),
     num(0),
-    rpm("/engines/engine[0]/rpm"),
     scale(1.0)
 
 {
+    rpms.clear();
     int i;
     for ( i = 0; i < node->nChildren(); ++i ) {
         SGPropertyNode *child = node->getChild(i);
@@ -25,7 +25,7 @@ VacuumSystem::VacuumSystem ( SGPropertyNode *node )
         } else if ( cname == "number" ) {
             num = child->getIntValue();
         } else if ( cname == "rpm" ) {
-            rpm = cval;
+            rpms.push_back(cval);
         } else if ( cname == "scale" ) {
             scale = child->getDoubleValue();
         } else {
@@ -41,7 +41,7 @@ VacuumSystem::VacuumSystem( int i )
 {
     name = "vacuum";
     num = i;
-    rpm = "/engines/engine[0]/rpm";
+    rpms.clear();
     scale = 1.0;
 }
 
@@ -52,12 +52,16 @@ VacuumSystem::~VacuumSystem ()
 void
 VacuumSystem::init()
 {
+    unsigned int i;
     string branch;
     branch = "/systems/" + name;
 
     SGPropertyNode *node = fgGetNode(branch.c_str(), num, true );
     _serviceable_node = node->getChild("serviceable", 0, true);
-    _rpm_node = fgGetNode(rpm.c_str(), true);
+    for ( i = 0; i < rpms.size(); i++ ) {
+      SGPropertyNode_ptr _rpm_node = fgGetNode(rpms[i].c_str(), true);
+      _rpm_nodes.push_back( _rpm_node );
+    }
     _pressure_node = fgGetNode("/environment/pressure-inhg", true);
     _suction_node = node->getChild("suction-inhg", 0, true);
 }
@@ -78,11 +82,19 @@ VacuumSystem::update (double dt)
     // Model taken from steam.cxx
 
     double suction;
+    unsigned int i;
 
     if (!_serviceable_node->getBoolValue()) {
         suction = 0.0;
     } else {
-        double rpm = _rpm_node->getDoubleValue() * scale;
+	// select the source with the max rpm
+        double rpm = 0.0;
+	for ( i = 0; i < _rpm_nodes.size(); i++ ) {
+	  double tmp = _rpm_nodes[i]->getDoubleValue() * scale;
+	  if ( tmp > rpm ) {
+	    rpm = tmp;
+	  }
+	}
         double pressure = _pressure_node->getDoubleValue();
         // This magic formula yields about 4 inhg at 700 rpm
         suction = pressure * rpm / (rpm + 4875.0);
diff --git a/src/Systems/vacuum.hxx b/src/Systems/vacuum.hxx
index d3034e16f..d03cb758c 100644
--- a/src/Systems/vacuum.hxx
+++ b/src/Systems/vacuum.hxx
@@ -11,6 +11,7 @@
 # error This library requires C++
 #endif
 
+#include <simgear/math/sg_types.hxx>
 #include <simgear/props/props.hxx>
 #include <simgear/structure/subsystem_mgr.hxx>
 
@@ -18,11 +19,13 @@
 /**
  * Model a vacuum-pump system.
  *
- * This first, simple draft is hard-wired to engine #1.
+ * Multiple pumps (i.e. for a multiengine aircraft) can be specified.
  *
  * Input properties:
  *
- * "rpm"
+ * "rpm1"
+ * "rpm2"
+ * "..."
  * /environment/pressure-inhg
  * /systems/"name"/serviceable
  *
@@ -48,10 +51,10 @@ private:
 
     string name;
     int num;
-    string rpm;
+    string_list rpms;
     double scale;
     SGPropertyNode_ptr _serviceable_node;
-    SGPropertyNode_ptr _rpm_node;
+    vector<SGPropertyNode_ptr> _rpm_nodes;
     SGPropertyNode_ptr _pressure_node;
     SGPropertyNode_ptr _suction_node;