Set the format default to float instead of int.

[flightgear.git] / src / AIModel / AIBase.cxx

diff --git a/src/AIModel/AIBase.cxx b/src/AIModel/AIBase.cxx
index 57a6ed5a322ffed8ee028fc5862082e06eb26eef..db566a1ef19bd17a71ddea692dd06f6dc53ff25c 100644 (file)
--- a/src/AIModel/AIBase.cxx
+++ b/src/AIModel/AIBase.cxx
@@ -43,6 +43,11 @@
 #include "AIBase.hxx"
 #include "AIManager.hxx"
 
+
+const double FGAIBase::e = 2.71828183;
+const double FGAIBase::lbs_to_slugs = 0.031080950172;   //conversion factor
+
+
 FGAIBase::FGAIBase()
  :  fp( NULL ),
     model( NULL ),
@@ -75,8 +80,40 @@ FGAIBase::~FGAIBase() {
 void FGAIBase::update(double dt) {
     ft_per_deg_lat = 366468.96 - 3717.12 * cos(pos.lat()/SG_RADIANS_TO_DEGREES);
     ft_per_deg_lon = 365228.16 * cos(pos.lat() / SG_RADIANS_TO_DEGREES);
-}
 
+    // Calculate rho at altitude, using standard atmosphere
+    // For the temperature T and the pressure p,
+
+    if (altitude < 36152) {            // curve fits for the troposphere
+      T = 59 - 0.00356 * altitude;
+      p = 2116 * pow( ((T + 459.7) / 518.6) , 5.256);
+
+    } else if ( 36152 < altitude && altitude < 82345 ) {    // lower stratosphere
+      T = -70;
+      p = 473.1 * pow( e , 1.73 - (0.000048 * altitude) );
+
+    } else {                                    //  upper stratosphere
+      T = -205.05 + (0.00164 * altitude);
+      p = 51.97 * pow( ((T + 459.7) / 389.98) , -11.388);
+    }
+
+    rho = p / (1718 * (T + 459.7));
+       
+       // calculate the speed of sound at altitude
+       // a = sqrt ( g * R * (T + 459.7))
+       // where:
+       // a = speed of sound [ft/s]
+       // g = specific heat ratio, which is usually equal to 1.4  
+       // R = specific gas constant, which equals 1716 ft-lb/slug/°R 
+       
+       a = sqrt ( 1.4 * 1716 * (T + 459.7));
+       
+       // calculate Mach number
+       
+       Mach = speed/a;
+       
+//     cout  << "Speed(ft/s) "<< speed <<" Altitude(ft) "<< altitude << " Mach " << Mach;
+}
 
 void FGAIBase::Transform() {
     if (!invisible) {