+
+void FGAIBase::CalculateMach() {
+ // 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;
+}
+
+int FGAIBase::_newAIModelID() {
+ static int id = 0;
+ if (!++id) id++; // id = 0 is not allowed.
+ return id;
+}
+