TACAN: fix distance calculations and some other problems.

[flightgear.git] / src / Systems / pitot.cxx

diff --git a/src/Systems/pitot.cxx b/src/Systems/pitot.cxx
index 78d1d2bd301a2b11cbe6e67349e3f260d81c9d01..cf3eb2590a03af3ac93ce0125af390f58c71ae4b 100644 (file)
--- a/src/Systems/pitot.cxx
+++ b/src/Systems/pitot.cxx
@@ -1,41 +1,28 @@
 // pitot.cxx - the pitot air system.
 // Written by David Megginson, started 2002.
 //
+// Last modified by Eric van den Berg, 01 Nov 2013
 // This file is in the Public Domain and comes with no warranty.
 
-#include "pitot.hxx"
+#ifdef HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#include <simgear/constants.h>
+
 #include <Main/fg_props.hxx>
 #include <Main/util.hxx>
 
+#include "pitot.hxx"
 
 
 PitotSystem::PitotSystem ( SGPropertyNode *node )
     :
-    num(0),
-    name("pitot")
-{
-    int i;
-    for ( i = 0; i < node->nChildren(); ++i ) {
-        SGPropertyNode *child = node->getChild(i);
-        string cname = child->getName();
-        string cval = child->getStringValue();
-        if ( cname == "name" ) {
-            name = cval;
-        } else if ( cname == "number" ) {
-            num = child->getIntValue();
-        } else {
-            SG_LOG( SG_SYSTEMS, SG_WARN, "Error in systems config logic" );
-            if ( name.length() ) {
-                SG_LOG( SG_SYSTEMS, SG_WARN, "Section = " << name );
-            }
-        }
-    }
-}
-
-PitotSystem::PitotSystem ( int i )
+    _name(node->getStringValue("name", "pitot")),
+    _num(node->getIntValue("number", 0)),
+    _stall_factor(cos(node->getDoubleValue("stall-deg", 60.0) * SGD_DEGREES_TO_RADIANS ))
+                       // this is the projection factor for the stall angle.
 {
-    num = i;
-    name = "pitot";
 }
 
 PitotSystem::~PitotSystem ()
@@ -46,14 +33,19 @@ void
 PitotSystem::init ()
 {
     string branch;
-    branch = "/systems/" + name;
+    branch = "/systems/" + _name;
 
-    SGPropertyNode *node = fgGetNode(branch.c_str(), num, true );
+    SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true );
     _serviceable_node = node->getChild("serviceable", 0, true);
     _pressure_node = fgGetNode("/environment/pressure-inhg", true);
-    _density_node = fgGetNode("/environment/density-slugft3", true);
-    _velocity_node = fgGetNode("/velocities/airspeed-kt", true);
+    _mach_node = fgGetNode("/velocities/mach", true);
+    _alpha_deg_node = fgGetNode("/orientation/alpha-deg", true);
+    _beta_deg_node = fgGetNode("/orientation/side-slip-deg", true);
     _total_pressure_node = node->getChild("total-pressure-inhg", 0, true);
+    _measured_total_pressure_node = node->getChild("measured-total-pressure-inhg", 0, true);
+    if ( _stall_factor < 0 ) { // |stall angle| > 90°
+               _stall_factor = cos(60 * SGD_DEGREES_TO_RADIANS);
+       }
 }
 
 void
@@ -66,30 +58,30 @@ PitotSystem::unbind ()
 {
 }
 
-#ifndef INHGTOPSF
-# define INHGTOPSF (2116.217/29.9212)
-#endif
-
-#ifndef PSFTOINHG
-# define PSFTOINHG (1/INHGTOPSF)
-#endif
-
-#ifndef KTTOFPS
-# define KTTOFPS 1.68781
-#endif
-
-
 void
 PitotSystem::update (double dt)
 {
     if (_serviceable_node->getBoolValue()) {
-                                // The pitot tube sees the forward
-                                // velocity in the body axis.
-        double p = _pressure_node->getDoubleValue() * INHGTOPSF;
-        double r = _density_node->getDoubleValue();
-        double v = _velocity_node->getDoubleValue() * KTTOFPS;
-        double q = 0.5 * r * v * v; // dynamic
-        _total_pressure_node->setDoubleValue((p + q) * PSFTOINHG);
+        double p = _pressure_node->getDoubleValue();
+        double mach = _mach_node->getDoubleValue();
+        double alpha = _alpha_deg_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
+        double beta = _beta_deg_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
+           double x_proj_factor = cos(alpha) * fabs(cos(beta));  // the factor to project the total speed vector on the longitudinal body axis
+
+        double p_t = p;                                                                                // pitot tube stalled: total pressure = static pressure
+        double p_t_meas = p;
+
+        if ( x_proj_factor > _stall_factor ) {                         // NOTE: alpha: -180 - 180, beta: -90 - 90, pitot probe is stalled at more than 60 deg
+            p_t = p * pow(1 + 0.2 * mach*mach*x_proj_factor*x_proj_factor, 3.5 );              // total pressure in the pitot tube if not stalled
+            p_t_meas = p_t;
+
+            if (mach > 1) {
+                p_t_meas = p * pow( 1.2 * mach*mach, 3.5 ) * pow( 2.8/2.4*mach*mach - 0.4 / 2.4 , -2.5 );    // measured total pressure by pitot tube (Rayleigh formula, at Mach>1, normal shockwave in front of pitot tube)
+            }
+        }
+
+        _total_pressure_node->setDoubleValue(p_t);
+        _measured_total_pressure_node->setDoubleValue(p_t_meas);
     }
 }