diff --git a/src/Systems/pitot.cxx b/src/Systems/pitot.cxx index 7658f41a0..cf3eb2590 100644 --- a/src/Systems/pitot.cxx +++ b/src/Systems/pitot.cxx @@ -1,7 +1,7 @@ // pitot.cxx - the pitot air system. // Written by David Megginson, started 2002. // -// Last modified by Eric van den Berg, 24 Nov 2012 +// Last modified by Eric van den Berg, 01 Nov 2013 // This file is in the Public Domain and comes with no warranty. #ifdef HAVE_CONFIG_H @@ -19,7 +19,9 @@ PitotSystem::PitotSystem ( SGPropertyNode *node ) : _name(node->getStringValue("name", "pitot")), - _num(node->getIntValue("number", 0)) + _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. { } @@ -41,6 +43,9 @@ PitotSystem::init () _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 @@ -61,14 +66,21 @@ PitotSystem::update (double dt) 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; - mach = mach * fabs(cos(alpha)) * cos(beta); - mach = std::max( mach , 0.0 ); // we want a mach=0 if the airflow comes from behind - double p_t = p * pow(1 + 0.2 * mach*mach, 3.5 ); // true total pressure around aircraft - _total_pressure_node->setDoubleValue(p_t); - double 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) + 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); } } diff --git a/src/Systems/pitot.hxx b/src/Systems/pitot.hxx index cad000f22..f694439d9 100644 --- a/src/Systems/pitot.hxx +++ b/src/Systems/pitot.hxx @@ -1,7 +1,7 @@ // pitot.hxx - the pitot air system. // Written by David Megginson, started 2002. // -// Last modified by Eric van den Berg, 24 Nov 2012 +// Last modified by Eric van den Berg, 01 Nov 2013 // This file is in the Public Domain and comes with no warranty. @@ -55,6 +55,7 @@ private: std::string _name; int _num; + double _stall_factor; SGPropertyNode_ptr _serviceable_node; SGPropertyNode_ptr _pressure_node; SGPropertyNode_ptr _mach_node;