1 // pitot.cxx - the pitot air system.
2 // Written by David Megginson, started 2002.
4 // This file is in the Public Domain and comes with no warranty.
7 #include <Main/fg_props.hxx>
8 #include <Main/util.hxx>
11 PitotSystem::PitotSystem ()
15 PitotSystem::~PitotSystem ()
22 _serviceable_node = fgGetNode("/systems/pitot[0]/serviceable", true);
23 _pressure_node = fgGetNode("/environment/pressure-inhg", true);
24 _density_node = fgGetNode("/environment/density-slugft3", true);
25 _velocity_node = fgGetNode("/velocities/airspeed-kt", true);
26 _total_pressure_node =
27 fgGetNode("/systems/pitot[0]/total-pressure-inhg", true);
36 PitotSystem::unbind ()
41 # define INHGTOPSF (2116.217/29.9212)
45 # define PSFTOINHG (1/INHGTOPSF)
49 # define KTTOFPS 1.68781
54 PitotSystem::update (double dt)
56 if (_serviceable_node->getBoolValue()) {
57 // The pitot tube sees the forward
58 // velocity in the body axis.
59 double p = _pressure_node->getDoubleValue() * INHGTOPSF;
60 double r = _density_node->getDoubleValue();
61 double v = _velocity_node->getDoubleValue() * KTTOFPS;
62 double q = 0.5 * r * v * v; // dynamic
63 _total_pressure_node->setDoubleValue((p + q) * PSFTOINHG);