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flightgear/src/Systems/pitot.cxx

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Added pitot system and new airspeed indicator.
2002-09-28 20:48:53 +00:00
// pitot.cxx - the pitot air system.
// Written by David Megginson, started 2002.
//
// This file is in the Public Domain and comes with no warranty.
#include "pitot.hxx"
#include <Main/fg_props.hxx>
#include <Main/util.hxx>
PitotSystem::PitotSystem ()
{
}
PitotSystem::~PitotSystem ()
{
}
void
PitotSystem::init ()
{
_serviceable_node = fgGetNode("/systems/pitot[0]/serviceable", true);
_pressure_node = fgGetNode("/environment/pressure-inhg", true);
_density_node = fgGetNode("/environment/density-slugft3", true);
_velocity_node = fgGetNode("/velocities/uBody-fps", true);
_total_pressure_node =
fgGetNode("/systems/pitot[0]/total-pressure-inhg", true);
}
void
PitotSystem::bind ()
{
}
void
PitotSystem::unbind ()
{
}
Patch from Alex Perry: Ok, I found the problem. You're computing the dynamic pressure in "psf" and adding it to the static pressure in "inHg" to form the total pressure. The attached patch is the simple fix to the source. With that fix, failing the pitot while in cruise at 3k' will cause the airspeed to indicate beyond redline during climb ... well before 4k'. Thus, a pitot problem can be detected on any IFR altitude change. Similarly, failing the static (with working pitot) while cruising 4k' causes the airspeed to indicate beyond redline during a descent well before reaching 3k' (during which, of course, the ALT looks fine). Thus, a static failure can be detected before the aircraft breaks out of the pilot tolerance range and is blatantly conspicuous soon after.
2002-10-10 18:15:22 +00:00
#ifndef INHGTOPSF
# define INHGTOPSF (2116.217/29.9212)
#endif
Added pitot system and new airspeed indicator.
2002-09-28 20:48:53 +00:00
void
PitotSystem::update (double dt)
{
if (_serviceable_node->getBoolValue()) {
// The pitot tube sees the forward
// velocity in the body axis.
Patch from Alex Perry: Ok, I found the problem. You're computing the dynamic pressure in "psf" and adding it to the static pressure in "inHg" to form the total pressure. The attached patch is the simple fix to the source. With that fix, failing the pitot while in cruise at 3k' will cause the airspeed to indicate beyond redline during climb ... well before 4k'. Thus, a pitot problem can be detected on any IFR altitude change. Similarly, failing the static (with working pitot) while cruising 4k' causes the airspeed to indicate beyond redline during a descent well before reaching 3k' (during which, of course, the ALT looks fine). Thus, a static failure can be detected before the aircraft breaks out of the pilot tolerance range and is blatantly conspicuous soon after.
2002-10-10 18:15:22 +00:00
double p = _pressure_node->getDoubleValue(); // static
Added pitot system and new airspeed indicator.
2002-09-28 20:48:53 +00:00
double r = _density_node->getDoubleValue();
double v = _velocity_node->getDoubleValue();
Patch from Alex Perry: Ok, I found the problem. You're computing the dynamic pressure in "psf" and adding it to the static pressure in "inHg" to form the total pressure. The attached patch is the simple fix to the source. With that fix, failing the pitot while in cruise at 3k' will cause the airspeed to indicate beyond redline during climb ... well before 4k'. Thus, a pitot problem can be detected on any IFR altitude change. Similarly, failing the static (with working pitot) while cruising 4k' causes the airspeed to indicate beyond redline during a descent well before reaching 3k' (during which, of course, the ALT looks fine). Thus, a static failure can be detected before the aircraft breaks out of the pilot tolerance range and is blatantly conspicuous soon after.
2002-10-10 18:15:22 +00:00
double q = 0.5 * r * v * v / INHGTOPSF; // dynamic
Added pitot system and new airspeed indicator.
2002-09-28 20:48:53 +00:00
_total_pressure_node->setDoubleValue(p + q);
}
}
// end of pitot.cxx
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