Hi,
some days ago I was flying and experienced pitot icing due to malfunction of
the pitot heat :-(
The malfunction was clearly noticable at the airspeed indicator which dropped
to zero within a few seconds.
What happened?
The forward facing pitot tube was blocked by ice. The total pressure in the
tube relieved and dropped to static pressure.
Our implementation just stops calculation of the pitot/total pressure if the
serviceable flag is false. That keeps the static pressure at the (constant)
last calculated value and you don't see any changes at the airspeed indicator
unless you change you altitude. I have attached a tiny patch, that pumps the
current pressure thru a lowpass to target for static pressure. Toggeling
the /systems/pitot/serviceable flag in flight now makes the airspeed
indicator look like what I saw in the airplane some time ago.
The next release of the SenecaII will have functional pitot-icing and
deicing...
Torsten
Index: pitot.cxx
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/Systems/pitot.cxx,v
retrieving revision 1.9
diff -u -p -r1.9 pitot.cxx
--- pitot.cxx 17 Jul 2006 18:14:31 -0000 1.9
+++ pitot.cxx 6 Dec 2006 14:57:05 -0000
@@ -92,6 +92,10 @@ PitotSystem::update (double dt)
v = 0.0;
double q = 0.5 * r * v * v; // dynamic
_total_pressure_node->setDoubleValue((p + q) * PSFTOINHG);
+ } else {
+ _total_pressure_node->setDoubleValue(fgGetLowPass(
+ _total_pressure_node->getDoubleValue(),
+ _pressure_node->getDoubleValue(), dt ));
}
}
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