FGproperties/Systems/Pitot

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The pitot system measures impact pressure and is basically a tube pointing forward. Small aircraft have one, small IFR aircraft have one or two (of which at least one is heated) and larger commercial aircraft have three or even more. In those large aircraft the left pitot serves the pilot instruments, the right the co-pilot and the third system the back-up instruments. This might be different for each type of aircraft of course.

In FlightGear the pitot system outputs the total pressure to the following properties:

 /systems/pitot[n]/total-pressure-inhg and
 /systems/pitot[n]/measured-total-pressure-inhg

Which are the same except at supersonic speeds. For supersonic aircraft use the "measured" property. See also the README.airspeed-indicator. However it is advised for every aircraft to use the measured property. In future this will be the property where all the measurement faults are reflected.

The following "measurement failures" are currently applied:

  1. Decrease of total and measured pressure due to side-slip and angle of attack
  2. At 60 deg the pitot tube will stall and the value will fall back to static pressure
  3. For the "measured" property only: at Mach>1, a shock wave is assumed in front of the pitot tube, decreasing the total pressure.

The stall angle may be (optionally) set to any angle between 0 and 90 deg (default is 60 deg) like so:

  <pitot>
    <name>pitot</name>
    <number>0</number>
    <stall-deg>45</stall-deg>	
  </pitot>

Both the decrease of the pitot pressure and the default stall angle are based on a measurement on an AN5812 pitot tube.