It is a Nasal function defined in NasalSys.cxx:
https://sourceforge.net/p/flightgear/fl ... salSys.cxxThis calls sg_random, which is defined in:
https://sourceforge.net/p/flightgear/si ... g_random.cAs you can see from the comment on line 110, each call to it generates a random number between 0.0 and 1.0. So things like local weather will use it to randomly create clouds. Aircraft might use it to trigger things like failures, differences in fuel consumption between engines, slight differences in refuelling between tanks, etc.