For example, the airports are correct, the runway placing, approach lights, the sky and environment model are accurate qua stars, sun and moon given the time of day, the handling of the instruments are correct (the magnetic compass lags behind a bit just as in a real airplane), some planes may break when put under too much stress (although the pilot is likely to break before that!). The scenery uses the SRTM data that I also used to do the hillshading in mapnik (see previous post).
There are a lot of customization capabilities for FlightGear too, making it very suitable for research. The way it works is pretty simple. You specify an option parameter that states a direction of input or output (if input, then the simulator accepts an external file or socket for instructions to control ailerons, rudder, etc. ). More details can be found under /usr/share/games/FlightGear/Docs/README.IO if interested. The option looks roughly like this:
--generic=socket,out,10,localhost,16661,udp,myprotocolSo, this chooses a socket transport, outgoing data, 10 times per second, localhost, port 16661, udp protocol using the protocol as specified in the myprotocol.xml file. Easy!
The receiving application can then start processing a stream of data coming from the flight simulator. It can also send back a number of commands to control the aircraft, the environment, sounds, AI models or whatever. Basically, it's quite a nice way to try out a couple of concepts before having to dig too deep into the bowels of the flight simulator package itself. The same methods are actually used to store a flight path of a plane and then replay the flight later (at the specified frequency intervals). The same methods are used to connect flightgear instances together and do some multiplayer flights or track the positions of flightgear users on a large map.