src/Instrumentation/ - gauge and avionics support code This directory contains code to support gauges, avionics, and other instruments in FlightGear. The file instrument_mgr.[ch]xx contains a subsystem group that holds all of the individual instruments. Every instrument should extend FGSubsystem, and then should be added to the group in the FGInstrumentMgr constructor. Code is gradually moving into here from other areas, especially the src/Cockpit/ directory. Eventually, there will be an XML configuration file to select what instrumentation modules should be available, so that different aircraft can have appropriate support.