vasFMC – why do you need a freeware FMC?
Currently (real world) planes are equipped with systems allowing them to fly direct routes between any two points on earth. They are independent from any ground navaid-network and do not have to follow VOR radials like they did two decades ago (and earlier). FSX allows you to do that using GPS.
Unfortunately, a simple GPS included in FSX has limited capabilities and outdated navigation database. To follow real world procedures a pilot needs an FMC that is usually included in high-end payware add-ons.
If you want to fly (almost) any plane you choose with a navigation system that accepts Navigraph’s or Aerosoft’s AIRAC – vasFMC is for you.