FMS (Flying Model Simulator) is an RC Flight Simulator featuring several of their real model RC airplanes to train on before flying the real thing.
You can purchase a controller from them, but the keyboard keys work very well and are easy to configure if you just want to play around with the simulator. We found that the game is indeed a beta with some speed issues and some crashing in Windows 10. Other small annoyances show up like having to load a scenery numerous times.
It comes with about 20 models, including helicopters and about 15 sceneries.
It has a long way to go but most likely will work better on operating systems before Windows 10. Normally, this wouldn't make the cut here but your options in free RC flight simulators are non-existent. Any RC fan will tell you Real Flight is the way to go but you're looking at in the $150 plus range, with a controller, so if you just want a free alternative and want to appreciate why Real Flight is so expensive, here you go.
If you get "D3DRM.DLL is not loaded" error we have provided it inside the download. Open the zip file and copy D3DRM.DLL to the FMS directory which should be under "C:Program Files (x86) > FMS".