PicaSim is a flight simulator for radio controlled aircraft. At the moment it concentrates mainly on gliders, but it has a few other aircraft too and I expect the stable will expand in the near future. You can get it for free (no ads etc) on Android, or so-cheap-it's-nearly-free on the Apple app store, or free-but-donate-if-you-like-it on Windows.
Please do explore and post on the forums if you have any questions about PicaSim, or you can email me at the address below. Announcements about new versions will appear there, or on the Facebook page.
The forums are currently the most active source of new information, including lots of user-created planes and sceneries etc:
Aeroplanes and sceneries
These planes are currently available in the simulator - mostly gliders, but also a few powered R/C and control-line planes, a quadcopter and a hang glider:
These are the sceneries:
And there are three skyscapes for the 3D environments:
You can also modify and create your own planes and sceneries.