PicaSim - Free flight simulator

Learn to fly radio controlled gliders and powered planes in this highly realistic flight simulator. You can use it to practise aerobatics, have a lazy fly on a rainy day, or challenge yourself with tasks such as races.
This free version has all the simulation features of the full version, but just has a handful of planes and sceneries for you to try. It also includes one race. It focuses particularly on simulating soaring flight - with realistic models of wind flow, turbulence and thermals. You can fly with AI/computer controlled planes too, keeping you company in the air.
The full version includes lots more planes (powered, including a quadcopter, as well as gliders), sceneries and races.
The sceneries include a variety of slope and flat field sites. Some are panoramic, with high graphical quality, but a fixed viewpoint. Others are 3D scenes where you can fly in or behind the plane.
It is highly configurable, so you can create and explore new terrains from inside the app, as well as adjust settings such as the wind modelling, aeroplane settings (including size and ballast) etc. You can create your own planes and sceneries on your desktop computer and import them into the app (see the support website).
If you've never flown a radio-controlled plane before, you'll probably find it hard to fly at first. Check the support website for a video and hints on how to fly. PicaSim won't teach you how to fly, but it can help you learn - persevere and the sky is the limit!
You can read a detailed review of PicaSim in the February 2013 edition of Radio Controlled Soaring Digest at www.rcsoaringdigest.com - "PicaSim is a fantastic flight simulator ... after a short time it’s like having a real transmitter in your hands".