Flightgear is open source flight simulator. It is weighted ~300MB for windows (relatively low compared to other simulators). It can be used not only for gaming. There are some R/C models, which can be used to practice on them. For example Malolo aircraft. Download and extract it to C:\Program Files (x86)\FlightGear\data\Aircraft (Ubuntu: /usr/share/games/FlightGear/Aircraft/).
Then run the following from command line:
"C:\Program Files (x86)\FlightGear\bin\Win32\fgfs" ^
"--fg-root=C:\Program Files (x86)\FlightGear\data" ^
or in Ubuntu
Wait a minute, while the program finish loading, then you can drive the airplane using following keys.
V : Change viewpoint
Page-Up : Increase throttle
Page-Down : Decrease throttle
X : Zoom-in
Shift-X : Zoom-out
Arrow keys : Control elevator and aileron.
It is OK when you crash a plane just after a few seconds of flying :). Do some practice.
Flightgear has many useful features, and one of them is the ability to show the status of every components in the environment. Just run it adding the "--httpd=1234" argument and it creates a local web server. Navigating to http://localhost:1234 you can see a tree structure of all elements, which can be modified from browser also. For example start the program, change the viewpoint and navigate to http://localhost:1234/controls/engines/engine and click on throttle and change the value to 0.2.