Where could i download simulation games for free? (flight simulator, etc)?

Flgiht, train, ship, submarine or any other kind of a full version of a simulation game? (no demos or trials)Where could i download simulation games for free? (flight simulator, etc)?
you can try flightgear ( http://www.flightgear.org/ )

it's based on the X-Plane engine (the core program which does the simulation) and shares its main shortcoming:

the plane is suspended to wires; i saw them once, when i hit some key combination. there a yellow lines going up from the wings (mostly) and the fuselage (a few) and this leads to a jerky simulation (the plane reacts too promptly to joystick movements).

when flying fast and / or smooth this doesn't really matter, but when getting slow / landing, it's annoying.



M$-FlightSim (9/2004 too, i think, but certainly X) use two vectors under each wing (and possibly the tail) of the plane; the more the two vectors are open, the greater the surface between them and thus the lift the wings (tail) provide.

but it doesn't come free, alas.Where could i download simulation games for free? (flight simulator, etc)?
I am afraid only demos are available for free online. If you want the real quality and depth you should just purchase the game.