Take off from high altitude airport with heavies

[olseric]

using the ground effect to take off sounds nice but how to do this in proctice

Well, that's a great question! It's easier to do it than explain it. I would suggest starting by reading this article: [url]
http://www.avweb.com/news/airman/185905-1.html[/url]. It basically explains a little bit about wingtip vorticies (and a bit about wake
turbulance) and then goes into what ground effect is.

The principle of the short field takeoff is basically to use ground effect to your advantage to get the aircraft off from the runway and reduce
the rolling friction of the tires on the surface allowing for a quicker acceleration. In practice, start your takeoff roll, and get the tires off the
runway as soon as you can. This means applying some back pressure to the stick to get you into the air. Once up, maintain a VERY low
altitude, straight and level, and let the plane accelerate. As the plane accelerates, you can slowly increase back pressure to obtain the
desired rate of climb.

I would suggest you begin trying this in something like the Default FS9 Beech King Air. You'll get a better feel as to what should happen.
Once you have that mastered, try it in something like the Default 737-400. Eventually, you should be able to do this in a 747-400 without
issue.