Somewhere in the tutorial says about acceleration altitude at 3000 ft. What this means?

I'm very new to virtual aviation and have never read the MD11 manual but here goes nothing ;)I think this means that the plane should start accelerating to the next allowed speed after reaching certain hight above ground.If the airport was say 250ft above sea level, your acceleration altitude would be 3250ft.I think that the plane would maintain speed of V2 ( + 10?) Before reaching 3250ft. Then it would start to accelerating to the next allowed speed which might be 250 knots for example.

Acceleration altitudes are set by the airport in order to reduce noise. When following these procedures, maintain a climb attitude which keeps the speed at V2+10. Notice that I didn't say maintain a throttle setting. Your goal is to reach acceleration altitude as soon as little distance from the airport as possible. Once you have achieved acceleration altitude, you can pitch down, clean up the aircraft, and accelerate to the next speed limitation of the SID (ie 250 kts below 10,000).

In the US, very few airports set their own acceleration altitudes. Much more common is a company specific (FAA approved) acceleration altitude. For my company, it's 1000 ft above field elevation. At that altitude, we lower the pitch and maintain a climb rate somewhere between 50 ft per minute (if the autopilots is doing the flying) and 500 ft per minute (the rate is dependent on how fast we want to accelerate, sometimes terrain clearance has to be factored in), as we are descreasing the climb rate we also pull the power out of the T/O(FLEX) setting to the climb setting. There are two seperate entries in the MD-11 MCDU for this. One is the altitude at which the rate of climb is decreased, and the other is the altitude at which the power is reduced. Typically these will happen at the same altitude.The airspeed we accelerate to depends on the airspace and terrain. For terrain clearance, we'll only accelerate a few knots from V2+15 to VT which is the best rate of climb with flaps/slats retracted. If there isn't a terrain issue, then we accelerate to either 200 kts or 250 kts. The 200 kt speed is used when coming out of a Class C/D airport until we are at least 4 nautical miles from the aiport or at least 2500 ft above field elevation. After that we accelerate to 250 kts. If we come out of a Class B airport we accelerate to 250 kts until 10,000 ft MSL. Every once in a while a SID will have a different airspeed limitation that must be observed too.

Thank you all for your helpful answers. Now it is clearer to me