Paul, FLEX doesn't derate the engine.

Sorry to be pedantic, but yes, actually it does. That Boeing uses a different mechanism and different terms to acheive the same effects for the same reasons doesn't change the facts that the effective Rated power of the engine is reduced and the technical term for doing that is "derate".

Just to say thanks to everybody, your advices were very helpful. Special thanks to Mark (Aldridge?) who advised using F4 - instant full throttle. It worked and I just completed couple of takeoffs with auto-thrust engaging as it should.Seems that my joystick throttle responds too slow. I now discovered that if I push it swiftly to max (in one second) it works too. If you move it too slow, too gradually, it will be ignored.I'm not sure if that is a realistic way to handle throttles on a real plane, but I'm happy the solution was so simple and I'm back to flying.Thankyou once againDaniel Sagner

Daniel,you're right in assuming that it is not realistic to push the throttles from idle to TO thrust in 1 second. But it doesn't take more than 10 seconds either. If you reach 80kts before the thrust levers are at TO thrust, then ATS might get confused, so make sure you're not too slow with the levers. (I haven't tried this on the real MD-11, meaning to check what happens if you advance the levers too slowly. Might be that the code in the simulation for this is not there, hence you hear all speed callouts at once when hitting F4 later in the take-off roll)And if this doesn't help and you can only do a successful take-off using F4 then you'll definitely need to check your hardware for calibration issues, or maybe wear and tear changed its behaviour... like dirt/dust on the sensor...Regards,Markus