guys my understanding is that the moment the trhust levers are brought to idle the autu thrust is disconnected....and since you can't go to reverse without going thriugh idle///VOILA....here's some more info that i learnt on the sim...on an autoland..if the thrust levers are not brought to idle at 10 feet( reminder only) and are kept up at the climb gate the auto thrust remains engaged...and it is the auto thrust which gets thtust down to idle....I tried this down to 50 kts with the thrust lever at the climb gate....the thrust remained at idle...but the moment i disconnected the A/P the thrust went up to climb ,,,the auto thrust remained active.
