Autobrake.

I cannot substitute the FSX Boeing 747 Autobrake for the 'Standby Altimeter' in the FSX Airbus A321. Likewise I cannot substitute the Autobrake in to the FSX Lear 45.But I can substitute the Autobrake from the FS9 Boeing 777 into the FSX Airbus and the Lear 45. In the Airbus it works, but in the Lear 45 it does not work. As far as I can see there is no Autobrake in the FSX Airbus or Lear 45.Can anyone explain this please, and make it work? Thank you very much.Delta.