Hello,
when I use the Auto-throttle feature along with Auto-pilot it works fine, but when I use Auto-throttle with manual flying it doesn't seem to work, i.e doesn't maintain correct speed with changes in altitude, anyone knows a way to fix this in Aircraft.cfg file, or is it hardwired in the Air file?  So far I have tried it on the Lear 45 and FA 18.
Thanks

In most aircraft the Autothrottles are a part of the autopilot and as such the autopilot must be engaged for it to function. There are a few types (A320s come to mind) that have Autothrottles that can function with the autopilot disconnected however the power settings are still beforehand programmed into the FMC which is the brains of the autopilot effectively.