Originally Posted by
H Peacock
Well potentially the same issue when changing between QNH and Std; not unique to using QFE.
Now some AFCSs in ALT will try to climb or descend the ac if the sub-scale is changed (certainly some Bombardier ac will), while others remain level regardless. That all said, the sub-scale would normally only be changed when descending or climbing to a new Alt, Ht or FL, ie not when intending to remain level.
I’d agree for changing from STD to QNH, so in V/S or similar, but I think changing to QFE is typically done while level.