What is the advantage of not having automatic ALT SEL?
Once upon a time, when I was roaming the skies in the mighty ATR, I had alt preselect mode on my AFCP that automatically aremed alt hold whenever alt selector was moved from current altitude. Then I moved onto A320 and automatic alt arming was there too.
Now I'm on DHC-8 Q400 and whenever I leave altitude for some other, I have to press ALT SEL button to confirm that I really want to go to the selected altitude and no further. Being particularly unimaginative, I've struggled to come to reason behind this particular peculiarity but to no avail.
So if some good soul reveals what's the deal with manual ALT SEL, I'd be grateful.