Firstly, I read somewhere that doing "selected" precision approaches don't usually make sense to do, and they should and usually are managed, is this true?
If you are radar vectored until your interception of the localizer, you are turning(selecting) headings until you can ARM the "approach" and intercept both loc and g/s, is this not selected precision?
I assume you can only do a managed approach if you are cleared for the approach from the start.
a bit a while I did not fly airbus yet, but from memory, to be simple :
managed : you let the a/c do. You "just" monitor.
selected : you are still master, you use the A/P but you are more active coz you decise your speed, your heading etc
Manage mode, it good to save fuel, but when I flew I did not use a lot...coz under radar vectoring you use mostly selected mode of course. Because you have to change speed, heading etc many times.
IN manage mode, the plane follows your FMGS ! You can not do an approach from the start as you said, under managed mode, if your approach is not in the FMGS.
IN Asia, many times we had to fly under selected mode even from the start of the approach.
Airbus philosophy is to use manage mode the most possible... for them, the pilot is out of the loop.
In reality, and where I was, we can not use it most of the time. Many things do not go like in a book. There are many unexpected things .
Even if you fly a 320 you have to create radials yourself...so....