A320 managed vs selected speed
Hello all,
I have a general question about scenarios where you may experience light/moderate turbulence in the cruise.
in my first few hundred hours on the bus, I have observed people going from managed to selected speeds when it gets a bit choppy, to either select 0.76, or even select the current Mach the managed mode was already maintaining.
my question is, by going to a selected Mach, will the autothrust actually hold the speed better compared to that of a managed mach.
the FCOM suggests to me that unless you force it out of Mach mode, (by pressing SPD on FCU), alt soft mode will stay engaged (providing in alt crz and after 2 mins), allowing for minor deviations in Mach by allowing 50ft variation from the CRZ FL.
this makes me think that, unless you’re actually going to SPEED mode, it doesn’t actually matter if the mach is managed or selected, if you’re in mach (fma) and alt crz, you’ll still have alt soft mode engaged.
if this is the case, why do I see people on the line selecting the same mach? maybe I’m missing something?
The only time I think I really press the SPD button on the FCU is when ATC ask in the descent for x kts now when I’m still on a mach. Even then it seems to just want to go back to mach instantly anyway!
thanks all