Airbus and CFM spend billions optimising the airframe and systems. Airlines buy in software to help them optimise schedules matching runways slots to flight times and trip costs, one output of which is cost index. The company file a flight plan telling ATC that we will be flying a certain Mach No.
In Europe this data is fed into a computer which in turn tries to optimise ATC slot allocation to minimise overall delay.......only for Captain Bloggs thinks, mneh - I don’t like the look of it, I’m gonna add on a few extra knots because I like the way it looks on the PFD.
Quick question: in the pictures above, at the managed speed are you closer to the over speed protection or under speed (alpha) protection?
Having spent maybe 40 hours in the last 6 months cruising around in a profile similar to the second picture, it would appear that speed stability is not an issue. Don’t get me wrong - I wouldn’t try it in a jet stream crossing a big mountain range. It hasn’t caused any problems in light-moderate chop though.