Seems that all you need for a career is education
and money
Back to the plot. somebody advocated - just leave the aircraft as it is and it would fly stright and level more or less.
If, due to trim condition changes, for example have we got auto trim when auto pilot is out?
Is the aircraft/would the aircraft maintain S&L when in its little mind it thinks it is Overspeeding - even with the A/P out?
Take one aeroplane - set it up for straight and level and trim - aeroplane flies straight and level.
If the nose should rise or ondeed lower then ther would follow and ensuing climb or descent.
If left alone the aircraft in the descent would increase speed and eventually pitch up due to the increase in Lift it would then climb until the speed dropped off again when the nose would lower causing a descent and increase in speed ad-nauseam until (dependant on Trim setting and other things**) everything had equalled out and the aircraft had naturally stabilized in a descent or a climb or straight and level - but** with shifting CofG due to fuel being used at about 2180kgs per hour (in the case of a 320 in the crz, more for a 330) then a climb or descent would ensue. Perhaps then this would explain the climb up to service ceiling? and the descent down to . . see that chart above.