Originally Posted by
eckhard
It’s a good question and one that comes up seemingly frequently (see other threads).
In a multi-crew operation with high rates of climb, the consensus appears to be “when cleared to a flight level and above acceleration altitude”. In any case, the standby altimeter can remain on QNH until above MSA and Trans Alt.
In a slow climber, without a standby, maybe there would be more chance of getting a revised clearance to stop at an altitude and thus it might be better to wait until Trans Alt.
The first two paragraphs are great advice. I’d steer clear of the third, much more likely not to get stopped off and to forget or be distracted than to be stopped off; stopping off is itself a cue to ANC and resolve the potential problem.