MU3001A
That's why we have a climb checklist and a descent checklist, both triggered by TA/TL which is constant and standard
Are you saying that the TL is
constant in the U.S?
Please refer to
14 CFR 91.121 (b)
If the SOP/checklist is anchored to FL180, a crew could be setting up for an altitude bust when QNH is significantly lower than standard -- e.g.:
QNH is 29.11"
Aircraft is cleared to descend to 17,000.
Crew is descending at 2000 fpm and waits until "FL180" to set QNH.
What will the altimeters read when re-set from STD to 29.20?
How much room will remain to capture the assigned altitude?