Originally Posted by
1201alarm
That is why the Aircraft should automatically compare the QNH put (during cruise or early descent) into the FMGC approach page with the QNH set on the FCU during transition and give an alarm if off by more than one.
With the increase in PBN, we need more protection against wrong QNH. This would lead to a strong safety net against wrong QNH information or wrong setting.
Quite common for QNH to change by one, so chances are the alerting will go off a lot when it's not needed and the alerting system could be seen as a nuisance 99% of the time when it's not needed. Maybe the manufacturers thought about it already and possibly a reason why it's not implemented already, should be a way around that one perhaps as well... Including pilots comparing forecast to actual, RA... But it's a nasty one if the error is the wrong way additionally and actual alt is lower than indicated...